.. _health_checks:

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Health Checks
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Create default Health Check
---------------------------

The functional interface ``HealthCheck`` together with the annotations ``@Liveness`` and ``@Readiness`` are the key concepts to bring up a new
health check. Following code snipping shows a very basic example on how to use the interface. The parameter ``isDefault``
with value ``true`` makes sure that this health check is covered during server startup (see section :ref:`Settings <Endpoint_Settings>` in administration guide) and exposed to ``/health``.

.. code-block:: java

    @Liveness(isDefault = true)
    public class SampleHealthCheck implements HealthCheck{

        @Override
        public HealthCheckResponse call() {
            return HealthCheckResponse.named("sample-default")
                            .state(true)
                            .withData("key", "value")
                            .build();
        }

    }

.. important:: Make sure to use ``@Liveness`` and ``@Readiness`` from package ``io.ox.proxy.health.impl`` otherwise health checks could not be registered.

Create custom Health Check Endpoint
-----------------------------------

To create a health check which should not be exposed via ``/health`` ``/health/live`` or ``/health/ready`` change health check´s default to ``false``,  create a new resource class with proper ``@PATH`` annotation and send health check´s response back to caller.

Custom Health Check:
 .. code-block:: java

    @Liveness(isDefault = false)
    public class SampleHealthCheck implements HealthCheck{

        @Override
        public HealthCheckResponse call() {
            return HealthCheckResponse.named("sample-custom")
                            .state(true)
                            .withData("key", "value")
                            .build();
        }

    }

Custom Endpoint:
 .. code-block:: java

    @Path("/custom")
    public class SampleResource {

        @Path("/sample")
        @GET
        @Produces(MediaType.APPLICATION_JSON)
        public Response getCallHealthCheck() {
            // The Health Check to call
            return Response.ok().entity(new SampleHealthCheck().call()).build();
        }

    }

.. important:: The ``SampleHealthCheck`` class can be placed in a package of your choise but make sure to place ``SampleResource`` in package ``io.ox.proxy.jersey.resource`` otherwise this resource could not be bind to JAX-RS context.