README.md

spring

Provides annotation support for projects that use Spring.

Quickstart

Add the dependencies to your project.

Replace SPRING_VERSION with the version of spring you're using.

For Maven add to your pom.xml:

<dependencies>
  <!-- census -->
  <dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-api</artifactId>
    <version>0.26.0</version>
  </dependency>
  <dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-contrib-spring</artifactId>
    <version>0.26.0</version>
  </dependency>
  <dependency>
    <groupId>io.opencensus</groupId>
    <artifactId>opencensus-impl</artifactId>
    <version>0.26.0</version>
    <scope>runtime</scope>
  </dependency>
  
  <!-- spring aspects -->
  <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-aspects</artifactId>
    <version>SPRING_VERSION</version>
    <scope>runtime</scope>
  </dependency>
  
</dependencies>

For Gradle add to your dependencies:

compile 'io.opencensus:opencensus-api:0.26.0'
compile 'io.opencensus:opencensus-contrib-spring:0.26.0'
runtime 'io.opencensus:opencensus-impl:0.26.0'
runtime 'org.springframework:spring-aspects:SPRING_VERSION'

Features

Traced Annotation

The opencensus-contrib-spring package provides support for a @Traced annotation that can be applied to methods. When applied, the method will be wrapped in a Span, https://github.com/census-instrumentation/opencensus-specs/blob/master/trace/Span.md

If the method throws an exception, the Span will be marked with a status of Status.UNKNOWN and the stack trace will be added to the span as an annotation.

To enable the @Traced annotation, include the CensusSpringAspect bean.

  <!-- traces explicit calls to Traced -->
  <bean id="censusAspect" class="io.opencensus.contrib.spring.aop.CensusSpringAspect">
    <constructor-arg ref="tracer"/>
  </bean>

Database Support

The opencensus-contrib-spring package also includes support for tracing database calls. When database support is included, all calls to java.sql.PreparedStatement.execute* will be wrapped in a Span in the same way that @Traced wraps methods.

To enable database support, include the CensusSpringSqlAspect bean.

  <!-- traces all SQL calls -->
  <bean id="censusSQLAspect" class="io.opencensus.contrib.spring.aop.CensusSpringSqlAspect">
    <constructor-arg ref="tracer"/>
  </bean>

Complete Spring XML configuration

The following contains a complete spring xml file to configure opencensus-contrib-spring with support for both @Traced and database connection tracing.

Note: This example does not include the configuration of any exporters. That will need to be done separately.

TBD:* Include examples of spring with exporters.

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.2.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">

  <aop:aspectj-autoproxy/>

  <!-- traces explicit calls to Traced -->
  <bean id="censusAspect" class="io.opencensus.contrib.spring.aop.CensusSpringAspect">
    <constructor-arg ref="tracer"/>
  </bean>

  <!-- traces all SQL calls -->
  <bean id="censusSQLAspect" class="io.opencensus.contrib.spring.aop.CensusSpringSqlAspect">
    <constructor-arg ref="tracer"/>
  </bean>

  <!-- global tracer -->
  <bean id="tracer" class="io.opencensus.trace.Tracing" factory-method="getTracer"/>
</beans>

Traced Usage

Once configured, you can use the @Traced annotation to indicate that a method should be wrapped with a Span. By default, @Traced will use the name of the method as the span name. However, @Traced supports an optional name attribute to allow a custom span name to be specified.

  @Traced()
  void example1() {
    // do work
  }
  
  // a custom span name can also be provided to Traced
  @Traced(name = "custom-span-name")
  void example2() {
    // do moar work
  }

Notes

opencensus-contrib-spring support only enables annotations. You will still need to configure opencensus and register exporters / views.

Java Versions

Java 6 or above is required for using this artifact.

About the aop package

opencensus-contrib-spring makes heavy use of Aspect Oriented Programming AOP to add behavior to annotations. Fortunately, Spring supports this natively so we can leverage the capabilities they've already built in.