ansible/library/async_wrapper

#!/usr/bin/python

# (c) 2012, Michael DeHaan <michael.dehaan@gmail.com>, and others
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
#

try:
    import json
except ImportError:
    import simplejson as json
import shlex
import os
import subprocess
import sys
import datetime
import traceback
import signal
import time

def daemonize_self():
    # daemonizing code: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66012
    # logger.info("cobblerd started")
    try:
        pid = os.fork()
        if pid > 0:
            # exit first parent
            sys.exit(0)
    except OSError, e:
        print >>sys.stderr, "fork #1 failed: %d (%s)" % (e.errno, e.strerror)
        sys.exit(1)

    # decouple from parent environment
    os.chdir("/")
    os.setsid()
    os.umask(022)

    # do second fork
    try:
        pid = os.fork()
        if pid > 0:
            # print "Daemon PID %d" % pid
            sys.exit(0)
    except OSError, e:
        print >>sys.stderr, "fork #2 failed: %d (%s)" % (e.errno, e.strerror)
        sys.exit(1)

    dev_null = file('/dev/null','rw')
    os.dup2(dev_null.fileno(), sys.stdin.fileno())
    os.dup2(dev_null.fileno(), sys.stdout.fileno())
    os.dup2(dev_null.fileno(), sys.stderr.fileno()) 

if len(sys.argv) < 3:
    print json.dumps({
        "failed" : True,
        "msg"    : "usage: async_wrapper <jid> <time_limit> <modulescript> <argsfile>.  Humans, do not call directly!"
    })
    sys.exit(1)

jid = sys.argv[1]
time_limit = sys.argv[2]
wrapped_module = sys.argv[3]
argsfile = sys.argv[4]
cmd = "%s %s" % (wrapped_module, argsfile)

# setup logging directory
logdir = os.path.expanduser("~/.ansible_async")
log_path = os.path.join(logdir, jid)

if not os.path.exists(logdir):
    try:
        os.makedirs(logdir)
    except:
        print json.dumps({
            "failed" : 1,
            "msg" : "could not create: %s" % logdir
        })

def _run_command(wrapped_cmd, jid, log_path):

    logfile = open(log_path, "w")
    logfile.write(json.dumps({ "started" : 1, "ansible_job_id" : jid }))
    logfile.close()
    logfile = open(log_path, "w")
    result = {}
  
    outdata = ''
    try:
        cmd = shlex.split(wrapped_cmd)
        script = subprocess.Popen(cmd, shell=False, 
            stdin=None, stdout=logfile, stderr=logfile)
        script.communicate()
        outdata = file(log_path).read()
        result = json.loads(outdata)

    except (OSError, IOError), e:
        result = {
            "failed": 1,
            "cmd" : wrapped_cmd,
            "msg": str(e),
        }
        result['ansible_job_id'] = jid
        logfile.write(json.dumps(result))
    except:
        result = {
            "failed" : 1,
            "cmd" : wrapped_cmd,
            "data" : outdata, # temporary debug only
            "msg" : traceback.format_exc()
        }   
        result['ansible_job_id'] = jid
        logfile.write(json.dumps(result))
    logfile.close()

# immediately exit this process, leaving an orphaned process
# running which immediately forks a supervisory timing process

pid = os.fork()
if pid != 0:
   # the parent indicates the job has started
   # print "RETURNING SUCCESS IN PARENT"
   print json.dumps({ "started" : 1, "ansible_job_id" : jid, "results_file" : log_path })
   sys.stdout.flush()
   # we need to not return immmediately such that the launched command has an attempt
   # to initialize PRIOR to ansible trying to clean up the launch directory (and argsfile)
   # this probably could be done with some IPC later.  Modules should always read
   # the argsfile at the very first start of their execution anyway
   time.sleep(1)
   sys.exit(0)
else:
   # the kid manages the job
   # WARNING: the following call may be total overkill
   daemonize_self()

   # we are now daemonized in this other fork but still
   # want to create a supervisory process

   #print "DAEMONIZED KID MAKING MORE KIDS"
   sub_pid = os.fork()
   if sub_pid == 0:
       #print "RUNNING IN KID A"
       _run_command(cmd, jid, log_path)
       #print "KID A COMPLETE"
       sys.stdout.flush()
       sys.exit(0)
   else:
       #print "WATCHING IN KID B"
       remaining = int(time_limit)
       if os.path.exists("/proc/%s" % sub_pid):
           #print "STILL RUNNING"
           time.sleep(1)
           remaining = remaining - 1
       else:
           #print "DONE IN KID B"
           sys.stdout.flush()
           sys.exit(0)
       if remaining == 0:
           #print "SLAYING IN KID B"
           os.kill(sub_pid, signals.SIGKILL)
           sys.stdout.flush()
           sys.exit(1)

   sys.stdout.flush()
   sys.exit(0)