INT-4080: Add TcpConnectionFailedEvent

JIRA: https://jira.spring.io/browse/INT-4080

spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/connection/AbstractClientConnectionFactory.java

@@ -20,6 +20,8 @@ import java.net.Socket;
 import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
+import org.springframework.context.ApplicationEventPublisher;
+
 /**
  * Abstract class for client connection factories; client connection factories
  * establish outgoing connections.
@@ -64,7 +66,7 @@ public abstract class AbstractClientConnectionFactory extends AbstractConnection
 	@Override
 	public TcpConnectionSupport getConnection() throws Exception {
 		this.checkActive();
-		return this.obtainConnection();
+		return obtainConnection();
 	}
 
 	protected TcpConnectionSupport obtainConnection() throws Exception {
@@ -74,7 +76,7 @@ public abstract class AbstractClientConnectionFactory extends AbstractConnection
 				return connection;
 			}
 		}
-		return this.obtainNewConnection();
+		return obtainNewConnection();
 	}
 
 	protected final TcpConnectionSupport obtainSharedConnection() throws InterruptedException {
@@ -118,6 +120,13 @@ public abstract class AbstractClientConnectionFactory extends AbstractConnection
 			connection.publishConnectionOpenEvent();
 			return connection;
 		}
+		catch (Exception e) {
+			ApplicationEventPublisher applicationEventPublisher = getApplicationEventPublisher();
+			if (applicationEventPublisher != null) {
+				applicationEventPublisher.publishEvent(new TcpConnectionFailedEvent(this, e));
+			}
+			throw e;
+		}
 		finally {
 			if (!singleUse) {
 				this.theConnectionLock.writeLock().unlock();

spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/connection/TcpConnectionFailedEvent.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2016 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.integration.ip.tcp.connection;
+
+import org.springframework.integration.ip.event.IpIntegrationEvent;
+
+
+
+/**
+ * An event emitted when a connection could not be established for some
+ * reason.
+ *
+ * @author Gary Russell
+ * @since 4.3.2
+ *
+ */
+public class TcpConnectionFailedEvent extends IpIntegrationEvent {
+
+	private static final long serialVersionUID = -7460880274740273542L;
+
+	public TcpConnectionFailedEvent(Object source, Throwable cause) {
+		super(source, cause);
+	}
+
+}

spring-integration-ip/src/test/java/org/springframework/integration/ip/tcp/connection/ConnectionEventTests.java

@@ -39,6 +39,7 @@ import java.io.OutputStream;
 import java.net.BindException;
 import java.net.ServerSocket;
 import java.net.Socket;
+import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CountDownLatch;
@@ -325,4 +326,32 @@ public class ConnectionEventTests {
 		ss.close();
 	}
 
+	@Test
+	public void testFailConnect() {
+		TcpNetClientConnectionFactory ccf = new TcpNetClientConnectionFactory("junkjunk", 1234);
+		final AtomicReference<ApplicationEvent> failEvent = new AtomicReference<ApplicationEvent>();
+		ccf.setApplicationEventPublisher(new ApplicationEventPublisher() {
+
+			@Override
+			public void publishEvent(Object event) {
+			}
+
+			@Override
+			public void publishEvent(ApplicationEvent event) {
+				failEvent.set(event);
+			}
+
+		});
+		ccf.start();
+		try {
+			ccf.getConnection();
+			fail("expected exception");
+		}
+		catch (Exception e) {
+			assertThat(e, instanceOf(UnknownHostException.class));
+			TcpConnectionFailedEvent event = (TcpConnectionFailedEvent) failEvent.get();
+			assertSame(e, event.getCause());
+		}
+	}
+
 }

src/reference/asciidoc/ip.adoc

@@ -464,6 +464,9 @@ connect to the socket.
 IMPORTANT: To avoid delaying the listening thread from accepting connections, the event is published on a separate
 thread.
 
+Starting with _version 4.3.2_, a `TcpConnectionFailedEvent` is emitted whenever a client connection can't be created.
+The source of the event is the connection factory which can be used to determine the host and port to which the connection could not be established.
+
 [[tcp-adapters]]
 === TCP Adapters