Dart：并行处理传入的HTTP请求 [英] Dart: handle incoming HTTP requests in parallel
问题描述
我试图在Dart中编写一个HTTP服务器，可以并行处理多个请求。
I am trying to write an HTTP server in Dart that can handle multiple requests in parallel. I have been unsuccessful at achieving the "parallel" part thus far.
这是我第一次尝试的：
import 'dart:io';
main() {
HttpServer.bind(InternetAddress.ANY_IP_V4, 8080).then((HttpServer server) {
server.listen((HttpRequest request) {
Stopwatch stopwatch = new Stopwatch();
stopwatch.start();
while (stopwatch.elapsedMilliseconds < 1000) { /* do nothing */ }
request.response.statusCode = HttpStatus.OK;
request.response.write(stopwatch.elapsedMilliseconds.toString());
request.response.close().catchError(print);
});
});
}
在每个请求中，它忙一秒钟，然后完成。我让它处理这种方式的请求，使其时间是可预测的，所以我可以很容易地看到一个请求在Windows任务管理器（CPU内核跳到100％的使用率）的影响。
On each request it does busy work for one second, then completes. I made it handle requests this way so that its timing would be predictable, and so I could easily see the effect of a request in Windows task manager (a CPU core jumping to 100% usage).
我可以告诉这不是并行处理请求，因为：
I can tell this is not handling requests in parallel because:
-
到
http：// example：8080 /，然后全部刷新，标签会依次加载，每个加载大约1秒。
If I load up several browser tabs to
http://example:8080/and then refresh them all, the tabs load one after another in sequence, approximately 1 second between each.
如果我使用负载测试工具 wrk 使用这些设置... wrk -d 10 -c 8 -t 8 http：// example：8080 / ...它在10秒钟内完成5到8个请求。
If I use the load-testing tool wrk with these settings... wrk -d 10 -c 8 -t 8 http://example:8080/ ...it completes 5 to 8 requests in the 10 seconds I gave it. If the server was using all my 8 cores, I'd expect a number closer to 80 requests.
当我在wrk测试期间打开Windows任务管理器时，我观察到我的核心只有一个接近100％的使用率，其余的几乎空闲。
When I open the Windows task manager during the wrk test, I observe that only one of my cores is near 100% usage, and the rest are pretty much idle.
所以，然后我尝试使用隔离，希望手动产生一个新的隔离/线程为每个请求：
So, then I tried using isolates, hoping to manually spawn a new isolate/thread for each request:
import 'dart:io';
import 'dart:isolate';
main() {
HttpServer.bind(InternetAddress.ANY_IP_V4, 8080).then((HttpServer server) {
server.listen((HttpRequest request) {
spawnFunction(handleRequest).send(request);
});
});
}
handleRequest() {
port.receive((HttpRequest request, SendPort sender) {
Stopwatch stopwatch = new Stopwatch();
stopwatch.start();
while (stopwatch.elapsedMilliseconds < 1000) { /* do nothing */ }
request.response.statusCode = HttpStatus.OK;
request.response.write(stopwatch.elapsedMilliseconds.toString());
request.response.close().catchError(print);
});
}
这根本不起作用。它不喜欢我试图发送一个HttpRequest作为消息的隔离。这是错误：
This does not work at all. It doesn't like that I'm trying to send an HttpRequest as the message to the isolate. Here is the error:
#0 _SendPortImpl._sendInternal (dart:isolate-patch/isolate_patch.dart:122:3)
#1 _SendPortImpl._sendNow (dart:isolate-patch/isolate_patch.dart:95:18)
#2 _SendPortImpl.send (dart:isolate-patch/isolate_patch.dart:91:18)
#3 main.<anonymous closure>.<anonymous closure> (file:///C:/Development/dartbenchmark/simple2.dart:7:40)
#4 _StreamSubscriptionImpl._sendData (dart:async/stream_impl.dart:475:12)
#5 _StreamImpl._sendData.<anonymous closure> (dart:async/stream_impl.dart:251:29)
#6 _SingleStreamImpl._forEachSubscriber (dart:async/stream_impl.dart:335:11)
#7 _StreamImpl._sendData (dart:async/stream_impl.dart:249:23)
#8 _StreamImpl._add (dart:async/stream_impl.dart:51:16)
#9 StreamController.add (dart:async/stream_controller.dart:10:35)
#10 _HttpServer._handleRequest (http_impl.dart:1261:20)
#11 _HttpConnection._HttpConnection.<anonymous closure> (http_impl.dart:1188:33)
#12 _StreamSubscriptionImpl._sendData (dart:async/stream_impl.dart:475:12)
#13 _StreamImpl._sendData.<anonymous closure> (dart:async/stream_impl.dart:251:29)
#14 _SingleStreamImpl._forEachSubscriber (dart:async/stream_impl.dart:335:11)
#15 _StreamImpl._sendData (dart:async/stream_impl.dart:249:23)
#16 _StreamImpl._add (dart:async/stream_impl.dart:51:16)
#17 StreamController.add (dart:async/stream_controller.dart:10:35)
#18 _HttpParser._doParse (http_parser.dart:415:26)
#19 _HttpParser._parse (http_parser.dart:161:15)
#20 _HttpParser._onData._onData (http_parser.dart:509:11)
#21 _StreamSubscriptionImpl._sendData (dart:async/stream_impl.dart:475:12)
#22 _StreamImpl._sendData.<anonymous closure> (dart:async/stream_impl.dart:251:29)
#23 _SingleStreamImpl._forEachSubscriber (dart:async/stream_impl.dart:335:11)
#24 _StreamImpl._sendData (dart:async/stream_impl.dart:249:23)
#25 _StreamImpl._add (dart:async/stream_impl.dart:51:16)
#26 StreamController.add (dart:async/stream_controller.dart:10:35)
#27 _Socket._onData._onData (dart:io-patch/socket_patch.dart:726:42)
#28 _StreamSubscriptionImpl._sendData (dart:async/stream_impl.dart:475:12)
#29 _StreamImpl._sendData.<anonymous closure> (dart:async/stream_impl.dart:251:29)
#30 _SingleStreamImpl._forEachSubscriber (dart:async/stream_impl.dart:335:11)
#31 _StreamImpl._sendData (dart:async/stream_impl.dart:249:23)
#32 _StreamImpl._add (dart:async/stream_impl.dart:51:16)
#33 StreamController.add (dart:async/stream_controller.dart:10:35)
#34 _RawSocket._RawSocket.<anonymous closure> (dart:io-patch/socket_patch.dart:452:52)
#35 _NativeSocket.multiplex (dart:io-patch/socket_patch.dart:253:18)
#36 _NativeSocket.connectToEventHandler.<anonymous closure> (dart:io-patch/socket_patch.dart:338:54)
#37 _ReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:81:92)
Unhandled exception:
Illegal argument(s): Illegal argument in isolate message : (object is a closure)
#0 _throwDelayed.<anonymous closure> (dart:async/stream_impl.dart:22:5)
#1 _asyncRunCallback._asyncRunCallback (dart:async/event_loop.dart:15:17)
#2 _asyncRunCallback._asyncRunCallback (dart:async/event_loop.dart:25:9)
#3 Timer.run.<anonymous closure> (dart:async/timer.dart:17:21)
#4 Timer.run.<anonymous closure> (dart:async/timer.dart:25:13)
#5 Timer.Timer.<anonymous closure> (dart:async-patch/timer_patch.dart:9:15)
#6 _Timer._createTimerHandler._handleTimeout (timer_impl.dart:99:28)
#7 _Timer._createTimerHandler._handleTimeout (timer_impl.dart:107:7)
#8 _Timer._createTimerHandler.<anonymous closure> (timer_impl.dart:115:23)
#9 _ReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:81:92)
使用的版本：
- Dart编辑器版本0.5.9_r22879
- Dart SDK版本0.5.9.0_r22879
可以并行处理这些请求， ，使用Dart？
Is it possible to handle these requests in parallel, with all my machine's available cores, using Dart?
推荐答案
我写了一个叫dart-isoserver的库来做这个。
I wrote a library called dart-isoserver to do this a while back. It's severely bit rotted now, but you can see the approach.
https://code.google.com/p/dart-isoserver/
我所做的是通过隔离端口的代理HttpRequest和HttpResponse，因为你不能直接发送。它工作，虽然有几个警告：
What I did was proxy HttpRequest and HttpResponse via isolate ports, since you cannot send them directly. It worked, though there were a few caveats:
- I / O的请求和响应去了主要隔离，不平行。在工作隔离区中完成的其他工作没有阻塞主要隔离。真正应该发生的是，一个套接字连接应该可以在隔离之间传递。
- 隔离中的异常会导致整个服务器。
spawnFunction（）现在有一个未捕获的异常处理程序参数，所以这有点固定，但spawnUri（）没有。 dart-isoserver使用spawnUri（）实现热加载，所以必须删除。 - 隔离有点慢，启动，你可能不想要一个连接用于nginx和node.js目标的数千并发连接用例。具有工作队列的隔离池可能执行得更好，但这会消除您可以在工作程序中使用阻止I / O的好功能。
- I/O on the request and response went though the main isolate, so that part was not parallel. Other work done in the worker isolate didn't block the main isolate though. What really should happen is that a socket connection should be transferrable between isolates.
- Exceptions in the isolate would bring down the whole server.
spawnFunction()now has an uncaught exception handler parameter, so this is somewhat fixable, but spawnUri() doesn't. dart-isoserver used spawnUri() to implement hot-loading, so that would have to be removed. - Isolates are a little slow to start up, and you probably don't want one per connection for the thousands of concurrent connection use cases that nginx and node.js target. An isolate pool with work queues would probably perform better, though that would eliminate the nice feature you could use blocking I/O in a worker.
有关您的第一个代码示例的注释。这绝对不会并行运行，正如你所注意到的，因为Dart是单线程的。没有Dart代码在同一个隔离器中同时运行。
A note about your first code example. That definitely won't run in parallel, as you noticed, because Dart is single-threaded. No Dart code in the same isolate ever runs concurrently.
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