jmx-exporter in a Docker with extra features

This project consists of a dockerised JMX Exporter image, based on the original project created by sscaling (sscaling/docker-jmx-prometheus-exporter), using alpine-java, dumb-init and fetching the official released version of jmx_exporter from the maven central repository

The version of the official prometheus jmx-exporter currently built and supported is 0.9 (and the http version, not used as java agent).

This version of the docker includes the following extra features:

• Automatic Configuration: config.xml creation based on environment variables and templates.
• Static Configuration: if config.xml is mapped into /opt/jmx_exporter/config/, then environment variables won't be considered, and the provided configuration will be used.
• Flexible rules: via environment variables we can select the rules to apply to the configuration (only if Automatic Configuration feature is used and only 1 rules file allowed).
• check_init : With check init enabled (by default is disabled), jmx_exporter will wait until the remote jmx port is available (this feature uses nagios check_jmx plugin) before starting the exporter itself.

Environment variables supported to get different behavior/configuration:

• SERVICE_PORT -- Port to receive http /metrics requests from Prometheus.
• DEST_HOST -- Host to monitor via jmx.
• DEST_PORT -- JMX port of destination host.
• RULES_MODULE -- Rules to apply.
• JVM_LOCAL_OPTS -- Options for local jvm.
• JMX_LOCAL_PORT -- Port for local jmxremote.
• CHECK_INIT -- (true | false) - Enable/disable check_init feature.
• CHECK_INIT_ACTION -- (exit | continue) -- What to do in case of failing checks.
• CHECK_INIT_MAX_DELAY -- Maximum time to spend checking remote JVM.
• CHECK_INIT_INTERVAL -- Interval between attempts (in seconds).

Supported modules in current version (only one can be selected):

• default (this will translate all mbeans to metrics)
• kafka-0-2-8

The objectives of implementing these features are:

• Being able to use the same docker image of jmx_exporter for different scenarios, as the configuration can be built from environment variables.
• In a Kubernetes environment, run jmx_exporter docker as an extra container (sidecar) in the pod to monitor (in this case DEST_HOST should be localhost).
• In a Kubernetes environment, run jmx_exporter docker in a dedicated pod, in order to monitor another pod (in this case DEST_HOST should be the name of a k8s service pointing to the pod).

Default Settings

If no environment variables or volumes are provided to the image, the exporter will have the following default behavior:

• HTTP listening port: 9072
• Remote JVM to connect to: localhost: 7072
  • Rules to apply: default (which means a simple pattern: ".*" )
  • Local jmxremote port: 7071 (in case someone wants to check this JVM)
• CHECK_INIT module will be disabled by default.

Building docker image

docker build -t eedugon/jmx-exporter .

Running

docker run --rm -p "9072:9072" eedugon/jmx-exporter

Then you can visit the metrics endpoint: http://127.0.0.1:9072/metrics (assuming docker is running on localhost)

Note: If you want to test jmx_exporter monitoring it's own metrics, you could set DEST_PORT to 7071, which is the jmx port of the jmx_exporter itself.

docker run --rm -e "DEST_PORT=7071" -p "9072:9072" eedugon/jmx-exporter

Configuration modes: Auto generation of config.xml vs static configuration

This docker allows 2 configuration modes, automatic generation of config.xml (default) or providing a static configuration file via volume mount.

Example of setting our own config:

docker run --rm -p "9072:9072" -v "$PWD/config.yml:/opt/jmx_exporter/config/config.yml" eedugon/jmx-exporter

The configuration options are documented: https://github.com/prometheus/jmx_exporter

Environment variables

Additionally, the following environment variables can be defined

• SERVICE_PORT -- port to receive http /metrics requests
• DEST_HOST -- host to monitor via jmx
• DEST_PORT -- jmx port of destination host
• RULES_MODULE -- rules to apply
• JVM_LOCAL_OPTS -- options for local jvm
• JMX_LOCAL_PORT -- port for local jmxremote

CHECK_INIT considerations

I still need to check if we can use nagios check_jmx plugin inside this project. Anyway, it can be removed from the code easily:

• Remove from start.sh the block of CHECK_INIT feature plus all CHECK_INIT variables definition.
• Remove from Dockerfile the copy of resources/check_jmx to the docker.