High Availability

Two instances

IMPulse allows running multiple instances to ensure high availability.

The first IMPulse instance creates a .lock.d directory in the DATA_PATH↰ directory to lock file operations. Other instances start in standby mode and wait until the first instance is shut down or becomes unavailable.

Check the /readyz endpoint to get the instance state. It responds with 200 if the instance is ready and primary, and 503 if the instance is in standby.

The /livez endpoint is used for liveness checks and always returns 200 if the container is alive, regardless of whether it's in standby or primary mode. This endpoint is available in both modes and should be used for Kubernetes liveness probes.

When running multiple IMPulse instances, configure your proxy (Nginx or another) to use the /readyz endpoint for readiness checks, routing traffic only to the primary instance. Use /livez for liveness checks to ensure containers are restarted if they become unresponsive. See API for endpoint details.

Read-only filesystem

If the filesystem of the server where IMPulse is running becomes full, IMPulse will continue working. Data won't be lost as long as IMPulse continues running.

Danger

Do not stop or restart it

ERROR log messages about the issue will be produced.

This mechanism doesn't solve the problem, but protects from its consequences for some time.

To avoid such problems, configure monitoring for the server where IMPulse is running.