如何使用spring集成在TCP连接上实现keep alive连接？

Question

private static final int SERIALIZER_HEADER_SIZE = 2;

/**
 * Serializer used by connection factory to send and receive messages
 */
@Bean
public ByteArrayLengthHeaderSerializer byteArrayLengthHeaderSerializer() {
    return new ByteArrayLengthHeaderSerializer(SERIALIZER_HEADER_SIZE);
}

@Bean
public AbstractClientConnectionFactory tcpClientConnectionFactory() {
    TcpNetClientConnectionFactory connFactory =
        new TcpNetClientConnectionFactory(props.getUrl(), props.getPort());
    connFactory.setSerializer(byteArrayLengthHeaderSerializer());
    connFactory.setDeserializer(byteArrayLengthHeaderSerializer());
    connFactory.setSoTimeout(props.getSoTimeout());
    if (props.isUseSSL()) {
        connFactory.setTcpSocketFactorySupport(new DefaultTcpNetSSLSocketFactorySupport(() -> {
            return SSLContext.getDefault();
        }));
    }

    return connFactory;
}

/**
 * Connection factory used to create TCP client socket connections
 */
@Bean
public AbstractClientConnectionFactory tcpCachedClientConnectionFactory() {
    CachingClientConnectionFactory cachingConnFactory =
        new CachingClientConnectionFactory(tcpClientConnectionFactory(), props.getMaxPoolSize());
    cachingConnFactory.setConnectionWaitTimeout(props.getMaxPoolWait());
    return cachingConnFactory;
}

基于此，有人对如何使用spring Integration实现此功能有什么建议吗？

Answer 1

当使用简单的客户端连接工厂时，使用@InboundChannelAdapter设置应用程序级心跳消息非常容易。

简单的例子：

@SpringBootApplication
public class So46918267Application {

    public static void main(String[] args) throws IOException {
        // Simulated Server
        final ServerSocket server = ServerSocketFactory.getDefault().createServerSocket(1234);
        ExecutorService executor = Executors.newSingleThreadExecutor();
        executor.execute(() -> {
            try {
                Socket socket = server.accept();
                BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String line;
                while ((line = reader.readLine()) != null) {
                    System.out.println(line);
                    if (line.equals("keep_alive")) {
                        socket.getOutputStream().write("OK\r\n".getBytes());
                    }
                }
            }
            catch (IOException e) {
                e.printStackTrace();
            }
        });
        ConfigurableApplicationContext context = SpringApplication.run(So46918267Application.class, args);
        System.out.println("Hit enter to terminate");
        System.in.read();
        executor.shutdownNow();
        context.close();
        server.close();
    }

    @Bean
    public TcpNetClientConnectionFactory client() {
        return new TcpNetClientConnectionFactory("localhost", 1234);
    }

    @ServiceActivator(inputChannel = "toTcp")
    @Bean
    public TcpOutboundGateway gateway() {
        TcpOutboundGateway gateway = new TcpOutboundGateway();
        gateway.setConnectionFactory(client());
        return gateway;
    }

    // HEARTBEATS

    private final Message<?> heartbeatMessage = MessageBuilder.withPayload("keep_alive")
            .setReplyChannelName("heartbeatReplies")
            .build();

    @InboundChannelAdapter(channel = "toTcp", poller = @Poller(fixedDelay = "25000"))
    public Message<?> heartbeat() {
        return this.heartbeatMessage;
    }

    @ServiceActivator(inputChannel = "heartbeatReplies")
    public void reply(byte[] reply) {
        System.out.println(new String(reply));
    }

}

但是，在使用CachingClientConnectionFactory时，不清楚为什么要保持空闲连接池处于打开状态。但是，池的工作方式是将空闲连接保留在队列中，这样每个请求都将转到最早的连接，连接将返回到队列的末尾。

@InboundChannelAdapter(channel = "toTcp", 
    poller = @Poller(fixedDelay = "25000", maxMessagesPerPoll = "5"))