Async Daemon HealthChecks ​

Marten supports a customizable HealthChecks. This can be useful when running the async daemon in a containerized environment such as Kubernetes. The check will verify that no projection's progression lags more than maxEventLag behind the HighWaterMark. The default maxEventLag is 100. Read more about events progression tracking and HighWaterMark in Async Daemon documentation.

The maxEventLag setting controls how far behind the HighWaterMark any async projection is allowed to lag before it's considered unhealthy. E.g. if the HighWaterMark is 1000 and an a system with 3 async projections ProjA, ProjB and ProjC are processed respectively to sequence number 899, 901 and 901 then the system will be considered unhealthy with a maxEventLag of 100 (1000 - 899 = 101), BUT healthy with a mavEventLag of 101 or higher.

Example configuration: ​

// Add HealthCheck
Services.AddHealthChecks().AddMartenAsyncDaemonHealthCheck(maxEventLag: 500);

// Map HealthCheck Endpoint
app.MapHealthChecks("/health");