Change log

JMXFetch

JMXFetch is the new tool to collect metrics from JMX Servers in order to be sent to Datadog (http://www.datadoghq.com) It is called by the Datadog Agent (https://github.com/Datadog/datadog-agent) and sends metrics back to the Agent using the Java dogstatsd library.

How to contribute code?

First of all and most importantly, thank you for sharing.

If you want to submit code, please fork this repository and submit pull requests against the master branch.

Please note that the Agent is licensed for simplicity's sake under a simplified BSD license, as indicated in the LICENSE file. Exceptions are marked with LICENSE-xxx where xxx is the component name. If you do not agree with the licensing terms and wish to contribute code nonetheless, please email us at info@datadoghq.com before submitting your pull request.

Building from source

JMXFetch uses Maven for its build system. The repo contains a Maven Wrapper, so you don't need to download and install Maven.

In order to generate the JAR artifact, run the ./mvnw clean compile assembly:single command in the cloned directory.

The distribution will be created under target/.

To use this JAR in the Agent, see these docs.

To test your JAR with a local test-server, see below instructions for "Local Testing"

Note

If you want build all the JAR files for JMXFetch, you need to use an older JDK version like JDK 8. There is a known issue where the build can't find javadoc command on modern JDKs. The quickest way to build these JAR files is to use Docker:

docker run -it --rm \
    --name my-maven-project \
    -v "$(pwd)":/usr/src/app \
    -w /usr/src/app \
    eclipse-temurin:8-jdk ./mvnw -DskipTests clean package

Coding standards

JMXFetch uses Checkstyle with Google Java Style to enforce coding standards.

To perform a Checkstyle analysis and outputs violations, run:

./mvnw checkstyle::check

Checkstyle analysis is automatically executed prior to compiling the code, testing.

Generated code

JMXFetch uses Lombok to modify classes and generate additional code at runtime. You may need to enable annotation processors to compile in your IDE.

Useful Developer Settings

JDK version management

sdkman is recommended to manage multiple versions of Java. If you are an sdkman user, there is a config file present in this project with the recommended JDK version for development, use sdk env to activate it.

Logging Options

The logging output is configured in code in CustomLogger.java. The following system properties will affect the format of the log records.

• -Djmxfetch.filelinelogging=true
  • All log records will include the specific file and line number which emitted that log.
• -Djmxfetch.millisecondlogging=true
  • All log records will include milliseconds in the timestamp, rather than the default 'second' timestamp resolution.

Local Testing

You can utilize the provided testing server misbehaving-jmx-server with the preset ./docker-compose.yaml file. This runs two containers, one is the test server and the other is the Datadog Agent running your local JAR's version of JMXFetch.

1. docker compose up -d

Testing

To run unit test, issue the following command:

./mvnw test

Some tests utilize TestContainers which requires a docker client. You can rely on the CI to run these, or if you have docker installed on Linux these should work out of the box.

If you're on macOS or Windows, docker desktop is architected to run a linux VM which then runs all your containers. This makes the networking a bit different and you should use the following command to run the tests.

docker run -it --rm -e TESTCONTAINERS_HOST_OVERRIDE=host.docker.internal -v $PWD:$PWD -w $PWD -v /var/run/docker.sock:/var/run/docker.sock eclipse-temurin:8-jdk ./mvnw test

This version runs the maven jmxfetch tests within a container as well, which works as long as the TEST_CONTAINERS_HOST_OVERRIDE env var is set.

Testing Deployments

You can test the deployment by using the Nexus3 OSS image. To do so you need to:

• Use the local endpoints in the pom.xml:

...
    <distributionManagement>
        <snapshotRepository>
          <id>nexus</id>
          <url>http://localhost:8081/repository/maven-snapshots/</url>
        </snapshotRepository>
        <repository>
            <id>nexus</id>
            <url>http://localhost:8081/repository/maven-releases/</url>
        </repository>
    </distributionManagement>
...
    <build>
        <plugins>
            ...
            <plugin>
                <groupId>org.sonatype.plugins</groupId>
                ...
                <configuration>
                    <serverId>nexus</serverId>
                    <nexusUrl>http://localhost:8081/repository/maven-releases/</nexusUrl>
                    <autoReleaseAfterClose>false</autoReleaseAfterClose>
                </configuration>
            </plugin>
        </plugins>
    </build>
...

• Start the Nexus 3 container:

docker run --rm -d \
  --name nexus3 \
  -p 8081:8081 \
  -e INSTALL4J_ADD_VM_PARAMS='-Xms512m -Xmx512m -XX:MaxDirectMemorySize=512m -Djava.util.prefs.userRoot=/nexus-data/javaprefs' \
  sonatype/nexus3

• Wait for the server to be up on http://localhost:8081
• Get the administrator password:

docker exec -it nexus3 cat /nexus-data/admin.password

• Export those values for the build:

export GPG_KEY="<Key ID for signing the artifact>"
export GPG_PASSPHRASE="<Password for the private key of $GPG_KEY>"
export SONATYPE_USER="admin"
export SONATYPE_PASS="<Password for Nexus admin from previous step>"

• Run the deploy with the appropriate skipStaging flag:

./mvnw -DskipTests -DskipStaging=true -DperformRelease=true --settings settings.xml clean deploy

If you do this correctly, the artifact will be available in the Nexus container at http://localhost:8081/#browse/browse:maven-releases.

Note: If you are trying to redeploy the same version of the artifact to the local Nexus repository, you will need to change the Deployment Policy for maven-releases to Allow redeploy in the UI otherwise the subsequent publishes will fail.

Running:

Get help on usage:
java -jar jmxfetch-0.49.2-SNAPSHOT-jar-with-dependencies.jar --help

Updating Maven Wrapper

To upgrade the Maven Wrapper, you need to run:

./mvn wrapper:wrapper -Dmaven=<Maven Version X.Y.Z>

The easiest way to regenerate the wrapper files (mvnw, mvnw.cmd, .mvn/wrapper/maven-wrapper.jar and .mvn/wrapper/maven-wrapper.properties) is to use Docker:

docker run -it --rm \
    --name my-maven-project \
    -v "$(pwd)":/usr/src/app \
    -w /usr/src/app maven:3 mvn wrapper:wrapper -Dmaven=<Maven Version X.Y.Z>

Leave out the -Dmaven=<Maven Version X.Y.Z> to get the latest version of Maven.