Debugging any JVM in a Docker container

Thanks to JAVA_TOOL_OPTIONS variable it’s easy to run any JVM-based Docker image in debug mode. All we have to do is  add environment variable definition „JAVA_TOOL_OPTIONS=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005” in docker run or docker-compose.yml and expose port to connect debugger

# docker run
-e "JAVA_TOOL_OPTIONS=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005" \
-p 5005:5005

# docker-compose
    environment:
      - "JAVA_TOOL_OPTIONS=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005"
    ports:
      -  5005:5005

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If it's possible, it's handy to extend application entrypoint

# Set debug options if required
if [ x"${JAVA_ENABLE_DEBUG}" != x ] && [ "${JAVA_ENABLE_DEBUG}" != "false" ]; then
    java_debug_args="-agentlib:jdwp=transport=dt_socket,server=y,suspend=${JAVA_DEBUG_SUSPEND:-n},address=${JAVA_DEBUG_PORT:-5005}"
fi

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