Using module 'subprocess' with timeout

Question

Here's the Python code to run an arbitrary command returning its stdout data, or raise an exception on non-zero exit codes:

proc = subprocess.Popen(
    cmd,
    stderr=subprocess.STDOUT,  # Merge stdout and stderr
    stdout=subprocess.PIPE,
    shell=True)

communicate is used to wait for the process to exit:

stdoutdata, stderrdata = proc.communicate()

The subprocess module does not support timeout--ability to kill a process running for more than X number of seconds--therefore, communicate may take forever to run.

What is the simplest way to implement timeouts in a Python program meant to run on Windows and Linux?

Answer 1

I had the problem that I wanted to terminate a multithreading subprocess if it took longer than a given timeout length. I wanted to set a timeout in Popen(), but it did not work. Then, I realized that Popen().wait() is equal to call() and so I had the idea to set a timeout within the .wait(timeout=xxx) method, which finally worked. Thus, I solved it this way:

import os
import sys
import signal
import subprocess
from multiprocessing import Pool

cores_for_parallelization = 4
timeout_time = 15  # seconds

def main():
    jobs = [...YOUR_JOB_LIST...]
    with Pool(cores_for_parallelization) as p:
        p.map(run_parallel_jobs, jobs)

def run_parallel_jobs(args):
    # Define the arguments including the paths
    initial_terminal_command = 'C:\\Python34\\python.exe'  # Python executable
    function_to_start = 'C:\\temp\\xyz.py'  # The multithreading script
    final_list = [initial_terminal_command, function_to_start]
    final_list.extend(args)

    # Start the subprocess and determine the process PID
    subp = subprocess.Popen(final_list)  # starts the process
    pid = subp.pid

    # Wait until the return code returns from the function by considering the timeout. 
    # If not, terminate the process.
    try:
        returncode = subp.wait(timeout=timeout_time)  # should be zero if accomplished
    except subprocess.TimeoutExpired:
        # Distinguish between Linux and Windows and terminate the process if 
        # the timeout has been expired
        if sys.platform == 'linux2':
            os.kill(pid, signal.SIGTERM)
        elif sys.platform == 'win32':
            subp.terminate()

if __name__ == '__main__':
    main()

Answer 2

I don't know much about the low level details; but, given that in python 2.6 the API offers the ability to wait for threads and terminate processes, what about running the process in a separate thread?

import subprocess, threading

class Command(object):
    def __init__(self, cmd):
        self.cmd = cmd
        self.process = None

    def run(self, timeout):
        def target():
            print 'Thread started'
            self.process = subprocess.Popen(self.cmd, shell=True)
            self.process.communicate()
            print 'Thread finished'

        thread = threading.Thread(target=target)
        thread.start()

        thread.join(timeout)
        if thread.is_alive():
            print 'Terminating process'
            self.process.terminate()
            thread.join()
        print self.process.returncode

command = Command("echo 'Process started'; sleep 2; echo 'Process finished'")
command.run(timeout=3)
command.run(timeout=1)

The output of this snippet in my machine is:

Thread started
Process started
Process finished
Thread finished
0
Thread started
Process started
Terminating process
Thread finished
-15

where it can be seen that, in the first execution, the process finished correctly (return code 0), while the in the second one the process was terminated (return code -15).

I haven't tested in windows; but, aside from updating the example command, I think it should work since I haven't found in the documentation anything that says that thread.join or process.terminate is not supported.

Answer 3

If you're on Unix,

import signal
  ...
class Alarm(Exception):
    pass

def alarm_handler(signum, frame):
    raise Alarm

signal.signal(signal.SIGALRM, alarm_handler)
signal.alarm(5*60)  # 5 minutes
try:
    stdoutdata, stderrdata = proc.communicate()
    signal.alarm(0)  # reset the alarm
except Alarm:
    print "Oops, taking too long!"
    # whatever else

Answer 4

The solution I use is to prefix the shell command with timelimit. If the comand takes too long, timelimit will stop it and Popen will have a returncode set by timelimit. If it is > 128, it means timelimit killed the process.

See also python subprocess with timeout and large output (>64K)

Answer 5

import subprocess, optparse, os, sys, re, datetime, threading, time, glob, shutil, xml.dom.minidom, traceback

class OutputManager:
    def __init__(self, filename, mode, console, logonly):
        self.con = console
        self.logtoconsole = True
        self.logtofile = False

        if filename:
            try:
                self.f = open(filename, mode)
                self.logtofile = True
                if logonly == True:
                    self.logtoconsole = False
            except IOError:
                print (sys.exc_value)
                print ("Switching to console only output...\n")
                self.logtofile = False
                self.logtoconsole = True

    def write(self, data):
        if self.logtoconsole == True:
            self.con.write(data)
        if self.logtofile == True:
            self.f.write(data)
        sys.stdout.flush()

def getTimeString():
        return time.strftime("%Y-%m-%d", time.gmtime())

def runCommand(command):
    '''
    Execute a command in new thread and return the
    stdout and stderr content of it.
    '''
    try:
        Output = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True).communicate()[0]
    except Exception as e:
        print ("runCommand failed :%s" % (command))
        print (str(e))
        sys.stdout.flush()
        return None
    return Output

def GetOs():
    Os = ""
    if sys.platform.startswith('win32'):
        Os = "win"
    elif sys.platform.startswith('linux'):
        Os = "linux"
    elif sys.platform.startswith('darwin'):
        Os = "mac"
    return Os


def check_output(*popenargs, **kwargs):
    try:
        if 'stdout' in kwargs: 
            raise ValueError('stdout argument not allowed, it will be overridden.') 

        # Get start time.
        startTime = datetime.datetime.now()
        timeoutValue=3600

        cmd = popenargs[0]

        if sys.platform.startswith('win32'):
            process = subprocess.Popen( cmd, stdout=subprocess.PIPE, shell=True) 
        elif sys.platform.startswith('linux'):
            process = subprocess.Popen( cmd , stdout=subprocess.PIPE, shell=True ) 
        elif sys.platform.startswith('darwin'):
            process = subprocess.Popen( cmd , stdout=subprocess.PIPE, shell=True ) 

        stdoutdata, stderrdata = process.communicate( timeout = timeoutValue )
        retcode = process.poll()

        ####################################
        # Catch crash error and log it.
        ####################################
        OutputHandle = None
        try:
            if retcode >= 1:
                OutputHandle = OutputManager( 'CrashJob_' + getTimeString() + '.txt', 'a+', sys.stdout, False)
                OutputHandle.write( cmd )
                print (stdoutdata)
                print (stderrdata)
                sys.stdout.flush()
        except Exception as e:
            print (str(e))

    except subprocess.TimeoutExpired:
            ####################################
            # Catch time out error and log it.
            ####################################
            Os = GetOs()
            if Os == 'win':
                killCmd = "taskkill /FI \"IMAGENAME eq {0}\" /T /F"
            elif Os == 'linux':
                killCmd = "pkill {0)"
            elif Os == 'mac':
                # Linux, Mac OS
                killCmd = "killall -KILL {0}"

            runCommand(killCmd.format("java"))
            runCommand(killCmd.format("YouApp"))

            OutputHandle = None
            try:
                OutputHandle = OutputManager( 'KillJob_' + getTimeString() + '.txt', 'a+', sys.stdout, False)
                OutputHandle.write( cmd )
            except Exception as e:
                print (str(e))
    except Exception as e:
            for frame in traceback.extract_tb(sys.exc_info()[2]):
                        fname,lineno,fn,text = frame
                        print "Error in %s on line %d" % (fname, lineno)