Run specific health check

This commit improves the `health` endpoint to run health check for a
particular component or, if that component is itself a composite, an
instance of that component.

Concretely, it is now possible to issue a `GET` on
`/actuator/health/{component}` and
`/actuator/health/{component}/instance` to retrieve the health of a
component or an instance of a composite component, respectively.

If details cannot be showed for the current user, any request leads to a
404 and does not invoke the health check at all.

Closes gh-8865

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/asciidoc/endpoints/health.adoc

 [[health]]
 = Health (`health`)
-
 The `health` endpoint provides detailed information about the health of the application.
 
 
 
 [[health-retrieving]]
-== Retrieving the Health
-
+== Retrieving the Health of the application
 To retrieve the health of the application, make a `GET` request to `/actuator/health`,
 as shown in the following curl-based example:
 
@@ -21,9 +19,56 @@ include::{snippets}health/http-response.adoc[]
 
 [[health-retrieving-response-structure]]
 === Response Structure
-
 The response contains details of the health of the application. The following table
 describes the structure of the response:
 
 [cols="2,1,3"]
 include::{snippets}health/response-fields.adoc[]
+
+
+
+[[health-retrieving-component]]
+== Retrieving the Health of a component
+To retrieve the health of a particular component of the application, make a `GET` request
+to `/actuator/health/{component}`, as shown in the following curl-based example:
+
+include::{snippets}health/component/curl-request.adoc[]
+
+The resulting response is similar to the following:
+
+include::{snippets}health/component/http-response.adoc[]
+
+
+
+[[health-retrieving-component-response-structure]]
+=== Response Structure
+The response contains details of the health of a particular component of the application.
+The following table describes the structure of the response:
+
+[cols="2,1,3"]
+include::{snippets}health/component/response-fields.adoc[]
+
+
+
+[[health-retrieving-component-instance]]
+== Retrieving the Health of a component instance
+If a particular component consists of multiple instances (as the `broker` indicator in
+the example above), the health of a particular instance of that component can be retrieved
+by issuing a `GET` request to `/actuator/health/{component}/{instance}`, as shown in the
+following curl-based example:
+
+include::{snippets}health/instance/curl-request.adoc[]
+
+The resulting response is similar to the following:
+
+include::{snippets}health/instance/http-response.adoc[]
+
+
+
+[[health-retrieving-component-instance-response-structure]]
+=== Response Structure
+The response contains details of the health of an instance of a particular component of
+the application. The following table describes the structure of the response:
+
+[cols="2,1,3"]
+include::{snippets}health/instance/response-fields.adoc[]

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/CloudFoundryWebEndpointDiscovererTests.java

@@ -58,7 +58,7 @@ public class CloudFoundryWebEndpointDiscovererTests {
 			assertThat(endpoints.size()).isEqualTo(2);
 			for (ExposableWebEndpoint endpoint : endpoints) {
 				if (endpoint.getId().equals("health")) {
-					WebOperation operation = endpoint.getOperations().iterator().next();
+					WebOperation operation = findMainReadOperation(endpoint);
 					assertThat(operation.invoke(new InvocationContext(
 							mock(SecurityContext.class), Collections.emptyMap())))
 									.isEqualTo("cf");
@@ -67,6 +67,16 @@ public class CloudFoundryWebEndpointDiscovererTests {
 		});
 	}
 
+	private WebOperation findMainReadOperation(ExposableWebEndpoint endpoint) {
+		for (WebOperation operation : endpoint.getOperations()) {
+			if (operation.getRequestPredicate().getPath().equals("health")) {
+				return operation;
+			}
+		}
+		throw new IllegalStateException("No main read operation found from "
+				+ endpoint.getOperations());
+	}
+
 	private void load(Class<?> configuration,
 			Consumer<CloudFoundryWebEndpointDiscoverer> consumer) {
 		this.load((id) -> null, (id) -> id, configuration, consumer);

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/reactive/ReactiveCloudFoundryActuatorAutoConfigurationTests.java

@@ -284,8 +284,9 @@ public class ReactiveCloudFoundryActuatorAutoConfigurationTests {
 					Collection<ExposableWebEndpoint> endpoints = getHandlerMapping(
 							context).getEndpoints();
 					ExposableWebEndpoint endpoint = endpoints.iterator().next();
-					WebOperation webOperation = endpoint.getOperations().iterator()
-							.next();
+					assertThat(endpoint.getOperations()).hasSize(3);
+					WebOperation webOperation = findOperationWithRequestPath(endpoint,
+							"health");
 					Object invoker = ReflectionTestUtils.getField(webOperation,
 							"invoker");
 					assertThat(ReflectionTestUtils.getField(invoker, "target"))
@@ -346,6 +347,17 @@ public class ReactiveCloudFoundryActuatorAutoConfigurationTests {
 				CloudFoundryWebFluxEndpointHandlerMapping.class);
 	}
 
+	private WebOperation findOperationWithRequestPath(ExposableWebEndpoint endpoint,
+			String requestPath) {
+		for (WebOperation operation : endpoint.getOperations()) {
+			if (operation.getRequestPredicate().getPath().equals(requestPath)) {
+				return operation;
+			}
+		}
+		throw new IllegalStateException("No operation found with request path "
+				+ requestPath + " from " + endpoint.getOperations());
+	}
+
 	@Configuration
 	static class TestConfiguration {
 

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/cloudfoundry/servlet/CloudFoundryActuatorAutoConfigurationTests.java

@@ -279,8 +279,9 @@ public class CloudFoundryActuatorAutoConfigurationTests {
 									CloudFoundryWebEndpointServletHandlerMapping.class)
 							.getEndpoints();
 					ExposableWebEndpoint endpoint = endpoints.iterator().next();
-					WebOperation webOperation = endpoint.getOperations().iterator()
-							.next();
+					assertThat(endpoint.getOperations()).hasSize(3);
+					WebOperation webOperation = findOperationWithRequestPath(endpoint,
+							"health");
 					Object invoker = ReflectionTestUtils.getField(webOperation,
 							"invoker");
 					assertThat(ReflectionTestUtils.getField(invoker, "target"))
@@ -294,6 +295,17 @@ public class CloudFoundryActuatorAutoConfigurationTests {
 				CloudFoundryWebEndpointServletHandlerMapping.class);
 	}
 
+	private WebOperation findOperationWithRequestPath(ExposableWebEndpoint endpoint,
+			String requestPath) {
+		for (WebOperation operation : endpoint.getOperations()) {
+			if (operation.getRequestPredicate().getPath().equals(requestPath)) {
+				return operation;
+			}
+		}
+		throw new IllegalStateException("No operation found with request path "
+				+ requestPath + " from " + endpoint.getOperations());
+	}
+
 	@Configuration
 	static class TestConfiguration {
 

spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/documentation/HealthEndpointDocumentationTests.java

@@ -17,6 +17,9 @@
 package org.springframework.boot.actuate.autoconfigure.endpoint.web.documentation;
 
 import java.io.File;
+import java.util.Arrays;
+import java.util.LinkedHashMap;
+import java.util.List;
 import java.util.Map;
 
 import javax.sql.DataSource;
@@ -24,6 +27,8 @@ import javax.sql.DataSource;
 import org.junit.Test;
 
 import org.springframework.boot.actuate.health.CompositeHealthIndicator;
+import org.springframework.boot.actuate.health.DefaultHealthIndicatorRegistry;
+import org.springframework.boot.actuate.health.Health;
 import org.springframework.boot.actuate.health.HealthEndpoint;
 import org.springframework.boot.actuate.health.HealthIndicator;
 import org.springframework.boot.actuate.health.HealthIndicatorRegistryFactory;
@@ -35,6 +40,7 @@ import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
+import org.springframework.restdocs.payload.FieldDescriptor;
 
 import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
 import static org.springframework.restdocs.payload.PayloadDocumentation.fieldWithPath;
@@ -47,9 +53,17 @@ import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.
  * Tests for generating documentation describing the {@link HealthEndpoint}.
  *
  * @author Andy Wilkinson
+ * @author Stephane Nicoll
  */
 public class HealthEndpointDocumentationTests extends MockMvcEndpointDocumentationTests {
 
+	private static final List<FieldDescriptor> componentFields = Arrays.asList(
+			fieldWithPath("status")
+					.description("Status of a specific part of the application"),
+			subsectionWithPath("details").description(
+					"Details of the health of a specific part of the"
+							+ " application."));
+
 	@Test
 	public void health() throws Exception {
 		this.mockMvc.perform(get("/actuator/health")).andExpect(status().isOk())
@@ -66,6 +80,19 @@ public class HealthEndpointDocumentationTests extends MockMvcEndpointDocumentati
 										+ " application."))));
 	}
 
+	@Test
+	public void healthComponent() throws Exception {
+		this.mockMvc.perform(get("/actuator/health/db")).andExpect(status().isOk())
+				.andDo(document("health/component", responseFields(componentFields)));
+	}
+
+	@Test
+	public void healthComponentInstance() throws Exception {
+		this.mockMvc.perform(get("/actuator/health/broker/us1"))
+				.andExpect(status().isOk())
+				.andDo(document("health/instance", responseFields(componentFields)));
+	}
+
 	@Configuration
 	@Import(BaseDocumentationConfiguration.class)
 	@ImportAutoConfiguration(DataSourceAutoConfiguration.class)
@@ -84,11 +111,22 @@ public class HealthEndpointDocumentationTests extends MockMvcEndpointDocumentati
 		}
 
 		@Bean
-		public DataSourceHealthIndicator dataSourceHealthIndicator(
+		public DataSourceHealthIndicator dbHealthIndicator(
 				DataSource dataSource) {
 			return new DataSourceHealthIndicator(dataSource);
 		}
 
+		@Bean
+		public CompositeHealthIndicator brokerHealthIndicator() {
+			Map<String, HealthIndicator> indicators = new LinkedHashMap<>();
+			indicators.put("us1", () -> Health.up().withDetail("version", "1.0.2")
+					.build());
+			indicators.put("us2", () -> Health.up().withDetail("version", "1.0.4")
+					.build());
+			return new CompositeHealthIndicator(new OrderedHealthAggregator(),
+					new DefaultHealthIndicatorRegistry(indicators));
+		}
+
 	}
 
 }

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

@@ -17,18 +17,29 @@
 package org.springframework.boot.actuate.autoconfigure.health;
 
 import java.security.Principal;
+import java.util.HashMap;
+import java.util.Map;
 
 import org.junit.Test;
 
 import org.springframework.boot.actuate.endpoint.SecurityContext;
+import org.springframework.boot.actuate.endpoint.web.WebEndpointResponse;
+import org.springframework.boot.actuate.health.CompositeHealthIndicator;
+import org.springframework.boot.actuate.health.DefaultHealthIndicatorRegistry;
 import org.springframework.boot.actuate.health.Health;
 import org.springframework.boot.actuate.health.HealthEndpointWebExtension;
+import org.springframework.boot.actuate.health.HealthIndicator;
 import org.springframework.boot.actuate.health.HealthWebEndpointResponseMapper;
+import org.springframework.boot.actuate.health.OrderedHealthAggregator;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.HttpStatus;
 import org.springframework.test.util.ReflectionTestUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.entry;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.mock;
 
@@ -42,6 +53,7 @@ import static org.mockito.Mockito.mock;
 public class HealthEndpointWebExtensionTests {
 
 	private WebApplicationContextRunner contextRunner = new WebApplicationContextRunner()
+			.withUserConfiguration(HealthIndicatorsConfiguration.class)
 			.withConfiguration(
 					AutoConfigurations.of(HealthIndicatorAutoConfiguration.class,
 							HealthEndpointAutoConfiguration.class));
@@ -84,7 +96,7 @@ public class HealthEndpointWebExtensionTests {
 		this.contextRunner.run((context) -> {
 			HealthEndpointWebExtension extension = context
 					.getBean(HealthEndpointWebExtension.class);
-			assertThat(extension.getHealth(mock(SecurityContext.class)).getBody()
+			assertThat(extension.health(mock(SecurityContext.class)).getBody()
 					.getDetails()).isEmpty();
 		});
 	}
@@ -96,7 +108,7 @@ public class HealthEndpointWebExtensionTests {
 					.getBean(HealthEndpointWebExtension.class);
 			SecurityContext securityContext = mock(SecurityContext.class);
 			given(securityContext.getPrincipal()).willReturn(mock(Principal.class));
-			assertThat(extension.getHealth(securityContext).getBody().getDetails())
+			assertThat(extension.health(securityContext).getBody().getDetails())
 					.isEmpty();
 		});
 	}
@@ -113,7 +125,7 @@ public class HealthEndpointWebExtensionTests {
 					given(securityContext.getPrincipal())
 							.willReturn(mock(Principal.class));
 					assertThat(
-							extension.getHealth(securityContext).getBody().getDetails())
+							extension.health(securityContext).getBody().getDetails())
 									.isNotEmpty();
 				});
 	}
@@ -125,7 +137,7 @@ public class HealthEndpointWebExtensionTests {
 				.run((context) -> {
 					HealthEndpointWebExtension extension = context
 							.getBean(HealthEndpointWebExtension.class);
-					assertThat(extension.getHealth(null).getBody().getDetails())
+					assertThat(extension.health(null).getBody().getDetails())
 							.isNotEmpty();
 				});
 	}
@@ -137,7 +149,7 @@ public class HealthEndpointWebExtensionTests {
 				.run((context) -> {
 					HealthEndpointWebExtension extension = context
 							.getBean(HealthEndpointWebExtension.class);
-					assertThat(extension.getHealth(mock(SecurityContext.class)).getBody()
+					assertThat(extension.health(mock(SecurityContext.class)).getBody()
 							.getDetails()).isEmpty();
 				});
 	}
@@ -154,7 +166,7 @@ public class HealthEndpointWebExtensionTests {
 							.willReturn(mock(Principal.class));
 					given(securityContext.isUserInRole("ACTUATOR")).willReturn(false);
 					assertThat(
-							extension.getHealth(securityContext).getBody().getDetails())
+							extension.health(securityContext).getBody().getDetails())
 									.isEmpty();
 				});
 	}
@@ -171,11 +183,233 @@ public class HealthEndpointWebExtensionTests {
 							.willReturn(mock(Principal.class));
 					given(securityContext.isUserInRole("ACTUATOR")).willReturn(true);
 					assertThat(
-							extension.getHealth(securityContext).getBody().getDetails())
+							extension.health(securityContext).getBody().getDetails())
 									.isNotEmpty();
 				});
 	}
 
+	@Test
+	public void unauthenticatedUsersAreNotShownComponentByDefault() {
+		this.contextRunner.run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			assertDetailsNotFound(extension.healthForComponent(
+					mock(SecurityContext.class), "simple"));
+		});
+	}
+
+	@Test
+	public void authenticatedUsersAreNotShownComponentByDefault() {
+		this.contextRunner.run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			SecurityContext securityContext = mock(SecurityContext.class);
+			given(securityContext.getPrincipal()).willReturn(mock(Principal.class));
+			assertDetailsNotFound(extension.healthForComponent(securityContext,
+					"simple"));
+		});
+	}
+
+	@Test
+	public void authenticatedUsersWhenAuthorizedCanBeShownComponent() {
+		this.contextRunner
+				.withPropertyValues(
+						"management.endpoint.health.show-details=when-authorized")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					SecurityContext securityContext = mock(SecurityContext.class);
+					given(securityContext.getPrincipal())
+							.willReturn(mock(Principal.class));
+					assertSimpleComponent(extension.healthForComponent(
+							securityContext, "simple"));
+				});
+	}
+
+	@Test
+	public void unauthenticatedUsersCanBeShownComponent() {
+		this.contextRunner
+				.withPropertyValues("management.endpoint.health.show-details=always")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					assertSimpleComponent(extension.healthForComponent(null, "simple"));
+				});
+	}
+
+	@Test
+	public void componentCanBeHiddenFromAuthenticatedUsers() {
+		this.contextRunner
+				.withPropertyValues("management.endpoint.health.show-details=never")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					assertDetailsNotFound(extension.healthForComponent(
+							mock(SecurityContext.class), "simple"));
+				});
+	}
+
+	@Test
+	public void componentCanBeHiddenFromUnauthorizedUsers() {
+		this.contextRunner.withPropertyValues(
+				"management.endpoint.health.show-details=when-authorized",
+				"management.endpoint.health.roles=ACTUATOR").run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			SecurityContext securityContext = mock(SecurityContext.class);
+			given(securityContext.getPrincipal())
+					.willReturn(mock(Principal.class));
+			given(securityContext.isUserInRole("ACTUATOR")).willReturn(false);
+			assertDetailsNotFound(extension.healthForComponent(securityContext,
+					"simple"));
+		});
+	}
+
+	@Test
+	public void componentCanBeShownToAuthorizedUsers() {
+		this.contextRunner.withPropertyValues(
+				"management.endpoint.health.show-details=when-authorized",
+				"management.endpoint.health.roles=ACTUATOR").run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			SecurityContext securityContext = mock(SecurityContext.class);
+			given(securityContext.getPrincipal())
+					.willReturn(mock(Principal.class));
+			given(securityContext.isUserInRole("ACTUATOR")).willReturn(true);
+			assertSimpleComponent(extension.healthForComponent(securityContext,
+					"simple"));
+		});
+	}
+
+	@Test
+	public void componentThatDoesNotExistMapTo404() {
+		this.contextRunner
+				.withPropertyValues("management.endpoint.health.show-details=always")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					assertDetailsNotFound(extension.healthForComponent(null,
+							"does-not-exist"));
+				});
+	}
+
+	@Test
+	public void unauthenticatedUsersAreNotShownComponentInstanceByDefault() {
+		this.contextRunner.run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			assertDetailsNotFound(extension.healthForComponentInstance(
+					mock(SecurityContext.class), "composite", "one"));
+		});
+	}
+
+	@Test
+	public void authenticatedUsersAreNotShownComponentInstanceByDefault() {
+		this.contextRunner.run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			SecurityContext securityContext = mock(SecurityContext.class);
+			given(securityContext.getPrincipal()).willReturn(mock(Principal.class));
+			assertDetailsNotFound(extension.healthForComponentInstance(securityContext,
+					"composite", "one"));
+		});
+	}
+
+	@Test
+	public void authenticatedUsersWhenAuthorizedCanBeShownComponentInstance() {
+		this.contextRunner
+				.withPropertyValues(
+						"management.endpoint.health.show-details=when-authorized")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					SecurityContext securityContext = mock(SecurityContext.class);
+					given(securityContext.getPrincipal())
+							.willReturn(mock(Principal.class));
+					assertSimpleComponent(extension.healthForComponentInstance(
+							securityContext, "composite", "one"));
+				});
+	}
+
+	@Test
+	public void unauthenticatedUsersCanBeShownComponentInstance() {
+		this.contextRunner
+				.withPropertyValues("management.endpoint.health.show-details=always")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					assertSimpleComponent(extension.healthForComponentInstance(null,
+							"composite", "one"));
+				});
+	}
+
+	@Test
+	public void componentInstanceCanBeHiddenFromAuthenticatedUsers() {
+		this.contextRunner
+				.withPropertyValues("management.endpoint.health.show-details=never")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					assertDetailsNotFound(extension.healthForComponentInstance(
+							mock(SecurityContext.class), "composite", "one"));
+				});
+	}
+
+	@Test
+	public void componentInstanceCanBeHiddenFromUnauthorizedUsers() {
+		this.contextRunner.withPropertyValues(
+				"management.endpoint.health.show-details=when-authorized",
+				"management.endpoint.health.roles=ACTUATOR").run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			SecurityContext securityContext = mock(SecurityContext.class);
+			given(securityContext.getPrincipal())
+					.willReturn(mock(Principal.class));
+			given(securityContext.isUserInRole("ACTUATOR")).willReturn(false);
+			assertDetailsNotFound(extension.healthForComponentInstance(securityContext,
+					"composite", "one"));
+		});
+	}
+
+	@Test
+	public void componentInstanceCanBeShownToAuthorizedUsers() {
+		this.contextRunner.withPropertyValues(
+				"management.endpoint.health.show-details=when-authorized",
+				"management.endpoint.health.roles=ACTUATOR").run((context) -> {
+			HealthEndpointWebExtension extension = context
+					.getBean(HealthEndpointWebExtension.class);
+			SecurityContext securityContext = mock(SecurityContext.class);
+			given(securityContext.getPrincipal())
+					.willReturn(mock(Principal.class));
+			given(securityContext.isUserInRole("ACTUATOR")).willReturn(true);
+			assertSimpleComponent(extension.healthForComponentInstance(securityContext,
+					"composite", "one"));
+		});
+	}
+
+	@Test
+	public void componentInstanceThatDoesNotExistMapTo404() {
+		this.contextRunner
+				.withPropertyValues("management.endpoint.health.show-details=always")
+				.run((context) -> {
+					HealthEndpointWebExtension extension = context
+							.getBean(HealthEndpointWebExtension.class);
+					assertDetailsNotFound(extension.healthForComponentInstance(null,
+							"composite", "does-not-exist"));
+				});
+	}
+
+	private void assertDetailsNotFound(WebEndpointResponse<?> response) {
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.NOT_FOUND.value());
+		assertThat(response.getBody()).isNull();
+	}
+
+	private void assertSimpleComponent(WebEndpointResponse<Health> response) {
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.OK.value());
+		assertThat(response.getBody().getDetails()).containsOnly(
+				entry("counter", 42));
+	}
+
 	@Test
 	public void roleCanBeCustomized() {
 		this.contextRunner.withPropertyValues(
@@ -188,9 +422,28 @@ public class HealthEndpointWebExtensionTests {
 							.willReturn(mock(Principal.class));
 					given(securityContext.isUserInRole("ADMIN")).willReturn(true);
 					assertThat(
-							extension.getHealth(securityContext).getBody().getDetails())
+							extension.health(securityContext).getBody().getDetails())
 									.isNotEmpty();
 				});
 	}
 
+	@Configuration
+	static class HealthIndicatorsConfiguration {
+
+		@Bean
+		public HealthIndicator simpleHealthIndicator() {
+			return () -> Health.up().withDetail("counter", 42).build();
+		}
+
+		@Bean
+		public HealthIndicator compositeHealthIndicator() {
+			Map<String, HealthIndicator> nestedIndicators = new HashMap<>();
+			nestedIndicators.put("one", simpleHealthIndicator());
+			nestedIndicators.put("two", () -> Health.up().build());
+			return new CompositeHealthIndicator(new OrderedHealthAggregator(),
+					new DefaultHealthIndicatorRegistry(nestedIndicators));
+		}
+
+	}
+
 }

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

@@ -86,6 +86,15 @@ public class CompositeHealthIndicator implements HealthIndicator {
 		this.registry.register(name, indicator);
 	}
 
+	/**
+	 * Return the {@link HealthIndicatorRegistry} of this instance.
+	 * @return the registry of nested {@link HealthIndicator health indicators}
+	 * @since 2.1.0
+	 */
+	public HealthIndicatorRegistry getRegistry() {
+		return this.registry;
+	}
+
 	@Override
 	public Health health() {
 		Map<String, Health> healths = new LinkedHashMap<>();

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

@@ -18,6 +18,7 @@ package org.springframework.boot.actuate.health;
 
 import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
 import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
+import org.springframework.boot.actuate.endpoint.annotation.Selector;
 import org.springframework.util.Assert;
 
 /**
@@ -26,6 +27,7 @@ import org.springframework.util.Assert;
  * @author Dave Syer
  * @author Christian Dupuis
  * @author Andy Wilkinson
+ * @author Stephane Nicoll
  * @since 2.0.0
  */
 @Endpoint(id = "health")
@@ -48,4 +50,42 @@ public class HealthEndpoint {
 		return this.healthIndicator.health();
 	}
 
+	/**
+	 * Return the {@link Health} of a particular component or {@code null} if such
+	 * component does not exist.
+	 * @param component the name of a particular {@link HealthIndicator}
+	 * @return the {@link Health} for the component or {@code null}
+	 */
+	@ReadOperation
+	public Health healthForComponent(@Selector String component) {
+		HealthIndicator indicator = getNestedHealthIndicator(this.healthIndicator,
+				component);
+		return (indicator != null ? indicator.health() : null);
+	}
+
+	/**
+	 * Return the {@link Health} of a particular {@code instance} managed by the specified
+	 * {@code component} or {@code null} if that particular component is not a
+	 * {@link CompositeHealthIndicator} or if such instance does not exist.
+	 * @param component the name of a particular {@link CompositeHealthIndicator}
+	 * @param instance the name of an instance managed by that component
+	 * @return the {@link Health} for the component instance of {@code null}
+	 */
+	@ReadOperation
+	public Health healthForComponentInstance(@Selector String component,
+			@Selector String instance) {
+		HealthIndicator indicator = getNestedHealthIndicator(this.healthIndicator,
+				component);
+		HealthIndicator nestedIndicator = getNestedHealthIndicator(indicator, instance);
+		return (nestedIndicator != null ? nestedIndicator.health() : null);
+	}
+
+	private HealthIndicator getNestedHealthIndicator(HealthIndicator healthIndicator,
+			String name) {
+		if (healthIndicator instanceof CompositeHealthIndicator) {
+			return ((CompositeHealthIndicator) healthIndicator).getRegistry().get(name);
+		}
+		return null;
+	}
+
 }

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

@@ -16,8 +16,11 @@
 
 package org.springframework.boot.actuate.health;
 
+import java.util.function.Supplier;
+
 import org.springframework.boot.actuate.endpoint.SecurityContext;
 import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
+import org.springframework.boot.actuate.endpoint.annotation.Selector;
 import org.springframework.boot.actuate.endpoint.web.WebEndpointResponse;
 import org.springframework.boot.actuate.endpoint.web.annotation.EndpointWebExtension;
 
@@ -30,6 +33,7 @@ import org.springframework.boot.actuate.endpoint.web.annotation.EndpointWebExten
  * @author Phillip Webb
  * @author Eddú Meléndez
  * @author Madhura Bhave
+ * @author Stephane Nicoll
  * @since 2.0.0
  */
 @EndpointWebExtension(endpoint = HealthEndpoint.class)
@@ -46,10 +50,26 @@ public class HealthEndpointWebExtension {
 	}
 
 	@ReadOperation
-	public WebEndpointResponse<Health> getHealth(SecurityContext securityContext) {
+	public WebEndpointResponse<Health> health(SecurityContext securityContext) {
 		return this.responseMapper.map(this.delegate.health(), securityContext);
 	}
 
+	@ReadOperation
+	public WebEndpointResponse<Health> healthForComponent(SecurityContext securityContext,
+			@Selector String component) {
+		Supplier<Health> health = () -> this.delegate.healthForComponent(component);
+		return this.responseMapper.mapDetails(health, securityContext);
+	}
+
+	@ReadOperation
+	public WebEndpointResponse<Health> healthForComponentInstance(
+			SecurityContext securityContext, @Selector String component,
+			@Selector String instance) {
+		Supplier<Health> health = () -> this.delegate.healthForComponentInstance(
+				component, instance);
+		return this.responseMapper.mapDetails(health, securityContext);
+	}
+
 	public WebEndpointResponse<Health> getHealth(SecurityContext securityContext,
 			ShowDetails showDetails) {
 		return this.responseMapper.map(this.delegate.health(), securityContext,

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

@@ -17,6 +17,7 @@
 package org.springframework.boot.actuate.health;
 
 import java.util.Set;
+import java.util.function.Supplier;
 
 import org.springframework.boot.actuate.endpoint.SecurityContext;
 import org.springframework.boot.actuate.endpoint.web.WebEndpointResponse;
@@ -43,6 +44,28 @@ public class HealthWebEndpointResponseMapper {
 		this.authorizedRoles = authorizedRoles;
 	}
 
+	/**
+	 * Maps the given {@code health} details to a {@link WebEndpointResponse}, honouring
+	 * the mapper's default {@link ShowDetails} using the given {@code securityContext}.
+	 * <p>
+	 * If the current user does not have the right to see the details, the
+	 * {@link Supplier} is not invoked and a 404 response is returned instead.
+	 * @param health the provider of health details, invoked if the current user has the
+	 * right to see them
+	 * @param securityContext the security context
+	 * @return the mapped response
+	 */
+	public WebEndpointResponse<Health> mapDetails(Supplier<Health> health,
+			SecurityContext securityContext) {
+		if (canSeeDetails(securityContext, this.showDetails)) {
+			Health healthDetails = health.get();
+			if (healthDetails != null) {
+				return createWebEndpointResponse(healthDetails);
+			}
+		}
+		return new WebEndpointResponse<>(WebEndpointResponse.STATUS_NOT_FOUND);
+	}
+
 	/**
 	 * Maps the given {@code health} to a {@link WebEndpointResponse}, honouring the
 	 * mapper's default {@link ShowDetails} using the given {@code securityContext}.
@@ -71,10 +94,25 @@ public class HealthWebEndpointResponseMapper {
 								|| !isUserInRole(securityContext)))) {
 			health = Health.status(health.getStatus()).build();
 		}
+		return createWebEndpointResponse(health);
+	}
+
+	private WebEndpointResponse<Health> createWebEndpointResponse(Health health) {
 		Integer status = this.statusHttpMapper.mapStatus(health.getStatus());
 		return new WebEndpointResponse<>(health, status);
 	}
 
+	private boolean canSeeDetails(SecurityContext securityContext,
+			ShowDetails showDetails) {
+		if (showDetails == ShowDetails.NEVER
+				|| (showDetails == ShowDetails.WHEN_AUTHORIZED
+						&& (securityContext.getPrincipal() == null
+								|| !isUserInRole(securityContext)))) {
+			return false;
+		}
+		return true;
+	}
+
 	private boolean isUserInRole(SecurityContext securityContext) {
 		if (CollectionUtils.isEmpty(this.authorizedRoles)) {
 			return true;

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

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.actuate.health;
 
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -30,16 +31,21 @@ import static org.assertj.core.api.Assertions.entry;
  * @author Phillip Webb
  * @author Christian Dupuis
  * @author Andy Wilkinson
+ * @author Stephane Nicoll
  */
 public class HealthEndpointTests {
 
+	private static final HealthIndicator one = () -> new Health.Builder()
+			.status(Status.UP).withDetail("first", "1").build();
+
+	private static final HealthIndicator two = () -> new Health.Builder()
+			.status(Status.UP).withDetail("second", "2").build();
+
 	@Test
 	public void statusAndFullDetailsAreExposed() {
 		Map<String, HealthIndicator> healthIndicators = new HashMap<>();
-		healthIndicators.put("up", () -> new Health.Builder().status(Status.UP)
-				.withDetail("first", "1").build());
-		healthIndicators.put("upAgain", () -> new Health.Builder().status(Status.UP)
-				.withDetail("second", "2").build());
+		healthIndicators.put("up", one);
+		healthIndicators.put("upAgain", two);
 		HealthEndpoint endpoint = new HealthEndpoint(
 				createHealthIndicator(healthIndicators));
 		Health health = endpoint.health();
@@ -51,6 +57,56 @@ public class HealthEndpointTests {
 		assertThat(upAgainHealth.getDetails()).containsOnly(entry("second", "2"));
 	}
 
+	@Test
+	public void statusForComponentIsExposed() {
+		HealthEndpoint endpoint = new HealthEndpoint(createHealthIndicator(
+				Collections.singletonMap("test", one)));
+		Health health = endpoint.healthForComponent("test");
+		assertThat(health).isNotNull();
+		assertThat(health.getStatus()).isEqualTo(Status.UP);
+		assertThat(health.getDetails()).containsOnly(entry("first", "1"));
+	}
+
+	@Test
+	public void statusForUnknownComponentReturnNull() {
+		HealthEndpoint endpoint = new HealthEndpoint(createHealthIndicator(
+				Collections.emptyMap()));
+		Health health = endpoint.healthForComponent("does-not-exist");
+		assertThat(health).isNull();
+	}
+
+	@Test
+	public void statusForComponentInstanceIsExposed() {
+		CompositeHealthIndicator compositeIndicator = new CompositeHealthIndicator(
+				new OrderedHealthAggregator(), new DefaultHealthIndicatorRegistry(
+				Collections.singletonMap("sub", () -> Health.down().build())));
+		HealthEndpoint endpoint = new HealthEndpoint(createHealthIndicator(
+				Collections.singletonMap("test", compositeIndicator)));
+		Health health = endpoint.healthForComponentInstance("test", "sub");
+		assertThat(health).isNotNull();
+		assertThat(health.getStatus()).isEqualTo(Status.DOWN);
+		assertThat(health.getDetails()).isEmpty();
+	}
+
+	@Test
+	public void statusForUnknownComponentInstanceReturnNull() {
+		CompositeHealthIndicator compositeIndicator = new CompositeHealthIndicator(
+				new OrderedHealthAggregator(), new DefaultHealthIndicatorRegistry(
+				Collections.singletonMap("sub", () -> Health.down().build())));
+		HealthEndpoint endpoint = new HealthEndpoint(createHealthIndicator(
+				Collections.singletonMap("test", compositeIndicator)));
+		Health health = endpoint.healthForComponentInstance("test", "does-not-exist");
+		assertThat(health).isNull();
+	}
+
+	@Test
+	public void statusForComponentInstanceThatIsNotACompositeReturnNull() {
+		HealthEndpoint endpoint = new HealthEndpoint(createHealthIndicator(
+				Collections.singletonMap("test", () -> Health.up().build())));
+		Health health = endpoint.healthForComponentInstance("test", "does-not-exist");
+		assertThat(health).isNull();
+	}
+
 	private HealthIndicator createHealthIndicator(
 			Map<String, HealthIndicator> healthIndicators) {
 		return new CompositeHealthIndicator(new OrderedHealthAggregator(),

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

+/*
+ * 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.security.Principal;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Set;
+import java.util.function.Supplier;
+
+import org.junit.Test;
+import org.mockito.stubbing.Answer;
+
+import org.springframework.boot.actuate.endpoint.SecurityContext;
+import org.springframework.boot.actuate.endpoint.web.WebEndpointResponse;
+import org.springframework.http.HttpStatus;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyZeroInteractions;
+
+/**
+ * Tests for {@link HealthWebEndpointResponseMapper}.
+ *
+ * @author Stephane Nicoll
+ */
+public class HealthWebEndpointResponseMapperTests {
+
+	private final HealthStatusHttpMapper statusHttpMapper = new HealthStatusHttpMapper();
+
+	private Set<String> autorizedRoles = Collections.singleton("ACTUATOR");
+
+	@Test
+	public void mapDetailsWithDisableDetailsDoesNotInvokeSupplier() {
+		HealthWebEndpointResponseMapper mapper = createMapper(ShowDetails.NEVER);
+		Supplier<Health> supplier = mockSupplier();
+		SecurityContext securityContext = mock(SecurityContext.class);
+		WebEndpointResponse<Health> response = mapper.mapDetails(supplier,
+				securityContext);
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.NOT_FOUND.value());
+		verifyZeroInteractions(supplier);
+		verifyZeroInteractions(securityContext);
+	}
+
+	@Test
+	public void mapDetailsWithUnauthorizedUserDoesNotInvokeSupplier() {
+		HealthWebEndpointResponseMapper mapper = createMapper(ShowDetails.WHEN_AUTHORIZED);
+		Supplier<Health> supplier = mockSupplier();
+		SecurityContext securityContext = mockSecurityContext("USER");
+		WebEndpointResponse<Health> response = mapper.mapDetails(supplier,
+				securityContext);
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.NOT_FOUND.value());
+		assertThat(response.getBody()).isNull();
+		verifyZeroInteractions(supplier);
+		verify(securityContext).isUserInRole("ACTUATOR");
+	}
+
+	@Test
+	public void mapDetailsWithAuthorizedUserInvokeSupplier() {
+		HealthWebEndpointResponseMapper mapper = createMapper(ShowDetails.WHEN_AUTHORIZED);
+		Supplier<Health> supplier = mockSupplier();
+		given(supplier.get()).willReturn(Health.down().build());
+		SecurityContext securityContext = mockSecurityContext("ACTUATOR");
+		WebEndpointResponse<Health> response = mapper.mapDetails(supplier,
+				securityContext);
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.SERVICE_UNAVAILABLE.value());
+		assertThat(response.getBody().getStatus()).isEqualTo(Status.DOWN);
+		verify(supplier).get();
+		verify(securityContext).isUserInRole("ACTUATOR");
+	}
+
+	@Test
+	public void mapDetailsWithUnavailableHealth() {
+		HealthWebEndpointResponseMapper mapper = createMapper(ShowDetails.ALWAYS);
+		Supplier<Health> supplier = mockSupplier();
+		SecurityContext securityContext = mock(SecurityContext.class);
+		WebEndpointResponse<Health> response = mapper.mapDetails(supplier,
+				securityContext);
+		assertThat(response.getStatus()).isEqualTo(HttpStatus.NOT_FOUND.value());
+		assertThat(response.getBody()).isNull();
+		verify(supplier).get();
+		verifyZeroInteractions(securityContext);
+	}
+
+	@SuppressWarnings("unchecked")
+	private Supplier<Health> mockSupplier() {
+		return mock(Supplier.class);
+	}
+
+	private SecurityContext mockSecurityContext(String... roles) {
+		List<String> associatedRoles = Arrays.asList(roles);
+		SecurityContext securityContext = mock(SecurityContext.class);
+		given(securityContext.getPrincipal())
+				.willReturn(mock(Principal.class));
+		given(securityContext.isUserInRole(anyString())).will((Answer<Boolean>) invocation -> {
+			String expectedRole = invocation.getArgument(0);
+			return associatedRoles.contains(expectedRole);
+		});
+		return securityContext;
+	}
+
+	private HealthWebEndpointResponseMapper createMapper(ShowDetails showDetails) {
+		return new HealthWebEndpointResponseMapper(this.statusHttpMapper, showDetails,
+				this.autorizedRoles);
+	}
+
+}