Question

sorry for that title but it is very hard to explain in a few words.

I wrote a little web proxy -not apache or any kind of common webserver- who’s role is to execute some php code.

There are two ways of do it:

1) fork a new php -f file.php

2) call http://localhost/file.php from within the web proxy.

I think there would be a lot of concurrent requests to that proxy, and each request will keep alive for at least 20-30 seconds.

My question is: which is better between forking and requesting via http ?

Thanks for any hint!

Dario

Answer 1

I did a proxy too, recently. And – there’s a third option. Doesn’t even need to call itself or another script, it’s completely self-contained, and cross-platform…

So – first thing is that I have done this using sockets. I guess you did too, but just writing it here in case you did not. I set the proxy in browser to a specific port, which is allowed through firewall into the listening PHP script. To make it start listening, I have to “run” the script on port 80, so I also get a nice real-time console.

So – the script listens on the socket, and it is set to NON-BLOCKING. It works with a loop (infinite, times out using break when needed) – *@socket_accept()* is used to see if there is any new connection, checked if !== false.

Finally, the loop loops (:D) through all of the spawned children sockets, which are stored in an array. It’s an HTTP proxy, so all of them have a few specific stages (client sending headers, trying to reach remote server, sending client headers, receiving data from remote server). Things like reading which would (on remote socket opened with fsockopen()) normally be blocked, and there is no way to set that to non-blocking on these, are “emulating” non-blocking mode by a very extreme time out – like 5 microseconds, and max. chars read is 128.

tl;dr; essentially this is like processor multi-threading.

HOWEVER!!! you need sockets if it’s done like this.

EDIT: adding an example code stripped from all custom actions: (yeah, it’s long)

set_time_limit(0); // so we don't get a timeout from PHP
// - can lead to sockets left open...

$config_port = 85; // port
$config_address = "192.168.0.199"; // IP address, most likely local with router
// if there's not a router between server and wan, use the wan IP
$config_to = 30; // global timeout in seconds
$config_connect_to = 2; // timeout for connecting to remote server
$config_client_to = 0.1; // timeout for reading client data
$config_remote_to = 10; // timeout for reading remote data (microseconds)
$config_remote_stage_to = 15; // timeout for last stage (seconds)
$config_backlog = 5000; // max backlogs, the more the better (usually)

$parent_sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP); // parent socket
$tmp_res = @socket_bind($parent_sock, $config_address, $config_port);
if ($tmp_res === false){
    echo "Can't bind socket.";
    exit;
    // address or port in use, for example by Apache
}

$tmp_res = @socket_listen($parent_sock, $config_backlog);
if ($tmp_res === false){
    echo "Can't start socket listener.";
    exit;
    // hard to tell what can cause this
}

socket_set_nonblock($parent_sock); // non-blocking mode

$sockets = array(); // children sockets
$la = time(); // last activity
while (time() - $la < $config_to){
    $spawn = @socket_accept($parent_sock); // check for new connection
    if ($spawn !== false){
        $la = time();

        $ni = count($sockets);
        $sockets[$ni] = array();
        $sockets[$ni]["handle"] = $spawn;
        $sockets[$ni]["stage"] = 1;
        $sockets[$ni]["la"] = time(); // for some stages
        $sockets[$ni]["client_data"] = "";
        $sockets[$ni]["headers"] = array();
        $sockets[$ni]["remote"] = false;
    }

    foreach ($sockets as &$sock){ // &$sock because we're gonna edit the var
        switch ($sock["stage"]){
        case 1: // receive client data
        $read_data = @socket_read($sock["handle"], 2048);
        if ($read_data !== false && $read_data !== ""){
            $la = time();
            $sock["la"] = microtime(true);
            $sock["client_data"] .= $read_data;
        } else if (microtime(true) - $sock["la"] > $config_client_to) {
            // client data received (or too slow :D)
            $sock["stage"] = 2; // go on
        }
        break;
        case 2: // connect to remote
        $headers = explode("\r\n", $sock["client_data"]);
        foreach ($headers as $hdr){
            $h_pos = strpos($hdr, ":");
            if ($h_pos !== false){
                $nhid = count($sock["headers"]);
                $sock["headers"][strtolower(substr($hdr, 0, $h_pos))] = ltrim(substr($hdr, $h_pos + 1));
            }
        }

        // we'll have to use the "Host" header to know target server
        $sock["remote"] = @fsockopen($sock["headers"]["host"], 80, $sock["errno"], $sock["errstr"], $config_connect_to);
        if ($sock["remote"] === false){
            // error, echo it and close client socket, set stage to 0
            echo "Socket error: #".$sock["errno"].": ".$sock["errstr"]."<br />\n";
            flush(); // immediately show the error
            @socket_close($sock["handle"]);
            $sock["handle"] = 0;
        } else {
            $la = time();
            // okay - connected
            $sock["stage"] = 3;
        }
        break;
        case 3: // send client data
        $tmp_res = @fwrite($sock["remote"], $sock["client_data"]);
        // this currently supports just client data up to 8192 bytes long
        if ($tmp_res === false){
            // error
            echo "Couldn't send client data to remote server!<br />\n";
            flush();
            @socket_close($sock["handle"]);
            @fclose($sock["remote"]);
            $sock["stage"] = 0;
        } else {
            // client data sent
            $la = time();
            stream_set_timeout($sock["remote"], $config_remote_to);
            $sock["la"] = time(); // we'll need this in stage 4
            $sock["stage"] = 4;
        }
        break;
        case 4:
        $remote_read = @fread($sock["remote"], 128);
        if ($remote_read !== false && $remote_read !== ""){
            $la = time();
            $sock["la"] = time();
            @socket_write($sock["handle"], $remote_read);
        } else {
            if (time() - $sock["la"] >= $config_remote_stage_to){
                echo "Timeout.<br />\n";
                flush();
                @socket_close($sock["handle"]);
                @fclose($sock["remote"]);
                $sock["stage"] = 0;
            }
        }
        break;
        }
    }
}

foreach($sockets as $sock){
    @socket_close($sock["handle"]);
    @fclose($sock["remote"]);
}
@socket_close($parent_sock);