How to connect VisualVM to Docker


Connect Visual VM to a docker container

In order to connect Visual VM to Docker you need to open the ports between the host and the container as well as specify the jmxremote port because the container, from the local perspective, is a remote JVM. You need to start java with a few extra parameters, so your Dockerfile might end with something like this:

ENTRYPOINT ["java -jar", "myjar.jar" "<port>","","","<port>","-Djava.rmi.server.hostname=<docker ip>"]

Where <port> is something like 8000 throughout, and the <docker ip> is the IP address that you can get from your boot2docker or docker machine configuration. If you're using docker machine you can use:

docker-machine ls # find your machine name
docker-machine env <machine name>

Then you want to run your container with the port open and specified:

docker run -p 80:80 --expose <port> -p <port>:<port> t test 

And then in VisualVM you can click "Add JMX Connection" and specify the same <docker ip> and the port you've opened. Once you've done that you should have the connection open. If you perform heap dumps you'll need to copy the file from the docker container. You can copy a file from docker like so:

docker ps #get your container id
docker cp <container id>:/tmp/heapdump-1447875373977.hprof ~/Desktop/dump

Don't forget to copy the filename that VisualVM tells you when you click heap dump.

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