How to make Python script run as service?

Question

I want to run a python script in a CENTOS server:

#!/usr/bin/env python
import socket
try:    
    import thread 
except ImportError:
    import _thread as thread #Py3K changed it.
class Polserv(object):
    def __init__(self):
        self.numthreads = 0
        self.tidcount   = 0
        self.port       = 843
        self.sock       = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.sock.bind(('100.100.100.100', self.port))
        self.sock.listen(5)
    def run(self):
        while True:
            thread.start_new_thread(self.handle, self.sock.accept()) 
    def handle(self,conn,addr):
        self.numthreads += 1
        self.tidcount   += 1
        tid=self.tidcount
        while True:
            data=conn.recv(2048)
            if not data:
                conn.close()
                self.numthreads-=1
                break
            #if "<policy-file-request/>\0" in data:
            conn.sendall(b"<?xml version='1.0'?><cross-domain-policy><allow-access-from domain='*' to-ports='*'/></cross-domain-policy>")
            conn.close()
            self.numthreads-=1
            break
        #conn.sendall(b"[#%d (%d running)] %s" % (tid,self.numthreads,data) )
Polserv().run()

Im using $ python flashpolicyd.py and it works fine... The question is: How to keep this script running even after I close the terminal(console)?

possible duplicate of How to make a python script run like a service or daemon in linux — piokuc
– piokuc, Commented May 7, 2013 at 13:18
Not an exact duplicate -- the linked-to question is about a recurring task, this is about a network daemon; the solution to the other was cron, the solution to this is inetd (or equivalent). — Robᵩ
– Robᵩ, Commented May 7, 2013 at 13:33

pztrick · Accepted Answer · 2017-11-18 02:11:41Z

81

I offer two recommendations:

supervisord

1) Install the supervisor package (more verbose instructions here):

sudo apt-get install supervisor

2) Create a config file for your daemon at /etc/supervisor/conf.d/flashpolicyd.conf:

[program:flashpolicyd]
directory=/path/to/project/root
environment=ENV_VARIABLE=example,OTHER_ENV_VARIABLE=example2
command=python flashpolicyd.py
autostart=true
autorestart=true

3) Restart supervisor to load your new .conf

supervisorctl update
supervisorctl restart flashpolicyd

systemd (if currently used by your Linux distro)

[Unit]
Description=My Python daemon

[Service]
Type=simple
ExecStart=/usr/bin/python3 /opt/project/main.py
WorkingDirectory=/opt/project/
Environment=API_KEY=123456789
Environment=API_PASS=password
Restart=always
RestartSec=2

[Install]
WantedBy=sysinit.target

Place this file into /etc/systemd/system/my_daemon.service and enable it using systemctl daemon-reload && systemctl enable my_daemon && systemctl start my_daemon --no-block.

To view logs:

systemctl status my_daemon

edited Nov 18, 2017 at 2:11

answered May 7, 2013 at 13:36

pztrick

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5 Comments

Samad Over a year ago

super easy way :)

pztrick Over a year ago

Hi @Freude! I added a systemd daemon config to my answer. Many Linuxes now ship with systemd for init scripts and the config is very similar to supervisord.

Koorosh Over a year ago

.service file should be created under /lib/systemd/system/ in CentOS

ScipioAfricanus Over a year ago

is it possible to write relative paths on execstart?

PouJa Over a year ago

Using this systemd approach I could get the daemon working but it can not startup after reboot with the following error: Job active_controller.service/start deleted to break ordering cycle starting with sysinit.target/start

Community · Accepted Answer · 2017-05-23 12:34:37Z

80

I use this code to daemonize my applications. It allows you start/stop/restart the script using the following commands.

python myscript.py start
python myscript.py stop
python myscript.py restart

In addition to this I also have an init.d script for controlling my service. This allows you to automatically start the service when your operating system boots-up.

Here is a simple example to get your going. Simply move your code inside a class, and call it from the run function inside MyDeamon.

import sys
import time

from daemon import Daemon


class YourCode(object):
    def run(self):
        while True:
            time.sleep(1)


class MyDaemon(Daemon):
    def run(self):
        # Or simply merge your code with MyDaemon.
        your_code = YourCode()
        your_code.run()


if __name__ == "__main__":
    daemon = MyDaemon('/tmp/daemon-example.pid')
    if len(sys.argv) == 2:
        if 'start' == sys.argv[1]:
            daemon.start()
        elif 'stop' == sys.argv[1]:
            daemon.stop()
        elif 'restart' == sys.argv[1]:
            daemon.restart()
        else:
            print "Unknown command"
            sys.exit(2)
        sys.exit(0)
    else:
        print "usage: %s start|stop|restart" % sys.argv[0]
        sys.exit(2)

Upstart

If you are running an operating system that is using Upstart (e.g. CentOS 6) - you can also use Upstart to manage the service. If you use Upstart you can keep your script as is, and simply add something like this under /etc/init/my-service.conf

start on started sshd
stop on runlevel [!2345]

exec /usr/bin/python /opt/my_service.py
respawn

You can then use start/stop/restart to manage your service.

e.g.

start my-service
stop my-service
restart my-service

A more detailed example of working with upstart is available here.

Systemd

If you are running an operating system that uses Systemd (e.g. CentOS 7) you can take a look at the following Stackoverflow answer.

edited May 23, 2017 at 12:34

CommunityBot

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answered May 7, 2013 at 13:19

eandersson

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10 Comments

Filipe Tagliacozzi Over a year ago

Ok.. but i cant see how to use this class in my script... may you teach?

sigi Over a year ago

how would you use init.d script with MyDaemon? Assuming Daemon forks the MyDaemon process could this possibility fork a new process and then it might try to restart - because it thinks the script has finished (resulting in 1000's of running python processes). Can you maybe provide a quick / simple example of init.d with the simple python Dameon?

eandersson Over a year ago

@sigi: Unless the script actually finishes the python daemon should prevent any new processes from starting up, but you can always just check for the pid file in your init.d script. I can update the answer when I have time in a day or two if you need a proper example.

sigi Over a year ago

@eandersson: I thought the python daemon script you referred to does a process fork twice, and hence init.d (Upstart) I think needs to have an "expect daemon" command in the ".conf" file or something of that sort... I'm just wondering how you would make your Upstart .conf file look for a simple python daemon using the daemonizer script you reffered to - i.e. a simple example of how you use an init.d script for controlling your service would be really great... Thanks.

eandersson Over a year ago

@MohitC: That is a little off-topic unfortunately. I would recommend that you open a new question specifically for demonizing an multi process application.

|

psukys · Accepted Answer · 2016-08-08 16:35:39Z

9

My non pythonic approach would be using & suffix. That is:

python flashpolicyd.py &

To stop the script

killall flashpolicyd.py

also piping & suffix with disown would put the process under superparent (upper):

python flashpolicyd.pi & disown

edited Aug 8, 2016 at 16:35

answered May 4, 2014 at 15:12

psukys

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1 Comment

the_nuts Over a year ago

Last one not working (Ubuntu 16.04): -bash: syntax error near unexpected token '|'

Arsalan · Accepted Answer · 2014-05-04 14:57:18Z

first import os module in your app than with use from getpid function get pid's app and save in a file.for example :

import os
pid = os.getpid()
op = open("/var/us.pid","w")
op.write("%s" % pid)
op.close()

and create a bash file in /etc/init.d path: /etc/init.d/servername

PATHAPP="/etc/bin/userscript.py &"
PIDAPP="/var/us.pid"
case $1 in 
        start)
                echo "starting"
                $(python $PATHAPP)
        ;;
        stop)
                echo "stoping"
                PID=$(cat $PIDAPP)
                kill $PID
        ;;

esac

now , u can start and stop ur app with down command:

service servername stop service servername start

or

/etc/init.d/servername stop /etc/init.d/servername start

Roman · Accepted Answer · 2016-07-11 21:17:05Z

2

for my script of python, I use...

To START python script :

start-stop-daemon --start --background --pidfile $PIDFILE --make-pidfile --exec $DAEMON

To STOP python script :

PID=$(cat $PIDFILE)
kill -9 $PID
rm -f $PIDFILE

P.S.: sorry for poor English, I'm from CHILE :D

edited Jul 11, 2016 at 21:17

Roman

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answered Jul 11, 2016 at 20:43

Rodrigo Navarrete

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