Question

我使用siege对我的手工构建的文件服务器进行压力测试，它对于小文件（小于1KB）非常有效，而在使用1MB文件进行测试时，它无法按预期工作。

以下是使用小文件进行测试的结果：

neevek@~$ siege -c 1000 -r 10 -b http://127.0.0.1:9090/1KB.txt
** SIEGE 2.71
** Preparing 1000 concurrent users for battle.
The server is now under siege..      done.

Transactions:              10000 hits
Availability:             100.00 %
Elapsed time:               9.17 secs
Data transferred:           3.93 MB
Response time:              0.01 secs
Transaction rate:        1090.51 trans/sec
Throughput:             0.43 MB/sec
Concurrency:                7.29
Successful transactions:       10000
Failed transactions:               0
Longest transaction:            1.17
Shortest transaction:           0.00

以下是使用1MB文件进行测试的结果：

neevek@~$ siege -c 1000 -r 10 -b http://127.0.0.1:9090/1MB.txt
** SIEGE 2.71
** Preparing 1000 concurrent users for battle.
The server is now under siege...[error] socket: read error Connection reset by peer sock.c:460: Connection reset by peer
[error] socket: unable to connect sock.c:222: Connection reset by peer
[error] socket: unable to connect sock.c:222: Connection reset by peer
[error] socket: unable to connect sock.c:222: Connection reset by peer
[error] socket: read error Connection reset by peer sock.c:460: Connection reset by peer
[error] socket: unable to connect sock.c:222: Connection reset by peer
[error] socket: read error Connection reset by peer sock.c:460: Connection reset by peer
[error] socket: read error Connection reset by peer sock.c:460: Connection reset by peer
[error] socket: read error Connection reset by peer sock.c:460: Connection reset by peer
[error] socket: read error Connection reset by peer sock.c:460: Connection reset by peer

当siege因上述错误而终止时，我的文件服务器仍会使用固定数量的WRITABLE SelectionKey旋转，即Selector.select()会一直返回固定数字，例如50。

通过上述测试，我认为我的文件服务器不能接受不超过50个并发连接，因为当使用小文件运行测试时，我注意到服务器select s 1或2 SelectionKeys，当使用大文件运行时，select每次最多50个。

我试图在没有任何帮助的情况下增加backlog中的Socket.bind()。

问题可能是什么原因？

修改

更多信息：

使用1MB文件进行测试时，我注意到siege以Broken pipe错误终止，文件服务器只接受 198 连接，但我指定了1000个并发连接x 10轮（1000 * 10 = 10000）以充斥服务器。

编辑2

我已使用以下代码（单个类）进行测试以重现相同的问题，在此代码中，我只接受连接，我不读取或写，siege客户端在连接超时之前以Connection reset或Broken pipe错误终止。我还注意到Selector只能选择少于1000个键。您可以尝试下面的代码来见证问题。

public class TestNIO implements Runnable {
    ServerSocketChannel mServerSocketChannel;
    Selector mSelector;

    public static void main(String[] args) throws Exception {
        new TestNIO().start();
    }

    public TestNIO () throws Exception {
       mSelector = Selector.open();
    }

    public void start () throws Exception {
        mServerSocketChannel = ServerSocketChannel.open();
        mServerSocketChannel.configureBlocking(false);
        mServerSocketChannel.socket().bind(new InetSocketAddress(9090));
        mServerSocketChannel.socket().setSoTimeout(150000);
        mServerSocketChannel.register(mSelector, SelectionKey.OP_ACCEPT);

        int port = mServerSocketChannel.socket().getLocalPort();
        String serverName = "http://" + InetAddress.getLocalHost().getHostName() + ":" + port;
        System.out.println("Server start listening on " + serverName);

        new Thread(this).start();

    }

    @Override
    public void run() {
        try {
            Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
            while (true) {
                int num = mSelector.select();

                System.out.println("SELECT = " + num + "/" + mSelector.keys().size());
                if (num > 0) {
                    Iterator<SelectionKey> keys = mSelector.selectedKeys().iterator();

                    while (keys.hasNext()) {
                        final SelectionKey key = keys.next();

                        if (key.isValid() && key.isAcceptable()) {
                            accept(key);
                        }

                    }
                    // clear the selected keys
                    mSelector.selectedKeys().clear();
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void accept (SelectionKey key) throws IOException {
        SocketChannel socketChannel = mServerSocketChannel.accept();
        socketChannel.configureBlocking(false);
        socketChannel.socket().setSoTimeout(1000000);
        socketChannel.socket().setKeepAlive(true);
        // since we are connected, we are ready to READ
        socketChannel.register(mSelector, SelectionKey.OP_READ);
    }
}

Answer 1

它实际上与为ServerSocketChannel

设置的默认积压值相关

http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/sun/nio/ch/ServerSocketChannelImpl.java#138

您可以通过将积压值作为第二个参数传递给bind方法来解决问题。

mServerSocketChannel.socket（）。bind（new InetSocketAddress（9090），“backlog value”）

Answer 2

检查打开文件（文件描述符）数量的ulimit和硬限制

我猜你正在使用linux。你可以查看limits.conf /etc/security/limits.conf

Answer 3

此问题可能与我的代码无关，我对本地运行的nginx服务器（MacOSX）运行相同的测试，发生了同样的错误。所以它很可能与硬件或siege客户端有关。

Java NIO Selector可以选择不超过50个SelectionKeys？

3 个答案: