Introduce HealthIndicatorRegistry

This commit introduces HealthIndicatorRegistry which handles
registration of HealthIndicator instances. Registering new
HealthIndicator instances is now possible in runtime.

See gh-4965

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/DefaultHealthIndicatorRegistry.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2012-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.health;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.springframework.util.Assert;
+
+/**
+ * Default implementation of {@link HealthIndicatorRegistry}.
+ *
+ * @author Vedran Pavic
+ * @since 2.1.0
+ */
+public class DefaultHealthIndicatorRegistry implements HealthIndicatorRegistry {
+
+	private final Map<String, HealthIndicator> healthIndicators = new HashMap<>();
+
+	@Override
+	public void register(String name, HealthIndicator healthIndicator) {
+		Assert.notNull(healthIndicator, "HealthIndicator must not be null");
+		synchronized (this.healthIndicators) {
+			if (this.healthIndicators.get(name) != null) {
+				throw new IllegalStateException(
+						"HealthIndicator with name '" + name + "' already registered");
+			}
+			this.healthIndicators.put(name, healthIndicator);
+		}
+	}
+
+	@Override
+	public HealthIndicator unregister(String name) {
+		synchronized (this.healthIndicators) {
+			return this.healthIndicators.remove(name);
+		}
+	}
+
+	@Override
+	public HealthIndicator get(String name) {
+		synchronized (this.healthIndicators) {
+			return this.healthIndicators.get(name);
+		}
+	}
+
+	@Override
+	public Map<String, HealthIndicator> getAll() {
+		synchronized (this.healthIndicators) {
+			return Collections.unmodifiableMap(new HashMap<>(this.healthIndicators));
+		}
+	}
+
+}

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthEndpoint.java

@@ -26,25 +26,35 @@ import org.springframework.util.Assert;
  * @author Dave Syer
  * @author Christian Dupuis
  * @author Andy Wilkinson
+ * @author Vedran Pavic
  * @since 2.0.0
  */
 @Endpoint(id = "health")
 public class HealthEndpoint {
 
-	private final HealthIndicator healthIndicator;
+	private final HealthAggregator healthAggregator;
+
+	private final HealthIndicatorRegistry healthIndicatorRegistry;
 
 	/**
 	 * Create a new {@link HealthEndpoint} instance.
-	 * @param healthIndicator the health indicator
+	 * @param healthAggregator the health aggregator
+	 * @param healthIndicatorRegistry the health indicator registry
 	 */
-	public HealthEndpoint(HealthIndicator healthIndicator) {
-		Assert.notNull(healthIndicator, "HealthIndicator must not be null");
-		this.healthIndicator = healthIndicator;
+	public HealthEndpoint(HealthAggregator healthAggregator,
+			HealthIndicatorRegistry healthIndicatorRegistry) {
+		Assert.notNull(healthAggregator, "healthAggregator must not be null");
+		Assert.notNull(healthIndicatorRegistry, "healthIndicatorRegistry must not be null");
+		this.healthAggregator = healthAggregator;
+		this.healthIndicatorRegistry = healthIndicatorRegistry;
 	}
 
 	@ReadOperation
 	public Health health() {
-		return this.healthIndicator.health();
+		CompositeHealthIndicatorFactory factory = new CompositeHealthIndicatorFactory();
+		CompositeHealthIndicator healthIndicator = factory.createHealthIndicator(
+				this.healthAggregator, this.healthIndicatorRegistry.getAll());
+		return healthIndicator.health();
 	}
 
 }

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthEndpointWebExtension.java

@@ -35,11 +35,11 @@ import org.springframework.boot.actuate.endpoint.web.annotation.EndpointWebExten
 @EndpointWebExtension(endpoint = HealthEndpoint.class)
 public class HealthEndpointWebExtension {
 
-	private final HealthIndicator delegate;
+	private final HealthEndpoint delegate;
 
 	private final HealthWebEndpointResponseMapper responseMapper;
 
-	public HealthEndpointWebExtension(HealthIndicator delegate,
+	public HealthEndpointWebExtension(HealthEndpoint delegate,
 			HealthWebEndpointResponseMapper responseMapper) {
 		this.delegate = delegate;
 		this.responseMapper = responseMapper;

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/health/HealthIndicatorRegistry.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2012-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.health;
+
+import java.util.Map;
+
+/**
+ * A registry of {@link HealthIndicator}s.
+ * <p>
+ * Implementations <strong>must</strong> be thread-safe.
+ *
+ * @author Andy Wilkinson
+ * @author Vedran Pavic
+ * @since 2.1.0
+ */
+public interface HealthIndicatorRegistry {
+
+	/**
+	 * Registers the given {@code healthIndicator}, associating it with the given
+	 * {@code name}.
+	 * @param name the name of the indicator
+	 * @param healthIndicator the indicator
+	 * @throws IllegalStateException if an indicator with the given {@code name} is
+	 * already registered.
+	 */
+	void register(String name, HealthIndicator healthIndicator);
+
+	/**
+	 * Unregisters the {@code HealthIndicator} previously registered with the given
+	 * {@code name}.
+	 * @param name the name of the indicator
+	 * @return the unregistered indicator, or {@code null} if no indicator was found in
+	 * the registry for the given {@code name}.
+	 */
+	HealthIndicator unregister(String name);
+
+	/**
+	 * Returns the health indicator registered with the given {@code name}.
+	 * @param name the name of the indicator
+	 * @return the health indicator, or {@code null} if no indicator was registered with
+	 * the given {@code name}.
+	 */
+	HealthIndicator get(String name);
+
+	/**
+	 * Returns a snapshot of the registered health indicators and their names. The
+	 * contents of the map do not reflect subsequent changes to the registry.
+	 * @return the snapshot of registered health indicators
+	 */
+	Map<String, HealthIndicator> getAll();
+
+}

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/DefaultHealthIndicatorRegistryTest.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2012-2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.actuate.health;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link DefaultHealthIndicatorRegistry}.
+ *
+ * @author Vedran Pavic
+ */
+public class DefaultHealthIndicatorRegistryTest {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	private HealthIndicator one = mock(HealthIndicator.class);
+
+	private HealthIndicator two = mock(HealthIndicator.class);
+
+	private DefaultHealthIndicatorRegistry registry;
+
+	@Before
+	public void setUp() {
+		given(this.one.health()).willReturn(new Health.Builder().up().build());
+		given(this.two.health()).willReturn(new Health.Builder().unknown().build());
+
+		this.registry = new DefaultHealthIndicatorRegistry();
+	}
+
+	@Test
+	public void register() {
+		this.registry.register("one", this.one);
+		this.registry.register("two", this.two);
+		assertThat(this.registry.getAll()).hasSize(2);
+		assertThat(this.registry.get("one")).isSameAs(this.one);
+		assertThat(this.registry.get("two")).isSameAs(this.two);
+	}
+
+	@Test
+	public void registerAlreadyUsedName() {
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage("HealthIndicator with name 'one' already registered");
+		this.registry.register("one", this.one);
+		this.registry.register("one", this.two);
+	}
+
+	@Test
+	public void unregister() {
+		this.registry.register("one", this.one);
+		this.registry.register("two", this.two);
+		assertThat(this.registry.getAll()).hasSize(2);
+		HealthIndicator two = this.registry.unregister("two");
+		assertThat(two).isSameAs(this.two);
+		assertThat(this.registry.getAll()).hasSize(1);
+	}
+
+	@Test
+	public void unregisterNotKnown() {
+		this.registry.register("one", this.one);
+		assertThat(this.registry.getAll()).hasSize(1);
+		HealthIndicator two = this.registry.unregister("two");
+		assertThat(two).isNull();
+		assertThat(this.registry.getAll()).hasSize(1);
+	}
+
+}

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/HealthEndpointTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,6 +30,7 @@ import static org.assertj.core.api.Assertions.entry;
  * @author Phillip Webb
  * @author Christian Dupuis
  * @author Andy Wilkinson
+ * @author Vedran Pavic
  */
 public class HealthEndpointTests {
 
@@ -40,8 +41,8 @@ public class HealthEndpointTests {
 				.withDetail("first", "1").build());
 		healthIndicators.put("upAgain", () -> new Health.Builder().status(Status.UP)
 				.withDetail("second", "2").build());
-		HealthEndpoint endpoint = new HealthEndpoint(
-				createHealthIndicator(healthIndicators));
+		HealthEndpoint endpoint = new HealthEndpoint(new OrderedHealthAggregator(),
+				createHealthIndicatorRegistry(healthIndicators));
 		Health health = endpoint.health();
 		assertThat(health.getStatus()).isEqualTo(Status.UP);
 		assertThat(health.getDetails()).containsOnlyKeys("up", "upAgain");
@@ -51,10 +52,11 @@ public class HealthEndpointTests {
 		assertThat(upAgainHealth.getDetails()).containsOnly(entry("second", "2"));
 	}
 
-	private HealthIndicator createHealthIndicator(
+	private HealthIndicatorRegistry createHealthIndicatorRegistry(
 			Map<String, HealthIndicator> healthIndicators) {
-		return new CompositeHealthIndicatorFactory()
-				.createHealthIndicator(new OrderedHealthAggregator(), healthIndicators);
+		HealthIndicatorRegistry registry = new DefaultHealthIndicatorRegistry();
+		healthIndicators.forEach(registry::register);
+		return registry;
 	}
 
 }

spring-boot-project/spring-boot-actuator/src/test/java/org/springframework/boot/actuate/health/HealthEndpointWebIntegrationTests.java

@@ -35,6 +35,7 @@ import org.springframework.test.web.reactive.server.WebTestClient;
  * exposed by Jersey, Spring MVC, and WebFlux.
  *
  * @author Andy Wilkinson
+ * @author Vedran Pavic
  */
 @RunWith(WebEndpointRunners.class)
 public class HealthEndpointWebIntegrationTests {
@@ -66,17 +67,15 @@ public class HealthEndpointWebIntegrationTests {
 		@Bean
 		public HealthEndpoint healthEndpoint(
 				Map<String, HealthIndicator> healthIndicators) {
-			return new HealthEndpoint(
-					new CompositeHealthIndicatorFactory().createHealthIndicator(
-							new OrderedHealthAggregator(), healthIndicators));
+			HealthIndicatorRegistry registry = new DefaultHealthIndicatorRegistry();
+			healthIndicators.forEach(registry::register);
+			return new HealthEndpoint(new OrderedHealthAggregator(), registry);
 		}
 
 		@Bean
 		public HealthEndpointWebExtension healthWebEndpointExtension(
-				Map<String, HealthIndicator> healthIndicators) {
-			return new HealthEndpointWebExtension(
-					new CompositeHealthIndicatorFactory().createHealthIndicator(
-							new OrderedHealthAggregator(), healthIndicators),
+				HealthEndpoint healthEndpoint) {
+			return new HealthEndpointWebExtension(healthEndpoint,
 					new HealthWebEndpointResponseMapper(new HealthStatusHttpMapper(),
 							ShowDetails.ALWAYS,
 							new HashSet<>(Arrays.asList("ACTUATOR"))));