This page documents internal code details and design decisions.
The resulting Docker image contains the following:
- Base linux distribution - this provides standard Linux libraries (such as "glibc") and utilities (such as "ls" and "grep") required by MQ
- MQ installation (under
/opt/mqm
) - Three additional programs, to enable running in a containerized environment:
runmqserver
- The main process, which creates and runs a queue managerrunmqdevserver
- The main process for MQ Advanced for Developerschkmqhealthy
- Checks the health of the queue manager. This can be used by (say) a Kubernetes liveness probe.chkmqready
- Checks if the queue manager is ready for work. This can be used by (say) a Kubernetes readiness probe.chkmqstarted
- Checks if the queue manager has successfully started. This can be used by (say) a Kubernetes startup probe.
The runmqserver
command has the following responsibilities:
- Checks license acceptance
- Sets up
/var/mqm
- MQ data directory needs to be set up at container creation time. This is done using the
crtmqdir
utility, which was introduced in MQ V9.0.3 - It assumes that a storage volume for data is mounted under
/mnt/mqm
. It creates a sub-directory for the MQ data, so/var/mqm
is a symlink which resolves to/mnt/mqm/data
. The reason for this is that it's not always possible to change the ownership of an NFS mount point directly (/var/mqm
needs to be owned by "mqm"), but you can change the ownership of a sub-directory.
- MQ data directory needs to be set up at container creation time. This is done using the
- Acts like a daemon
- Handles UNIX signals, like SIGTERM
- Works as PID 1, so is responsible for reaping zombie processes
- Creating and starting a queue manager
- Configuring the queue manager, by running any MQSC scripts found under
/etc/mqm
- Starts the MQ web server (if enabled)
- Starting Prometheus metrics generation for the queue manager (if enabled)
- Indicates to the
chkmqready
command that configuration is complete, and that normal readiness checking can happen. This is done by writing a file into/run/runmqserver
In addition, for MQ Advanced for Developers only, the web server is started.
The runmqdevserver
command is added to the MQ Advanced for Developers image only. It does the following, before invoking runmqserver
:
- Sets passwords based on supplied environment variables
- Generates MQSC files to put in
/etc/mqm
, based on a template, which is updated with values based on supplied environment variables. - If requested, it creates TLS key stores under
/run/runmqserver
, and configures MQ and the web server to use them
Prometheus metrics are generated for the queue manager as follows:
- A connection is established with the queue manager
- Metrics are discovered by subscribing to topics that provide meta-data on metric classes, types and elements
- Subscriptions are then created for each topic that provides this metric data
- Metrics are initialised using Prometheus names mapped from their element descriptions
- The metrics are then registered with the Prometheus registry as Prometheus Gauges
- Publications are processed on a periodic basis to retrieve the metric data
- An HTTP server is setup to listen for requests from Prometheus on
/metrics
port9157
- Prometheus requests are handled by updating the Prometheus Gauges with the latest metric data
- These updated Prometheus Gauges are then collected by the Prometheus registry