How to send the output of Symfony’s process Component to a node.js server in Real Time with Socket.io


Today another crazy idea. Do you know Symfony Process Component? The Process Component is a simple component that executes commands in sub-processes. I like to use it when I need to execute commands in the operating system. The documentation is pretty straightforward. Normally when I want to collect the output of the script (imagine we run those scripts within a crontab) I save the output in a log file and I can check it even in real time with tail -f command.

This approach works, but I want to do it in a browser (call me crazy :)). I’ve written a couple of posts with something similar. What I want to do now? The idea is simple:

First I want to execute custom commands with process. Just follow the process documentation:

<?php
use Symfony\Component\Process\Process;

$process = new Process('ls -lsa');
$process->setTimeout(3600);
$process->run();
if (!$process->isSuccessful()) {
    throw new \RuntimeException($process->getErrorOutput());
}

print $process->getOutput();

Process has one cool feature, we can give feedback in real-time by passing an anonymous function to the run() method:

<?php
use Symfony\Component\Process\Process;

$process = new Process('ls -lsa');
$process->run(function ($type, $buffer) {
    if ('err' === $type) {
        echo 'ERR > '.$buffer;
    } else {
        echo 'OUT > '.$buffer;
    }
});

The idea now is to use this callback to send a TCP socket to one server with node.js

var LOCAL_PORT = 5600;
var server = require('net').createServer(function (socket) {
    socket.on('data', function (msg) {
        console.log(msg);
    });
}).listen(LOCAL_PORT);

server.on('listening', function () {
    console.log("TCP server accepting connection on port: " + LOCAL_PORT);
});

Now we change our php script to

<?php
include __DIR__ . "/../vendor/autoload.php";

use Symfony\Component\Process\Process;

function runProcess($command)
{
    $address = 'localhost';
    $port = 5600;
    $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
    socket_connect($socket, $address, $port);

    $process = new Process($command);
    $process->setTimeout(3600);
    $process->run(
        function ($type, $buffer) use ($socket) {
            if ('err' === $type) {
                socket_write($socket, "ERROR\n", strlen("ERROR\n"));
                socket_write($socket, $buffer, strlen($buffer));
            } else {

                socket_write($socket, $buffer, strlen($buffer));
            }
        }
    );
    if (!$process->isSuccessful()) {
        throw new \RuntimeException($process->getErrorOutput());
    }
    socket_close($socket);
}

runProcess('ls -latr /');

Now with the node.js started, if we run the php script, we will see the output of the process command in the node’s terminal. But we want to show it in a browser. What can we do? Of course, socket.io. We change the node.js command to:

var LOCAL_PORT = 5600;
var SOKET_IO_PORT = 8000;
var ioClients = [];

var io = require('socket.io').listen(SOKET_IO_PORT);

var server = require('net').createServer(function (socket) {
    socket.on('data', function (msg) {
        ioClients.forEach(function (ioClient) {
            ioClient.emit('log', msg.toString().trim());
        });
    });
}).listen(LOCAL_PORT);

io.sockets.on('connection', function (socketIo) {
    ioClients.push(socketIo);
});

server.on('listening', function () {
    console.log("TCP server accepting connection on port: " + LOCAL_PORT);
});

and finally we create a simple web client:

<script src="http://localhost:8000/socket.io/socket.io.js"></script>
<script>
    var socket = io.connect('http://localhost:8000');
    socket.on('log', function (data) {
        console.log(data);
    });
</script>

Now if we start one browser we will see the output of our command line process within the console tab of the browser.

If you want something like webConsole, I also have created the example, With a Web UI enabling to send custom commands. You can see it in github.

Obviously that’s only one experiment with a lot of security issues that we need to take into account if we want to use it in production. What do you think?

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About Gonzalo Ayuso

Web Architect. PHP, Python, Node, Angular, ionic, PostgreSQL, Linux, ... Always learning.

Posted on October 8, 2012, in node.js, php, socket.io, Technology and tagged , . Bookmark the permalink. 6 Comments.

  1. Great and very interesting post! This technique opens to a lot of interesting implementations! Good job and good idea!

    I only wonder how Symfony Process component really works: suppose you are running a process which will take a while (let me say for instance 2000 ms) to complete, then the “if” statement in the code example below will be executed after 2000 ms or, as the command is executed on a separate process the run() method will fork the command and it will move on the following php statement just after forking (a bounce of ms) and eventually finish the script execution?

    $process->run();
    if (!$process->isSuccessful()) {
    throw new \RuntimeException($process->getErrorOutput());
    }

    Thanks!

    • short answer: It blocks.

      You can get the output of the command in “realtime” without waiting for $process->isSuccessful() using a callback (as I use in the example or the post). But run() method blocks our script. In python for example we can use background processes easily (http://amoffat.github.com/sh/#background-processes), but AFAIK we can’t do it with sf2/process. If you want to run in parallel you need to do it yourself. I will think about it.

      • Now you can make it async:

        “The non-blocking feature was added in 2.1.

        You can also start the subprocess and then let it run asynchronously, retrieving output and the status in your main process whenever you need it. Use the start() method to start an asynchronous process, the isRunning() method to check if the process is done and the getOutput() method to get the output”

        Thank you for your article =)

      • I need to check this feature. I read about it before stable version but I never use. Sounds good. Thanks!

  2. Hello, I want command process asynchronously in symfony2. my code is this

    $process = new \Symfony\Component\Process\Process($command);
    $process->start();
    while ($process->isRunning()){

    }
    $process->getOutput();

    but why it’s taking realtime, it’s not making async. Please help

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