Probes

Functionality that gives the application two methods for obtaining probes on a private port about service readiness/liveness.

Requires a HTTP server module.

Liveness

This sample is responsible for indicating whether the application is currently alive. Kora tries to start giving this sample as early as possible, so that orchestrators know for sure that there are no problems at startup and don't try to restart the application.

Example of the HTTP server path configuration for probe ping described in the HttpServerConfig class (default values are specified):

Hocon YAML

httpServer {
    privateApiHttpLivenessPath = "/system/liveness"
}

httpServer:
  privateApiHttpLivenessPath: "/system/liveness"

Creating your custom viability sample requires the component to implement the interface:

public interface LivenessProbe {

    @Nullable
    LivenessProbeFailure probe();
}

The sample shall return LivenessProbeFailure on error, and null on success.

Readiness

This sample is responsible for indicating whether the application is currently ready to run.

Example of the HTTP server path configuration for probe ping described in the HttpServerConfig class (default values are specified):

Hocon YAML

httpServer {
    privateApiHttpReadinessPath = "/system/readiness"
}

httpServer:
  privateApiHttpReadinessPath: "/system/readiness"

Creating your custom viability sample requires the component to implement the interface:

public interface ReadinessProbe {

    @Nullable
    ReadinessProbeFailure probe();
}

The sample shall return ReadinessProbeFailure in case of error, and null in case of success.

Recommendations

Tip

We strongly discourage runs that test external dependencies such as databases or other services.

If external dependencies are not available, we recommend using the CircuitBreaker pattern.

A good example for ReadinessProbe is prob that returns an error while the service is warming up.