Enabling the Java Profiler

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The profiler is shipped within Datadog tracing libraries. If you are already using APM to collect traces for your application, you can skip installing the library and go directly to enabling the profiler.

Requirements

The Datadog Profiler requires JDK Flight Recorder. The Datadog Profiler library is supported in OpenJDK 11+, Oracle JDK 11+, OpenJDK 8 (version 8u262+) and Azul Zulu 8+ (version 8u212+). It is not supported in OpenJ9 as it doesn’t support the JDK Flight Recorder.

All JVM-based languages, such as Java, Scala, Groovy, Kotlin, and Clojure are supported.

Installation

To begin profiling applications:

If you are already using Datadog, upgrade your Agent to version 7.20.2+ or 6.20.2+. If you don’t have APM enabled to set up your application to send data to Datadog, in your Agent, set the DD_APM_ENABLED environment variable to true and listening to the port 8126/TCP.
Download dd-java-agent.jar, which contains the Java Agent class files:
```
wget -O dd-java-agent.jar 'https://dtdg.co/latest-java-tracer'
```
Note: Profiler is available in the dd-java-agent.jar library in versions 0.55+.

Set -Ddd.profiling.enabled flag or DD_PROFILING_ENABLED environment variable to true. Your service invocation should look like:

java \
    -javaagent:dd-java-agent.jar \
    -Ddd.service=<YOUR_SERVICE> \
    -Ddd.env=<YOUR_ENVIRONMENT> \
    -Ddd.version=<YOUR_VERSION> \
    -Ddd.profiling.enabled=true \
    -XX:FlightRecorderOptions=stackdepth=256 \
    -jar <YOUR_SERVICE>.jar <YOUR_SERVICE_FLAGS>

Recommendation: Specify dd.service, dd.env, and dd.version so you can slice and dice your profiles across these dimensions.

You can also use environment variables to set the parameters as such:

export DD_SERVICE=<YOUR_SERVICE>
export DD_ENV=<YOUR_ENV>
export DD_VERSION=<YOUR_VERSION>
export DD_PROFILING_ENABLED=true
java \
    -javaagent:dd-java-agent.jar \
    -XX:FlightRecorderOptions=stackdepth=256 \
    -jar <YOUR_SERVICE>.jar <YOUR_SERVICE_FLAGS>

Note: The -javaagent argument needs to be before -jar, adding it as a JVM option rather than an application argument. For more information, see the Oracle documentation:

# Good:
java -javaagent:dd-java-agent.jar ... -jar my-service.jar -more-flags
# Bad:
java -jar my-service.jar -javaagent:dd-java-agent.jar ...

After a minute or two, you can visualize your profiles on the Datadog APM > Profiling page.

Enabling the allocation profiler

In dd-java-agent v0.84.0+ and Java 15 and lower, the allocation profiler is opt-in because it can use excessive CPU in allocation-heavy applications. This isn’t common, so you may want to try it in a staging environment to see if it affects your application. To enable it, see Enabling the allocation profiler.

Configuration

You can configure the profiler using the following environment variables:

Environment variable	Type	Description
`DD_PROFILING_ENABLED`	Boolean	Alternate for `-Ddd.profiling.enabled` argument. Set to `true` to enable profiler.
`DD_PROFILING_ALLOCATION_ENABLED`	Boolean	Alternate for `-Ddd.profiling.allocation.enabled` argument. Set to `true` to enable the allocation profiler. It requires the profiler to be enabled already.
`DD_SERVICE`	String	Your service name, for example, `web-backend`.
`DD_ENV`	String	Your environment name, for example: `production`.
`DD_VERSION`	String	The version of your service.
`DD_TAGS`	String	Tags to apply to an uploaded profile. Must be a list of `<key>:<value>` separated by commas such as: `layer:api, team:intake`.

Not sure what to do next?

The Getting Started with Profiler guide takes a sample service with a performance problem and shows you how to use Continuous Profiler to understand and fix the problem.

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