Non-blocking health check for load balancers

[megian]

Context

A new health check endpoint available at /lb-check was added in v23.0.2. The execution is running in the event loop which means this check is responsive also in overloaded situations when Keycloak needs to handle many requests waiting in request queue. This behavior is useful, for example, in multi-site deployment where we do not want to fail over to the other site under heavy load. The endpoint is currently checking availability of the embedded and external Infinispan caches. Other checks may be added later.

This endpoint is not available by default. To enable it, run Keycloak with feature multi-site. Proceed to Enabling and disabling features guide for more details.

Alternatives

Keep the current