Cloud Native is a style of application development that encourages easy adoption of best practices in the areas of continuous delivery and value-driven development. +A related discipline is that of building 12-factor Applications, in which development practices are aligned with delivery and operations goals — for instance, by using declarative programming and management and monitoring. +Spring Cloud facilitates these styles of development in a number of specific ways. + The starting point is a set of features to which all components in a distributed system need easy access.
+Many of those features are covered by Spring Boot, on which Spring Cloud builds. Some more features are delivered by Spring Cloud as two libraries: Spring Cloud Context and Spring Cloud Commons.
+Spring Cloud Context provides utilities and special services for the ApplicationContext of a Spring Cloud application (bootstrap context, encryption, refresh scope, and environment endpoints). Spring Cloud Commons is a set of abstractions and common classes used in different Spring Cloud implementations (such as Spring Cloud Netflix and Spring Cloud Consul).
If you get an exception due to "Illegal key size" and you use Sun’s JDK, you need to install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files. +See the following links for more information:
+-
+
- + + +
- + + +
- + + +
Extract the files into the JDK/jre/lib/security folder for whichever version of JRE/JDK x64/x86 you use.
+| + + | ++Spring Cloud is released under the non-restrictive Apache 2.0 license. +If you would like to contribute to this section of the documentation or if you find an error, you can find the source code and issue trackers for the project at github. + | +
Spring Cloud Context: Application Context Services
+Spring Boot has an opinionated view of how to build an application with Spring. +For instance, it has conventional locations for common configuration files and has endpoints for common management and monitoring tasks. +Spring Cloud builds on top of that and adds a few features that probably all components in a system would use or occasionally need.
+The Bootstrap Application Context
+A Spring Cloud application operates by creating a “bootstrap” context, which is a parent context for the main application.
+It is responsible for loading configuration properties from the external sources and for decrypting properties in the local external configuration files.
+The two contexts share an Environment, which is the source of external properties for any Spring application.
+By default, bootstrap properties (not bootstrap.properties but properties that are loaded during the bootstrap phase) are added with high precedence, so they cannot be overridden by local configuration.
The bootstrap context uses a different convention for locating external configuration than the main application context.
+Instead of application.yml (or .properties), you can use bootstrap.yml, keeping the external configuration for bootstrap and main context
+nicely separate.
+The following listing shows an example:
spring:
+ application:
+ name: foo
+ cloud:
+ config:
+ uri: ${SPRING_CONFIG_URI:http://localhost:8888}
+If your application needs any application-specific configuration from the server, it is a good idea to set the spring.application.name (in bootstrap.yml or application.yml).
+In order for the property spring.application.name to be used as the application’s context ID you
+must set it in bootstrap.[properties | yml].
You can disable the bootstrap process completely by setting spring.cloud.bootstrap.enabled=false (for example, in system properties).
Application Context Hierarchies
+If you build an application context from SpringApplication or SpringApplicationBuilder, then the Bootstrap context is added as a parent to that context.
+It is a feature of Spring that child contexts inherit property sources and profiles from their parent, so the “main” application context contains additional property sources, compared to building the same context without Spring Cloud Config.
+The additional property sources are:
-
+
-
+
“bootstrap”: If any
+PropertySourceLocatorsare found in the Bootstrap context and if they have non-empty properties, an optionalCompositePropertySourceappears with high priority. +An example would be properties from the Spring Cloud Config Server. +See “Customizing the Bootstrap Property Sources” for instructions on how to customize the contents of this property source.
+ -
+
“applicationConfig: [classpath:bootstrap.yml]” (and related files if Spring profiles are active): If you have a
+bootstrap.yml(or.properties), those properties are used to configure the Bootstrap context. +Then they get added to the child context when its parent is set. +They have lower precedence than theapplication.yml(or.properties) and any other property sources that are added to the child as a normal part of the process of creating a Spring Boot application. +See “Changing the Location of Bootstrap Properties” for instructions on how to customize the contents of these property sources.
+
Because of the ordering rules of property sources, the “bootstrap” entries take precedence.
+However, note that these do not contain any data from bootstrap.yml, which has very low precedence but can be used to set defaults.
You can extend the context hierarchy by setting the parent context of any ApplicationContext you create — for example, by using its own interface or with the SpringApplicationBuilder convenience methods (parent(), child() and sibling()).
+The bootstrap context is the parent of the most senior ancestor that you create yourself.
+Every context in the hierarchy has its own “bootstrap” (possibly empty) property source to avoid promoting values inadvertently from parents down to their descendants.
+If there is a Config Server, every context in the hierarchy can also (in principle) have a different spring.application.name and, hence, a different remote property source.
+Normal Spring application context behavior rules apply to property resolution: properties from a child context override those in
+the parent, by name and also by property source name.
+(If the child has a property source with the same name as the parent, the value from the parent is not included in the child).
Note that the SpringApplicationBuilder lets you share an Environment amongst the whole hierarchy, but that is not the default.
+Thus, sibling contexts, in particular, do not need to have the same profiles or property sources, even though they may share common values with their parent.
Changing the Location of Bootstrap Properties
+The bootstrap.yml (or .properties) location can be specified by setting spring.cloud.bootstrap.name (default: bootstrap) or spring.cloud.bootstrap.location (default: empty) — for example, in System properties.
+Those properties behave like the spring.config.* variants with the same name.
+In fact, they are used to set up the bootstrap ApplicationContext by setting those properties in its Environment.
+If there is an active profile (from spring.profiles.active or through the Environment API in the
+context you are building), properties in that profile get loaded as well, the same as in a regular Spring Boot app — for example, from bootstrap-development.properties for a development profile.
Overriding the Values of Remote Properties
+The property sources that are added to your application by the bootstrap context are often “remote” (from example, from Spring Cloud Config Server).
+By default, they cannot be overridden locally.
+If you want to let your applications override the remote properties with their own System properties or config files, the remote property source has to grant it permission by setting spring.cloud.config.allowOverride=true (it does not work to set this locally).
+Once that flag is set, two finer-grained settings control the location of the remote properties in relation to system properties and the application’s local configuration:
-
+
-
+
+spring.cloud.config.overrideNone=true: Override from any local property source.
+ -
+
+spring.cloud.config.overrideSystemProperties=false: Only system properties, command line arguments, and environment variables (but not the local config files) should override the remote settings.
+
Customizing the Bootstrap Configuration
+The bootstrap context can be set to do anything you like by adding entries to /META-INF/spring.factories under a key named org.springframework.cloud.bootstrap.BootstrapConfiguration.
+This holds a comma-separated list of Spring @Configuration classes that are used to create the context.
+Any beans that you want to be available to the main application context for autowiring can be created here.
+There is a special contract for @Beans of type ApplicationContextInitializer.
+If you want to control the startup sequence, classes can be marked with an @Order annotation (the default order is last).
| + + | +
+When adding custom BootstrapConfiguration, be careful that the classes you add are not @ComponentScanned by mistake into your “main” application context, where they might not be needed.
+Use a separate package name for boot configuration classes and make sure that name is not already covered by your @ComponentScan or @SpringBootApplication annotated configuration classes.
+ |
+
The bootstrap process ends by injecting initializers into the main SpringApplication instance (which is the normal Spring Boot startup sequence, whether it is running as a standalone application or deployed in an application server).
+First, a bootstrap context is created from the classes found in spring.factories.
+Then, all @Beans of type ApplicationContextInitializer are added to the main SpringApplication before it is started.
Customizing the Bootstrap Property Sources
+The default property source for external configuration added by the bootstrap process is the Spring Cloud Config Server, but you can add additional sources by adding beans of type PropertySourceLocator to the bootstrap context (through spring.factories).
+For instance, you can insert additional properties from a different server or from a database.
As an example, consider the following custom locator:
+@Configuration
+public class CustomPropertySourceLocator implements PropertySourceLocator {
+
+ @Override
+ public PropertySource<?> locate(Environment environment) {
+ return new MapPropertySource("customProperty",
+ Collections.<String, Object>singletonMap("property.from.sample.custom.source", "worked as intended"));
+ }
+
+}The Environment that is passed in is the one for the ApplicationContext about to be created — in other words, the one for which we supply additional property sources for.
+It already has its normal Spring Boot-provided property sources, so you can use those to locate a property source specific to this Environment (for example, by keying it on spring.application.name, as is done in the default Spring Cloud Config Server property source locator).
If you create a jar with this class in it and then add a META-INF/spring.factories containing the following, the customProperty PropertySource appears in any application that includes that jar on its classpath:
org.springframework.cloud.bootstrap.BootstrapConfiguration=sample.custom.CustomPropertySourceLocator+
Logging Configuration
+If you are going to use Spring Boot to configure log settings than +you should place this configuration in `bootstrap.[yml | properties] +if you would like it to apply to all events.
+| + + | +
+For Spring Cloud to initialize logging configuration properly you cannot use a custom prefix. For example,
+using custom.loggin.logpath will not be recognized by Spring Cloud when initializing the logging system.
+ |
+
Environment Changes
+The application listens for an EnvironmentChangeEvent and reacts to the change in a couple of standard ways (additional ApplicationListeners can be added as @Beans by the user in the normal way).
+When an EnvironmentChangeEvent is observed, it has a list of key values that have changed, and the application uses those to:
-
+
-
+
Re-bind any
+@ConfigurationPropertiesbeans in the context
+ -
+
Set the logger levels for any properties in
+logging.level.*
+
Note that the Config Client does not, by default, poll for changes in the Environment.
+Generally, we would not recommend that approach for detecting changes (although you could set it up with a
+@Scheduled annotation).
+If you have a scaled-out client application, it is better to broadcast the EnvironmentChangeEvent to all the instances instead of having them polling for changes (for example, by using the Spring Cloud Bus).
The EnvironmentChangeEvent covers a large class of refresh use cases, as long as you can actually make a change to the Environment and publish the event.
+Note that those APIs are public and part of core Spring).
+You can verify that the changes are bound to @ConfigurationProperties beans by visiting the /configprops endpoint (a normal Spring Boot Actuator feature).
+For instance, a DataSource can have its maxPoolSize changed at runtime (the default DataSource created by Spring Boot is an @ConfigurationProperties bean) and grow capacity dynamically.
+Re-binding @ConfigurationProperties does not cover another large class of use cases, where you need more control over the refresh and where you need a change to be atomic over the whole ApplicationContext.
+To address those concerns, we have @RefreshScope.
Refresh Scope
+When there is a configuration change, a Spring @Bean that is marked as @RefreshScope gets special treatment.
+This feature addresses the problem of stateful beans that only get their configuration injected when they are initialized.
+For instance, if a DataSource has open connections when the database URL is changed via the Environment, you probably want the holders of those connections to be able to complete what they are doing.
+Then, the next time something borrows a connection from the pool, it gets one with the new URL.
Sometimes, it might even be mandatory to apply the @RefreshScope
+annotation on some beans which can be only initialized once. If a bean
+is "immutable", you will have to either annotate the bean with @RefreshScope
+or specify the classname under the property key
+spring.cloud.refresh.extra-refreshable.
| + + | +
+If you create a DataSource bean yourself and the implementation is a HikariDataSource, return the
+most specific type, in this case HikariDataSource. Otherwise, you will need to set
+spring.cloud.refresh.extra-refreshable=javax.sql.DataSource.
+ |
+
Refresh scope beans are lazy proxies that initialize when they are used (that is, when a method is called), and the scope acts as a cache of initialized values. +To force a bean to re-initialize on the next method call, you must invalidate its cache entry.
+The RefreshScope is a bean in the context and has a public refreshAll() method to refresh all beans in the scope by clearing the target cache.
+The /refresh endpoint exposes this functionality (over HTTP or JMX).
+To refresh an individual bean by name, there is also a refresh(String) method.
To expose the /refresh endpoint, you need to add following configuration to your application:
management:
+ endpoints:
+ web:
+ exposure:
+ include: refresh| + + | +
+@RefreshScope works (technically) on an @Configuration class, but it might lead to surprising behavior.
+For example, it does not mean that all the @Beans defined in that class are themselves in @RefreshScope.
+Specifically, anything that depends on those beans cannot rely on them being updated when a refresh is initiated, unless it is itself in @RefreshScope.
+In that case, it is rebuilt on a refresh and its dependencies are re-injected. At that point, they are re-initialized from the refreshed @Configuration).
+ |
+
Encryption and Decryption
+Spring Cloud has an Environment pre-processor for decrypting property values locally.
+It follows the same rules as the Config Server and has the same external configuration through encrypt.*.
+Thus, you can use encrypted values in the form of {cipher}* and, as long as there is a valid key, they are decrypted before the main application context gets the Environment settings.
+To use the encryption features in an application, you need to include Spring Security RSA in your classpath (Maven co-ordinates: "org.springframework.security:spring-security-rsa"), and you also need the full strength JCE extensions in your JVM.
If you get an exception due to "Illegal key size" and you use Sun’s JDK, you need to install the Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files. +See the following links for more information:
+-
+
- + + +
- + + +
- + + +
Extract the files into the JDK/jre/lib/security folder for whichever version of JRE/JDK x64/x86 you use.
+Endpoints
+For a Spring Boot Actuator application, some additional management endpoints are available. You can use:
+-
+
-
+
+POSTto/actuator/envto update theEnvironmentand rebind@ConfigurationPropertiesand log levels.
+ -
+
+/actuator/refreshto re-load the boot strap context and refresh the@RefreshScopebeans.
+ -
+
+/actuator/restartto close theApplicationContextand restart it (disabled by default).
+ -
+
+/actuator/pauseand/actuator/resumefor calling theLifecyclemethods (stop()andstart()on theApplicationContext).
+
| + + | +
+If you disable the /actuator/restart endpoint then the /actuator/pause and /actuator/resume endpoints
+will also be disabled since they are just a special case of /actuator/restart.
+ |
+
Spring Cloud Commons: Common Abstractions
+Patterns such as service discovery, load balancing, and circuit breakers lend themselves to a common abstraction layer that can be consumed by all Spring Cloud clients, independent of the implementation (for example, discovery with Eureka or Consul).
+@EnableDiscoveryClient
+Spring Cloud Commons provides the @EnableDiscoveryClient annotation.
+This looks for implementations of the DiscoveryClient interface with META-INF/spring.factories.
+Implementations of the Discovery Client add a configuration class to spring.factories under the org.springframework.cloud.client.discovery.EnableDiscoveryClient key.
+Examples of DiscoveryClient implementations include Spring Cloud Netflix Eureka, Spring Cloud Consul Discovery, and Spring Cloud Zookeeper Discovery.
By default, implementations of DiscoveryClient auto-register the local Spring Boot server with the remote discovery server.
+This behavior can be disabled by setting autoRegister=false in @EnableDiscoveryClient.
| + + | +
+@EnableDiscoveryClient is no longer required.
+You can put a DiscoveryClient implementation on the classpath to cause the Spring Boot application to register with the service discovery server.
+ |
+
Health Indicator
+Commons creates a Spring Boot HealthIndicator that DiscoveryClient implementations can participate in by implementing DiscoveryHealthIndicator.
+To disable the composite HealthIndicator, set spring.cloud.discovery.client.composite-indicator.enabled=false.
+A generic HealthIndicator based on DiscoveryClient is auto-configured (DiscoveryClientHealthIndicator).
+To disable it, set spring.cloud.discovery.client.health-indicator.enabled=false.
+To disable the description field of the DiscoveryClientHealthIndicator, set spring.cloud.discovery.client.health-indicator.include-description=false.
+Otherwise, it can bubble up as the description of the rolled up HealthIndicator.
Ordering DiscoveryClient instances
+DiscoveryClient interface extends Ordered. This is useful when using multiple discovery
+ clients, as it allows you to define the order of the returned discovery clients, similar to
+how you can order the beans loaded by a Spring application. By default, the order of any DiscoveryClient is set to
+0. If you want to set a different order for your custom DiscoveryClient implementations, you just need to override
+the getOrder() method so that it returns the value that is suitable for your setup. Apart from this, you can use
+properties to set the order of the DiscoveryClient
+implementations provided by Spring Cloud, among others ConsulDiscoveryClient, EurekaDiscoveryClient and
+ZookeeperDiscoveryClient. In order to do it, you just need to set the
+spring.cloud.{clientIdentifier}.discovery.order (or eureka.client.order for Eureka) property to the desired value.
ServiceRegistry
+Commons now provides a ServiceRegistry interface that provides methods such as register(Registration) and deregister(Registration), which let you provide custom registered services.
+Registration is a marker interface.
The following example shows the ServiceRegistry in use:
@Configuration
+@EnableDiscoveryClient(autoRegister=false)
+public class MyConfiguration {
+ private ServiceRegistry registry;
+
+ public MyConfiguration(ServiceRegistry registry) {
+ this.registry = registry;
+ }
+
+ // called through some external process, such as an event or a custom actuator endpoint
+ public void register() {
+ Registration registration = constructRegistration();
+ this.registry.register(registration);
+ }
+}Each ServiceRegistry implementation has its own Registry implementation.
-
+
-
+
+ZookeeperRegistrationused withZookeeperServiceRegistry
+ -
+
+EurekaRegistrationused withEurekaServiceRegistry
+ -
+
+ConsulRegistrationused withConsulServiceRegistry
+
If you are using the ServiceRegistry interface, you are going to need to pass the
+correct Registry implementation for the ServiceRegistry implementation you
+are using.
ServiceRegistry Auto-Registration
+By default, the ServiceRegistry implementation auto-registers the running service.
+To disable that behavior, you can set:
+* @EnableDiscoveryClient(autoRegister=false) to permanently disable auto-registration.
+* spring.cloud.service-registry.auto-registration.enabled=false to disable the behavior through configuration.
ServiceRegistry Auto-Registration Events
+There are two events that will be fired when a service auto-registers. The first event, called
+InstancePreRegisteredEvent, is fired before the service is registered. The second
+event, called InstanceRegisteredEvent, is fired after the service is registered. You can register an
+ApplicationListener(s) to listen to and react to these events.
| + + | +
+These events will not be fired if spring.cloud.service-registry.auto-registration.enabled is set to false.
+ |
+
Service Registry Actuator Endpoint
+Spring Cloud Commons provides a /service-registry actuator endpoint.
+This endpoint relies on a Registration bean in the Spring Application Context.
+Calling /service-registry with GET returns the status of the Registration.
+Using POST to the same endpoint with a JSON body changes the status of the current Registration to the new value.
+The JSON body has to include the status field with the preferred value.
+Please see the documentation of the ServiceRegistry implementation you use for the allowed values when updating the status and the values returned for the status.
+For instance, Eureka’s supported statuses are UP, DOWN, OUT_OF_SERVICE, and UNKNOWN.
Spring RestTemplate as a Load Balancer Client
+RestTemplate can be automatically configured to use ribbon.
+To create a load-balanced RestTemplate, create a RestTemplate @Bean and use the @LoadBalanced qualifier, as shown in the following example:
@Configuration
+public class MyConfiguration {
+
+ @LoadBalanced
+ @Bean
+ RestTemplate restTemplate() {
+ return new RestTemplate();
+ }
+}
+
+public class MyClass {
+ @Autowired
+ private RestTemplate restTemplate;
+
+ public String doOtherStuff() {
+ String results = restTemplate.getForObject("http://stores/stores", String.class);
+ return results;
+ }
+}| + + | +
+A RestTemplate bean is no longer created through auto-configuration.
+Individual applications must create it.
+ |
+
The URI needs to use a virtual host name (that is, a service name, not a host name).
+The Ribbon client is used to create a full physical address.
+See RibbonAutoConfiguration for details of how the RestTemplate is set up.
Spring WebClient as a Load Balancer Client
+WebClient can be automatically configured to use the LoadBalancerClient.
+To create a load-balanced WebClient, create a WebClient.Builder @Bean and use the @LoadBalanced qualifier, as shown in the following example:
@Configuration
+public class MyConfiguration {
+
+ @Bean
+ @LoadBalanced
+ public WebClient.Builder loadBalancedWebClientBuilder() {
+ return WebClient.builder();
+ }
+}
+
+public class MyClass {
+ @Autowired
+ private WebClient.Builder webClientBuilder;
+
+ public Mono<String> doOtherStuff() {
+ return webClientBuilder.build().get().uri("http://stores/stores")
+ .retrieve().bodyToMono(String.class);
+ }
+}The URI needs to use a virtual host name (that is, a service name, not a host name). +The Ribbon client is used to create a full physical address.
+Retrying Failed Requests
+A load-balanced RestTemplate can be configured to retry failed requests.
+By default, this logic is disabled.
+You can enable it by adding Spring Retry to your application’s classpath.
+The load-balanced RestTemplate honors some of the Ribbon configuration values related to retrying failed requests.
+You can use client.ribbon.MaxAutoRetries, client.ribbon.MaxAutoRetriesNextServer, and client.ribbon.OkToRetryOnAllOperations properties.
+If you would like to disable the retry logic with Spring Retry on the classpath, you can set spring.cloud.loadbalancer.retry.enabled=false.
+See the Ribbon documentation for a description of what these properties do.
If you would like to implement a BackOffPolicy in your retries, you need to create a bean of type LoadBalancedRetryFactory and override the createBackOffPolicy method:
@Configuration
+public class MyConfiguration {
+ @Bean
+ LoadBalancedRetryFactory retryFactory() {
+ return new LoadBalancedRetryFactory() {
+ @Override
+ public BackOffPolicy createBackOffPolicy(String service) {
+ return new ExponentialBackOffPolicy();
+ }
+ };
+ }
+}| + + | +
+client in the preceding examples should be replaced with your Ribbon client’s name.
+ |
+
If you want to add one or more RetryListener implementations to your retry functionality, you need to
+create a bean of type LoadBalancedRetryListenerFactory and return the RetryListener array
+you would like to use for a given service, as shown in the following example:
@Configuration
+public class MyConfiguration {
+ @Bean
+ LoadBalancedRetryListenerFactory retryListenerFactory() {
+ return new LoadBalancedRetryListenerFactory() {
+ @Override
+ public RetryListener[] createRetryListeners(String service) {
+ return new RetryListener[]{new RetryListener() {
+ @Override
+ public <T, E extends Throwable> boolean open(RetryContext context, RetryCallback<T, E> callback) {
+ //TODO Do you business...
+ return true;
+ }
+
+ @Override
+ public <T, E extends Throwable> void close(RetryContext context, RetryCallback<T, E> callback, Throwable throwable) {
+ //TODO Do you business...
+ }
+
+ @Override
+ public <T, E extends Throwable> void onError(RetryContext context, RetryCallback<T, E> callback, Throwable throwable) {
+ //TODO Do you business...
+ }
+ }};
+ }
+ };
+ }
+}Multiple RestTemplate objects
+If you want a RestTemplate that is not load-balanced, create a RestTemplate bean and inject it.
+To access the load-balanced RestTemplate, use the @LoadBalanced qualifier when you create your @Bean, as shown in the following example:\
@Configuration
+public class MyConfiguration {
+
+ @LoadBalanced
+ @Bean
+ RestTemplate loadBalanced() {
+ return new RestTemplate();
+ }
+
+ @Primary
+ @Bean
+ RestTemplate restTemplate() {
+ return new RestTemplate();
+ }
+}
+
+public class MyClass {
+ @Autowired
+ private RestTemplate restTemplate;
+
+ @Autowired
+ @LoadBalanced
+ private RestTemplate loadBalanced;
+
+ public String doOtherStuff() {
+ return loadBalanced.getForObject("http://stores/stores", String.class);
+ }
+
+ public String doStuff() {
+ return restTemplate.getForObject("http://example.com", String.class);
+ }
+}| + + | +
+Notice the use of the @Primary annotation on the plain RestTemplate declaration in the preceding example to disambiguate the unqualified @Autowired injection.
+ |
+
| + + | +
+If you see errors such as java.lang.IllegalArgumentException: Can not set org.springframework.web.client.RestTemplate field com.my.app.Foo.restTemplate to com.sun.proxy.$Proxy89, try injecting RestOperations or setting spring.aop.proxyTargetClass=true.
+ |
+
Spring WebFlux WebClient as a Load Balancer Client
+WebClient can be configured to use the LoadBalancerClient. LoadBalancerExchangeFilterFunction is auto-configured if spring-webflux is on the classpath. The following example shows how to configure a WebClient to use load balancer:
public class MyClass {
+ @Autowired
+ private LoadBalancerExchangeFilterFunction lbFunction;
+
+ public Mono<String> doOtherStuff() {
+ return WebClient.builder().baseUrl("http://stores")
+ .filter(lbFunction)
+ .build()
+ .get()
+ .uri("/stores")
+ .retrieve()
+ .bodyToMono(String.class);
+ }
+}The URI needs to use a virtual host name (that is, a service name, not a host name).
+The LoadBalancerClient is used to create a full physical address.
Ignore Network Interfaces
+Sometimes, it is useful to ignore certain named network interfaces so that they can be excluded from Service Discovery registration (for example, when running in a Docker container).
+A list of regular expressions can be set to cause the desired network interfaces to be ignored.
+The following configuration ignores the docker0 interface and all interfaces that start with veth:
spring: + cloud: + inetutils: + ignoredInterfaces: + - docker0 + - veth.*+
You can also force the use of only specified network addresses by using a list of regular expressions, as shown in the following example:
+spring: + cloud: + inetutils: + preferredNetworks: + - 192.168 + - 10.0+
You can also force the use of only site-local addresses, as shown in the following example: +.application.yml
+spring: + cloud: + inetutils: + useOnlySiteLocalInterfaces: true+
See Inet4Address.html.isSiteLocalAddress() for more details about what constitutes a site-local address.
+HTTP Client Factories
+Spring Cloud Commons provides beans for creating both Apache HTTP clients (ApacheHttpClientFactory) and OK HTTP clients (OkHttpClientFactory).
+The OkHttpClientFactory bean is created only if the OK HTTP jar is on the classpath.
+In addition, Spring Cloud Commons provides beans for creating the connection managers used by both clients: ApacheHttpClientConnectionManagerFactory for the Apache HTTP client and OkHttpClientConnectionPoolFactory for the OK HTTP client.
+If you would like to customize how the HTTP clients are created in downstream projects, you can provide your own implementation of these beans.
+In addition, if you provide a bean of type HttpClientBuilder or OkHttpClient.Builder, the default factories use these builders as the basis for the builders returned to downstream projects.
+You can also disable the creation of these beans by setting spring.cloud.httpclientfactories.apache.enabled or spring.cloud.httpclientfactories.ok.enabled to false.
Enabled Features
+Spring Cloud Commons provides a /features actuator endpoint.
+This endpoint returns features available on the classpath and whether they are enabled.
+The information returned includes the feature type, name, version, and vendor.
Feature types
+There are two types of 'features': abstract and named.
+Abstract features are features where an interface or abstract class is defined and that an implementation the creates, such as DiscoveryClient, LoadBalancerClient, or LockService.
+The abstract class or interface is used to find a bean of that type in the context.
+The version displayed is bean.getClass().getPackage().getImplementationVersion().
Named features are features that do not have a particular class they implement, such as "Circuit Breaker", "API Gateway", "Spring Cloud Bus", and others. These features require a name and a bean type.
+Declaring features
+Any module can declare any number of HasFeature beans, as shown in the following examples:
@Bean
+public HasFeatures commonsFeatures() {
+ return HasFeatures.abstractFeatures(DiscoveryClient.class, LoadBalancerClient.class);
+}
+
+@Bean
+public HasFeatures consulFeatures() {
+ return HasFeatures.namedFeatures(
+ new NamedFeature("Spring Cloud Bus", ConsulBusAutoConfiguration.class),
+ new NamedFeature("Circuit Breaker", HystrixCommandAspect.class));
+}
+
+@Bean
+HasFeatures localFeatures() {
+ return HasFeatures.builder()
+ .abstractFeature(Foo.class)
+ .namedFeature(new NamedFeature("Bar Feature", Bar.class))
+ .abstractFeature(Baz.class)
+ .build();
+}Each of these beans should go in an appropriately guarded @Configuration.
Spring Cloud Compatibility Verification
+Due to the fact that some users have problem with setting up Spring Cloud application, we’ve decided +to add a compatibility verification mechanism. It will break if your current setup is not compatible +with Spring Cloud requirements, together with a report, showing what exactly went wrong.
+At the moment we verify which version of Spring Boot is added to your classpath.
+Example of a report
+*************************** +APPLICATION FAILED TO START +*************************** + +Description: + +Your project setup is incompatible with our requirements due to following reasons: + +- Spring Boot [2.1.0.RELEASE] is not compatible with this Spring Cloud release train + + +Action: + +Consider applying the following actions: + +- Change Spring Boot version to one of the following versions [1.2.x, 1.3.x] . +You can find the latest Spring Boot versions here [https://spring.io/projects/spring-boot#learn]. +If you want to learn more about the Spring Cloud Release train compatibility, you can visit this page [https://spring.io/projects/spring-cloud#overview] and check the [Release Trains] section.+
In order to disable this feature, set spring.cloud.compatibility-verifier.enabled to false.
+If you want to override the compatible Spring Boot versions, just set the
+spring.cloud.compatibility-verifier.compatible-boot-versions property with a comma separated list
+of compatible Spring Boot versions.