Monitoring QIE HA Node Instances

In this article a node instance is a running QIE engine in a high availability cluster. The term does not refer to the mapping, condition, or destination nodes that make up a channel.

Monitoring the node instances in a cluster becomes an important aspect of deploying QIE in a docker environment. QIE needs to ensure that every node instance is healthy and that an instance which crashes is replaced with a new one.

To monitor a QIE node instance, you must first set the -Dqie.probePort={somePort} (QIE_PROBEPORT environment variable) so that QIE starts a listening service on the port.

Once the service is listening, you can configure your container manager to use this port for status checks. It is configured using a simple HTTP-GET command on that port. When QIE is healthy and running the response is an HTTP Status 200. If it is not running then there is no response, and if QIE is not available due to starting up or shutting down, then the response be an HTTP Status 503.

It can also be used for Kubernetes startup, readiness, and health probes. See Appendix A for an example.