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，它不能按预期工作。
下面是用小文件测试的结果：
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
以下是一个 1MB 文件的测试结果：
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以上述错误终止时，我的文件服务器仍然以固定数量的WRITABLESelectionKey 旋转，即Selector.select()不断返回一个固定的数字，比如 50。
通过上面的测试，在我看来我的文件服务器不能接受不超过 50 个并发连接，因为当用小文件运行测试时，我注意到服务器有select1 个或 2 个 SelectionKeys，当用大文件运行时，它select是每次最多50个。
我试图backlog在Socket.bind()没有帮助的情况下增加。
问题的原因可能是什么？
编辑
更多信息：
在使用 1MB 文件进行测试时，我注意到它因错误而siege终止Broken pipe，并且文件服务器只接受了198 个连接，尽管我指定了 1000 个并发连接 x 10 轮（1000*10=10000）来淹没服务器。
编辑 2
我已经使用以下代码（单个类）进行了测试以重现相同的问题，在此代码中，我只接受连接，我不读取或写入，客户端在连接超时之前siege终止Connection reset或错误。Broken pipe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);
}
}