Allow user to pause and resume.

[sjs7007]

The pause and resumption can be based on saving neural network weights and resuming from there or actually pausing the script.

First working on pausing the script and resuming.

Stackoverflow : http://stackoverflow.com/questions/7180914/pause-resume-a-python-script-in-middle

Seems cont and stop from kill can be used : http://www.pervasivecode.com/blog/2010/04/03/unix-tip-kill-stop-and-kill-cont/comment-page-1/

Try on python script : works and then from nodejs process.kill() : works, syntax is proces.kill(,'SIGSTOP') to stop

sigstop sends stop signal, similarly sigcont sends continue signal.

signals :

http://linux.die.net/man/7/signal https://nodejs.org/api/process.html#process_process_kill_pid_signal

and then the #4 example.

[sjs7007]

It seems using SIGSTP would be better as SIGSTOP can't be caught in python

http://www.gossamer-threads.com/lists/python/python/953193

def handler(signalnum, stackframe): 
print "Received signal %d" % signalnum 
os.kill(os.getpid(), signal.SIGSTOP) # Hit myself with a brick. 

signal.signal(signal.SIGTSTP, handler) 

works

[sjs7007]

Tried pause and continue on browser also, works.

Sample Client Code:

<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/1.4.8/socket.io.js"></script>
<script>
  var socket = io.connect('http://localhost:9090');
  socket.on('pythonSocket',function( data ) {
    document.write(data+"<br>");
  });
  socket.emit('pause');
  socket.emit('continue');
</script>

Sample Server Code :

var app = express();
var server = require('http').Server(app);
var io = require('socket.io')(server);
var count = 0;

server.listen(9090);

app.get('/', function (req, res) {
  res.sendfile(__dirname + '/index.html');
});

io.on('connection', function (socket) {
    console.log("here 2");
    var spawn = require('child_process').spawn;
    var py = spawn('python',['test.py']);

    py.stdout.on('data',function(pyStdout) {
        console.log("godyt data count : "+count++)
        console.log(pyStdout.toString());
        socket.emit('pythonSocket',pyStdout.toString());
    });

    //to stop process 
    socket.on("pause",function() {
        console.log("pausing pid : "+py.pid);
        socket.emit("pythonSocket","pausing pid : "+py.pid);
        process.kill(py.pid,"SIGTSTP");
    });

    //to resume process
    socket.on("continue",function() {
        console.log("resuming pid : "+py.pid);
        socket.emit("pythonSocket","resuming pid : "+py.pid);
        process.kill(py.pid,"SIGCONT");
    }); 

});