// Do not edit this file (e.g. go instead to src/main/asciidoc)
:jdkversion: 1.8
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]
image::https://badges.gitter.im/spring-cloud/spring-cloud-sleuth.svg[Gitter, link="https://gitter.im/spring-cloud/spring-cloud-sleuth?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge"]
== 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, timestamped events, key-value
annotations (tags), 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.
*Annotation:* is used to record existence of an event in time. Some of the core annotations used to define
the start and stop of a request are:
- *cs* - Client Sent - The client has made a request. This annotation depicts the start of the span.
- *sr* - Server Received - The server side got the request and will start processing it.
If one subtracts the cs timestamp from this timestamp one will receive the network latency.
- *ss* - Server Sent - Annotated upon completion of request processing (when the response
got sent back to the client). If one subtracts the sr timestamp from this timestamp one
will receive the time needed by the server side to process the request.
- *cr* - Client Received - Signifies the end of the span. The client has successfully received the
response from the server side. If one subtracts the cs timestamp from this timestamp one
will receive the whole time needed by the client to receive the response from the server.
Visualization of what *Span* and *Trace* will look in a system together with the Zipkin annotations:
image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-sleuth/master/docs/src/main/asciidoc/images/trace-id.png[Trace Info propagation]
Each color of a note signifies a span (7 spans - from *A* to *G*). If you have such information in the note:
[source]
Trace Id = X
Span Id = D
Client Sent
That means that the current span has *Trace-Id* set to *X*, *Span-Id* set to *D*. It also has emitted
*Client Sent* event.
This is how the visualization of the parent / child relationship of spans would look like:
image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-sleuth/master/docs/src/main/asciidoc/images/parents.png[Parent child relationship]
=== Purpose
In the following sections the example from the image above will be taken into consideration.
==== Distributed tracing with Zipkin
Altogether there are *10 spans* . If you go to traces in Zipkin you will see this number:
image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-sleuth/master/docs/src/main/asciidoc/images/zipkin-traces.png[Traces]
However if you pick a particular trace then you will see *7 spans*:
image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-sleuth/master/docs/src/main/asciidoc/images/zipkin-ui.png[Traces Info propagation]
NOTE: When picking a particular trace you will see merged spans. That means that if there were 2 spans sent to
Zipkin with Server Received and Server Sent / Client Received and Client Sent
annotations then they will presented as a single span.
In the image depicting the visualization of what *Span* and *Trace* is you can see 20
colorful labels. How does it happen that in Zipkin 10 spans are received?
- 2 span *A* labels signify span started and closed. Upon closing a single span is sent to Zipkin.
- 4 span *B* labels are in fact are single span with 4 annotations. However this span is composed of
two separate instances. One sent from service 1 and one from service 2. So in fact two span instances will be sent
to Zipkin and merged there.
- 2 span *C* labels signify span started and closed. Upon closing a single span is sent to Zipkin.
- 4 span *B* labels are in fact are single span with 4 annotations. However this span is composed of
two separate instances. One sent from service 2 and one from service 3. So in fact two span instances will be sent
to Zipkin and merged there.
- 2 span *E* labels signify span started and closed. Upon closing a single span is sent to Zipkin.
- 4 span *B* labels are in fact are single span with 4 annotations. However this span is composed of
two separate instances. One sent from service 2 and one from service 4. So in fact two span instances will be sent
to Zipkin and merged there.
- 2 span *G* labels signify span started and closed. Upon closing a single span is sent to Zipkin.
So 1 span from *A*, 2 spans from *B*, 1 span from *C*, 2 spans from *D*, 1 span from *E*, 2 spans from *F* and 1 from *G*.
Altogether *10* spans.
==== Log correlation
When grepping the logs of those four applications by trace id equal to e.g. `2485ec27856c56f4` one would get the following:
[source]
service1.log:2016-02-26 11:15:47.561 INFO [service1,2485ec27856c56f4,2485ec27856c56f4,true] 68058 --- [nio-8081-exec-1] i.s.c.sleuth.docs.service1.Application : Hello from service1. Calling service2
service2.log:2016-02-26 11:15:47.710 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Hello from service2. Calling service3 and then service4
service3.log:2016-02-26 11:15:47.895 INFO [service3,2485ec27856c56f4,1210be13194bfe5,true] 68060 --- [nio-8083-exec-1] i.s.c.sleuth.docs.service3.Application : Hello from service3
service2.log:2016-02-26 11:15:47.924 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Got response from service3 [Hello from service3]
service4.log:2016-02-26 11:15:48.134 INFO [service4,2485ec27856c56f4,1b1845262ffba49d,true] 68061 --- [nio-8084-exec-1] i.s.c.sleuth.docs.service4.Application : Hello from service4
service2.log:2016-02-26 11:15:48.156 INFO [service2,2485ec27856c56f4,9aa10ee6fbde75fa,true] 68059 --- [nio-8082-exec-1] i.s.c.sleuth.docs.service2.Application : Got response from service4 [Hello from service4]
service1.log:2016-02-26 11:15:48.182 INFO [service1,2485ec27856c56f4,2485ec27856c56f4,true] 68058 --- [nio-8081-exec-1] i.s.c.sleuth.docs.service1.Application : Got response from service2 [Hello from service2, response from service3 [Hello from service3] and from service4 [Hello from service4]]
If you're using a log aggregating tool like https://www.elastic.co/products/kibana[Kibana],
http://www.splunk.com/[Splunk] etc. you can order the events that took place. An example of
Kibana would look like this:
image::https://raw.githubusercontent.com/spring-cloud/spring-cloud-sleuth/master/docs/src/main/asciidoc/images/kibana.png[Log correlation with Kibana]
If you want to use https://www.elastic.co/guide/en/logstash/current/index.html[Logstash] here is the Grok pattern for Logstash:
[source]
filter {
# pattern matching logback pattern
grok {
match => { "message" => "%{TIMESTAMP_ISO8601:timestamp}\s+%{LOGLEVEL:severity}\s+\[%{DATA:service},%{DATA:trace},%{DATA:span},%{DATA:exportable}\]\s+%{DATA:pid}---\s+\[%{DATA:thread}\]\s+%{DATA:class}\s+:\s+%{GREEDYDATA:rest}" }
}
}
NOTE: If you want to use Grok together with the logs from Cloud Foundry you have to use this pattern:
[source]
filter {
# pattern matching logback pattern
grok {
match => { "message" => "(?m)OUT\s+%{TIMESTAMP_ISO8601:timestamp}\s+%{LOGLEVEL:severity}\s+\[%{DATA:service},%{DATA:trace},%{DATA:span},%{DATA:exportable}\]\s+%{DATA:pid}---\s+\[%{DATA:thread}\]\s+%{DATA:class}\s+:\s+%{GREEDYDATA:rest}" }
}
}
=== Adding to the project
In general if you want to profit only from Spring Cloud Sleuth without the Zipkin integration just add
the *spring-cloud-starter-sleuth* module to your project.
If you want both Sleuth and Zipkin just add the *spring-cloud-starter-zipkin* dependency.
== 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 logs:
+
----
2016-02-02 15:30:57.902 INFO [bar,6bfd228dc00d216b,6bfd228dc00d216b,false] 23030 --- [nio-8081-exec-3] ...
2016-02-02 15:30:58.372 ERROR [bar,6bfd228dc00d216b,6bfd228dc00d216b,false] 23030 --- [nio-8081-exec-3] ...
2016-02-02 15:31:01.936 INFO [bar,46ab0d418373cbc9,46ab0d418373cbc9,false] 23030 --- [nio-8081-exec-4] ...
----
+
notice the `[appname,traceId,spanId,exportable]` entries from the MDC:
- *spanId* - the id of a specific operation that took place
- *appname* - the name of the application that logged the span
- *traceId* - the id of the latency graph that contains the span
- *exportable* - whether the log should be exported to Zipkin or not. When would you like the span not to be
exportable? In the case in which you want to wrap some operation in a Span and have it written to the logs
only.
* 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.
* Sleuth records timing information to aid in latency analysis. Using sleuth, you can pinpoint causes of
latency in your applications. Sleuth is written to not log too much, and to not cause your production application to crash.
- propagates structural data about your call-graph in-band, and the rest out-of-band.
- includes opinionated instrumentation of layers such as HTTP
- includes sampling policy to manage volume
- can report to a Zipkin system for query and visualization
* Instruments common ingress and egress points from Spring applications (servlet filter, async endpoints,
rest template, scheduled actions, message channels, zuul filters, feign client).
* Sleuth includes default logic to join a trace across http or messaging boundaries. For example, http propagation
works via Zipkin-compatible request headers. This propagation logic is defined and customized via
`SpanInjector` and `SpanExtractor` implementations.
* Provides simple metrics of accepted / dropped spans.
* If `spring-cloud-sleuth-zipkin` then the app will generate and collect Zipkin-compatible traces.
By default it sends them via HTTP to a Zipkin server on localhost (port 9411).
Configure the location of the service using `spring.zipkin.baseUrl`.
* If `spring-cloud-sleuth-stream` then the app will generate and collect traces via https://github.com/spring-cloud/spring-cloud-stream[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).
IMPORTANT: If using Zipkin or Stream, configure the percentage of spans exported using `spring.sleuth.sampler.percentage`
(default 0.1, i.e. 10%). *Otherwise you might think that Sleuth is not working cause it's omitting some spans.*
NOTE: the SLF4J MDC is always set and logback users will immediately see the trace and span ids in logs per the example
above. Other logging systems have to configure their own formatter to get the same result. The default is
`logging.pattern.level` set to `%clr(%5p) %clr([${spring.application.name:},%X{X-B3-TraceId:-},%X{X-B3-SpanId:-},%X{X-Span-Export:-}]){yellow}`
(this is a Spring Boot feature for logback users).
*This means that if you're not using SLF4J this pattern WILL NOT be automatically applied*.
== Building
=== 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.
IMPORTANT: There are 2 different versions of language level used in Spring Cloud Sleuth. Java 1.7 is used for main sources and
Java 1.8 is used for tests. When importing your project to an IDE please activate the `ide` Maven profile to turn on
Java 1.8 for both main and test sources. Of course remember that you MUST NOT use Java 1.8 features in the main sources. If you do
so your app will break during the Maven build.
== 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 of Conduct
This project adheres to the Contributor Covenant https://github.com/spring-cloud/spring-cloud-build/blob/master/docs/src/main/asciidoc/code-of-conduct.adoc[code of
conduct]. By participating, you are expected to uphold this code. Please report
unacceptable behavior to spring-code-of-conduct@pivotal.io.
=== 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://raw.githubusercontent.com/spring-cloud/spring-cloud-build/master/spring-cloud-dependencies-parent/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).