How to debug exceptions in TCP connection when App is restarted?

Question

I have an application that uses Spring Integration to send messages to a vendor application over TCP and receive and process responses. The vendor sends messages without a length header or an message-ending token and the message contains carriage returns so I have implemented a custom deserializer. The messages are sent as XML strings so I have to process the input stream, looking for a specific closing tag to know when the message is complete. The application works as expected until the vendor application is restarted or a port switch occurs on my application, at which time the CPU usage on my application spikes and the application becomes unresponsive. The application throws a SocketException: o.s.integration.handler.LoggingHandler : org.springframework.messaging.MessagingException: Send Failed; nested exception is java.net.SocketException: Connection or outbound has closed when the socket closes. I have set the SocketTimeout to be 1 minute.

Here is the connection factory implementation:

    @Bean
    public AbstractClientConnectionFactory tcpConnectionFactory() {
        TcpNetClientConnectionFactory factory = new TcpNetClientConnectionFactory(this.serverIp,
                Integer.parseInt(this.port));

        return getAbstractClientConnectionFactory(factory, keyStoreName, trustStoreName,
                keyStorePassword, trustStorePassword, hostVerify);
    }

    private AbstractClientConnectionFactory getAbstractClientConnectionFactory(
            TcpNetClientConnectionFactory factory, String keyStoreName, String trustStoreName,
            String keyStorePassword, String trustStorePassword, boolean hostVerify) {

        TcpSSLContextSupport sslContextSupport = new DefaultTcpSSLContextSupport(keyStoreName,
                trustStoreName, keyStorePassword, trustStorePassword);
        DefaultTcpNetSSLSocketFactorySupport tcpSocketFactorySupport =
                new DefaultTcpNetSSLSocketFactorySupport(sslContextSupport);
        factory.setTcpSocketFactorySupport(tcpSocketFactorySupport);
        factory.setTcpSocketSupport(new DefaultTcpSocketSupport(hostVerify));
        factory.setDeserializer(new MessageSerializerDeserializer());
        factory.setSerializer(new MessageSerializerDeserializer());
        factory.setSoKeepAlive(true);
        factory.setSoTimeout(60000);

        return factory;
    }

Here is the deserialize method:

    private String readUntil(InputStream inputStream) throws IOException {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        String s = "";
        byte[] closingTag = CLOSING_MESSAGE_TAG.getBytes(ASCII);
        try {
            Integer bite;
            while (true) {
                bite = inputStream.read();
                byteArrayOutputStream.write(bite);
                byte[] bytes = byteArrayOutputStream.toByteArray();
                int start = bytes.length - closingTag.length;
                if (start > closingTag.length) {
                    byte[] subarray = Arrays.copyOfRange(bytes, start, bytes.length);
                    if (Arrays.equals(subarray, closingTag)) {
                        s = new String(bytes, ASCII);
                        break;
                    }
                }
            }
        } catch (SocketTimeoutException e) {
            logger.error("Expected SocketTimeoutException thrown");
        } catch (Exception e) {
            logger.error("Exception thrown when deserializing message {}", s);
            throw e;
        }

        return s;
    }

Any help in identifying the cause of the CPU spike or a suggested fix would be greatly appreciated.

EDIT #1 Adding serialize method.

    @Override
    public void serialize(String string, OutputStream outputStream) throws IOException {
        if (StringUtils.isNotEmpty(string) && StringUtils.startsWith(string, OPENING_MESSAGE_TAG) &&
                StringUtils.endsWith(string, CLOSING_MESSAGE_TAG)) {

            outputStream.write(string.getBytes(UTF8));
            outputStream.flush();
        }
    }

the inbound-channel-adapter uses the ConnectionFactory

<int-ip:tcp-inbound-channel-adapter id="tcpInboundChannelAdapter"          
    channel="inboundReceivingChannel"
    connection-factory="tcpConnectionFactory"
    error-channel="errorChannel"
/>

EDIT #2 Outbound Channel Adapter

<int-ip:tcp-outbound-channel-adapter
            id="tcpOutboundChannelAdapter"
            channel="sendToTcpChannel"
            connection-factory="tcpConnectionFactory"/>

Edit #3 We have added in the throw for the Exception and are still seeing the CPU spike, although it is not as dramatic. Could we still be receiving bytes from socket in the inputStream.read() method? The metrics seem to indicate that the read method is consuming server resources.

---

@Artem Bilan Thank you for your continued feedback on this. My server metrics seem to indicate that they deserialize method is what is consuming the CPU. I was thinking that the SendFailed error occurs because of the vendor restarting their application.

Thus far, I have been unable to replicate this issue other than in production. The only exception I can find in production logs is the SocketException mentioned above.

Thank you.