Amazon X-Ray SDK for Java

The X-Ray SDK for Java is a set of libraries for Java web applications that provide classes and methods for generating and sending trace data to the X-Ray daemon. Trace data includes information about incoming HTTP requests served by the application, and calls that the application makes to downstream services using the Amazon SDK, HTTP clients, or an SQL database connector. You can also create segments manually and add debug information in annotations and metadata.

The X-Ray SDK for Java is an open source project. You can follow the project and submit issues and pull requests on GitHub: github.com/aws/aws-xray-sdk-java

Start by adding AWSXRayServletFilter as a servlet filter to trace incoming requests. A servlet filter creates a segment. While the segment is open, you can use the SDK client's methods to add information to the segment and create subsegments to trace downstream calls. The SDK also automatically records exceptions that your application throws while the segment is open.

Starting in release 1.3, you can instrument your application using aspect-oriented programming (AOP) in Spring. What this means is that you can instrument your application, while it is running on Amazon, without adding any code to your application's runtime.

Next, use the X-Ray SDK for Java to instrument your Amazon SDK for Java clients by including the SDK Instrumentor submodule in your build configuration. Whenever you make a call to a downstream Amazon Web Service or resource with an instrumented client, the SDK records information about the call in a subsegment. Amazon Web Services and the resources that you access within the services appear as downstream nodes on the trace map to help you identify errors and throttling issues on individual connections.

If you don't want to instrument all downstream calls to Amazon Web Services, you can leave out the Instrumentor submodule and choose which clients to instrument. Instrument individual clients by adding a TracingHandler to an Amazon SDK service client.

Other X-Ray SDK for Java submodules provide instrumentation for downstream calls to HTTP web APIs and SQL databases. You can use the X-Ray SDK for Java versions of HTTPClient and HTTPClientBuilder in the Apache HTTP submodule to instrument Apache HTTP clients. To instrument SQL queries, add the SDK's interceptor to your data source.

After you start using the SDK, customize its behavior by configuring the recorder and servlet filter. You can add plugins to record data about the compute resources running your application, customize sampling behavior by defining sampling rules, and set the log level to see more or less information from the SDK in your application logs.

Record additional information about requests and the work that your application does in annotations and metadata. Annotations are simple key-value pairs that are indexed for use with filter expressions, so that you can search for traces that contain specific data. Metadata entries are less restrictive and can record entire objects and arrays — anything that can be serialized into JSON.

When you have a lot of instrumented clients in your code, a single request segment can contain many subsegments, one for each call made with an instrumented client. You can organize and group subsegments by wrapping client calls in custom subsegments. You can create a custom subsegment for an entire function or any section of code, and record metadata and annotations on the subsegment instead of writing everything on the parent segment.

Submodules

You can download the X-Ray SDK for Java from Maven. The X-Ray SDK for Java is split into submodules by use case, with a bill of materials for version management:

If you use Maven or Gradle to build your application, add the X-Ray SDK for Java to your build configuration.

For reference documentation of the SDK's classes and methods, see Amazon X-Ray SDK for Java API Reference.

Requirements

The X-Ray SDK for Java requires Java 8 or later, Servlet API 3, the Amazon SDK, and Jackson.

The SDK depends on the following libraries at compile and runtime:

These dependencies are declared in the SDK's pom.xml file and are included automatically if you build using Maven or Gradle.

If you use a library that is included in the X-Ray SDK for Java, you must use the included version. For example, if you already depend on Jackson at runtime and include JAR files in your deployment for that dependency, you must remove those JAR files because the SDK JAR includes its own versions of Jackson libraries.

Dependency management

The X-Ray SDK for Java is available from Maven:

If you use Maven to build your application, add the SDK as a dependency in your pom.xml file.

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.amazonaws</groupId>
      <artifactId>aws-xray-recorder-sdk-bom</artifactId>
      <version>2.11.0</version>
      <type>pom</type>
      <scope>import</scope>
    </dependency>
  </dependencies>
</dependencyManagement>
<dependencies>
  <dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-xray-recorder-sdk-core</artifactId>
  </dependency>
  <dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-xray-recorder-sdk-apache-http</artifactId>
  </dependency>
  <dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-xray-recorder-sdk-aws-sdk</artifactId>
  </dependency>
  <dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-xray-recorder-sdk-aws-sdk-instrumentor</artifactId>
  </dependency>
  <dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-xray-recorder-sdk-sql-postgres</artifactId>
  </dependency>
  <dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-xray-recorder-sdk-sql-mysql</artifactId>
  </dependency>
</dependencies>

For Gradle, add the SDK as a compile-time dependency in your build.gradle file.

dependencies {
  compile("org.springframework.boot:spring-boot-starter-web")
  testCompile("org.springframework.boot:spring-boot-starter-test")
  compile("com.amazonaws:aws-java-sdk-dynamodb")
  compile("com.amazonaws:aws-xray-recorder-sdk-core")
  compile("com.amazonaws:aws-xray-recorder-sdk-aws-sdk")
  compile("com.amazonaws:aws-xray-recorder-sdk-aws-sdk-instrumentor")
  compile("com.amazonaws:aws-xray-recorder-sdk-apache-http")
  compile("com.amazonaws:aws-xray-recorder-sdk-sql-postgres")
  compile("com.amazonaws:aws-xray-recorder-sdk-sql-mysql")
  testCompile("junit:junit:4.11")
}
dependencyManagement {
    imports {
        mavenBom('com.amazonaws:aws-java-sdk-bom:1.11.39')
        mavenBom('com.amazonaws:aws-xray-recorder-sdk-bom:2.11.0')
    }
}

If you use Elastic Beanstalk to deploy your application, you can use Maven or Gradle to build on-instance each time you deploy, instead of building and uploading a large archive that includes all of your dependencies. See the sample application for an example that uses Gradle.

Amazon X-Ray metrics for the X-Ray SDK for Java

This topic describes the Amazon X-Ray namespace, metrics, and dimensions. You can use the X-Ray SDK for Java to publish unsampled Amazon CloudWatch metrics from your collected X-Ray segments. These metrics are derived from the segment’s start and end time, and the error, fault, and throttled status flags. Use these trace metrics to expose retries and dependency issues within subsegments.

CloudWatch is a metrics repository. A metric is the fundamental concept in CloudWatch and represents a time-ordered set of data points. You (or Amazon Web Services) publish metrics data points into CloudWatch and you retrieve statistics about those data points as an ordered set of time-series data.

Metrics are uniquely defined by a name, a namespace, and one or more dimensions. Each data point has a timestamp and, optionally, a unit of measure. When you request statistics, the returned data stream is identified by namespace, metric name, and dimension.

For more information about CloudWatch, see the Amazon CloudWatch User Guide.

X-Ray CloudWatch metrics

The ServiceMetrics/SDK namespace includes the following metrics.

X-Ray CloudWatch dimensions

Use the dimensions in the following table to refine the metrics returned for your X-Ray instrumented Java applications.

Enable X-Ray CloudWatch metrics

Use the following procedure to enable trace metrics in your instrumented Java application.