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v0.31.2 / Operations-Guide / Enable Jmx

Monitoring Your Metabase Instance

This guide assumes that you have the VisualVM tool installed locally. VisualVM is included with OpenJDK and the Oracle JDK and is found in the bin directory of the JDK install. Some Linux distributions separate VisualVM from the JDK, in which case it’s a separate visualvm package.

Connecting to a Local Metabase Instance

If you have VisualVM installed on your Metabase server and are able to run VisualVM there, this is the easiest path as there is no need to setup remote communication with your metabase instance. In this scenario, start Metabase like you would normally and separately start VisualVM. Metabase will be listed under are running your Metabase instance

localprocess

Connecting to a Remote Metabase Instance

Monitoring a remote Metabase instance (or a local instance running in a docker container) is probably more common, but requires a more setup. First we need to specify some system properties that lets the JVM know that we want to allow remote monitoring. Assuming we are running Metabase using java -jar metabase.jar, we’d need change the invocation to the below command, which includes the properties:

java --add-to-start=jmx,jmx-remote \
     -Dcom.sun.management.jmxremote \
     -Dcom.sun.management.jmxremote.port=1099 \
     -Dcom.sun.management.jmxremote.rmi.port=1099 \
     -Dcom.sun.management.jmxremote.authenticate=false \
     -Dcom.sun.management.jmxremote.ssl=false \
     -Dcom.sun.management.jmxremote.local.only=false \
     -Djava.rmi.server.hostname=<Metabase Hostname> \
     -jar metabase.jar

Port 1099 is a typical RMI/JMX port, but it can be any accessible port.

Note: The above command opens up your application to monitoring by anyone and should only be used when on a trusted network for a short period of time. Securing this connection is possible, see the Oracle docs for more information.

Users running Metabase in a docker container will need to specify the system properties detailed above and will also need to ensure the port is open. Docker allows specifying environment variables via a separate file that can be passed into the docker run invocation. You can create a file called metabase-vars.env with JAVA_OPTS specified:

JAVA_OPTS=-Dcom.sun.management.jmxremote.port=1099 -Dcom.sun.management.jmxremote.rmi.port=1099 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.local.only=false -Djava.rmi.server.hostname=<Metabase Hostname>

Note: This file expects to have each environment variable on it’s own line with no line breaks

docker run --env-file=metabase-vars.env -d -p 3000:3000 -p 1099:1099 -h <Metabase Hostname> --name metabase metabase/metabase

The addition -p 1099:1099 opens the JMX port for monitoring and the --env-file=metabase-vars.env passes in the extra JMX related environment variables. With the instance started, VisualVM needs to know how to connect to the running instance. First add a new remote instance:

addremotehost

Then use the hostname you specified above:

sethostname

Note: Your local machine needs to be able to refer to the hostname you specified which might require a hosts entry

addjmxhost

The port specified for the JMX host needs to match the system property and the exposed port (if using Docker):

jmxport

Next open the new remote JMX process:

jmxinstance

Runtime Information

Connecting to a running Metabase instance with VisualVM will make lots of runtime information available. This guide won’t go over all of possibilities of the tool, but will highlight a few important pieces.

When running into memory related issues, typically the first question we want to know is what is consuming extra memory? A heap dump will take a snapshot of everything in memory at that specific point of time. That memory snapshot can be analyzed later by tools like the Eclipse Memory Analyzer Tool. Create a heap dump from the “Monitor” tab:

heapdump

Another useful picture of a running Metabase system is a Thread Dump. In cases when Metabase appears hung or extremely slow, a thread dump will indicate what each thread is executing (or blocked on) for that specific point in time. Collect a thread dump via the “Threads” tab:

threaddump