Monitoring Docker using JMX
---------------------------

You can monitor |cp| Docker deployments by using Java Management Extensions (JMX).

Configure Environment
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To use JMX with Docker containers, you must set the following properties:

.. codewithvars:: bash

    java.rmi.server.hostname=<JMX_HOSTNAME>
    com.sun.management.jmxremote.local.only=false
    com.sun.management.jmxremote.rmi.port=<JMX_PORT>
    com.sun.management.jmxremote.port=<JMX_PORT>

Note about ``hostname``:
  The JMX client needs to be able to connect to ``java.rmi.server.hostname``.
  The default for bridged network is the bridged IP so you will only be able to connect from another Docker container.
  For host network, this is the IP that the hostname on the host resolves to.

  The hostname is set to ``hostname -i`` in the Docker container. If you have more that one network configured for the container, ``hostname -i`` gives you all the IPs, the default is to pick the first IP (or network).

Configure Security
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To set security on JMX, you can follow the SSL and authentication sections in this guide: https://docs.oracle.com/javase/8/docs/technotes/guides/management/agent.html.

Configure Kafka and |zk|
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Settings
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``KAFKA_JMX_PORT``
    JMX Port.


``KAFKA_JMX_OPTS``
    JMX options.

``KAFKA_JMX_HOSTNAME``
    hostname associated with locally created remote objects.

The default setting is as follows:

.. codewithvars:: bash

  -Djava.rmi.server.hostname=127.0.0.1 -Dcom.sun.management.jmxremote=true -Dcom.sun.management.jmxremote.authenticate=false  -Dcom.sun.management.jmxremote.ssl=false

Launching Kafka and |zk| with JMX Enabled
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To launch Kafka and |zk| with JMX enabled, set the ``KAFKA_JMX_PORT`` and ``KAFKA_JMX_HOSTNAME`` for both components.  Here are examples of the Docker ``run`` commands for each service:

.. codewithvars:: bash

  docker run -d \
    --name=zk-jmx \
    --net=host \
    -e ZOOKEEPER_TICK_TIME=2000 \
    -e ZOOKEEPER_CLIENT_PORT=32181 \
    -e KAFKA_JMX_PORT=39999 \
    -e KAFKA_JMX_HOSTNAME=`docker-machine ip confluent`
    confluentinc/cp-zookeeper:|release|

  docker run -d \
    --name=kafka-jmx \
    --net=host \
    -e KAFKA_BROKER_ID=1 \
    -e KAFKA_ZOOKEEPER_CONNECT=localhost:32181/jmx \
    -e KAFKA_ADVERTISED_LISTENERS=PLAINTEXT://localhost:39092 \
    -e KAFKA_JMX_PORT=49999 \
    -e KAFKA_JMX_HOSTNAME=`docker-machine ip confluent` \
    -e KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR=1 \
    confluentinc/cp-kafka:|release|

Note: in the KAFKA_JMX_HOSTNAME environment variable example above, it assumes you have a Docker machine named "Confluent".  You should substitute with your Docker machine name where appropriate.