Question

我有一个简单的套接字服务器（用于HL7通信）。当它在生产中运行时间更长时，套接字线程会挂起并消耗大量的CPU时间。

这是侦听器线程的相关代码（缩写）：

public void run() {
    try {
        serverSocket = new ServerSocket(port, backlog, bindAddress);
        serverSocket.setSoTimeout(timeout); // 1000 ms
        do {
            Socket socket = null;
            try {
                socket = serverSocket.accept();
            } catch (SocketTimeoutException to) {
                socket = null;
            } catch (InterruptedIOException io) {
                socket = null;
            } catch (IOException e) {
                logger.fatal("IO exception while socket accept", e);
                socket = null;
            }

            try {
                if (socket != null)
                    processConnection(socket);
            } catch (RuntimeException e) {
                logger.fatal("caught RuntimeException trying to terminate listener thread", e);
            }
        } while (running);
    } catch (IOException e) {
        logger.fatal("error binding server socket - listener thread stopped", e);
    }
}

此代码启动一个新线程来处理传入连接：

protected void processConnection(Socket socket) {
    Hl7RequestHandler requestHandler = createRequestHandler();
    requestHandler.setSocket(socket);
    requestHandler.start();
}

这是请求处理程序线程的代码（keepAlive设置为true）：

public void run() {
    try {
        setName("Hl7RequestHandler-" + socket.getPort());
        processRequest();
    } catch (IOException e) {
        logger.fatal("IO exception during socket communication", e);
    }
}

public void processRequest() 
throws IOException {
    socket.setSoTimeout(socketTimeout); // 1000 ms

    InputStream inputStream = socket.getInputStream();
    OutputStream outputStream = socket.getOutputStream();

    BufferedReader inputReader = new BufferedReader(new InputStreamReader(inputStream, encoding));
    Writer outputWriter = new OutputStreamWriter(outputStream, encoding);

    int timeouts = 0;
    boolean failure = false;
    do {
        StringBuilder message = new StringBuilder();
        try {
            char c;
            do {
                c = (char)inputReader.read();
                if ((c == CARRIAGE_RETURN || c == START_OF_MESSAGE) &&
                    message.length() == 0)
                else if (c != END_OF_MESSAGE && ((short)c) != -1)
                    // ein Byte "Nutzlast"
                    message.append(c);
            } while (c != END_OF_MESSAGE && ((short)c) != -1);
        } catch (SocketTimeoutException te) {
            timeouts++;
            if(!keepAlive && timeouts >= 3 ) {
                socket.close();
                return;
            }
        }

        String messageStr = message.toString();
        if (messageStr.length() == 0)
            continue;

        failure = !processMessage(messageStr, outputWriter);
        outputWriter.flush();
        outputStream.flush();

        // nächste Runde?
        if (!keepAlive || failure)
            socket.close();
    } while (keepAlive && !failure);
}

当我在本地测试时，效果很好。

但是在生产中，有多个请求处理程序线程“挂起”。 “Keep Alive”用于保持打开连接等待更多消息。（为了避免一直打开新的连接。）我假设inputReader.read（）在超时1s后返回-1，这导致再次调用该方法。为什么这会占用所有CPU时间？

你有什么建议吗？

提前致谢，的Matthias

Answer 1

我能直接看到的一件事是：

         char c;
        do {
            c = (char)inputReader.read();
            if ((c == CARRIAGE_RETURN || c == START_OF_MESSAGE) &&
                message.length() == 0)
            else if (c != END_OF_MESSAGE && ((short)c) != -1)
                // ein Byte "Nutzlast"
                message.append(c);
        } while (c != END_OF_MESSAGE && ((short)c) != -1);

是inputReader.read（）到char的强制转换。 BufferedReader.read（）返回一个有符号值的int。您将其转换为无符号值的char，如果存在负号，则丢弃负号，即缩小转换。然后转换为short并不会带回负号（如果有的话）。尝试重写为：

         char c;
         int val;
        do {
            val = inputReader.read();
            // do this if you want, you don't have to
            c = (char) val;
            if ((c == CARRIAGE_RETURN || c == START_OF_MESSAGE) &&
                message.length() == 0)
            else if (c != END_OF_MESSAGE && ((short)c) != -1)
                // ein Byte "Nutzlast"
                message.append(c);
        } while (c != END_OF_MESSAGE && val != -1);

我再看看你的循环，我很困惑。

        char c;
        do {
            c = (char)inputReader.read();
            if ((c == CARRIAGE_RETURN || c == START_OF_MESSAGE) &&
                message.length() == 0)
            else if (c != END_OF_MESSAGE && ((short)c) != -1)
                // ein Byte "Nutzlast"
                message.append(c);
        } while (c != END_OF_MESSAGE && ((short)c) != -1);

你的if语句的逻辑令人困惑（至少对我来说）。第一个if子句没有语句，甚至没有空语句。你必须有{}或a;你的代码是否编译？

套接字通信：线程挂起

1 个答案: