Spring Integration tcp client multiple connections

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