diff --git a/spring-cloud-netflix/1.2.3.RELEASE/ghpages.sh b/spring-cloud-netflix/1.2.3.RELEASE/ghpages.sh new file mode 100644 index 00000000..57c5da3a --- /dev/null +++ b/spring-cloud-netflix/1.2.3.RELEASE/ghpages.sh @@ -0,0 +1,330 @@ +#!/bin/bash -x + +set -e + +# Set default props like MAVEN_PATH, ROOT_FOLDER etc. +function set_default_props() { + # The script should be executed from the root folder + ROOT_FOLDER=`pwd` + echo "Current folder is ${ROOT_FOLDER}" + + if [[ ! -e "${ROOT_FOLDER}/.git" ]]; then + echo "You're not in the root folder of the project!" + exit 1 + fi + + # Prop that will let commit the changes + COMMIT_CHANGES="no" + MAVEN_PATH=${MAVEN_PATH:-} + echo "Path to Maven is [${MAVEN_PATH}]" + REPO_NAME=${PWD##*/} + echo "Repo name is [${REPO_NAME}]" + SPRING_CLOUD_STATIC_REPO=${SPRING_CLOUD_STATIC_REPO:-git@github.com:spring-cloud/spring-cloud-static.git} + echo "Spring Cloud Static repo is [${SPRING_CLOUD_STATIC_REPO}" +} + +# Check if gh-pages exists and docs have been built +function check_if_anything_to_sync() { + git remote set-url --push origin `git config remote.origin.url | sed -e 's/^git:/https:/'` + + if ! (git remote set-branches --add origin gh-pages && git fetch -q); then + echo "No gh-pages, so not syncing" + exit 0 + fi + + if ! [ -d docs/target/generated-docs ] && ! [ "${BUILD}" == "yes" ]; then + echo "No gh-pages sources in docs/target/generated-docs, so not syncing" + exit 0 + fi +} + +function retrieve_current_branch() { + # Code getting the name of the current branch. For master we want to publish as we did until now + # http://stackoverflow.com/questions/1593051/how-to-programmatically-determine-the-current-checked-out-git-branch + # If there is a branch already passed will reuse it - otherwise will try to find it + CURRENT_BRANCH=${BRANCH} + if [[ -z "${CURRENT_BRANCH}" ]] ; then + CURRENT_BRANCH=$(git symbolic-ref -q HEAD) + CURRENT_BRANCH=${CURRENT_BRANCH##refs/heads/} + CURRENT_BRANCH=${CURRENT_BRANCH:-HEAD} + fi + echo "Current branch is [${CURRENT_BRANCH}]" + git checkout ${CURRENT_BRANCH} || echo "Failed to check the branch... continuing with the script" +} + +# Switches to the provided value of the release version. We always prefix it with `v` +function switch_to_tag() { + git checkout v${VERSION} +} + +# Build the docs if switch is on +function build_docs_if_applicable() { + if [[ "${BUILD}" == "yes" ]] ; then + ./mvnw clean install -P docs -pl docs -DskipTests + fi +} + +# Get the name of the `docs.main` property +# Get whitelisted branches - assumes that a `docs` module is available under `docs` profile +function retrieve_doc_properties() { + MAIN_ADOC_VALUE=$("${MAVEN_PATH}"mvn -q \ + -Dexec.executable="echo" \ + -Dexec.args='${docs.main}' \ + --non-recursive \ + org.codehaus.mojo:exec-maven-plugin:1.3.1:exec) + echo "Extracted 'main.adoc' from Maven build [${MAIN_ADOC_VALUE}]" + + + WHITELIST_PROPERTY=${WHITELIST_PROPERTY:-"docs.whitelisted.branches"} + WHITELISTED_BRANCHES_VALUE=$("${MAVEN_PATH}"mvn -q \ + -Dexec.executable="echo" \ + -Dexec.args="\${${WHITELIST_PROPERTY}}" \ + org.codehaus.mojo:exec-maven-plugin:1.3.1:exec \ + -P docs \ + -pl docs) + echo "Extracted '${WHITELIST_PROPERTY}' from Maven build [${WHITELISTED_BRANCHES_VALUE}]" +} + +# Stash any outstanding changes +function stash_changes() { + git diff-index --quiet HEAD && dirty=$? || (echo "Failed to check if the current repo is dirty. Assuming that it is." && dirty="1") + if [ "$dirty" != "0" ]; then git stash; fi +} + +# Switch to gh-pages branch to sync it with current branch +function add_docs_from_target() { + local DESTINATION_REPO_FOLDER + if [[ -z "${DESTINATION}" && -z "${CLONE}" ]] ; then + DESTINATION_REPO_FOLDER=${ROOT_FOLDER} + elif [[ "${CLONE}" == "yes" ]]; then + mkdir -p ${ROOT_FOLDER}/target + local clonedStatic=${ROOT_FOLDER}/target/spring-cloud-static + if [[ ! -e "${clonedStatic}/.git" ]]; then + echo "Cloning Spring Cloud Static to target" + git clone ${SPRING_CLOUD_STATIC_REPO} ${clonedStatic} && git checkout gh-pages + else + echo "Spring Cloud Static already cloned - will pull changes" + cd ${clonedStatic} && git checkout gh-pages && git pull origin gh-pages + fi + DESTINATION_REPO_FOLDER=${clonedStatic}/${REPO_NAME} + mkdir -p ${DESTINATION_REPO_FOLDER} + else + if [[ ! -e "${DESTINATION}/.git" ]]; then + echo "[${DESTINATION}] is not a git repository" + exit 1 + fi + DESTINATION_REPO_FOLDER=${DESTINATION}/${REPO_NAME} + mkdir -p ${DESTINATION_REPO_FOLDER} + echo "Destination was provided [${DESTINATION}]" + fi + cd ${DESTINATION_REPO_FOLDER} + git checkout gh-pages + git pull origin gh-pages + + # Add git branches + ################################################################### + if [[ -z "${VERSION}" ]] ; then + copy_docs_for_current_version + else + copy_docs_for_provided_version + fi + commit_changes_if_applicable +} + + +# Copies the docs by using the retrieved properties from Maven build +function copy_docs_for_current_version() { + if [[ "${CURRENT_BRANCH}" == "master" ]] ; then + echo -e "Current branch is master - will copy the current docs only to the root folder" + for f in docs/target/generated-docs/*; do + file=${f#docs/target/generated-docs/*} + if ! git ls-files -i -o --exclude-standard --directory | grep -q ^$file$; then + # Not ignored... + cp -rf $f ${ROOT_FOLDER}/ + git add -A ${ROOT_FOLDER}/$file + fi + done + COMMIT_CHANGES="yes" + else + echo -e "Current branch is [${CURRENT_BRANCH}]" + # http://stackoverflow.com/questions/29300806/a-bash-script-to-check-if-a-string-is-present-in-a-comma-separated-list-of-strin + if [[ ",${WHITELISTED_BRANCHES_VALUE}," = *",${CURRENT_BRANCH},"* ]] ; then + mkdir -p ${ROOT_FOLDER}/${CURRENT_BRANCH} + echo -e "Branch [${CURRENT_BRANCH}] is whitelisted! Will copy the current docs to the [${CURRENT_BRANCH}] folder" + for f in docs/target/generated-docs/*; do + file=${f#docs/target/generated-docs/*} + if ! git ls-files -i -o --exclude-standard --directory | grep -q ^$file$; then + # Not ignored... + # We want users to access 1.0.0.RELEASE/ instead of 1.0.0.RELEASE/spring-cloud.sleuth.html + if [[ "${file}" == "${MAIN_ADOC_VALUE}.html" ]] ; then + # We don't want to copy the spring-cloud-sleuth.html + # we want it to be converted to index.html + cp -rf $f ${ROOT_FOLDER}/${CURRENT_BRANCH}/index.html + git add -A ${ROOT_FOLDER}/${CURRENT_BRANCH}/index.html + else + cp -rf $f ${ROOT_FOLDER}/${CURRENT_BRANCH} + git add -A ${ROOT_FOLDER}/${CURRENT_BRANCH}/$file + fi + fi + done + COMMIT_CHANGES="yes" + else + echo -e "Branch [${CURRENT_BRANCH}] is not on the white list! Check out the Maven [${WHITELIST_PROPERTY}] property in + [docs] module available under [docs] profile. Won't commit any changes to gh-pages for this branch." + fi + fi +} + +# Copies the docs by using the explicitly provided version +function copy_docs_for_provided_version() { + local FOLDER=${DESTINATION_REPO_FOLDER}/${VERSION} + mkdir -p ${FOLDER} + echo -e "Current tag is [v${VERSION}] Will copy the current docs to the [${FOLDER}] folder" + for f in ${ROOT_FOLDER}/docs/target/generated-docs/*; do + file=${f#${ROOT_FOLDER}/docs/target/generated-docs/*} + copy_docs_for_branch ${file} ${FOLDER} + done + COMMIT_CHANGES="yes" + CURRENT_BRANCH="v${VERSION}" +} + +# Copies the docs from target to the provided destination +# Params: +# $1 - file from target +# $2 - destination to which copy the files +function copy_docs_for_branch() { + local file=$1 + local destination=$2 + if ! git ls-files -i -o --exclude-standard --directory | grep -q ^${file}$; then + # Not ignored... + # We want users to access 1.0.0.RELEASE/ instead of 1.0.0.RELEASE/spring-cloud.sleuth.html + if [[ ("${file}" == "${MAIN_ADOC_VALUE}.html") || ("${file}" == "${REPO_NAME}.html") ]] ; then + # We don't want to copy the spring-cloud-sleuth.html + # we want it to be converted to index.html + cp -rf $f ${destination}/index.html + git add -A ${destination}/index.html + else + cp -rf $f ${destination} + git add -A ${destination}/$file + fi + fi +} + +function commit_changes_if_applicable() { + if [[ "${COMMIT_CHANGES}" == "yes" ]] ; then + COMMIT_SUCCESSFUL="no" + git commit -a -m "Sync docs from ${CURRENT_BRANCH} to gh-pages" && COMMIT_SUCCESSFUL="yes" || echo "Failed to commit changes" + + # Uncomment the following push if you want to auto push to + # the gh-pages branch whenever you commit to master locally. + # This is a little extreme. Use with care! + ################################################################### + if [[ "${COMMIT_SUCCESSFUL}" == "yes" ]] ; then + git push origin gh-pages + fi + fi +} + +# Switch back to the previous branch and exit block +function checkout_previous_branch() { + # If -version was provided we need to come back to root project + cd ${ROOT_FOLDER} + git checkout ${CURRENT_BRANCH} || echo "Failed to check the branch... continuing with the script" + if [ "$dirty" != "0" ]; then git stash pop; fi + exit 0 +} + +# Assert if properties have been properly passed +function assert_properties() { +echo "VERSION [${VERSION}], DESTINATION [${DESTINATION}], CLONE [${CLONE}]" +if [[ "${VERSION}" != "" && (-z "${DESTINATION}" && -z "${CLONE}") ]] ; then echo "Version was set but destination / clone was not!"; exit 1;fi +if [[ ("${DESTINATION}" != "" && "${CLONE}" != "") && -z "${VERSION}" ]] ; then echo "Destination / clone was set but version was not!"; exit 1;fi +if [[ "${DESTINATION}" != "" && "${CLONE}" == "yes" ]] ; then echo "Destination and clone was set. Pick one!"; exit 1;fi +} + +# Prints the usage +function print_usage() { +cat </` +- if the destination switch is passed (-d) then the script will check if the provided dir is a git repo and then will + switch to gh-pages of that repo and copy the generated docs to `docs//` + +USAGE: + +You can use the following options: + +-v|--version - the script will apply the whole procedure for a particular library version +-d|--destination - the root of destination folder where the docs should be copied. You have to use the full path. + E.g. point to spring-cloud-static folder. Can't be used with (-c) +-b|--build - will run the standard build process after checking out the branch +-c|--clone - will automatically clone the spring-cloud-static repo instead of providing the destination. + Obviously can't be used with (-d) + +EOF +} + + +# ========================================== +# ____ ____ _____ _____ _____ _______ +# / ____|/ ____| __ \|_ _| __ \__ __| +# | (___ | | | |__) | | | | |__) | | | +# \___ \| | | _ / | | | ___/ | | +# ____) | |____| | \ \ _| |_| | | | +# |_____/ \_____|_| \_\_____|_| |_| +# +# ========================================== + +while [[ $# > 0 ]] +do +key="$1" +case ${key} in + -v|--version) + VERSION="$2" + shift # past argument + ;; + -d|--destination) + DESTINATION="$2" + shift # past argument + ;; + -b|--build) + BUILD="yes" + ;; + -c|--clone) + CLONE="yes" + ;; + -h|--help) + print_usage + exit 0 + ;; + *) + echo "Invalid option: [$1]" + print_usage + exit 1 + ;; +esac +shift # past argument or value +done + +assert_properties +set_default_props +check_if_anything_to_sync +if [[ -z "${VERSION}" ]] ; then + retrieve_current_branch +else + switch_to_tag +fi +build_docs_if_applicable +retrieve_doc_properties +stash_changes +add_docs_from_target +checkout_previous_branch \ No newline at end of file diff --git a/spring-cloud-netflix/1.2.3.RELEASE/images/.gitkeep b/spring-cloud-netflix/1.2.3.RELEASE/images/.gitkeep new file mode 100644 index 00000000..e69de29b diff --git a/spring-cloud-netflix/1.2.3.RELEASE/images/Hystrix.png b/spring-cloud-netflix/1.2.3.RELEASE/images/Hystrix.png new file mode 100644 index 00000000..7d4e17ed Binary files /dev/null and b/spring-cloud-netflix/1.2.3.RELEASE/images/Hystrix.png differ diff --git a/spring-cloud-netflix/1.2.3.RELEASE/images/HystrixFallback.png b/spring-cloud-netflix/1.2.3.RELEASE/images/HystrixFallback.png new file mode 100644 index 00000000..372018c7 Binary files /dev/null and b/spring-cloud-netflix/1.2.3.RELEASE/images/HystrixFallback.png differ diff --git a/spring-cloud-netflix/1.2.3.RELEASE/images/HystrixGraph.png b/spring-cloud-netflix/1.2.3.RELEASE/images/HystrixGraph.png new file mode 100644 index 00000000..c07c6bd5 Binary files /dev/null and b/spring-cloud-netflix/1.2.3.RELEASE/images/HystrixGraph.png differ diff --git a/spring-cloud-netflix/1.2.3.RELEASE/images/RequestLatency.png b/spring-cloud-netflix/1.2.3.RELEASE/images/RequestLatency.png new file mode 100644 index 00000000..6c7e93be Binary files /dev/null and b/spring-cloud-netflix/1.2.3.RELEASE/images/RequestLatency.png differ diff --git a/spring-cloud-netflix/1.2.3.RELEASE/index.html b/spring-cloud-netflix/1.2.3.RELEASE/index.html new file mode 100644 index 00000000..dfef6c7b --- /dev/null +++ b/spring-cloud-netflix/1.2.3.RELEASE/index.html @@ -0,0 +1,3238 @@ + + + + + + + +Spring Cloud Netflix + + + + + +
+
+
+
+

1.2.3.RELEASE

+
+
+

This project provides Netflix OSS integrations for Spring Boot apps through autoconfiguration +and binding to the Spring Environment and other Spring programming model idioms. With a few +simple annotations you can quickly enable and configure the common patterns inside your +application and build large distributed systems with battle-tested Netflix components. The +patterns provided include Service Discovery (Eureka), Circuit Breaker (Hystrix), +Intelligent Routing (Zuul) and Client Side Load Balancing (Ribbon).

+
+
+
+
+

Service Discovery: Eureka Clients

+
+
+

Service Discovery is one of the key tenets of a microservice based architecture. Trying to hand configure each client or some form of convention can be very difficult to do and can be very brittle. Eureka is the Netflix Service Discovery Server and Client. The server can be configured and deployed to be highly available, with each server replicating state about the registered services to the others.

+
+
+

How to Include Eureka Client

+
+

To include Eureka Client in your project use the starter with group org.springframework.cloud +and artifact id spring-cloud-starter-eureka. See the Spring Cloud Project page +for details on setting up your build system with the current Spring Cloud Release Train.

+
+
+
+

Registering with Eureka

+
+

When a client registers with Eureka, it provides meta-data about itself +such as host and port, health indicator URL, home page etc. Eureka +receives heartbeat messages from each instance belonging to a service. +If the heartbeat fails over a configurable timetable, the instance is +normally removed from the registry.

+
+
+

Example eureka client:

+
+
+
+
@Configuration
+@ComponentScan
+@EnableAutoConfiguration
+@EnableEurekaClient
+@RestController
+public class Application {
+
+    @RequestMapping("/")
+    public String home() {
+        return "Hello world";
+    }
+
+    public static void main(String[] args) {
+        new SpringApplicationBuilder(Application.class).web(true).run(args);
+    }
+
+}
+
+
+
+

(i.e. utterly normal Spring Boot app). In this example we use +@EnableEurekaClient explicitly, but with only Eureka available you +could also use @EnableDiscoveryClient. Configuration is required to +locate the Eureka server. Example:

+
+
+
application.yml
+
+
eureka:
+  client:
+    serviceUrl:
+      defaultZone: http://localhost:8761/eureka/
+
+
+
+

where "defaultZone" is a magic string fallback value that provides the +service URL for any client that doesn’t express a preference +(i.e. it’s a useful default).

+
+
+

The default application name (service ID), virtual host and non-secure +port, taken from the Environment, are ${spring.application.name}, +${spring.application.name} and ${server.port} respectively.

+
+
+

@EnableEurekaClient makes the app into both a Eureka "instance" +(i.e. it registers itself) and a "client" (i.e. it can query the +registry to locate other services). The instance behaviour is driven +by eureka.instance.* configuration keys, but the defaults will be +fine if you ensure that your application has a +spring.application.name (this is the default for the Eureka service +ID, or VIP).

+
+
+

See EurekaInstanceConfigBean and EurekaClientConfigBean for more details of the configurable options.

+
+
+
+

Authenticating with the Eureka Server

+
+

HTTP basic authentication will be automatically added to your eureka +client if one of the eureka.client.serviceUrl.defaultZone URLs has +credentials embedded in it (curl style, like +http://user:password@localhost:8761/eureka). For more complex needs +you can create a @Bean of type DiscoveryClientOptionalArgs and +inject ClientFilter instances into it, all of which will be applied +to the calls from the client to the server.

+
+
+ + + + + +
+
Note
+		 +Because of a limitation in Eureka it isn’t possible to support +per-server basic auth credentials, so only the first set that are +found will be used. +
+
+
+
+

Status Page and Health Indicator

+
+

The status page and health indicators for a Eureka instance default to +"/info" and "/health" respectively, which are the default locations of +useful endpoints in a Spring Boot Actuator application. You need to +change these, even for an Actuator application if you use a +non-default context path or servlet path +(e.g. server.servletPath=/foo) or management endpoint path +(e.g. management.contextPath=/admin). Example:

+
+
+
application.yml
+
+
eureka:
+  instance:
+    statusPageUrlPath: ${management.context-path}/info
+    healthCheckUrlPath: ${management.context-path}/health
+
+
+
+

These links show up in the metadata that is consumed by clients, and +used in some scenarios to decide whether to send requests to your +application, so it’s helpful if they are accurate.

+
+
+
+

Registering a Secure Application

+
+

If your app wants to be contacted over HTTPS you can set two flags in +the EurekaInstanceConfig, viz +eureka.instance.[nonSecurePortEnabled,securePortEnabled]=[false,true] +respectively. This will make Eureka publish instance information +showing an explicit preference for secure communication. The Spring +Cloud DiscoveryClient will always return an https://…​; URI for a +service configured this way, and the Eureka (native) instance +information will have a secure health check URL.

+
+
+

Because of the way +Eureka works internally, it will still publish a non-secure URL for +status and home page unless you also override those explicitly. +You can use placeholders to configure the eureka instance urls, +e.g.

+
+
+
application.yml
+
+
eureka:
+  instance:
+    statusPageUrl: https://${eureka.hostname}/info
+    healthCheckUrl: https://${eureka.hostname}/health
+    homePageUrl: https://${eureka.hostname}/
+
+
+
+

(Note that ${eureka.hostname} is a native placeholder only available +in later versions of Eureka. You could achieve the same thing with +Spring placeholders as well, e.g. using ${eureka.instance.hostName}.)

+
+
+ + + + + +
+
Note
+		 +If your app is running behind a proxy, and the SSL termination +is in the proxy (e.g. if you run in Cloud Foundry or other platforms +as a service) then you will need to ensure that the proxy "forwarded" +headers are intercepted and handled by the application. An embedded +Tomcat container in a Spring Boot app does this automatically if it +has explicit configuration for the 'X-Forwarded-\*` headers. A sign +that you got this wrong will be that the links rendered by your app to +itself will be wrong (the wrong host, port or protocol). +
+
+
+
+

Eureka’s Health Checks

+
+

By default, Eureka uses the client heartbeat to determine if a client is up. +Unless specified otherwise the Discovery Client will not propagate the +current health check status of the application per the Spring Boot Actuator. Which means +that after successful registration Eureka will always announce that the +application is in 'UP' state. This behaviour can be altered by enabling +Eureka health checks, which results in propagating application status +to Eureka. As a consequence every other application won’t be sending +traffic to application in state other then 'UP'.

+
+
+
application.yml
+
+
eureka:
+  client:
+    healthcheck:
+      enabled: true
+
+
+
+ + + + + +
+
Warning
+		 +eureka.client.healthcheck.enabled=true should only be set in application.yml. Setting the value in bootstrap.yml will cause undesirable side effects like registering in eureka with an UNKNOWN status. +
+
+
+

If you require more control over the health checks, you may consider +implementing your own com.netflix.appinfo.HealthCheckHandler.

+
+
+
+

Eureka Metadata for Instances and Clients

+
+

It’s worth spending a bit of time understanding how the Eureka metadata works, so you can use it in a way that makes sense in your platform. There is standard metadata for things like hostname, IP address, port numbers, status page and health check. These are published in the service registry and used by clients to contact the services in a straightforward way. Additional metadata can be added to the instance registration in the eureka.instance.metadataMap, and this will be accessible in the remote clients, but in general will not change the behaviour of the client, unless it is made aware of the meaning of the metadata. There are a couple of special cases described below where Spring Cloud already assigns meaning to the metadata map.

+
+
+

Using Eureka on Cloudfoundry

+
+

Cloudfoundry has a global router so that all instances of the same app have the same hostname (it’s the same in other PaaS solutions with a similar architecture). This isn’t necessarily a barrier to using Eureka, but if you use the router (recommended, or even mandatory depending on the way your platform was set up), you need to explicitly set the hostname and port numbers (secure or non-secure) so that they use the router. You might also want to use instance metadata so you can distinguish between the instances on the client (e.g. in a custom load balancer). By default, the eureka.instance.instanceId is vcap.application.instance_id. For example:

+
+
+
application.yml
+
+
eureka:
+  instance:
+    hostname: ${vcap.application.uris[0]}
+    nonSecurePort: 80
+
+
+
+

Depending on the way the security rules are set up in your Cloudfoundry instance, you might be able to register and use the IP address of the host VM for direct service-to-service calls. This feature is not (yet) available on Pivotal Web Services (PWS).

+
+
+
+

Using Eureka on AWS

+
+

If the application is planned to be deployed to an AWS cloud, then the Eureka instance will have to be configured to be Amazon aware and this can be done by customizing the EurekaInstanceConfigBean the following way:

+
+
+
+
@Bean
+@Profile("!default")
+public EurekaInstanceConfigBean eurekaInstanceConfig() {
+  EurekaInstanceConfigBean b = new EurekaInstanceConfigBean();
+  AmazonInfo info = AmazonInfo.Builder.newBuilder().autoBuild("eureka");
+  b.setDataCenterInfo(info);
+  return b;
+}
+
+
+
+
+

Changing the Eureka Instance ID

+
+

A vanilla Netflix Eureka instance is registered with an ID that is equal to its host name (i.e. only one service per host). Spring Cloud Eureka provides a sensible default that looks like this: ${spring.cloud.client.hostname}:${spring.application.name}:${spring.application.instance_id:${server.port}}}. For example myhost:myappname:8080.

+
+
+

Using Spring Cloud you can override this by providing a unique identifier in eureka.instance.instanceId. For example:

+
+
+
application.yml
+
+
eureka:
+  instance:
+    instanceId: ${spring.application.name}:${vcap.application.instance_id:${spring.application.instance_id:${random.value}}}
+
+
+
+

With this metadata, and multiple service instances deployed on +localhost, the random value will kick in there to make the instance +unique. In Cloudfoundry the vcap.application.instance_id will be +populated automatically in a Spring Boot application, so the +random value will not be needed.

+
+
+
+
+

Using the EurekaClient

+
+

Once you have an app that is @EnableDiscoveryClient (or @EnableEurekaClient) you can use it to +discover service instances from the Eureka Server. One way to do that is to use the native +com.netflix.discovery.EurekaClient (as opposed to the Spring +Cloud DiscoveryClient), e.g.

+
+
+
+
@Autowired
+private EurekaClient discoveryClient;
+
+public String serviceUrl() {
+    InstanceInfo instance = discoveryClient.getNextServerFromEureka("STORES", false);
+    return instance.getHomePageUrl();
+}
+
+
+
+ + + + + +
+
Tip
+		 +
+

Don’t use the EurekaClient in @PostConstruct method or in a +@Scheduled method (or anywhere where the ApplicationContext might +not be started yet). It is initialized in a SmartLifecycle (with +phase=0) so the earliest you can rely on it being available is in +another SmartLifecycle with higher phase.

+
+
+
+
+
+

Alternatives to the native Netflix EurekaClient

+
+

You don’t have to use the raw Netflix EurekaClient and usually it +is more convenient to use it behind a wrapper of some sort. Spring +Cloud has support for Feign (a REST client +builder) and also Spring RestTemplate using +the logical Eureka service identifiers (VIPs) instead of physical +URLs. To configure Ribbon with a fixed list of physical servers you +can simply set <client>.ribbon.listOfServers to a comma-separated +list of physical addresses (or hostnames), where <client> is the ID +of the client.

+
+
+

You can also use the org.springframework.cloud.client.discovery.DiscoveryClient +which provides a simple API for discovery clients that is not specific +to Netflix, e.g.

+
+
+
+
@Autowired
+private DiscoveryClient discoveryClient;
+
+public String serviceUrl() {
+    List<ServiceInstance> list = discoveryClient.getInstances("STORES");
+    if (list != null && list.size() > 0 ) {
+        return list.get(0).getUri();
+    }
+    return null;
+}
+
+
+
+
+

Why is it so Slow to Register a Service?

+
+

Being an instance also involves a periodic heartbeat to the registry +(via the client’s serviceUrl) with default duration 30 seconds. A +service is not available for discovery by clients until the instance, +the server and the client all have the same metadata in their local +cache (so it could take 3 heartbeats). You can change the period using +eureka.instance.leaseRenewalIntervalInSeconds and this will speed up +the process of getting clients connected to other services. In +production it’s probably better to stick with the default because +there are some computations internally in the server that make +assumptions about the lease renewal period.

+
+
+
+
+
+

Service Discovery: Eureka Server

+
+
+

How to Include Eureka Server

+
+

To include Eureka Server in your project use the starter with group org.springframework.cloud +and artifact id spring-cloud-starter-eureka-server. See the Spring Cloud Project page +for details on setting up your build system with the current Spring Cloud Release Train.

+
+
+
+

How to Run a Eureka Server

+
+

Example eureka server;

+
+
+
+
@SpringBootApplication
+@EnableEurekaServer
+public class Application {
+
+    public static void main(String[] args) {
+        new SpringApplicationBuilder(Application.class).web(true).run(args);
+    }
+
+}
+
+
+
+

The server has a home page with a UI, and HTTP API endpoints per the +normal Eureka functionality under /eureka/*.

+
+
+

Eureka background reading: see flux capacitor and google group discussion.

+
+
+ + + + + +
+
Tip
+		 +
+

Due to Gradle’s dependency resolution rules and the lack of a parent bom feature, simply depending on spring-cloud-starter-eureka-server can cause failures on application startup. To remedy this the Spring Boot Gradle plugin must be added and the Spring cloud starter parent bom must be imported like so:

+
+
+
build.gradle
+
+
buildscript {
+  dependencies {
+    classpath("org.springframework.boot:spring-boot-gradle-plugin:1.3.5.RELEASE")
+  }
+}
+
+apply plugin: "spring-boot"
+
+dependencyManagement {
+  imports {
+    mavenBom "org.springframework.cloud:spring-cloud-dependencies:Brixton.RELEASE"
+  }
+}
+
+
+
+
+
+
+

High Availability, Zones and Regions

+
+

The Eureka server does not have a backend store, but the service +instances in the registry all have to send heartbeats to keep their +registrations up to date (so this can be done in memory). Clients also +have an in-memory cache of eureka registrations (so they don’t have to +go to the registry for every single request to a service).

+
+
+

By default every Eureka server is also a Eureka client and requires +(at least one) service URL to locate a peer. If you don’t provide it +the service will run and work, but it will shower your logs with a lot +of noise about not being able to register with the peer.

+
+
+

See also below for details of Ribbon +support on the client side for Zones and Regions.

+
+
+
+

Standalone Mode

+
+

The combination of the two caches (client and server) and the +heartbeats make a standalone Eureka server fairly resilient to +failure, as long as there is some sort of monitor or elastic runtime +keeping it alive (e.g. Cloud Foundry). In standalone mode, you might +prefer to switch off the client side behaviour, so it doesn’t keep +trying and failing to reach its peers. Example:

+
+
+
application.yml (Standalone Eureka Server)
+
+
server:
+  port: 8761
+
+eureka:
+  instance:
+    hostname: localhost
+  client:
+    registerWithEureka: false
+    fetchRegistry: false
+    serviceUrl:
+      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/
+
+
+
+

Notice that the serviceUrl is pointing to the same host as the local +instance.

+
+
+
+

Peer Awareness

+
+

Eureka can be made even more resilient and available by running +multiple instances and asking them to register with each other. In +fact, this is the default behaviour, so all you need to do to make it +work is add a valid serviceUrl to a peer, e.g.

+
+
+
application.yml (Two Peer Aware Eureka Servers)
+
+
---
+spring:
+  profiles: peer1
+eureka:
+  instance:
+    hostname: peer1
+  client:
+    serviceUrl:
+      defaultZone: http://peer2/eureka/
+
+---
+spring:
+  profiles: peer2
+eureka:
+  instance:
+    hostname: peer2
+  client:
+    serviceUrl:
+      defaultZone: http://peer1/eureka/
+
+
+
+

In this example we have a YAML file that can be used to run the same +server on 2 hosts (peer1 and peer2), by running it in different +Spring profiles. You could use this configuration to test the peer +awareness on a single host (there’s not much value in doing that in +production) by manipulating /etc/hosts to resolve the host names. In +fact, the eureka.instance.hostname is not needed if you are running +on a machine that knows its own hostname (it is looked up using +java.net.InetAddress by default).

+
+
+

You can add multiple peers to a system, and as long as they are all +connected to each other by at least one edge, they will synchronize +the registrations amongst themselves. If the peers are physically +separated (inside a data centre or between multiple data centres) then +the system can in principle survive split-brain type failures.

+
+
+
+

Prefer IP Address

+
+

In some cases, it is preferable for Eureka to advertise the IP Adresses +of services rather than the hostname. Set eureka.instance.preferIpAddress +to true and when the application registers with eureka, it will use its +IP Address rather than its hostname.

+
+
+
+
+
+

Circuit Breaker: Hystrix Clients

+
+
+

Netflix has created a library called Hystrix that implements the circuit breaker pattern. In a microservice architecture it is common to have multiple layers of service calls.

+
+
+
+HystrixGraph +
+
Figure 1. Microservice Graph
+
+
+

A service failure in the lower level of services can cause cascading failure all the way up to the user. When calls to a particular service reach a certain threshold (20 failures in 5 seconds is the default in Hystrix), the circuit opens and the call is not made. In cases of error and an open circuit a fallback can be provided by the developer.

+
+
+
+HystrixFallback +
+
Figure 2. Hystrix fallback prevents cascading failures
+
+
+

Having an open circuit stops cascading failures and allows overwhelmed or failing services time to heal. The fallback can be another Hystrix protected call, static data or a sane empty value. Fallbacks may be chained so the first fallback makes some other business call which in turn falls back to static data.

+
+
+

How to Include Hystrix

+
+

To include Hystrix in your project use the starter with group org.springframework.cloud +and artifact id spring-cloud-starter-hystrix. See the Spring Cloud Project page +for details on setting up your build system with the current Spring Cloud Release Train.

+
+
+

Example boot app:

+
+
+
+
@SpringBootApplication
+@EnableCircuitBreaker
+public class Application {
+
+    public static void main(String[] args) {
+        new SpringApplicationBuilder(Application.class).web(true).run(args);
+    }
+
+}
+
+@Component
+public class StoreIntegration {
+
+    @HystrixCommand(fallbackMethod = "defaultStores")
+    public Object getStores(Map<String, Object> parameters) {
+        //do stuff that might fail
+    }
+
+    public Object defaultStores(Map<String, Object> parameters) {
+        return /* something useful */;
+    }
+}
+
+
+
+

The @HystrixCommand is provided by a Netflix contrib library called +"javanica". +Spring Cloud automatically wraps Spring beans with that +annotation in a proxy that is connected to the Hystrix circuit +breaker. The circuit breaker calculates when to open and close the +circuit, and what to do in case of a failure.

+
+
+

To configure the @HystrixCommand you can use the commandProperties +attribute with a list of @HystrixProperty annotations. See +here +for more details. See the Hystrix wiki +for details on the properties available.

+
+
+
+

Propagating the Security Context or using Spring Scopes

+
+

If you want some thread local context to propagate into a @HystrixCommand the default declaration will not work because it executes the command in a thread pool (in case of timeouts). You can switch Hystrix to use the same thread as the caller using some configuration, or directly in the annotation, by asking it to use a different "Isolation Strategy". For example:

+
+
+
+
@HystrixCommand(fallbackMethod = "stubMyService",
+    commandProperties = {
+      @HystrixProperty(name="execution.isolation.strategy", value="SEMAPHORE")
+    }
+)
+...
+
+
+
+

The same thing applies if you are using @SessionScope or @RequestScope. You will know when you need to do this because of a runtime exception that says it can’t find the scoped context.

+
+
+

You also have the option to set the hystrix.shareSecurityContext property to true. Doing so will auto configure an Hystrix concurrency strategy plugin hook who will transfer the SecurityContext from your main thread to the one used by the Hystrix command. Hystrix does not allow multiple hystrix concurrency strategy to be registered so an extension mechanism is available by declaring your own HystrixConcurrencyStrategy as a Spring bean. Spring Cloud will lookup for your implementation within the Spring context and wrap it inside its own plugin.

+
+
+
+

Health Indicator

+
+

The state of the connected circuit breakers are also exposed in the +/health endpoint of the calling application.

+
+
+
+
{
+    "hystrix": {
+        "openCircuitBreakers": [
+            "StoreIntegration::getStoresByLocationLink"
+        ],
+        "status": "CIRCUIT_OPEN"
+    },
+    "status": "UP"
+}
+
+
+
+
+

Hystrix Metrics Stream

+
+

To enable the Hystrix metrics stream include a dependency on spring-boot-starter-actuator. This will expose the /hystrix.stream as a management endpoint.

+
+
+
+
    <dependency>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-actuator</artifactId>
+    </dependency>
+
+
+
+
+
+
+

Circuit Breaker: Hystrix Dashboard

+
+
+

One of the main benefits of Hystrix is the set of metrics it gathers about each HystrixCommand. The Hystrix Dashboard displays the health of each circuit breaker in an efficient manner.

+
+
+
+Hystrix +
+
Figure 3. Hystrix Dashboard
+
+
+

How to Include Hystrix Dashboard

+
+

To include the Hystrix Dashboard in your project use the starter with group org.springframework.cloud +and artifact id spring-cloud-starter-hystrix-dashboard. See the Spring Cloud Project page +for details on setting up your build system with the current Spring Cloud Release Train.

+
+
+

To run the Hystrix Dashboard annotate your Spring Boot main class with @EnableHystrixDashboard. You then visit /hystrix and point the dashboard to an individual instances /hystrix.stream endpoint in a Hystrix client application.

+
+
+
+

Turbine

+
+

Looking at an individual instances Hystrix data is not very useful in terms of the overall health of the system. Turbine is an application that aggregates all of the relevant /hystrix.stream endpoints into a combined /turbine.stream for use in the Hystrix Dashboard. Individual instances are located via Eureka. Running Turbine is as simple as annotating your main class with the @EnableTurbine annotation (e.g. using spring-cloud-starter-turbine to set up the classpath). All of the documented configuration properties from the Turbine 1 wiki apply. The only difference is that the turbine.instanceUrlSuffix does not need the port prepended as this is handled automatically unless turbine.instanceInsertPort=false.

+
+
+ + + + + +
+
Note
+		 +By default, Turbine looks for the /hystrix.stream endpoint on a registered instance by looking up its homePageUrl entry in Eureka, then appending /hystrix.stream to it. This means that if spring-boot-actuator is running on its own port (which is the default), the call to /hystrix.stream will fail. +To make turbine find the Hystrix stream at the correct port, you need to add management.port to the instances' metadata: +
+
+
+
+
eureka:
+  instance:
+    metadata-map:
+      management.port: ${management.port:8081}
+
+
+
+

The configuration key turbine.appConfig is a list of eureka serviceIds that turbine will use to lookup instances. The turbine stream is then used in the Hystrix dashboard using a url that looks like: http://my.turbine.sever:8080/turbine.stream?cluster=<CLUSTERNAME>; (the cluster parameter can be omitted if the name is "default"). The cluster parameter must match an entry in turbine.aggregator.clusterConfig. Values returned from eureka are uppercase, thus we expect this example to work if there is an app registered with Eureka called "customers":

+
+
+
+
turbine:
+  aggregator:
+    clusterConfig: CUSTOMERS
+  appConfig: customers
+
+
+
+

The clusterName can be customized by a SPEL expression in turbine.clusterNameExpression with root an instance of InstanceInfo. The default value is appName, which means that the Eureka serviceId ends up as the cluster key (i.e. the InstanceInfo for customers has an appName of "CUSTOMERS"). A different example would be turbine.clusterNameExpression=aSGName, which would get the cluster name from the AWS ASG name. Another example:

+
+
+
+
turbine:
+  aggregator:
+    clusterConfig: SYSTEM,USER
+  appConfig: customers,stores,ui,admin
+  clusterNameExpression: metadata['cluster']
+
+
+
+

In this case, the cluster name from 4 services is pulled from their metadata map, and is expected to have values that include "SYSTEM" and "USER".

+
+
+

To use the "default" cluster for all apps you need a string literal expression (with single quotes, and escaped with double quotes if it is in YAML as well):

+
+
+
+
turbine:
+  appConfig: customers,stores
+  clusterNameExpression: "'default'"
+
+
+
+

Spring Cloud provides a spring-cloud-starter-turbine that has all the dependencies you need to get a Turbine server running. Just create a Spring Boot application and annotate it with @EnableTurbine.

+
+
+ + + + + +
+
Note
+		 +by default Spring Cloud allows Turbine to use the host and port to allow multiple processes per host, per cluster. If you want the native Netflix behaviour built into Turbine that does not allow multiple processes per host, per cluster (the key to the instance id is the hostname), then set the property turbine.combineHostPort=false. +
+
+
+
+

Turbine Stream

+
+

In some environments (e.g. in a PaaS setting), the classic Turbine model of pulling metrics from all the distributed Hystrix commands doesn’t work. In that case you might want to have your Hystrix commands push metrics to Turbine, and Spring Cloud enables that with messaging. All you need to do on the client is add a dependency to spring-cloud-netflix-hystrix-stream and the spring-cloud-starter-stream-* of your choice (see Spring Cloud Stream documentation for details on the brokers, and how to configure the client credentials, but it should work out of the box for a local broker).

+
+
+

On the server side Just create a Spring Boot application and annotate it with @EnableTurbineStream and by default it will come up on port 8989 (point your Hystrix dashboard to that port, any path). You can customize the port using either server.port or turbine.stream.port. If you have spring-boot-starter-web and spring-boot-starter-actuator on the classpath as well, then you can open up the Actuator endpoints on a separate port (with Tomcat by default) by providing a management.port which is different.

+
+
+

You can then point the Hystrix Dashboard to the Turbine Stream Server instead of individual Hystrix streams. If Turbine Stream is running on port 8989 on myhost, then put http://myhost:8989 in the stream input field in the Hystrix Dashboard. Circuits will be prefixed by their respective serviceId, followed by a dot, then the circuit name.

+
+
+

Spring Cloud provides a spring-cloud-starter-turbine-stream that has all the dependencies you need to get a Turbine Stream server running - just add the Stream binder of your choice, e.g. spring-cloud-starter-stream-rabbit. You need Java 8 to run the app because it is Netty-based.

+
+
+
+
+
+

Client Side Load Balancer: Ribbon

+
+
+

Ribbon is a client side load balancer which gives you a lot of control +over the behaviour of HTTP and TCP clients. Feign already uses Ribbon, +so if you are using @FeignClient then this section also applies.

+
+
+

A central concept in Ribbon is that of the named client. Each load +balancer is part of an ensemble of components that work together to +contact a remote server on demand, and the ensemble has a name that +you give it as an application developer (e.g. using the @FeignClient +annotation). Spring Cloud creates a new ensemble as an +ApplicationContext on demand for each named client using +RibbonClientConfiguration. This contains (amongst other things) an +ILoadBalancer, a RestClient, and a ServerListFilter.

+
+
+

How to Include Ribbon

+
+

To include Ribbon in your project use the starter with group org.springframework.cloud +and artifact id spring-cloud-starter-ribbon. See the Spring Cloud Project page +for details on setting up your build system with the current Spring Cloud Release Train.

+
+
+
+

Customizing the Ribbon Client

+
+

You can configure some bits of a Ribbon client using external +properties in <client>.ribbon.*, which is no different than using +the Netflix APIs natively, except that you can use Spring Boot +configuration files. The native options can +be inspected as static fields in CommonClientConfigKey (part of +ribbon-core).

+
+
+

Spring Cloud also lets you take full control of the client by +declaring additional configuration (on top of the +RibbonClientConfiguration) using @RibbonClient. Example:

+
+
+
+
@Configuration
+@RibbonClient(name = "foo", configuration = FooConfiguration.class)
+public class TestConfiguration {
+}
+
+
+
+

In this case the client is composed from the components already in +RibbonClientConfiguration together with any in FooConfiguration +(where the latter generally will override the former).

+
+
+ + + + + +
+
Warning
+		 +The FooConfiguration has to be @Configuration but take +care that it is not in a @ComponentScan for the main application +context, otherwise it will be shared by all the @RibbonClients. If +you use @ComponentScan (or @SpringBootApplication) you need to +take steps to avoid it being included (for instance put it in a +separate, non-overlapping package, or specify the packages to scan +explicitly in the @ComponentScan). +
+
+
+

Spring Cloud Netflix provides the following beans by default for ribbon +(BeanType beanName: ClassName):

+
+
+
    +
  • +

    IClientConfig ribbonClientConfig: DefaultClientConfigImpl

    +
    • +
  • +

    IRule ribbonRule: ZoneAvoidanceRule

    +
    • +
  • +

    IPing ribbonPing: NoOpPing

    +
    • +
  • +

    ServerList<Server> ribbonServerList: ConfigurationBasedServerList

    +
    • +
  • +

    ServerListFilter<Server> ribbonServerListFilter: ZonePreferenceServerListFilter

    +
    • +
  • +

    ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer

    +
    • +
+
+
+

Creating a bean of one of those type and placing it in a @RibbonClient +configuration (such as FooConfiguration above) allows you to override each +one of the beans described. Example:

+
+
+
+
@Configuration
+public class FooConfiguration {
+    @Bean
+    public IPing ribbonPing(IClientConfig config) {
+        return new PingUrl();
+    }
+}
+
+
+
+

This replaces the NoOpPing with PingUrl.

+
+
+
+

Customizing the Ribbon Client using properties

+
+

Starting with version 1.2.0, Spring Cloud Netflix now supports customizing Ribbon clients using properties to be compatible with the Ribbon documentation.

+
+
+

This allows you to change behavior at start up time in different environments.

+
+
+

The supported properties are listed below and should be prefixed by <clientName>.ribbon.:

+
+
+
    +
  • +

    NFLoadBalancerClassName: should implement ILoadBalancer

    +
    • +
  • +

    NFLoadBalancerRuleClassName: should implement IRule

    +
    • +
  • +

    NFLoadBalancerPingClassName: should implement IPing

    +
    • +
  • +

    NIWSServerListClassName: should implement ServerList

    +
    • +
  • +

    NIWSServerListFilterClassName should implement ServerListFilter

    +
    • +
+
+
+ + + + + +
+
Note
+		 +Classes defined in these properties have precedence over beans defined using @RibbonClient(configuration=MyRibbonConfig.class) and the defaults provided by Spring Cloud Netflix. +
+
+
+

To set the IRule for a service name users you could set the following:

+
+
+
application.yml
+
+
users:
+  ribbon:
+    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.WeightedResponseTimeRule
+
+
+
+

See the Ribbon documentation for implementations provided by Ribbon.

+
+
+
+

Using Ribbon with Eureka

+
+

When Eureka is used in conjunction with Ribbon (i.e., both are on the classpath) the ribbonServerList +is overridden with an extension of DiscoveryEnabledNIWSServerList +which populates the list of servers from Eureka. It also replaces the +IPing interface with NIWSDiscoveryPing which delegates to Eureka +to determine if a server is up. The ServerList that is installed by +default is a DomainExtractingServerList and the purpose of this is +to make physical metadata available to the load balancer without using +AWS AMI metadata (which is what Netflix relies on). By default the +server list will be constructed with "zone" information as provided in +the instance metadata (so on the remote clients set +eureka.instance.metadataMap.zone), and if that is missing it can use +the domain name from the server hostname as a proxy for zone (if the +flag approximateZoneFromHostname is set). Once the zone information +is available it can be used in a ServerListFilter. By default it +will be used to locate a server in the same zone as the client because +the default is a ZonePreferenceServerListFilter. The zone of the +client is determined the same way as the remote instances by default, +i.e. via eureka.instance.metadataMap.zone.

+
+
+ + + + + +
+
Note
+		 +The orthodox "archaius" way to set the client zone is via a +configuration property called "@zone", and Spring Cloud will use that +in preference to all other settings if it is available (note that the +key will have to be quoted in YAML configuration). +
+
+
+ + + + + +
+
Note
+		 +If there is no other source of zone data then a guess is made +based on the client configuration (as opposed to the instance +configuration). We take eureka.client.availabilityZones, which is a +map from region name to a list of zones, and pull out the first zone +for the instance’s own region (i.e. the eureka.client.region, which +defaults to "us-east-1" for comatibility with native Netflix). +
+
+
+
+

Example: How to Use Ribbon Without Eureka

+
+

Eureka is a convenient way to abstract the discovery of remote servers +so you don’t have to hard code their URLs in clients, but if you +prefer not to use it, Ribbon and Feign are still quite +amenable. Suppose you have declared a @RibbonClient for "stores", +and Eureka is not in use (and not even on the classpath). The Ribbon +client defaults to a configured server list, and you can supply the +configuration like this

+
+
+
application.yml
+
+
stores:
+  ribbon:
+    listOfServers: example.com,google.com
+
+
+
+
+

Example: Disable Eureka use in Ribbon

+
+

Setting the property ribbon.eureka.enabled = false will explicitly +disable the use of Eureka in Ribbon.

+
+
+
application.yml
+
+
ribbon:
+  eureka:
+   enabled: false
+
+
+
+
+

Using the Ribbon API Directly

+
+

You can also use the LoadBalancerClient directly. Example:

+
+
+
+
public class MyClass {
+    @Autowired
+    private LoadBalancerClient loadBalancer;
+
+    public void doStuff() {
+        ServiceInstance instance = loadBalancer.choose("stores");
+        URI storesUri = URI.create(String.format("http://%s:%s", instance.getHost(), instance.getPort()));
+        // ... do something with the URI
+    }
+}
+
+
+
+
+
+
+

Declarative REST Client: Feign

+
+
+

Feign is a declarative web service client. It makes writing web service clients easier. To use Feign create an interface and annotate it. It has pluggable annotation support including Feign annotations and JAX-RS annotations. Feign also supports pluggable encoders and decoders. Spring Cloud adds support for Spring MVC annotations and for using the same HttpMessageConverters used by default in Spring Web. Spring Cloud integrates Ribbon and Eureka to provide a load balanced http client when using Feign.

+
+
+

How to Include Feign

+
+

To include Feign in your project use the starter with group org.springframework.cloud +and artifact id spring-cloud-starter-feign. See the Spring Cloud Project page +for details on setting up your build system with the current Spring Cloud Release Train.

+
+
+

Example spring boot app

+
+
+
+
@Configuration
+@ComponentScan
+@EnableAutoConfiguration
+@EnableEurekaClient
+@EnableFeignClients
+public class Application {
+
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+
+}
+
+
+
+
StoreClient.java
+
+
@FeignClient("stores")
+public interface StoreClient {
+    @RequestMapping(method = RequestMethod.GET, value = "/stores")
+    List<Store> getStores();
+
+    @RequestMapping(method = RequestMethod.POST, value = "/stores/{storeId}", consumes = "application/json")
+    Store update(@PathVariable("storeId") Long storeId, Store store);
+}
+
+
+
+

In the @FeignClient annotation the String value ("stores" above) is +an arbitrary client name, which is used to create a Ribbon load +balancer (see below for details of Ribbon +support). You can also specify a URL using the url attribute +(absolute value or just a hostname). The name of the bean in the +application context is the fully qualified name of the interface. +An alias is also created which is the 'name' attribute plus 'FeignClient'. +For the example above, @Qualifier("storesFeignClient") could be used to +reference the bean. If you want to change the default @Qualifier value, +this can be done with the qualifier value in @FeignClient.

+
+
+

The Ribbon client above will want to discover the physical addresses +for the "stores" service. If your application is a Eureka client then +it will resolve the service in the Eureka service registry. If you +don’t want to use Eureka, you can simply configure a list of servers +in your external configuration (see +above for example).

+
+
+
+

Overriding Feign Defaults

+
+

A central concept in Spring Cloud’s Feign support is that of the named client. Each feign client is part of an ensemble of components that work together to contact a remote server on demand, and the ensemble has a name that you give it as an application developer using the @FeignClient annotation. Spring Cloud creates a new ensemble as an +ApplicationContext on demand for each named client using FeignClientsConfiguration. This contains (amongst other things) an feign.Decoder, a feign.Encoder, and a feign.Contract.

+
+
+

Spring Cloud lets you take full control of the feign client by declaring additional configuration (on top of the FeignClientsConfiguration) using @FeignClient. Example:

+
+
+
+
@FeignClient(name = "stores", configuration = FooConfiguration.class)
+public interface StoreClient {
+    //..
+}
+
+
+
+

In this case the client is composed from the components already in FeignClientsConfiguration together with any in FooConfiguration (where the latter will override the former).

+
+
+ + + + + +
+
Warning
+		 +The FooConfiguration has to be @Configuration but take care that it is not in a @ComponentScan for the main application context, otherwise it will be used for every @FeignClient. If you use @ComponentScan (or @SpringBootApplication) you need to take steps to avoid it being included (for instance put it in a separate, non-overlapping package, or specify the packages to scan explicitly in the @ComponentScan). +
+
+
+ + + + + +
+
Note
+		 +The serviceId attribute is now deprecated in favor of the name attribute. +
+
+
+ + + + + +
+
Warning
+		 +Previously, using the url attribute, did not require the name attribute. Using name is now required. +
+
+
+

Placeholders are supported in the name and url attributes.

+
+
+
+
@FeignClient(name = "${feign.name}", url = "${feign.url}")
+public interface StoreClient {
+    //..
+}
+
+
+
+

Spring Cloud Netflix provides the following beans by default for feign (BeanType beanName: ClassName):

+
+
+
    +
  • +

    Decoder feignDecoder: ResponseEntityDecoder (which wraps a SpringDecoder)

    +
    • +
  • +

    Encoder feignEncoder: SpringEncoder

    +
    • +
  • +

    Logger feignLogger: Slf4jLogger

    +
    • +
  • +

    Contract feignContract: SpringMvcContract

    +
    • +
  • +

    Feign.Builder feignBuilder: HystrixFeign.Builder

    +
    • +
  • +

    Client feignClient: if Ribbon is enabled it is a LoadBalancerFeignClient, otherwise the default feign client is used.

    +
    • +
+
+
+

The OkHttpClient and ApacheHttpClient feign clients can be used by setting feign.okhttp.enabled or feign.httpclient.enabled to true, respectively, and having them on the classpath.

+
+
+

Spring Cloud Netflix does not provide the following beans by default for feign, but still looks up beans of these types from the application context to create the feign client:

+
+
+
    +
  • +

    Logger.Level

    +
    • +
  • +

    Retryer

    +
    • +
  • +

    ErrorDecoder

    +
    • +
  • +

    Request.Options

    +
    • +
  • +

    Collection<RequestInterceptor>

    +
    • +
+
+
+

Creating a bean of one of those type and placing it in a @FeignClient configuration (such as FooConfiguration above) allows you to override each one of the beans described. Example:

+
+
+
+
@Configuration
+public class FooConfiguration {
+    @Bean
+    public Contract feignContract() {
+        return new feign.Contract.Default();
+    }
+
+    @Bean
+    public BasicAuthRequestInterceptor basicAuthRequestInterceptor() {
+        return new BasicAuthRequestInterceptor("user", "password");
+    }
+}
+
+
+
+

This replaces the SpringMvcContract with feign.Contract.Default and adds a RequestInterceptor to the collection of RequestInterceptor.

+
+
+

Default configurations can be specified in the @EnableFeignClients attribute defaultConfiguration in a similar manner as described above. The difference is that this configuration will apply to all feign clients.

+
+
+
+

Creating Feign Clients Manually

+
+

In some cases it might be necessary to customize your Feign Clients in a way that is not +possible using the methods above. In this case you can create Clients using the +Feign Builder API. Below is an example +which creates two Feign Clients with the same interface but configures each one with +a separate request interceptor.

+
+
+
+
@Import(FeignClientsConfiguration.class)
+class FooController {
+
+	private FooClient fooClient;
+
+	private FooClient adminClient;
+
+    @Autowired
+	public FooController(
+			ResponseEntityDecoder decoder, SpringEncoder encoder, Client client) {
+		this.fooClient = Feign.builder().client(client)
+				.encoder(encoder)
+				.decoder(decoder)
+				.requestInterceptor(new BasicAuthRequestInterceptor("user", "user"))
+				.target(FooClient.class, "http://PROD-SVC");
+		this.adminClient = Feign.builder().client(client)
+				.encoder(encoder)
+				.decoder(decoder)
+				.requestInterceptor(new BasicAuthRequestInterceptor("admin", "admin"))
+				.target(FooClient.class, "http://PROD-SVC");
+    }
+}
+
+
+
+ + + + + +
+
Note
+		 +In the above example FeignClientsConfiguration.class is the default configuration +provided by Spring Cloud Netflix. +
+
+
+ + + + + +
+
Note
+		 +PROD-SVC is the name of the service the Clients will be making requests to. +
+
+
+
+

Feign Hystrix Support

+
+

If Hystrix is on the classpath, by default Feign will wrap all methods with a circuit breaker. Returning a com.netflix.hystrix.HystrixCommand is also available. This lets you use reactive patterns (with a call to .toObservable() or .observe() or asynchronous use (with a call to .queue()).

+
+
+

To disable Hystrix support for Feign, set feign.hystrix.enabled=false.

+
+
+

To disable Hystrix support on a per-client basis create a vanilla Feign.Builder with the "prototype" scope, e.g.:

+
+
+
+
@Configuration
+public class FooConfiguration {
+    @Bean
+	@Scope("prototype")
+	public Feign.Builder feignBuilder() {
+		return Feign.builder();
+	}
+}
+
+
+
+
+

Feign Hystrix Fallbacks

+
+

Hystrix supports the notion of a fallback: a default code path that is executed when they circuit is open or there is an error. To enable fallbacks for a given @FeignClient set the fallback attribute to the class name that implements the fallback.

+
+
+
+
@FeignClient(name = "hello", fallback = HystrixClientFallback.class)
+protected interface HystrixClient {
+    @RequestMapping(method = RequestMethod.GET, value = "/hello")
+    Hello iFailSometimes();
+}
+
+static class HystrixClientFallback implements HystrixClient {
+    @Override
+    public Hello iFailSometimes() {
+        return new Hello("fallback");
+    }
+}
+
+
+
+

If one needs access to the cause that made the fallback trigger, one can use the fallbackFactory attribute inside @FeignClient.

+
+
+
+
@FeignClient(name = "hello", fallbackFactory = HystrixClientFallbackFactory.class)
+protected interface HystrixClient {
+	@RequestMapping(method = RequestMethod.GET, value = "/hello")
+	Hello iFailSometimes();
+}
+
+@Component
+static class HystrixClientFallbackFactory implements FallbackFactory<HystrixClient> {
+	@Override
+	public HystrixClient create(Throwable cause) {
+		return new HystrixClientWithFallBackFactory() {
+			@Override
+			public Hello iFailSometimes() {
+				return new Hello("fallback; reason was: " + cause.getMessage());
+			}
+		};
+	}
+}
+
+
+
+ + + + + +
+
Warning
+		 +There is a limitation with the implementation of fallbacks in Feign and how Hystrix fallbacks work. Fallbacks are currently not supported for methods that return com.netflix.hystrix.HystrixCommand and rx.Observable. +
+
+
+
+

Feign Inheritance Support

+
+

Feign supports boilerplate apis via single-inheritance interfaces. +This allows grouping common operations into convenient base interfaces.

+
+
+
UserService.java
+
+
public interface UserService {
+
+    @RequestMapping(method = RequestMethod.GET, value ="/users/{id}")
+    User getUser(@PathVariable("id") long id);
+}
+
+
+
+
UserResource.java
+
+
@RestController
+public class UserResource implements UserService {
+
+}
+
+
+
+
UserClient.java
+
+
package project.user;
+
+@FeignClient("users")
+public interface UserClient extends UserService {
+
+}
+
+
+
+ + + + + +
+
Note
+		 +It is generally not advisable to share an interface between a +server and a client. It introduces tight coupling, and also actually +doesn’t work with Spring MVC in its current form (method parameter +mapping is not inherited). +
+
+
+
+

Feign request/response compression

+
+

You may consider enabling the request or response GZIP compression for your +Feign requests. You can do this by enabling one of the properties:

+
+
+
+
feign.compression.request.enabled=true
+feign.compression.response.enabled=true
+
+
+
+

Feign request compression gives you settings similar to what you may set for your web server:

+
+
+
+
feign.compression.request.enabled=true
+feign.compression.request.mime-types=text/xml,application/xml,application/json
+feign.compression.request.min-request-size=2048
+
+
+
+

These properties allow you to be selective about the compressed media types and minimum request threshold length.

+
+
+
+

Feign logging

+
+

A logger is created for each Feign client created. By default the name of the logger is the full class name of the interface used to create the Feign client. Feign logging only responds to the DEBUG level.

+
+
+
application.yml
+
+
logging.level.project.user.UserClient: DEBUG
+
+
+
+

The Logger.Level object that you may configure per client, tells Feign how much to log. Choices are:

+
+
+
    +
  • +

    NONE, No logging (DEFAULT).

    +
    • +
  • +

    BASIC, Log only the request method and URL and the response status code and execution time.

    +
    • +
  • +

    HEADERS, Log the basic information along with request and response headers.

    +
    • +
  • +

    FULL, Log the headers, body, and metadata for both requests and responses.

    +
    • +
+
+
+

For example, the following would set the Logger.Level to FULL:

+
+
+
+
@Configuration
+public class FooConfiguration {
+    @Bean
+    Logger.Level feignLoggerLevel() {
+        return Logger.Level.FULL;
+    }
+}
+
+
+
+
+
+
+

External Configuration: Archaius

+
+
+

Archaius is the Netflix client side configuration library. It is the library used by all of the Netflix OSS components for configuration. Archaius is an extension of the Apache Commons Configuration project. It allows updates to configuration by either polling a source for changes or for a source to push changes to the client. Archaius uses Dynamic<Type>Property classes as handles to properties.

+
+
+
Archaius Example
+
+
class ArchaiusTest {
+    DynamicStringProperty myprop = DynamicPropertyFactory
+            .getInstance()
+            .getStringProperty("my.prop");
+
+    void doSomething() {
+        OtherClass.someMethod(myprop.get());
+    }
+}
+
+
+
+

Archaius has its own set of configuration files and loading priorities. Spring applications should generally not use Archaius directly, but the need to configure the Netflix tools natively remains. Spring Cloud has a Spring Environment Bridge so Archaius can read properties from the Spring Environment. This allows Spring Boot projects to use the normal configuration toolchain, while allowing them to configure the Netflix tools, for the most part, as documented.

+
+
+
+
+

Router and Filter: Zuul

+
+
+

Routing in an integral part of a microservice architecture. For example, / may be mapped to your web application, /api/users is mapped to the user service and /api/shop is mapped to the shop service. Zuul is a JVM based router and server side load balancer by Netflix.

+
+
+

Netflix uses Zuul for the following:

+
+
+
    +
  • +

    Authentication

    +
    • +
  • +

    Insights

    +
    • +
  • +

    Stress Testing

    +
    • +
  • +

    Canary Testing

    +
    • +
  • +

    Dynamic Routing

    +
    • +
  • +

    Service Migration

    +
    • +
  • +

    Load Shedding

    +
    • +
  • +

    Security

    +
    • +
  • +

    Static Response handling

    +
    • +
  • +

    Active/Active traffic management

    +
    • +
+
+
+

Zuul’s rule engine allows rules and filters to be written in essentially any JVM language, with built in support for Java and Groovy.

+
+
+ + + + + +
+
Note
+		 +The configuration property zuul.max.host.connections has been replaced by two new properties, zuul.host.maxTotalConnections and zuul.host.maxPerRouteConnections which default to 200 and 20 respectively. +
+
+
+ + + + + +
+
Note
+		 +Default Hystrix isolation pattern (ExecutionIsolationStrategy) for all routes is SEMAPHORE. zuul.ribbonIsolationStrategy can be changed to THREAD if this isolation pattern is preferred. +
+
+
+

How to Include Zuul

+
+

To include Zuul in your project use the starter with group org.springframework.cloud +and artifact id spring-cloud-starter-zuul. See the Spring Cloud Project page +for details on setting up your build system with the current Spring Cloud Release Train.

+
+
+
+

Embedded Zuul Reverse Proxy

+
+

Spring Cloud has created an embedded Zuul proxy to ease the +development of a very common use case where a UI application wants to +proxy calls to one or more back end services. This feature is useful +for a user interface to proxy to the backend services it requires, +avoiding the need to manage CORS and authentication concerns +independently for all the backends.

+
+
+

To enable it, annotate a Spring Boot main class with +@EnableZuulProxy, and this forwards local calls to the appropriate +service. By convention, a service with the ID "users", will +receive requests from the proxy located at /users (with the prefix +stripped). The proxy uses Ribbon to locate an instance to forward to +via discovery, and all requests are executed in a +hystrix command, so +failures will show up in Hystrix metrics, and once the circuit is open +the proxy will not try to contact the service.

+
+
+ + + + + +
+
Note
+		 +the Zuul starter does not include a discovery client, so for +routes based on service IDs you need to provide one of those +on the classpath as well (e.g. Eureka is one choice). +
+
+
+

To skip having a service automatically added, set +zuul.ignored-services to a list of service id patterns. If a service +matches a pattern that is ignored, but also included in the explicitly +configured routes map, then it will be unignored. Example:

+
+
+
application.yml
+
+
 zuul:
+  ignoredServices: '*'
+  routes:
+    users: /myusers/**
+
+
+
+

In this example, all services are ignored except "users".

+
+
+

To augment or change +the proxy routes, you can add external configuration like the +following:

+
+
+
application.yml
+
+
 zuul:
+  routes:
+    users: /myusers/**
+
+
+
+

This means that http calls to "/myusers" get forwarded to the "users" +service (for example "/myusers/101" is forwarded to "/101").

+
+
+

To get more fine-grained control over a route you can specify the path +and the serviceId independently:

+
+
+
application.yml
+
+
 zuul:
+  routes:
+    users:
+      path: /myusers/**
+      serviceId: users_service
+
+
+
+

This means that http calls to "/myusers" get forwarded to the +"users_service" service. The route has to have a "path" which can be +specified as an ant-style pattern, so "/myusers/*" only matches one +level, but "/myusers/**" matches hierarchically.

+
+
+

The location of the backend can be specified as either a "serviceId" +(for a service from discovery) or a "url" (for a physical location), e.g.

+
+
+
application.yml
+
+
 zuul:
+  routes:
+    users:
+      path: /myusers/**
+      url: http://example.com/users_service
+
+
+
+

These simple url-routes don’t get executed as a HystrixCommand nor can you loadbalance multiple URLs with Ribbon. +To achieve this, specify a service-route and configure a Ribbon client for the +serviceId (this currently requires disabling Eureka support in Ribbon: +see above for more information), e.g.

+
+
+
application.yml
+
+
zuul:
+  routes:
+    users:
+      path: /myusers/**
+      serviceId: users
+
+ribbon:
+  eureka:
+    enabled: false
+
+users:
+  ribbon:
+    listOfServers: example.com,google.com
+
+
+
+

You can provide convention between serviceId and routes using +regexmapper. It uses regular expression named groups to extract +variables from serviceId and inject them into a route pattern.

+
+
+
ApplicationConfiguration.java
+
+
@Bean
+public PatternServiceRouteMapper serviceRouteMapper() {
+    return new PatternServiceRouteMapper(
+        "(?<name>^.+)-(?<version>v.+$)",
+        "${version}/${name}");
+}
+
+
+
+

This means that a serviceId "myusers-v1" will be mapped to route +"/v1/myusers/**". Any regular expression is accepted but all named +groups must be present in both servicePattern and routePattern. If +servicePattern does not match a serviceId, the default behavior is +used. In the example above, a serviceId "myusers" will be mapped to route +"/myusers/**" (no version detected) This feature is disable by +default and only applies to discovered services.

+
+
+

To add a prefix to all mappings, set zuul.prefix to a value, such as +/api. The proxy prefix is stripped from the request before the +request is forwarded by default (switch this behaviour off with +zuul.stripPrefix=false). You can also switch off the stripping of +the service-specific prefix from individual routes, e.g.

+
+
+
application.yml
+
+
 zuul:
+  routes:
+    users:
+      path: /myusers/**
+      stripPrefix: false
+
+
+
+ + + + + +
+
Note
+		 +zuul.stripPrefix only applies to the prefix set in zuul.prefix. It does have any effect on prefixes +defined within a given route’s path. +
+
+
+

In this example, requests to "/myusers/101" will be forwarded to "/myusers/101" on the "users" service.

+
+
+

The zuul.routes entries actually bind to an object of type ZuulProperties. If you +look at the properties of that object you will see that it also has a "retryable" flag. +Set that flag to "true" to have the Ribbon client automatically retry failed requests +(and if you need to you can modify the parameters of the retry operations using +the Ribbon client configuration).

+
+
+

The X-Forwarded-Host header is added to the forwarded requests by +default. To turn it off set zuul.addProxyHeaders = false. The +prefix path is stripped by default, and the request to the backend +picks up a header "X-Forwarded-Prefix" ("/myusers" in the examples +above).

+
+
+

An application with @EnableZuulProxy could act as a standalone +server if you set a default route ("/"), for example zuul.route.home: +/ would route all traffic (i.e. "/**") to the "home" service.

+
+
+

If more fine-grained ignoring is needed, you can specify specific patterns to ignore. +These patterns are evaluated at the start of the route location process, which +means prefixes should be included in the pattern to warrant a match. Ignored patterns +span all services and supersede any other route specification.

+
+
+
application.yml
+
+
 zuul:
+  ignoredPatterns: /**/admin/**
+  routes:
+    users: /myusers/**
+
+
+
+

This means that all calls such as "/myusers/101" will be forwarded to "/101" on the "users" service. +But calls including "/admin/" will not resolve.

+
+
+ + + + + +
+
Warning
+		 +If you need your routes to have their order preserved you need to use a YAML +file as the ordering will be lost using a properties file. For example: +
+
+
+
application.yml
+
+
 zuul:
+  routes:
+    users:
+      path: /myusers/**
+    legacy:
+      path: /**
+
+
+
+

If you were to use a properties file, the legacy path may end up in front of the users +path rendering the users path unreachable.

+
+
+
+

Zuul Http Client

+
+

The default HTTP client used by zuul is now backed by the Apache HTTP Client instead of the +deprecated Ribbon RestClient. To use RestClient or to use the okhttp3.OkHttpClient set +ribbon.restclient.enabled=true or ribbon.okhttp.enabled=true respectively.

+
+
+
+

Cookies and Sensitive Headers

+
+

It’s OK to share headers between services in the same system, but you +probably don’t want sensitive headers leaking downstream into external +servers. You can specify a list of ignored headers as part of the +route configuration. Cookies play a special role because they have +well-defined semantics in browsers, and they are always to be treated +as sensitive. If the consumer of your proxy is a browser, then cookies +for downstream services also cause problems for the user because they +all get jumbled up (all downstream services look like they come from +the same place).

+
+
+

If you are careful with the design of your services, for example if +only one of the downstream services sets cookies, then you might be +able to let them flow from the backend all the way up to the +caller. Also, if your proxy sets cookies and all your back end +services are part of the same system, it can be natural to simply +share them (and for instance use Spring Session to link them up to some +shared state). Other than that, any cookies that get set by downstream +services are likely to be not very useful to the caller, so it is +recommended that you make (at least) "Set-Cookie" and "Cookie" into +sensitive headers for routes that are not part of your domain. Even +for routes that are part of your domain, try to think carefully +about what it means before allowing cookies to flow between them and +the proxy.

+
+
+

The sensitive headers can be configured as a comma-separated list per +route, e.g.

+
+
+
application.yml
+
+
 zuul:
+  routes:
+    users:
+      path: /myusers/**
+      sensitiveHeaders: Cookie,Set-Cookie,Authorization
+      url: https://downstream
+
+
+
+

Sensitive headers can also be set globally by setting zuul.sensitiveHeaders. If sensitiveHeaders is set on a route, this will override the global sensitiveHeaders setting.

+
+
+ + + + + +
+
Note
+		 +this is the default value for sensitiveHeaders, so you don’t +need to set it unless you want it to be different. N.B. this is new in +Spring Cloud Netflix 1.1 (in 1.0 the user had no control over headers +and all cookies flow in both directions). +
+
+
+
+

Ignored Headers

+
+

In addition to the per-route sensitive headers, you can set a global +value for zuul.ignoredHeaders for values that should be discarded +(both request and response) during interactions with downstream +services. By default these are empty, if Spring Security is not on the +classpath, and otherwise they are initialized to a set of well-known +"security" headers (e.g. involving caching) as specified by Spring +Security. The assumption in this case is that the downstream services +might add these headers too, and we want the values from the proxy. +To not discard these well known security headers in case Spring Security is on the classpath you can set zuul.ignoreSecurityHeaders to false. This can be useful if you disabled the HTTP Security response headers in Spring Security and want the values provided by downstream services

+
+
+
+

The Routes Endpoint

+
+

If you are using @EnableZuulProxy with tha Spring Boot Actuator you +will enable (by default) an additional endpoint, available via HTTP as +/routes. A GET to this endpoint will return a list of the mapped +routes. A POST will force a refresh of the existing routes (e.g. in +case there have been changes in the service catalog).

+
+
+ + + + + +
+
Note
+		 +the routes should respond automatically to changes in the +service catalog, but the POST to /routes is a way to force the change +to happen immediately. +
+
+
+
+

Strangulation Patterns and Local Forwards

+
+

A common pattern when migrating an existing application or API is to +"strangle" old endpoints, slowly replacing them with different +implementations. The Zuul proxy is a useful tool for this because you +can use it to handle all traffic from clients of the old endpoints, +but redirect some of the requests to new ones.

+
+
+

Example configuration:

+
+
+
application.yml
+
+
 zuul:
+  routes:
+    first:
+      path: /first/**
+      url: http://first.example.com
+    second:
+      path: /second/**
+      url: forward:/second
+    third:
+      path: /third/**
+      url: forward:/3rd
+    legacy:
+      path: /**
+      url: http://legacy.example.com
+
+
+
+

In this example we are strangling the "legacy" app which is mapped to +all requests that do not match one of the other patterns. Paths in +/first/** have been extracted into a new service with an external +URL. And paths in /second/** are forwared so they can be handled +locally, e.g. with a normal Spring @RequestMapping. Paths in +/third/** are also forwarded, but with a different prefix +(i.e. /third/foo is forwarded to /3rd/foo).

+
+
+ + + + + +
+
Note
+		 +The ignored patterns aren’t completely ignored, they just +aren’t handled by the proxy (so they are also effectively forwarded +locally). +
+
+
+
+

Uploading Files through Zuul

+
+

If you @EnableZuulProxy you can use the proxy paths to +upload files and it should just work as long as the files +are small. For large files there is an alternative path +which bypasses the Spring DispatcherServlet (to +avoid multipart processing) in "/zuul/*". I.e. if +zuul.routes.customers=/customers/** then you can +POST large files to "/zuul/customers/*". The servlet +path is externalized via zuul.servletPath. Extremely +large files will also require elevated timeout settings +if the proxy route takes you through a Ribbon load +balancer, e.g.

+
+
+
application.yml
+
+
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 60000
+ribbon:
+  ConnectTimeout: 3000
+  ReadTimeout: 60000
+
+
+
+

Note that for streaming to work with large files, you need to use chunked encoding in the request (which some browsers +do not do by default). E.g. on the command line:

+
+
+
+
$ curl -v -H "Transfer-Encoding: chunked" \
+    -F "file=@mylarge.iso" localhost:9999/zuul/simple/file
+
+
+
+
+

Plain Embedded Zuul

+
+

You can also run a Zuul server without the proxying, or switch on parts of the proxying platform selectively, if you +use @EnableZuulServer (instead of @EnableZuulProxy). Any beans that you add to the application of type ZuulFilter +will be installed automatically, as they are with @EnableZuulProxy, but without any of the proxy filters being added +automatically.

+
+
+

In this case the routes into the Zuul server are still specified by +configuring "zuul.routes.*", but there is no service +discovery and no proxying, so the "serviceId" and "url" settings are +ignored. For example:

+
+
+
application.yml
+
+
 zuul:
+  routes:
+    api: /api/**
+
+
+
+

maps all paths in "/api/**" to the Zuul filter chain.

+
+
+
+

Disable Zuul Filters

+
+

Zuul for Spring Cloud comes with a number of ZuulFilter beans enabled by default +in both proxy and server mode. See the zuul filters package for the +possible filters that are enabled. If you want to disable one, simply set +zuul.<SimpleClassName>.<filterType>.disable=true. By convention, the package after +filters is the Zuul filter type. For example to disable +org.springframework.cloud.netflix.zuul.filters.post.SendResponseFilter set +zuul.SendResponseFilter.post.disable=true.

+
+
+
+

Providing Hystrix Fallbacks For Routes

+
+

When a circuit for a given route in Zuul is tripped you can provide a fallback response +by creating a bean of type ZuulFallbackProvider. Within this bean you need to specify +the route ID the fallback is for and provide a ClientHttpResponse to return +as a fallback. Here is a very simple ZuulFallbackProvider implementation.

+
+
+
+
class MyFallbackProvider implements ZuulFallbackProvider {
+    @Override
+    public String getRoute() {
+        return "customers";
+    }
+
+    @Override
+    public ClientHttpResponse fallbackResponse() {
+        return new ClientHttpResponse() {
+            @Override
+            public HttpStatus getStatusCode() throws IOException {
+                return HttpStatus.OK;
+            }
+
+            @Override
+            public int getRawStatusCode() throws IOException {
+                return 200;
+            }
+
+            @Override
+            public String getStatusText() throws IOException {
+                return "OK";
+            }
+
+            @Override
+            public void close() {
+
+            }
+
+            @Override
+            public InputStream getBody() throws IOException {
+                return new ByteArrayInputStream("fallback".getBytes());
+            }
+
+            @Override
+            public HttpHeaders getHeaders() {
+                HttpHeaders headers = new HttpHeaders();
+                headers.setContentType(MediaType.APPLICATION_JSON);
+                return headers;
+            }
+        };
+    }
+}
+
+
+
+

And here is what the route configuration would look like.

+
+
+
+
zuul:
+  routes:
+    customers: /customers/**
+
+
+
+
+

Polyglot support with Sidecar

+
+

Do you have non-jvm languages you want to take advantage of Eureka, Ribbon and +Config Server? The Spring Cloud Netflix Sidecar was inspired by +Netflix Prana. It includes a simple http api +to get all of the instances (ie host and port) for a given service. You can +also proxy service calls through an embedded Zuul proxy which gets its route +entries from Eureka. The Spring Cloud Config Server can be accessed directly +via host lookup or through the Zuul Proxy. The non-jvm app should implement +a health check so the Sidecar can report to eureka if the app is up or down.

+
+
+

To include Sidecar in your project use the dependency with group org.springframework.cloud +and artifact id spring-cloud-netflix-sidecar.

+
+
+

To enable the Sidecar, create a Spring Boot application with @EnableSidecar. +This annotation includes @EnableCircuitBreaker, @EnableDiscoveryClient, +and @EnableZuulProxy. Run the resulting application on the same host as the +non-jvm application.

+
+
+

To configure the side car add sidecar.port and sidecar.health-uri to application.yml. +The sidecar.port property is the port the non-jvm app is listening on. This +is so the Sidecar can properly register the app with Eureka. The sidecar.health-uri +is a uri accessible on the non-jvm app that mimicks a Spring Boot health +indicator. It should return a json document like the following:

+
+
+
health-uri-document
+
+
{
+  "status":"UP"
+}
+
+
+
+

Here is an example application.yml for a Sidecar application:

+
+
+
application.yml
+
+
server:
+  port: 5678
+spring:
+  application:
+    name: sidecar
+
+sidecar:
+  port: 8000
+  health-uri: http://localhost:8000/health.json
+
+
+
+

The api for the DiscoveryClient.getInstances() method is /hosts/{serviceId}. +Here is an example response for /hosts/customers that returns two instances on +different hosts. This api is accessible to the non-jvm app (if the sidecar is +on port 5678) at http://localhost:5678/hosts/{serviceId}.

+
+
+
/hosts/customers
+
+
[
+    {
+        "host": "myhost",
+        "port": 9000,
+        "uri": "http://myhost:9000",
+        "serviceId": "CUSTOMERS",
+        "secure": false
+    },
+    {
+        "host": "myhost2",
+        "port": 9000,
+        "uri": "http://myhost2:9000",
+        "serviceId": "CUSTOMERS",
+        "secure": false
+    }
+]
+
+
+
+

The Zuul proxy automatically adds routes for each service known in eureka to +/<serviceId>, so the customers service is available at /customers. The +Non-jvm app can access the customer service via http://localhost:5678/customers +(assuming the sidecar is listening on port 5678).

+
+
+

If the Config Server is registered with Eureka, non-jvm application can access +it via the Zuul proxy. If the serviceId of the ConfigServer is configserver +and the Sidecar is on port 5678, then it can be accessed at +http://localhost:5678/configserver

+
+
+

Non-jvm app can take advantage of the Config Server’s ability to return YAML +documents. For example, a call to http://sidecar.local.spring.io:5678/configserver/default-master.yml +might result in a YAML document like the following

+
+
+
+
eureka:
+  client:
+    serviceUrl:
+      defaultZone: http://localhost:8761/eureka/
+  password: password
+info:
+  description: Spring Cloud Samples
+  url: https://github.com/spring-cloud-samples
+
+
+
+
+
+
+

RxJava with Spring MVC

+
+
+

Spring Cloud Netflix includes the RxJava.

+
+
+
+
+

RxJava is a Java VM implementation of Reactive Extensions: a library for composing asynchronous and event-based programs by using observable sequences.

+
+
+
+
+

Spring Cloud Netflix provides support for returning rx.Single objects from Spring MVC Controllers. It also supports using rx.Observable objects for Server-sent events (SSE). This can be very convenient if your internal APIs are already built using RxJava (see Feign Hystrix Support for examples).

+
+
+

Here are some examples of using rx.Single:

+
+
+
+
@RequestMapping(method = RequestMethod.GET, value = "/single")
+public Single<String> single() {
+	return Single.just("single value");
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/singleWithResponse")
+public ResponseEntity<Single<String>> singleWithResponse() {
+	return new ResponseEntity<>(Single.just("single value"),
+			HttpStatus.NOT_FOUND);
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/singleCreatedWithResponse")
+public Single<ResponseEntity<String>> singleOuterWithResponse() {
+	return Single.just(new ResponseEntity<>("single value", HttpStatus.CREATED));
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/throw")
+public Single<Object> error() {
+	return Single.error(new RuntimeException("Unexpected"));
+}
+
+
+
+

If you have an Observable, rather than a single, you can use .toSingle() or .toList().toSingle(). Here are some examples:

+
+
+
+
@RequestMapping(method = RequestMethod.GET, value = "/single")
+public Single<String> single() {
+    return Observable.just("single value").toSingle();
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/multiple")
+public Single<List<String>> multiple() {
+    return Observable.just("multiple", "values").toList().toSingle();
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/responseWithObservable")
+public ResponseEntity<Single<String>> responseWithObservable() {
+
+    Observable<String> observable = Observable.just("single value");
+    HttpHeaders headers = new HttpHeaders();
+    headers.setContentType(APPLICATION_JSON_UTF8);
+    return new ResponseEntity<>(observable.toSingle(), headers, HttpStatus.CREATED);
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/timeout")
+public Observable<String> timeout() {
+    return Observable.timer(1, TimeUnit.MINUTES).map(new Func1<Long, String>() {
+        @Override
+        public String call(Long aLong) {
+            return "single value";
+        }
+    });
+}
+
+
+
+

If you have a streaming endpoint and client, SSE could be an option. To convert rx.Observable to a Spring SseEmitter use RxResponse.sse(). Here are some examples:

+
+
+
+
@RequestMapping(method = RequestMethod.GET, value = "/sse")
+public SseEmitter single() {
+	return RxResponse.sse(Observable.just("single value"));
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/messages")
+public SseEmitter messages() {
+	return RxResponse.sse(Observable.just("message 1", "message 2", "message 3"));
+}
+
+@RequestMapping(method = RequestMethod.GET, value = "/events")
+public SseEmitter event() {
+	return RxResponse.sse(APPLICATION_JSON_UTF8,
+			Observable.just(new EventDto("Spring io", getDate(2016, 5, 19)),
+					new EventDto("SpringOnePlatform", getDate(2016, 8, 1))));
+}
+
+
+
+
+
+

Metrics: Spectator, Servo, and Atlas

+
+
+

When used together, Spectator/Servo and Atlas provide a near real-time operational insight platform.

+
+
+

Spectator and Servo are Netflix’s metrics collection libraries. Atlas is a Netflix metrics backend to manage dimensional time series data.

+
+
+

Servo served Netflix for several years and is still usable, but is gradually being phased out in favor of Spectator, which is only designed to work with Java 8. Spring Cloud Netflix provides support for both, but Java 8 based applications are encouraged to use Spectator.

+
+
+

Dimensional vs. Hierarchical Metrics

+
+

Spring Boot Actuator metrics are hierarchical and metrics are separated only by name. These names often follow a naming convention that embeds key/value attribute pairs (dimensions) into the name separated by periods. Consider the following metrics for two endpoints, root and star-star:

+
+
+
+
{
+    "counter.status.200.root": 20,
+    "counter.status.400.root": 3,
+    "counter.status.200.star-star": 5,
+}
+
+
+
+

The first metric gives us a normalized count of successful requests against the root endpoint per unit of time. But what if the system had 20 endpoints and you want to get a count of successful requests against all the endpoints? Some hierarchical metrics backends would allow you to specify a wild card such as counter.status.200. that would read all 20 metrics and aggregate the results. Alternatively, you could provide a HandlerInterceptorAdapter that intercepts and records a metric like counter.status.200.all for all successful requests irrespective of the endpoint, but now you must write 20+1 different metrics. Similarly if you want to know the total number of successful requests for all endpoints in the service, you could specify a wild card such as counter.status.2.*.

+
+
+

Even in the presence of wildcarding support on a hierarchical metrics backend, naming consistency can be difficult. Specifically the position of these tags in the name string can slip with time, breaking queries. For example, suppose we add an additional dimension to the hierarchical metrics above for HTTP method. Then counter.status.200.root becomes counter.status.200.method.get.root, etc. Our counter.status.200.* suddenly no longer has the same semantic meaning. Furthermore, if the new dimension is not applied uniformly across the codebase, certain queries may become impossible. This can quickly get out of hand.

+
+
+

Netflix metrics are tagged (a.k.a. dimensional). Each metric has a name, but this single named metric can contain multiple statistics and 'tag' key/value pairs that allows more querying flexibility. In fact, the statistics themselves are recorded in a special tag.

+
+
+

Recorded with Netflix Servo or Spectator, a timer for the root endpoint described above contains 4 statistics per status code, where the count statistic is identical to Spring Boot Actuator’s counter. In the event that we have encountered an HTTP 200 and 400 thus far, there will be 8 available data points:

+
+
+
+
{
+    "root(status=200,stastic=count)": 20,
+    "root(status=200,stastic=max)": 0.7265630630000001,
+    "root(status=200,stastic=totalOfSquares)": 0.04759702862580789,
+    "root(status=200,stastic=totalTime)": 0.2093076914666667,
+    "root(status=400,stastic=count)": 1,
+    "root(status=400,stastic=max)": 0,
+    "root(status=400,stastic=totalOfSquares)": 0,
+    "root(status=400,stastic=totalTime)": 0,
+}
+
+
+
+
+

Default Metrics Collection

+
+

Without any additional dependencies or configuration, a Spring Cloud based service will autoconfigure a Servo MonitorRegistry and begin collecting metrics on every Spring MVC request. By default, a Servo timer with the name rest will be recorded for each MVC request which is tagged with:

+
+
+
    +
  1. +

    HTTP method

    +
    2. +
  2. +

    HTTP status (e.g. 200, 400, 500)

    +
    3. +
  3. +

    URI (or "root" if the URI is empty), sanitized for Atlas

    +
    4. +
  4. +

    The exception class name, if the request handler threw an exception

    +
    5. +
  5. +

    The caller, if a request header with a key matching netflix.metrics.rest.callerHeader is set on the request. There is no default key for netflix.metrics.rest.callerHeader. You must add it to your application properties if you wish to collect caller information.

    +
    6. +
+
+
+

Set the netflix.metrics.rest.metricName property to change the name of the metric from rest to a name you provide.

+
+
+

If Spring AOP is enabled and org.aspectj:aspectjweaver is present on your runtime classpath, Spring Cloud will also collect metrics on every client call made with RestTemplate. A Servo timer with the name of restclient will be recorded for each MVC request which is tagged with:

+
+
+
    +
  1. +

    HTTP method

    +
    2. +
  2. +

    HTTP status (e.g. 200, 400, 500), "CLIENT_ERROR" if the response returned null, or "IO_ERROR" if an IOException occurred during the execution of the RestTemplate method

    +
    3. +
  3. +

    URI, sanitized for Atlas

    +
    4. +
  4. +

    Client name

    +
    5. +
+
+
+ + + + + +
+
Warning
+		 +Avoid using hardcoded url parameters within RestTemplate. When targeting dynamic endpoints use URL variables. This will avoid potential "GC Overhead Limit Reached" issues where ServoMonitorCache treats each url as a unique key. +
+
+
+
+
// recommended
+String orderid = "1";
+restTemplate.getForObject("http://testeurekabrixtonclient/orders/{orderid}", String.class, orderid)
+
+// avoid
+restTemplate.getForObject("http://testeurekabrixtonclient/orders/1", String.class)
+
+
+
+
+

Metrics Collection: Spectator

+
+

To enable Spectator metrics, include a dependency on spring-boot-starter-spectator:

+
+
+
+
    <dependency>
+        <groupId>org.springframework.cloud</groupId>
+        <artifactId>spring-cloud-starter-spectator</artifactId>
+    </dependency>
+
+
+
+

In Spectator parlance, a meter is a named, typed, and tagged configuration and a metric represents the value of a given meter at a point in time. Spectator meters are created and controlled by a registry, which currently has several different implementations. Spectator provides 4 meter types: counter, timer, gauge, and distribution summary.

+
+
+

Spring Cloud Spectator integration configures an injectable com.netflix.spectator.api.Registry instance for you. Specifically, it configures a ServoRegistry instance in order to unify the collection of REST metrics and the exporting of metrics to the Atlas backend under a single Servo API. Practically, this means that your code may use a mixture of Servo monitors and Spectator meters and both will be scooped up by Spring Boot Actuator MetricReader instances and both will be shipped to the Atlas backend.

+
+
+

Spectator Counter

+
+

A counter is used to measure the rate at which some event is occurring.

+
+
+
+
// create a counter with a name and a set of tags
+Counter counter = registry.counter("counterName", "tagKey1", "tagValue1", ...);
+counter.increment(); // increment when an event occurs
+counter.increment(10); // increment by a discrete amount
+
+
+
+

The counter records a single time-normalized statistic.

+
+
+
+

Spectator Timer

+
+

A timer is used to measure how long some event is taking. Spring Cloud automatically records timers for Spring MVC requests and conditionally RestTemplate requests, which can later be used to create dashboards for request related metrics like latency:

+
+
+
Request Latency
+

image::RequestLatency.png []

+
+
+
+
// create a timer with a name and a set of tags
+Timer timer = registry.timer("timerName", "tagKey1", "tagValue1", ...);
+
+// execute an operation and time it at the same time
+T result = timer.record(() -> fooReturnsT());
+
+// alternatively, if you must manually record the time
+Long start = System.nanoTime();
+T result = fooReturnsT();
+timer.record(System.nanoTime() - start, TimeUnit.NANOSECONDS);
+
+
+
+

The timer simultaneously records 4 statistics: count, max, totalOfSquares, and totalTime. The count statistic will always match the single normalized value provided by a counter if you had called increment() once on the counter for each time you recorded a timing, so it is rarely necessary to count and time separately for a single operation.

+
+
+

For long running operations, Spectator provides a special LongTaskTimer.

+
+
+
+

Spectator Gauge

+
+

Gauges are used to determine some current value like the size of a queue or number of threads in a running state. Since gauges are sampled, they provide no information about how these values fluctuate between samples.

+
+
+

The normal use of a gauge involves registering the gauge once in initialization with an id, a reference to the object to be sampled, and a function to get or compute a numeric value based on the object. The reference to the object is passed in separately and the Spectator registry will keep a weak reference to the object. If the object is garbage collected, then Spectator will automatically drop the registration. See the note in Spectator’s documentation about potential memory leaks if this API is misused.

+
+
+
+
// the registry will automatically sample this gauge periodically
+registry.gauge("gaugeName", pool, Pool::numberOfRunningThreads);
+
+// manually sample a value in code at periodic intervals -- last resort!
+registry.gauge("gaugeName", Arrays.asList("tagKey1", "tagValue1", ...), 1000);
+
+
+
+
+

Spectator Distribution Summaries

+
+

A distribution summary is used to track the distribution of events. It is similar to a timer, but more general in that the size does not have to be a period of time. For example, a distribution summary could be used to measure the payload sizes of requests hitting a server.

+
+
+
+
// the registry will automatically sample this gauge periodically
+DistributionSummary ds = registry.distributionSummary("dsName", "tagKey1", "tagValue1", ...);
+ds.record(request.sizeInBytes());
+
+
+
+
+
+

Metrics Collection: Servo

+
+ + + + + +
+
Warning
+		 +If your code is compiled on Java 8, please use Spectator instead of Servo as Spectator is destined to replace Servo entirely in the long term. +
+
+
+

In Servo parlance, a monitor is a named, typed, and tagged configuration and a metric represents the value of a given monitor at a point in time. Servo monitors are logically equivalent to Spectator meters. Servo monitors are created and controlled by a MonitorRegistry. In spite of the above warning, Servo does have a wider array of monitor options than Spectator has meters.

+
+
+

Spring Cloud integration configures an injectable com.netflix.servo.MonitorRegistry instance for you. Once you have created the appropriate Monitor type in Servo, the process of recording data is wholly similar to Spectator.

+
+
+

Creating Servo Monitors

+
+

If you are using the Servo MonitorRegistry instance provided by Spring Cloud (specifically, an instance of DefaultMonitorRegistry), Servo provides convenience classes for retrieving counters and timers. These convenience classes ensure that only one Monitor is registered for each unique combination of name and tags.

+
+
+

To manually create a Monitor type in Servo, especially for the more exotic monitor types for which convenience methods are not provided, instantiate the appropriate type by providing a MonitorConfig instance:

+
+
+
+
MonitorConfig config = MonitorConfig.builder("timerName").withTag("tagKey1", "tagValue1").build();
+
+// somewhere we should cache this Monitor by MonitorConfig
+Timer timer = new BasicTimer(config);
+monitorRegistry.register(timer);
+
+
+
+
+
+

Metrics Backend: Atlas

+
+

Atlas was developed by Netflix to manage dimensional time series data for near real-time operational insight. Atlas features in-memory data storage, allowing it to gather and report very large numbers of metrics, very quickly.

+
+
+

Atlas captures operational intelligence. Whereas business intelligence is data gathered for analyzing trends over time, operational intelligence provides a picture of what is currently happening within a system.

+
+
+

Spring Cloud provides a spring-cloud-starter-atlas that has all the dependencies you need. Then just annotate your Spring Boot application with @EnableAtlas and provide a location for your running Atlas server with the netflix.atlas.uri property.

+
+
+

Global tags

+
+

Spring Cloud enables you to add tags to every metric sent to the Atlas backend. Global tags can be used to separate metrics by application name, environment, region, etc.

+
+
+

Each bean implementing AtlasTagProvider will contribute to the global tag list:

+
+
+
+
@Bean
+AtlasTagProvider atlasCommonTags(
+    @Value("${spring.application.name}") String appName) {
+  return () -> Collections.singletonMap("app", appName);
+}
+
+
+
+
+

Using Atlas

+
+

To bootstrap a in-memory standalone Atlas instance:

+
+
+
+
$ curl -LO https://github.com/Netflix/atlas/releases/download/v1.4.2/atlas-1.4.2-standalone.jar
+$ java -jar atlas-1.4.2-standalone.jar
+
+
+
+ + + + + +
+
Tip
+		 +An Atlas standalone node running on an r3.2xlarge (61GB RAM) can handle roughly 2 million metrics per minute for a given 6 hour window. +
+
+
+

Once running and you have collected a handful of metrics, verify that your setup is correct by listing tags on the Atlas server:

+
+
+
+
$ curl http://ATLAS/api/v1/tags
+
+
+
+ + + + + +
+
Tip
+		 +After executing several requests against your service, you can gather some very basic information on the request latency of every request by pasting the following url in your browser: http://ATLAS/api/v1/graph?q=name,rest,:eq,:avg +
+
+
+

The Atlas wiki contains a compilation of sample queries for various scenarios.

+
+
+

Make sure to check out the alerting philosophy and docs on using double exponential smoothing to generate dynamic alert thresholds.

+
+
+
+
+
+
+ + \ No newline at end of file