spring-cloud-sleuth/README.adoc

// Do not edit this file (e.g. go instead to src/main/asciidoc)

image::https://api.travis-ci.org/spring-cloud/spring-cloud-sleuth.svg?branch=master[Build Status, link=https://travis-ci.org/spring-cloud/spring-cloud-sleuth]

== Spring Cloud Sleuth

Spring Cloud Sleuth implements a distributed tracing solution for http://cloud.spring.io[Spring Cloud].

=== Terminology

Spring Cloud Sleuth borrows http://research.google.com/pubs/pub36356.html[Dapper's] terminology.

*Span:* The basic unit of work. For example, sending an RPC is a new span, as is sending a response to an RPC. Span's are identified by a unique 64-bit ID for the span and another 64-bit ID for the trace the span is a part of.  Spans also have other data, such as descriptions, key-value annotations, the ID of the span that caused them, and process ID's (normally IP address).

Spans are started and stopped, and they keep track of their timing information.  Once you create a span, you must stop it at some point in the future.

*Trace:* A set of spans forming a tree-like structure.  For example, if you are running a distributed big-data store, a trace might be formed by a put request.



== Features

* Adds trace and span ids to the Slf4J MDC, so you can extract all the logs from a given trace or span in a log aggregator. Example configuration:
+
[source,yaml]
----
logging:
  pattern:
    level: '[trace=%X{X-Trace-Id:-},span=%X{X-Span-Id:-}] %5p'
----
+
(notice the `%X` entries from the MDC).

* Optionally log span data in JSON format for harvesting in a log aggregator (set `spring.sleuth.log.json.enabled=true`).

* Provides an abstraction over common distributed tracing data models: traces, spans (forming a DAG), annotations, key-value annotations. Loosely based on HTrace, but Zipkin (Dapper) compatible.

* Instruments common ingress and egress points from Spring applications (servlet filter, rest template, scheduled actions, message channels, zuul filters, feign client).

* If `spring-cloud-sleuth-zipkin` then the app will generate and collect Zipkin-compatible traces (using Brave). By default it sends them via Thrift to a Zipkin collector service on localhost (port 9410). Configure the location of the service using `spring.zipkin.[host,port]`.

* If `spring-cloud-sleuth-stream` then the app will generate and collect traces via Spring Cloud Stream. Your app automatically becomes a producer of tracer messages that are sent over your broker of choice (e.g. RabbitMQ, Apache Kafka, Redis).

== Running the samples

1. Optionally run https://github.com/openzipkin/zipkin[Zipkin], e.g. via docker compose (there's a `docker-compose.yml` in https://github.com/spring-cloud-incubator/spring-cloud-sleuth[Spring Cloud Sleuth], or in https://github.com/openzipkin/docker-zipkin[Docker Zipkin]
7. Run the zipkin sample application (and set `sample.zipkin.enabled=false` if you have no collector running)
8. Hit `http://localhost:3380`, `http://localhost:3380/call`, `http://localhost:3380/async` for some interesting sample traces (the app callas back to itself).
9. Goto `http://localhost:8082` for zipkin web (8080 if running locally from source, the host is the docker host, so if you are using boot2docker it will be different)

NOTE: You can see the zipkin spans without the UI (in logs) if you run the sample with `sample.zipkin.enabled=false`.

There are a few samples with slightly different features:

* `spring-cloud-sleuth-sample`: vanilla (no zipkin) web app that calls back to itself on various endpoints ("/", "/call", "/async")

* `spring-cloud-sleuth-sample-zipkin`: same as vanilla sample but with zipkin

* `spring-cloud-sleuth-sample-messaging`: a Spring Integration application with two HTTP endpoints ("/" and "/xform")

* `spring-cloud-sleuth-sample-ribbon`: two endpoints ("/" and "/call") that make calls to the "zipkin" sample via Ribbon. Also has `@EnableZUulProxy" so if the other samples are running they are proxied at "/messaging", "/zipkin", "/vanilla" (see "/routes" for a list).

The Ribbon sample makes an interesting demo or playground for learning about zipkin. In the screenshot below you can see a trace with 3 spans - it starts in the "testSleuthRibbon" app and crosses to "testSleuthMessaging" for the next 2 spans.

image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-sleuth/master/docs/src/main/asciidoc/images/zipkin-trace-screenshot.png[Eample Zipkin Screenshot]

> The fact that the first trace in says "testSleuthMessaging" seems to be a bug in the UI (it has some annotations from that service, but it originates in the "testSleuthRibbon" service).

== Building

:jdkversion: 1.7

=== Basic Compile and Test

To build the source you will need to install JDK {jdkversion}.

Spring Cloud uses Maven for most build-related activities, and you
should be able to get off the ground quite quickly by cloning the
project you are interested in and typing

----
$ ./mvnw install
----

NOTE: You can also install Maven (>=3.3.3) yourself and run the `mvn` command
in place of `./mvnw` in the examples below. If you do that you also
might need to add `-P spring` if your local Maven settings do not
contain repository declarations for spring pre-release artifacts.

NOTE: Be aware that you might need to increase the amount of memory
available to Maven by setting a `MAVEN_OPTS` environment variable with
a value like `-Xmx512m -XX:MaxPermSize=128m`. We try to cover this in
the `.mvn` configuration, so if you find you have to do it to make a
build succeed, please raise a ticket to get the settings added to
source control.

For hints on how to build the project look in `.travis.yml` if there
is one. There should be a "script" and maybe "install" command. Also
look at the "services" section to see if any services need to be
running locally (e.g. mongo or rabbit).  Ignore the git-related bits
that you might find in "before_install" since they're related to setting git
credentials and you already have those.

The projects that require middleware generally include a
`docker-compose.yml`, so consider using
http://compose.docker.io/[Docker Compose] to run the middeware servers
in Docker containers. See the README in the
https://github.com/spring-cloud-samples/scripts[scripts demo
repository] for specific instructions about the common cases of mongo,
rabbit and redis.

NOTE: If all else fails, build with the command from `.travis.yml` (usually
`./mvnw install`).

=== Documentation

The spring-cloud-build module has a "docs" profile, and if you switch
that on it will try to build asciidoc sources from
`src/main/asciidoc`. As part of that process it will look for a
`README.adoc` and process it by loading all the includes, but not
parsing or rendering it, just copying it to `${main.basedir}`
(defaults to `${basedir}`, i.e. the root of the project). If there are
any changes in the README it will then show up after a Maven build as
a modified file in the correct place. Just commit it and push the change.

=== Working with the code
If you don't have an IDE preference we would recommend that you use
http://www.springsource.com/developer/sts[Spring Tools Suite] or
http://eclipse.org[Eclipse] when working with the code. We use the
http://eclipse.org/m2e/[m2eclipe] eclipse plugin for maven support. Other IDEs and tools
should also work without issue.

==== Importing into eclipse with m2eclipse
We recommend the http://eclipse.org/m2e/[m2eclipe] eclipse plugin when working with
eclipse. If you don't already have m2eclipse installed it is available from the "eclipse
marketplace".

Unfortunately m2e does not yet support Maven 3.3, so once the projects
are imported into Eclipse you will also need to tell m2eclipse to use
the `.settings.xml` file for the projects.  If you do not do this you
may see many different errors related to the POMs in the
projects.  Open your Eclipse preferences, expand the Maven
preferences, and select User Settings.  In the User Settings field
click Browse and navigate to the Spring Cloud project you imported
selecting the `.settings.xml` file in that project.  Click Apply and
then OK to save the preference changes.

NOTE: Alternatively you can copy the repository settings from https://github.com/spring-cloud/spring-cloud-build/blob/master/.settings.xml[`.settings.xml`] into your own `~/.m2/settings.xml`.

==== Importing into eclipse without m2eclipse
If you prefer not to use m2eclipse you can generate eclipse project metadata using the
following command:

[indent=0]
----
	$ ./mvnw eclipse:eclipse
----

The generated eclipse projects can be imported by selecting `import existing projects`
from the `file` menu.

==== Adding Project Lombok Agent

Spring Cloud uses http://projectlombok.org/features/index.html[Project Lombok]
to generate getters and setters etc. Compiling from the command line this
shouldn't cause any problems, but in an IDE you need to add an agent
to the JVM. Full instructions can be found in the Lombok website. The
sign that you need to do this is a lot of compiler errors to do with
missing methods and fields, e.g.

[indent=0]
----
The method getInitialStatus() is undefined for the type EurekaInstanceConfigBean    EurekaDiscoveryClientConfiguration.java /spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka   line 120    Java Problem
The method getInitialStatus() is undefined for the type EurekaInstanceConfigBean    EurekaDiscoveryClientConfiguration.java /spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka   line 121    Java Problem
The method setNonSecurePort(int) is undefined for the type EurekaInstanceConfigBean EurekaDiscoveryClientConfiguration.java /spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka   line 112    Java Problem
The type EurekaInstanceConfigBean.IdentifyingDataCenterInfo must implement the inherited abstract method DataCenterInfo.getName()   EurekaInstanceConfigBean.java   /spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/eureka   line 131    Java Problem
The method getId() is undefined for the type ProxyRouteLocator.ProxyRouteSpec   PreDecorationFilter.java    /spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/pre line 60 Java Problem
The method getLocation() is undefined for the type ProxyRouteLocator.ProxyRouteSpec PreDecorationFilter.java    /spring-cloud-netflix-core/src/main/java/org/springframework/cloud/netflix/zuul/filters/pre line 55 Java Problem
----

==== Importing into Intellij
Spring Cloud projects use annotation processing, particularly Lombok, which requires configuration
or you will encounter compile problems. It also needs a specific version of maven and a profile
enabled. Intellij 14.1+ requires some configuration to ensure these are setup properly.

 1. Click Preferences, Plugins. *Ensure Lombok is installed*
 2. Click New, Project from Existing Sources, choose your spring-cloud-sleuth directory
 3. Choose Maven, and select Environment Settings. *Ensure you are using Maven 3.3.3*
 4. In the next screen, *Select the profile `spring`* click Next until Finish.
 5. Click Preferences, "Build, Execution, Deployment", Compiler, Annotation Processors. *Click Enable Annotation Processing*
 6. Click Build, Rebuild Project, and you are ready to go!

==== Importing into other IDEs
Maven is well supported by most Java IDEs. Refer to you vendor documentation.


== Contributing

Spring Cloud is released under the non-restrictive Apache 2.0 license,
and follows a very standard Github development process, using Github
tracker for issues and merging pull requests into master. If you want
to contribute even something trivial please do not hesitate, but
follow the guidelines below.

=== Sign the Contributor License Agreement
Before we accept a non-trivial patch or pull request we will need you to sign the
https://support.springsource.com/spring_committer_signup[contributor's agreement].
Signing the contributor's agreement does not grant anyone commit rights to the main
repository, but it does mean that we can accept your contributions, and you will get an
author credit if we do.  Active contributors might be asked to join the core team, and
given the ability to merge pull requests.

=== Code Conventions and Housekeeping
None of these is essential for a pull request, but they will all help.  They can also be
added after the original pull request but before a merge.

* Use the Spring Framework code format conventions. If you use Eclipse
  you can import formatter settings using the
  `eclipse-code-formatter.xml` file from the
  https://github.com/spring-cloud/spring-cloud-build/blob/master/spring-cloud-build/eclipse-code-formatter.xml[Spring
  Cloud Build] project. If using IntelliJ, you can use the
  http://plugins.jetbrains.com/plugin/6546[Eclipse Code Formatter
  Plugin] to import the same file.
* Make sure all new `.java` files to have a simple Javadoc class comment with at least an
  `@author` tag identifying you, and preferably at least a paragraph on what the class is
  for.
* Add the ASF license header comment to all new `.java` files (copy from existing files
  in the project)
* Add yourself as an `@author` to the .java files that you modify substantially (more
  than cosmetic changes).
* Add some Javadocs and, if you change the namespace, some XSD doc elements.
* A few unit tests would help a lot as well -- someone has to do it.
* If no-one else is using your branch, please rebase it against the current master (or
  other target branch in the main project).
* When writing a commit message please follow http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html[these conventions],
  if you are fixing an existing issue please add `Fixes gh-XXXX` at the end of the commit
  message (where XXXX is the issue number).