Internals

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 manager
- chkmqhealthy - 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.

runmqserver

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.
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