Adds a local docker-compose env to test JMXFetch inside the agent

Dockerfile.agentbase

@@ -0,0 +1,25 @@
+FROM eclipse-temurin:8u382-b05-jdk AS build
+
+WORKDIR /app
+
+# Copy the pom.xml and Maven files and install the dependencies
+COPY .mvn .mvn/
+COPY pom.xml mvnw mvnw.cmd ./
+
+# Use a maven cache to speed up iteration
+RUN --mount=type=cache,id=mavenCache,target=/root/.m2,sharing=locked \
+    set -eu &&  \
+    ./mvnw dependency:resolve;
+
+# Copy the source code and build the JAR file
+COPY src/ src/
+
+RUN --mount=type=cache,id=mavenCache,target=/root/.m2,sharing=locked \
+    set -eu &&  \
+    ./mvnw -DskipTests clean package assembly:single;
+
+
+FROM datadog/agent:7-jmx AS final
+
+COPY --from=build /app/target/jmxfetch-*-jar-with-dependencies.jar /opt/datadog-agent/bin/agent/dist/jmx/jmxfetch.jar
+

README.md

@@ -30,6 +30,8 @@ The distribution will be created under ```target/```.
 
 To use this JAR in the Agent, see [these docs](https://github.com/DataDog/datadog-agent/blob/main/docs/dev/checks/jmxfetch.md).
 
+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.
@@ -72,6 +74,15 @@ the recommended JDK version for development, use `sdk env` to activate it.
 If you set the system property `-Djmxfetch.filelinelogging=true`, this will enable all log output to
 include the line number which emitted a given log.
 
+### Local Testing
+You can utilize the provided testing server `misbehaving-jmx-server` with the
+preset `./docker-compose.yaml` file. This will run 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
 

docker-compose.yaml

@@ -0,0 +1,28 @@
+---
+version: "3.9"
+
+services:
+  # The docker compose service name is used as the hostname for the misbehaving-jmx-server
+  # Note it is in the entrypoint as the --rmi-host and in the AD label as the hostname
+  # that the Agent should reach out to.
+  jmx-test-server:
+    build:
+      context: ./tools/misbehaving-jmx-server/
+    # Override entrypoint to specify the docker-compose service name as the RMI host
+    entrypoint: ["java", "-cp", "misbehavingjmxserver-1.0-SNAPSHOT-jar-with-dependencies.jar", "org.datadog.misbehavingjmxserver.App", "--rmi-host", "jmx-test-server"]
+    ports:
+      - "1099:1099"
+    labels:
+      com.datadoghq.ad.checks: '{"misbehaving":{"init_config":{"is_jmx":true},"instances":[{"host":"jmx-test-server","port":"1099","collect_default_jvm_metrics":false,"max_returned_metrics":300000,"conf":[{"include":{"domain":"Bohnanza"}}]}]}}'
+  datadog:
+    build:
+      context: .
+      dockerfile: ./Dockerfile.agentbase
+    pid: host
+    environment:
+     - DD_API_KEY=000000001
+     - DD_JMX_TELEMETRY_ENABLED=true
+    volumes:
+     - /var/run/docker.sock:/var/run/docker.sock
+     - /proc/:/host/proc/:ro
+     - /sys/fs/cgroup:/host/sys/fs/cgroup:ro