Add Reactive probe (#1201)

spring-cloud-commons/src/main/java/org/springframework/cloud/client/discovery/ReactiveDiscoveryClient.java

@@ -16,7 +16,10 @@
 
 package org.springframework.cloud.client.discovery;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
 
 import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.core.Ordered;
@@ -26,9 +29,12 @@
  * Eureka or consul.io.
  *
  * @author Tim Ysewyn
+ * @author Olga Maciaszek-Sharma
  */
 public interface ReactiveDiscoveryClient extends Ordered {
 
+	Log LOG = LogFactory.getLog(ReactiveDiscoveryClient.class);
+
 	/**
 	 * Default order of the discovery client.
 	 */
@@ -60,11 +66,35 @@ public interface ReactiveDiscoveryClient extends Ordered {
 	 * <p>
 	 * The default implementation simply calls {@link #getServices()} - client
 	 * implementations can override with a lighter weight operation if they choose to.
+	 * @deprecated in favour of {@link ReactiveDiscoveryClient#reactiveProbe()}. This
+	 * method should not be used as is, as it contains a bug - the method called within
+	 * returns a {@link Flux}, which is not accessible for subscription or blocking from
+	 * within. We are leaving it with a deprecation in order not to bring downstream
+	 * implementations.
 	 */
+	@Deprecated
 	default void probe() {
+		if (LOG.isWarnEnabled()) {
+			LOG.warn("ReactiveDiscoveryClient#probe has been called. If you're calling this method directly, "
+					+ "use ReactiveDiscoveryClient#reactiveProbe instead.");
+		}
 		getServices();
 	}
 
+	/**
+	 * Can be used to verify the client is still valid and able to make calls.
+	 * <p>
+	 * A successful invocation with no exception thrown implies the client is able to make
+	 * calls.
+	 * <p>
+	 * The default implementation simply calls {@link #getServices()} and wraps it with a
+	 * {@link Mono} - client implementations can override with a lighter weight operation
+	 * if they choose to.
+	 */
+	default Mono<Void> reactiveProbe() {
+		return getServices().then();
+	}
+
 	/**
 	 * Default implementation for getting order of discovery clients.
 	 * @return order

spring-cloud-commons/src/main/java/org/springframework/cloud/client/discovery/health/reactive/ReactiveDiscoveryClientHealthIndicator.java

@@ -33,21 +33,21 @@
 import static java.util.Collections.emptyList;
 
 /**
- * A health indicator which indicates whether or not the discovery client has been
- * initialized.
+ * A health indicator which indicates whether the discovery client has been initialized.
  *
  * @author Tim Ysewyn
  * @author Chris Bono
+ * @author Olga Maciaszek-Sharma
  */
 public class ReactiveDiscoveryClientHealthIndicator
 		implements ReactiveDiscoveryHealthIndicator, Ordered, ApplicationListener<InstanceRegisteredEvent<?>> {
 
+	private static final Log LOG = LogFactory.getLog(ReactiveDiscoveryClientHealthIndicator.class);
+
 	private final ReactiveDiscoveryClient discoveryClient;
 
 	private final DiscoveryClientHealthIndicatorProperties properties;
 
-	private final Log log = LogFactory.getLog(ReactiveDiscoveryClientHealthIndicator.class);
-
 	private AtomicBoolean discoveryInitialized = new AtomicBoolean(false);
 
 	private int order = Ordered.HIGHEST_PRECEDENCE;
@@ -60,14 +60,14 @@ public ReactiveDiscoveryClientHealthIndicator(ReactiveDiscoveryClient discoveryC
 
 	@Override
 	public void onApplicationEvent(InstanceRegisteredEvent<?> event) {
-		if (this.discoveryInitialized.compareAndSet(false, true)) {
-			this.log.debug("Discovery Client has been initialized");
+		if (discoveryInitialized.compareAndSet(false, true)) {
+			LOG.debug("Discovery Client has been initialized");
 		}
 	}
 
 	@Override
 	public Mono<Health> health() {
-		if (this.discoveryInitialized.get()) {
+		if (discoveryInitialized.get()) {
 			return doHealthCheck();
 		}
 		else {
@@ -78,38 +78,39 @@ public Mono<Health> health() {
 
 	private Mono<Health> doHealthCheck() {
 		// @formatter:off
-		return Mono.just(this.properties.isUseServicesQuery())
+		return Mono.just(properties.isUseServicesQuery())
 				.flatMap(useServices -> useServices ? doHealthCheckWithServices() : doHealthCheckWithProbe())
 				.onErrorResume(exception -> {
-					this.log.error("Error", exception);
+					if (LOG.isErrorEnabled()) {
+						LOG.error("Error", exception);
+					}
 					return Mono.just(Health.down().withException(exception).build());
 				});
 		// @formatter:on
 	}
 
 	private Mono<Health> doHealthCheckWithProbe() {
-		// @formatter:off
-		return Mono.justOrEmpty(this.discoveryClient)
-				.flatMap(client -> {
-					client.probe();
-					return Mono.just(client);
-				})
-				.map(client -> {
-					String description = (this.properties.isIncludeDescription()) ? client.description() : "";
-					return Health.status(new Status("UP", description)).build();
-				});
-		// @formatter:on
+		return discoveryClient.reactiveProbe().doOnError(exception -> {
+			if (LOG.isErrorEnabled()) {
+				LOG.error("Probe has failed.", exception);
+			}
+		}).then(buildHealthUp(discoveryClient));
+	}
+
+	private Mono<Health> buildHealthUp(ReactiveDiscoveryClient discoveryClient) {
+		String description = (properties.isIncludeDescription()) ? discoveryClient.description() : "";
+		return Mono.just(Health.status(new Status("UP", description)).build());
 	}
 
 	private Mono<Health> doHealthCheckWithServices() {
 		// @formatter:off
-		return Mono.justOrEmpty(this.discoveryClient)
+		return Mono.justOrEmpty(discoveryClient)
 				.flatMapMany(ReactiveDiscoveryClient::getServices)
 				.collectList()
 				.defaultIfEmpty(emptyList())
 				.map(services -> {
-					String description = (this.properties.isIncludeDescription()) ?
-						this.discoveryClient.description() : "";
+					String description = (properties.isIncludeDescription()) ?
+						discoveryClient.description() : "";
 					return Health.status(new Status("UP", description))
 						.withDetail("services", services).build();
 				});
@@ -123,7 +124,7 @@ public String getName() {
 
 	@Override
 	public int getOrder() {
-		return this.order;
+		return order;
 	}
 
 	public void setOrder(int order) {

spring-cloud-commons/src/test/java/org/springframework/cloud/client/discovery/health/reactive/ReactiveDiscoveryClientHealthIndicatorTests.java

@@ -27,6 +27,8 @@
 
 import org.springframework.boot.actuate.health.Health;
 import org.springframework.boot.actuate.health.Status;
+import org.springframework.cloud.client.DefaultServiceInstance;
+import org.springframework.cloud.client.ServiceInstance;
 import org.springframework.cloud.client.discovery.ReactiveDiscoveryClient;
 import org.springframework.cloud.client.discovery.event.InstanceRegisteredEvent;
 import org.springframework.cloud.client.discovery.health.DiscoveryClientHealthIndicatorProperties;
@@ -35,12 +37,12 @@
 import static java.util.Collections.emptyList;
 import static java.util.Collections.singletonList;
 import static org.assertj.core.api.Assertions.assertThat;
-import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.when;
 
 /**
  * @author Tim Ysewyn
  * @author Chris Bono
+ * @author Olga Maciaszek-Sharma
  */
 @ExtendWith(MockitoExtension.class)
 class ReactiveDiscoveryClientHealthIndicatorTests {
@@ -78,6 +80,9 @@ public void shouldReturnUnknownStatusWhenNotInitialized() {
 	@Test
 	public void shouldReturnUpStatusWhenNotUsingServicesQueryAndProbeSucceeds() {
 		when(properties.isUseServicesQuery()).thenReturn(false);
+		ReactiveDiscoveryClient discoveryClient = new TestDiscoveryClient();
+		ReactiveDiscoveryClientHealthIndicator indicator = new ReactiveDiscoveryClientHealthIndicator(discoveryClient,
+				properties);
 		Health expectedHealth = Health.status(new Status(Status.UP.getCode(), "")).build();
 
 		indicator.onApplicationEvent(new InstanceRegisteredEvent<>(this, null));
@@ -88,10 +93,10 @@ public void shouldReturnUpStatusWhenNotUsingServicesQueryAndProbeSucceeds() {
 
 	@Test
 	public void shouldReturnDownStatusWhenNotUsingServicesQueryAndProbeFails() {
-		when(properties.isUseServicesQuery()).thenReturn(false);
-		RuntimeException ex = new RuntimeException("something went wrong");
-		doThrow(ex).when(discoveryClient).probe();
-		Health expectedHealth = Health.down(ex).build();
+		ExceptionThrowingDiscoveryClient discoveryClient = new ExceptionThrowingDiscoveryClient();
+		ReactiveDiscoveryClientHealthIndicator indicator = new ReactiveDiscoveryClientHealthIndicator(discoveryClient,
+				properties);
+		Health expectedHealth = Health.down(discoveryClient.exception).build();
 
 		indicator.onApplicationEvent(new InstanceRegisteredEvent<>(this, null));
 		Mono<Health> health = indicator.health();
@@ -140,4 +145,44 @@ public void shouldReturnDownStatusWhenUsingServicesQueryAndCallFails() {
 		StepVerifier.create(health).expectNext(expectedHealth).expectComplete().verify();
 	}
 
+	static class TestDiscoveryClient implements ReactiveDiscoveryClient {
+
+		@Override
+		public String description() {
+			return "Test";
+		}
+
+		@Override
+		public Flux<ServiceInstance> getInstances(String serviceId) {
+			return Flux.just(new DefaultServiceInstance());
+		}
+
+		@Override
+		public Flux<String> getServices() {
+			return Flux.just("Test");
+		}
+
+	}
+
+	static class ExceptionThrowingDiscoveryClient implements ReactiveDiscoveryClient {
+
+		RuntimeException exception = new RuntimeException("something went wrong");
+
+		@Override
+		public String description() {
+			return "Exception";
+		}
+
+		@Override
+		public Flux<ServiceInstance> getInstances(String serviceId) {
+			throw new RuntimeException("Test!");
+		}
+
+		@Override
+		public Flux<String> getServices() {
+			throw new RuntimeException("something went wrong");
+		}
+
+	}
+
 }

src/checkstyle/checkstyle-suppressions.xml

@@ -17,4 +17,5 @@
 	<suppress files=".*RefreshScopeConfigurationTests.*" checks="JavadocStyle"/>
 	<suppress files=".*RefreshScopeConfigurationTests.*" checks="JavadocMethod"/>
 	<suppress files=".*CachingServiceInstanceListSupplierTests.*" checks="RegexpSinglelineJava"/>
+	<suppress files=".*ReactiveDiscoveryClient.*" checks="JavadocVariable"/>
 </suppressions>