Java套接字性能瓶颈: where?

Question

我最近开始开发一个大量使用网络的应用程序。第一次尝试是使用 RMI，出于几个原因，我们切换到纯套接字。然而，当通过网络测试套接字时，甚至在本地主机上，我们的速度下降到 25 个请求/秒。使用 RMI 时，它高出两个数量级。

通过更多的测试，我们获得了以下信息(针对本地主机):

• 始终发送相同的对象:31628 个请求/秒
• 始终发送新对象:25 个请求/秒
• 仅对象创建速率:每秒 3-4 百万(因此这不是瓶颈)

这是客户端代码:(服务器端只是回复一个“ACK”)

public static void main(String[] args) throws IOException, ClassNotFoundException
{
    Socket kkSocket = null;
    ObjectOutputStream out = null;
    ObjectInputStream in = null;


    kkSocket = new Socket("barium", 4444);
    out = new ObjectOutputStream(kkSocket.getOutputStream());
    in = new ObjectInputStream(kkSocket.getInputStream());


    long throughput;
    long millis;

    TcpRequest hello = null;


    throughput = 0;
    millis = System.currentTimeMillis();
    while (System.currentTimeMillis() < millis + 1000)
    {
        hello = new TcpRequest();
        hello.service = "hello";
        hello.payload = Math.random();
        throughput++;
    }

    System.out.println("-------------------------------------------------------");
    System.out.println("|        Objects created: " + (throughput)  + " requests/sec.");
    System.out.println("-------------------------------------------------------");


    throughput = 0;
    millis = System.currentTimeMillis();
    while (System.currentTimeMillis() < millis + 1000)
    {
        out.writeObject(hello);
        Object res = in.readObject();
        throughput++;
    }
    System.out.println("-------------------------------------------------------");
    System.out.println("|        Same object throughput: " + (throughput)  + " requests/sec.");
    System.out.println("-------------------------------------------------------");


    throughput = 0;
    millis = System.currentTimeMillis();
    while (System.currentTimeMillis() < millis + 1000)
    {
        hello = new TcpRequest();
        out.writeObject(hello);
        Object res = in.readObject();
        throughput++;
    }
    System.out.println("-------------------------------------------------------");
    System.out.println("|        New objetcs throughput: " + (throughput)  + " requests/sec.");
    System.out.println("-------------------------------------------------------");


    out.close();
    in.close();

    kkSocket.close();
}

TcpRequest 类只是一个虚拟类，没有任何特殊之处。

那么，如果创建对象很快，如果通过网络发送它也很快......为什么通过网络发送一个新对象这么慢？!？!

如果你保留一个相同的对象并在发送之前修改它的内容，你也会有很高的传输率......但是陷入了令人讨厌的陷阱:

When working with object serialization it is important to keep in mind that the ObjectOutputStream maintains a hashtable mapping the objects written into the stream to a handle. When an object is written to the stream for the first time, its contents will be copied to the stream. Subsequent writes, however, result in a handle to the object being written to the stream.

...这发生在我们身上，导致我们调试了几个小时才弄明白。

所以基本上...您如何使用套接字实现高吞吐量？ (...我的意思是，RMI 是它的包装器，我们已经高出两个数量级!)

已解决:

通过替换:

out = new ObjectOutputStream(kkSocket.getOutputStream());

与:

out = new ObjectOutputStream(new BufferedOutputStream(kkSocket.getOutputStream()))

性能再次正常(与相同对象情况几乎相同的高吞吐量)

Answer 1

找到了:

代替:

out = new ObjectOutputStream(kkSocket.getOutputStream());

你应该使用:

out = new ObjectOutputStream(new BufferedOutputStream(kkSocket.getOutputStream()));

和

out.flush();

发送消息时。

...有很大的不同...虽然我不知道为什么。