NIO+Multithreaded TCPSocket listener, very low cpu utilisation

Wed Nov 15 11:46:22 UTC 2017

Do not use your own taskPool, just use global taskPool proerty (import
std.parallelism: taskPool).

You should not set blocking to false. And dont use Thread here.  There is
no reason to do that.  Just move that code into the main

Dne 15. 11. 2017 12:15 odp. napsal uživatel "ade90036 via
Digitalmars-d-learn" <digitalmars-d-learn at puremagic.com>:

So thanks for the suggestions,  i have fixed HTTP response not postman cal
also parse the headers correctly!! happy days.

I have removed the duration from the Socket.select but the application
seems to process a bunch or requests and then it stalls for several seconds
(3/5) and then it resumes.

The httpclinet which i'm using to test the application is reporting:
"connection timeout".

Could this be caused by the GC?

```updated code

import std.algorithm : remove;
import std.conv : to;
import core.thread: Thread;
import std.socket : InternetAddress, Socket, SocketException, SocketSet,
TcpSocket, SocketShutdown;
import core.time : Duration, dur;
import std.stdio : writeln, writefln;
import std.parallelism : task, TaskPool;

string to_retlf (string s)
{
   import std.algorithm;
   import std.string;
   return s
      .lineSplitter
      .map!(a => chomp (a))
      .join ("\r\n");
}

void main(string[] args)
{
    ushort port;

    if (args.length >= 2)
        port = to!ushort(args[1]);
    else
        port = 4444;

    auto listener = new TcpSocket();
    assert(listener.isAlive);
    listener.blocking = false;
    listener.bind(new InternetAddress(port));
    listener.listen(100);
    writefln("Listening on port %d.", port);

    auto taskPool = new TaskPool(8);

    string response = "HTTP/1.1 200 OK

Server: dland:v2.076.1
Date: Tue, 11 Nov 2017 15:56:02 GMT
Content-Type: text/html; charset=UTF-8
Content-Length: 51

<html><head></head><body>Hello World!</body></html>".to_retlf;

    new Thread({
        auto listeningSet = new SocketSet();
        while(true) {
            listeningSet.add(listener);
            if (Socket.select(listeningSet, null, null)) {

                if (listeningSet.isSet(listener))        // connection
request
                {
                    Socket socket = listener.accept();
                    assert(socket.isAlive);

                    //writefln("Connection from %s established.",
socket.remoteAddress().toString());
                    auto task = task!handle_socket(socket, response);
                    taskPool.put(task);
                }
            }
            listeningSet.reset();
        }
    }).start();
}

void handle_socket(Socket socket, string response) {

    auto socketSet = new SocketSet();
    while(true) {
        socketSet.add(socket);
        if (Socket.select(socketSet, null, null)) {

            char[1024] buf;
            auto datLength = socket.receive(buf[]);

            if (datLength == Socket.ERROR)
                writeln("Connection error.");
            else if (datLength != 0)
            {
                //writefln("Received %d bytes from %s: \"%s\"", datLength,
socket.remoteAddress().toString(), buf[0..datLength]);
                //writefln("Writing response");
                socket.send(response);

            }
            // release socket resources now

            socket.close();

            break;

        }
        socketSet.reset();
    }
```

Regards
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