Execute registration on startup asynchronously to not block startup

spring-boot-admin-starter-client/src/main/java/de/codecentric/boot/admin/services/RegistrationApplicationListener.java

@@ -9,27 +9,39 @@ import org.springframework.context.event.ContextClosedEvent;
 import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.core.Ordered;
 import org.springframework.core.annotation.Order;
+import org.springframework.core.task.SimpleAsyncTaskExecutor;
+import org.springframework.core.task.TaskExecutor;
 
 import de.codecentric.boot.admin.config.AdminProperties;
 
 @Order(Ordered.LOWEST_PRECEDENCE)
-public class RegistrationApplicationListener implements
-ApplicationListener<ApplicationEvent> {
+public class RegistrationApplicationListener implements ApplicationListener<ApplicationEvent> {
 	private final AdminProperties admin;
 	private final ApplicationRegistrator registrator;
+	private final TaskExecutor executor;
 
 	public RegistrationApplicationListener(AdminProperties admin,
-			ApplicationRegistrator registrator) {
+			ApplicationRegistrator registrator, TaskExecutor executor) {
 		this.admin = admin;
 		this.registrator = registrator;
+		this.executor = executor;
+	}
+
+	public RegistrationApplicationListener(AdminProperties admin,
+			ApplicationRegistrator registrator) {
+		this(admin, registrator, new SimpleAsyncTaskExecutor());
 	}
 
+	@Override
 	public void onApplicationEvent(ApplicationEvent event) {
 		if (startedDeployedWar(event) || startedEmbeddedServer(event)) {
+			executor.execute(new Runnable() {
+				@Override
+				public void run() {
 					registrator.register();
 				}
-		else if (admin.isAutoDeregistration()
-				&& event instanceof ContextClosedEvent) {
+			});
+		} else if (admin.isAutoDeregistration() && event instanceof ContextClosedEvent) {
 			registrator.deregister();
 		}
 	}
@@ -50,4 +62,3 @@ ApplicationListener<ApplicationEvent> {
 		return false;
 	}
 }
-

spring-boot-admin-starter-client/src/test/java/de/codecentric/boot/admin/services/RegistrationApplicationListenerTest.java

@@ -12,6 +12,7 @@ import org.springframework.boot.context.embedded.EmbeddedServletContainerInitial
 import org.springframework.boot.context.embedded.EmbeddedWebApplicationContext;
 import org.springframework.context.event.ContextClosedEvent;
 import org.springframework.context.event.ContextRefreshedEvent;
+import org.springframework.core.task.SyncTaskExecutor;
 
 import de.codecentric.boot.admin.config.AdminProperties;
 
@@ -27,12 +28,11 @@ public class RegistrationApplicationListenerTest {
 	@Test
 	public void test_register_embedded() {
 		ApplicationRegistrator registrator = mock(ApplicationRegistrator.class);
-		RegistrationApplicationListener listener = new RegistrationApplicationListener(
-				admin, registrator);
+		RegistrationApplicationListener listener = new RegistrationApplicationListener(admin,
+				registrator, new SyncTaskExecutor());
 
 		listener.onApplicationEvent(new EmbeddedServletContainerInitializedEvent(
-				mock(EmbeddedWebApplicationContext.class),
-				mock(EmbeddedServletContainer.class)));
+				mock(EmbeddedWebApplicationContext.class), mock(EmbeddedServletContainer.class)));
 
 		verify(registrator).register();
 	}
@@ -40,11 +40,11 @@ public class RegistrationApplicationListenerTest {
 	@Test
 	public void test_register_war() {
 		ApplicationRegistrator registrator = mock(ApplicationRegistrator.class);
-		RegistrationApplicationListener listener = new RegistrationApplicationListener(
-				admin, registrator);
+		RegistrationApplicationListener listener = new RegistrationApplicationListener(admin,
+				registrator, new SyncTaskExecutor());
 
-		listener.onApplicationEvent(new ContextRefreshedEvent(
-				mock(EmbeddedWebApplicationContext.class)));
+		listener.onApplicationEvent(
+				new ContextRefreshedEvent(mock(EmbeddedWebApplicationContext.class)));
 
 		verify(registrator).register();
 	}
@@ -52,12 +52,12 @@ public class RegistrationApplicationListenerTest {
 	@Test
 	public void test_no_register_war() {
 		ApplicationRegistrator registrator = mock(ApplicationRegistrator.class);
-		RegistrationApplicationListener listener = new RegistrationApplicationListener(
-				admin, registrator);
+		RegistrationApplicationListener listener = new RegistrationApplicationListener(admin,
+				registrator, new SyncTaskExecutor());
 
 		EmbeddedWebApplicationContext context = mock(EmbeddedWebApplicationContext.class);
-		when(context.getEmbeddedServletContainer()).thenReturn(
-				mock(EmbeddedServletContainer.class));
+		when(context.getEmbeddedServletContainer())
+				.thenReturn(mock(EmbeddedServletContainer.class));
 		listener.onApplicationEvent(new ContextRefreshedEvent(context));
 
 		verify(registrator, never()).register();
@@ -66,11 +66,11 @@ public class RegistrationApplicationListenerTest {
 	@Test
 	public void test_no_deregister() {
 		ApplicationRegistrator registrator = mock(ApplicationRegistrator.class);
-		RegistrationApplicationListener listener = new RegistrationApplicationListener(
-				admin, registrator);
+		RegistrationApplicationListener listener = new RegistrationApplicationListener(admin,
+				registrator, new SyncTaskExecutor());
 
-		listener.onApplicationEvent(new ContextClosedEvent(
-				mock(EmbeddedWebApplicationContext.class)));
+		listener.onApplicationEvent(
+				new ContextClosedEvent(mock(EmbeddedWebApplicationContext.class)));
 
 		verify(registrator, never()).deregister();
 	}
@@ -78,13 +78,13 @@ public class RegistrationApplicationListenerTest {
 	@Test
 	public void test_deregister() {
 		ApplicationRegistrator registrator = mock(ApplicationRegistrator.class);
-		RegistrationApplicationListener listener = new RegistrationApplicationListener(
-				admin, registrator);
+		RegistrationApplicationListener listener = new RegistrationApplicationListener(admin,
+				registrator);
 
 		admin.setAutoDeregistration(true);
 
-		listener.onApplicationEvent(new ContextClosedEvent(
-				mock(EmbeddedWebApplicationContext.class)));
+		listener.onApplicationEvent(
+				new ContextClosedEvent(mock(EmbeddedWebApplicationContext.class)));
 
 		verify(registrator).deregister();
 	}