Spring Integration tcp client multiple connections - tcp

Question

I use Spring Integration tcp-outbound-adapter and tcp-inbound-adapter in order to communicate with a third party external system through TCP.
The connection factory I use is of type "client" and has single-use="false", because the nature of communication with the external system is a session of several dozens requests and replies.
The external system expects I will open a new TCP connection for each session.
Is there any way to do that with Spring Integration?
My code uses SI successfully for one such session. But I want my system to open several such connections so I can handle several concurrent sessions.
Currently, if I send a message of a new session to the inbound adapter, it uses the same TCP connection.
Please help.
UPDATE:
While using the ThreadAffinity solution given by Gary here, we get this exception when we do more than 4 concurrent requests. Any idea why is that?
11:08:02.083 [pool-1-thread-2] 193.xxx.yyy.zz:443:55729:46c71372-5933-4707-a27b-93cc4bf78c59 Message sent GenericMessage [payload=byte[326], headers={replyChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel#2fb866, errorChannel=org.springframework.messaging.core.GenericMessagingTemplate$TemporaryReplyChannel#2fb866, ip_tcp_remotePort=55718, ip_connectionId=127.0.0.1:55718:4444:7f71ce96-eaac-4b21-8b2c-bf736102f818, ip_localInetAddress=/127.0.0.1, ip_address=127.0.0.1, id=2dc3e330-d703-8a61-c46c-012233cadf6f, ip_hostname=127.0.0.1, timestamp=1481706480700}]
11:08:12.093 [pool-1-thread-2] Remote Timeout on 193.xxx.yyy.zz:443:55729:46c71372-5933-4707-a27b-93cc4bf78c59
11:08:12.093 [pool-1-thread-2] Tcp Gateway exception
org.springframework.integration.MessageTimeoutException: Timed out waiting for response
at org.springframework.integration.ip.tcp.TcpOutboundGateway.handleRequestMessage(TcpOutboundGateway.java:146)
at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:109)
at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127)
at org.springframework.integration.dispatcher.AbstractDispatcher.tryOptimizedDispatch(AbstractDispatcher.java:116)
at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:148)
at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:121)
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:77)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:373)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:45)
at org.springframework.messaging.core.AbstractMessageSendingTemplate.send(AbstractMessageSendingTemplate.java:105)
at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutput(AbstractMessageProducingHandler.java:292)
at org.springframework.integration.handler.AbstractMessageProducingHandler.produceOutput(AbstractMessageProducingHandler.java:212)
at org.springframework.integration.handler.AbstractMessageProducingHandler.sendOutputs(AbstractMessageProducingHandler.java:129)
at org.springframework.integration.handler.AbstractReplyProducingMessageHandler.handleMessageInternal(AbstractReplyProducingMessageHandler.java:115)
at org.springframework.integration.handler.AbstractMessageHandler.handleMessage(AbstractMessageHandler.java:127)
at org.springframework.integration.dispatcher.AbstractDispatcher.tryOptimizedDispatch(AbstractDispatcher.java:116)
at org.springframework.integration.dispatcher.UnicastingDispatcher.doDispatch(UnicastingDispatcher.java:148)
at org.springframework.integration.dispatcher.UnicastingDispatcher.dispatch(UnicastingDispatcher.java:121)
at org.springframework.integration.channel.AbstractSubscribableChannel.doSend(AbstractSubscribableChannel.java:77)
at org.springframework.integration.channel.AbstractMessageChannel.send(AbstractMessageChannel.java:423)
at org.springframework.messaging.core.GenericMessagingTemplate.doSend(GenericMessagingTemplate.java:115)
at org.springframework.messaging.core.GenericMessagingTemplate.doSendAndReceive(GenericMessagingTemplate.java:150)
at org.springframework.messaging.core.GenericMessagingTemplate.doSendAndReceive(GenericMessagingTemplate.java:45)
at org.springframework.messaging.core.AbstractMessagingTemplate.sendAndReceive(AbstractMessagingTemplate.java:42)
at org.springframework.integration.core.MessagingTemplate.sendAndReceive(MessagingTemplate.java:97)
at org.springframework.integration.gateway.MessagingGatewaySupport.doSendAndReceive(MessagingGatewaySupport.java:441)
at org.springframework.integration.gateway.MessagingGatewaySupport.sendAndReceiveMessage(MessagingGatewaySupport.java:409)
at org.springframework.integration.ip.tcp.TcpInboundGateway.doOnMessage(TcpInboundGateway.java:120)
at org.springframework.integration.ip.tcp.TcpInboundGateway.onMessage(TcpInboundGateway.java:98)
at org.springframework.integration.ip.tcp.connection.TcpConnectionInterceptorSupport.onMessage(TcpConnectionInterceptorSupport.java:159)
at org.springframework.integration.ip.tcp.connection.TcpNetConnection.run(TcpNetConnection.java:182)
at org.springframework.integration.ip.tcp.connection.TcpConnectionInterceptorSupport.run(TcpConnectionInterceptorSupport.java:111)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

Answer 1

It depends on what constitutes a "session" - if all the requests from a session on the client side all run on a single thread, you could write a simple wrapper for the connection factory that stores the connection in a ThreadLocal. You would need some mechanism to call the factory wrapper after the last request to close the connection and remove it from the ThreadLocal.
If the requests for a session can occur on multiple threads, it would be a bit more complicated but you could still do it with a ThreadLocal that maps to a connection instance.
EDIT
Here's an example...
#SpringBootApplication
public class So40507731Application {
public static void main(String[] args) throws Exception {
ConfigurableApplicationContext context = SpringApplication.run(So40507731Application.class, args);
MessageChannel channel = context.getBean("clientFlow.input", MessageChannel.class);
MessagingTemplate template = new MessagingTemplate(channel);
ThreadAffinityClientConnectionFactory affinityCF = context.getBean(ThreadAffinityClientConnectionFactory.class);
ExecutorService exec = Executors.newCachedThreadPool();
CountDownLatch latch = new CountDownLatch(2);
exec.execute(() -> {
String result = new String(template.convertSendAndReceive("foo", byte[].class));
System.out.println(Thread.currentThread().getName() + " " + result);
result = new String(template.convertSendAndReceive("foo", byte[].class));
System.out.println(Thread.currentThread().getName() + " " + result);
affinityCF.release();
latch.countDown();
});
exec.execute(() -> {
String result = new String(template.convertSendAndReceive("foo", byte[].class));
System.out.println(Thread.currentThread().getName() + " " + result);
result = new String(template.convertSendAndReceive("foo", byte[].class));
System.out.println(Thread.currentThread().getName() + " " + result);
affinityCF.release();
latch.countDown();
});
latch.await(10, TimeUnit.SECONDS);
context.close();
exec.shutdownNow();
}
#Bean
public TcpNetClientConnectionFactory delegateCF() {
TcpNetClientConnectionFactory clientCF = new TcpNetClientConnectionFactory("localhost", 1234);
clientCF.setSingleUse(true); // so each thread gets his own connection
return clientCF;
}
#Bean
public ThreadAffinityClientConnectionFactory affinityCF() {
return new ThreadAffinityClientConnectionFactory(delegateCF());
}
#Bean
public TcpOutboundGateway outGate() {
TcpOutboundGateway outGate = new TcpOutboundGateway();
outGate.setConnectionFactory(affinityCF());
return outGate;
}
#Bean
public IntegrationFlow clientFlow() {
return f -> f.handle(outGate());
}
#Bean
public TcpNetServerConnectionFactory serverCF() {
return new TcpNetServerConnectionFactory(1234);
}
#Bean
public TcpInboundGateway inGate() {
TcpInboundGateway inGate = new TcpInboundGateway();
inGate.setConnectionFactory(serverCF());
return inGate;
}
#Bean
public IntegrationFlow serverFlow() {
return IntegrationFlows.from(inGate())
.transform(Transformers.objectToString())
.transform("headers['ip_connectionId'] + ' ' + payload")
.get();
}
public static class ThreadAffinityClientConnectionFactory extends AbstractClientConnectionFactory
implements TcpListener {
private final AbstractClientConnectionFactory delegate;
private final ThreadLocal<TcpConnectionSupport> connection = new ThreadLocal<>();
public ThreadAffinityClientConnectionFactory(AbstractClientConnectionFactory delegate) {
super("", 0);
delegate.registerListener(this);
this.delegate = delegate;
}
#Override
protected TcpConnectionSupport obtainConnection() throws Exception {
TcpConnectionSupport tcpConnection = this.connection.get();
if (tcpConnection == null || !tcpConnection.isOpen()) {
tcpConnection = this.delegate.getConnection();
this.connection.set(tcpConnection);
}
return tcpConnection;
}
public void release() {
TcpConnectionSupport connection = this.connection.get();
if (connection != null) {
connection.close();
this.connection.remove();
}
}
#Override
public void start() {
this.delegate.start();
setActive(true);
super.start();
}
#Override
public void stop() {
this.delegate.stop();
setActive(false);
super.stop();
}
#Override
public boolean onMessage(Message<?> message) {
return getListener().onMessage(message);
}
}
}
Result:
pool-2-thread-2 localhost:64559:1234:3d898822-ea91-421d-97f2-5f9620b9d369 foo
pool-2-thread-1 localhost:64560:1234:227f8a9f-1461-41bf-943c-68a56f708b0c foo
pool-2-thread-2 localhost:64559:1234:3d898822-ea91-421d-97f2-5f9620b9d369 foo
pool-2-thread-1 localhost:64560:1234:227f8a9f-1461-41bf-943c-68a56f708b0c foo