python - How to create Celery Windows Service?

Question

I'm trying to create a Windows Service to launch Celery. I have come across an article that does it using Task Scheduler. However it seems to launch numerous celery instances and keeps eating up memory till the machine dies. Is there any way to launch it as a Windows service?

Answer 1

I got the answer from another website. Celeryd (daemon service for Celery) runs as a paster application, searching for 'Paster Windows Service' lead me here. It describes how to run a Pylons application as a Windows Service. Being new to paster framework and hosting python web services, it didn't cross my mind to check it at first. But that solution works for Celery with a slight change here and there in the script.

I've modified the script to make it easier for modifying Celery settings. The essential changes are:

1. Create an INI file with the settings for Celery service (shown below)
2. Create a python script to create a Windows service.

INI file settings (celeryd.ini):

[celery:service]
service_name = CeleryService
service_display_name = Celery Service
service_description = WSCGI Windows Celery Service
service_logfile = celeryd.log

Python script to create Windows Service (CeleryService.py):

"""
The most basic (working) Windows service possible.
Requires Mark Hammond's pywin32 package.  
Most of the code was taken from a  CherryPy 2.2 example of how to set up a service
"""
import pkg_resources
import win32serviceutil
from paste.script.serve import ServeCommand as Server
import os, sys
import ConfigParser

import win32service
import win32event

SCRIPT_DIR          = os.path.abspath(os.path.dirname(__file__))
INI_FILE            = 'celeryd.ini'
SERV_SECTION        = 'celery:service'
SERV_NAME           = 'service_name'
SERV_DISPLAY_NAME   = 'service_display_name'
SERV_DESC           = 'service_description'
SERV_LOG_FILE       = 'service_logfile'
SERV_APPLICATION    = 'celeryd'
SERV_LOG_FILE_VAR   = 'CELERYD_LOG_FILE'

# Default Values
SERV_NAME_DEFAULT           = 'CeleryService'
SERV_DISPLAY_NAME_DEFAULT   = 'Celery Service'
SERV_DESC_DEFAULT           = 'WSCGI Windows Celery Service'
SERV_LOG_FILE_DEFAULT       = r'D:logscelery.log'

class DefaultSettings(object):
    def __init__(self):
        if SCRIPT_DIR:
            os.chdir(SCRIPT_DIR)
        # find the ini file
        self.ini = os.path.join(SCRIPT_DIR,INI_FILE)
        # create a config parser opject and populate it with the ini file
        c = ConfigParser.SafeConfigParser()
        c.read(self.ini)
        self.c = c

    def getDefaults(self):
        '''
        Check for and get the default settings
        '''
        if (
            (not self.c.has_section(SERV_SECTION)) or
            (not self.c.has_option(SERV_SECTION, SERV_NAME)) or
            (not self.c.has_option(SERV_SECTION, SERV_DISPLAY_NAME)) or
            (not self.c.has_option(SERV_SECTION, SERV_DESC)) or
            (not self.c.has_option(SERV_SECTION, SERV_LOG_FILE))
            ):
            print 'setting defaults'
            self.setDefaults()
        service_name = self.c.get(SERV_SECTION, SERV_NAME)
        service_display_name = self.c.get(SERV_SECTION, SERV_DISPLAY_NAME)
        service_description = self.c.get(SERV_SECTION, SERV_DESC)
        iniFile = self.ini
        service_logfile = self.c.get(SERV_SECTION, SERV_LOG_FILE)
        return service_name, service_display_name, service_description, iniFile, service_logfile

    def setDefaults(self):
        '''
        set and add the default setting to the ini file
        '''
        if not self.c.has_section(SERV_SECTION):
            self.c.add_section(SERV_SECTION)
        self.c.set(SERV_SECTION, SERV_NAME, SERV_NAME_DEFAULT)
        self.c.set(SERV_SECTION, SERV_DISPLAY_NAME, SERV_DISPLAY_NAME_DEFAULT)
        self.c.set(SERV_SECTION, SERV_DESC, SERV_DESC_DEFAULT)
        self.c.set(SERV_SECTION, SERV_LOG_FILE, SERV_LOG_FILE_DEFAULT)
        cfg = file(self.ini, 'wr')
        self.c.write(cfg)
        cfg.close()
        print '''
you must set the celery:service section service_name, service_display_name,
and service_description options to define the service 
in the %s file
''' % self.ini
        sys.exit()


class CeleryService(win32serviceutil.ServiceFramework):
    """NT Service."""

    d = DefaultSettings()
    service_name, service_display_name, service_description, iniFile, logFile = d.getDefaults()

    _svc_name_ = service_name
    _svc_display_name_ = service_display_name
    _svc_description_ = service_description

    def __init__(self, args):
        win32serviceutil.ServiceFramework.__init__(self, args)
        # create an event that SvcDoRun can wait on and SvcStop
        # can set.
        self.stop_event = win32event.CreateEvent(None, 0, 0, None)

    def SvcDoRun(self):
        os.chdir(SCRIPT_DIR)
        s = Server(SERV_APPLICATION)
        os.environ[SERV_LOG_FILE_VAR] = self.logFile
        s.run([self.iniFile])
        win32event.WaitForSingleObject(self.stop_event, win32event.INFINITE)

    def SvcStop(self):
        self.ReportServiceStatus(win32service.SERVICE_STOP_PENDING)
        #win32event.SetEvent(self.stop_event)
        self.ReportServiceStatus(win32service.SERVICE_STOPPED)
        sys.exit()

if __name__ == '__main__':
    win32serviceutil.HandleCommandLine(CeleryService)

To install the service run python CeleryService.py install and then python CeleryService.py start to start the service. NOTE: These commands should be run in command-line with administrator rights.

If the service needs to be removed, run python CeleryService.py remove.

I was trying to host Celery as part of enhancing my RhodeCode installation. This solution seems to work. Hope this will help someone.