Package ratpack.core.health

Interface HealthCheck

All Known Implementing Classes:

HikariHealthCheck

public interface HealthCheck

Reports on the health of some aspect of the system.

Health checks are typically used for reporting and monitoring purposes. The results exposed by health checks can be reported via HTTP by a HealthCheckHandler.

The actual check is implemented by the check(Registry) method, that returns a promise for a HealthCheck.Result.

The inspiration for health checks in Ratpack comes from the Dropwizard Metrics library. Ratpack health checks are different in that they support non blocking checks, and all health checks require a unique name.

See Also:

HealthCheckHandler

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	HealthCheck.Result	The result of a health check.

Method Summary

Modifier and Type	Method	Description
Promise<HealthCheck.Result>	check(Registry registry)	Checks the health of the component, providing a promise for the result.
static Promise<HealthCheckResults>	checkAll(Registry registry, Iterable<? extends HealthCheck> healthChecks)	Execute health checks.
static Promise<HealthCheckResults>	checkAll(Registry registry, Throttle throttle, Iterable<? extends HealthCheck> healthChecks)	Execute health checks.
String	getName()	The unique name of the health check.
static HealthCheck	of(String name, Function<? super Registry,? extends Promise<HealthCheck.Result>> func)	Convenience factory for health check implementations.

Method Detail

getName

String getName()

The unique name of the health check.

Each health check within an application must have a unique name.

Returns:

the name of the health check

check

Promise<HealthCheck.Result> check(Registry registry)
                           throws Exception

Checks the health of the component, providing a promise for the result.

This method returns a promise to allow check implementations to be asynchronous. If the implementation does not need to be asynchronous, the result can be returned via Promise.value(Object).

The registry argument is the server registry, from which other supporting objects can be obtained.

If this method throws an exception, it is logically equivalent to returned an unhealthy result with the thrown exception.

If the method returns a failed promise, it will be converted to a result using HealthCheck.Result.unhealthy(Throwable).

Parameters:

registry - the server registry

Returns:

a promise for the result

Throws:

Exception - any

of

static HealthCheck of(String name,
                      Function<? super Registry,? extends Promise<HealthCheck.Result>> func)

Convenience factory for health check implementations.

 import ratpack.test.exec.ExecHarness;
 import ratpack.exec.Promise;
 import ratpack.exec.registry.Registry;
 import ratpack.core.health.HealthCheck;
 import static org.junit.jupiter.api.Assertions.*;

 public class Example {
   public static void main(String... args) throws Exception {
     HealthCheck.Result result = ExecHarness.yieldSingle(e ->
       HealthCheck.of("test", registry ->
         Promise.value(HealthCheck.Result.healthy())
       ).check(Registry.empty())
     ).getValue();

     assertTrue(result.isHealthy());
   }
 }
 

Parameters:

name - a name of health check

func - a health check implementation

Returns:

a named health check implementation

checkAll

static Promise<HealthCheckResults> checkAll(Registry registry,
                                            Iterable<? extends HealthCheck> healthChecks)

Execute health checks.

The checks will be executed in parallel.

Parameters:

registry - the registry to pass to each health check

healthChecks - the health checks to execute

Returns:

the results

Since:

1.5

checkAll

static Promise<HealthCheckResults> checkAll(Registry registry,
                                            Throttle throttle,
                                            Iterable<? extends HealthCheck> healthChecks)

Execute health checks.

The checks will be executed in parallel.

Parameters:

registry - the registry to pass to each health check

throttle - the throttle to use to constrain the parallelism of the checks

healthChecks - the health checks to execute

Returns:

the results

Since:

1.5