ansible/utilities/logic/async_wrapper.py

#!/usr/bin/python
# -*- coding: utf-8 -*-

# (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 traceback
import signal
import time
import syslog

PY3 = sys.version_info[0] == 3

syslog.openlog('ansible-%s' % os.path.basename(__file__))
syslog.syslog(syslog.LOG_NOTICE, 'Invoked with %s' % " ".join(sys.argv[1:]))

def notice(msg):
    syslog.syslog(syslog.LOG_NOTICE, msg)

def daemonize_self():
    # daemonizing code: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/66012
    try:
        pid = os.fork()
        if pid > 0:
            # exit first parent
            sys.exit(0)
    except OSError:
        e = sys.exc_info()[1]
        sys.exit("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))

    # decouple from parent environment (does not chdir / to keep the directory context the same as for non async tasks)
    os.setsid()
    os.umask(int('022', 8))

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

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

# NB: this function copied from module_utils/json_utils.py. Ensure any changes are propagated there.
# FUTURE: AnsibleModule-ify this module so it's Ansiballz-compatible and can use the module_utils copy of this function.
def _filter_non_json_lines(data):
    '''
    Used to filter unrelated output around module JSON output, like messages from
    tcagetattr, or where dropbear spews MOTD on every single command (which is nuts).

    Filters leading lines before first line-starting occurrence of '{' or '[', and filter all
    trailing lines after matching close character (working from the bottom of output).
    '''
    warnings = []

    # Filter initial junk
    lines = data.splitlines()

    for start, line in enumerate(lines):
        line = line.strip()
        if line.startswith(u'{'):
            endchar = u'}'
            break
        elif line.startswith(u'['):
            endchar = u']'
            break
    else:
        raise ValueError('No start of json char found')

    # Filter trailing junk
    lines = lines[start:]

    for reverse_end_offset, line in enumerate(reversed(lines)):
        if line.strip().endswith(endchar):
            break
    else:
        raise ValueError('No end of json char found')

    if reverse_end_offset > 0:
        # Trailing junk is uncommon and can point to things the user might
        # want to change.  So print a warning if we find any
        trailing_junk = lines[len(lines) - reverse_end_offset:]
        warnings.append('Module invocation had junk after the JSON data: %s' % '\n'.join(trailing_junk))

    lines = lines[:(len(lines) - reverse_end_offset)]

    return ('\n'.join(lines), warnings)

def _run_module(wrapped_cmd, jid, job_path):

    tmp_job_path = job_path + ".tmp"
    jobfile = open(tmp_job_path, "w")
    jobfile.write(json.dumps({ "started" : 1, "finished" : 0, "ansible_job_id" : jid }))
    jobfile.close()
    os.rename(tmp_job_path, job_path)
    jobfile = open(tmp_job_path, "w")
    result = {}

    outdata = ''
    filtered_outdata = ''
    stderr = ''
    try:
        cmd = shlex.split(wrapped_cmd)
        script = subprocess.Popen(cmd, shell=False, stdin=None, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
        (outdata, stderr) = script.communicate()
        if PY3:
            outdata = outdata.decode('utf-8', 'surrogateescape')
            stderr = stderr.decode('utf-8', 'surrogateescape')

        (filtered_outdata, json_warnings) = _filter_non_json_lines(outdata)

        result = json.loads(filtered_outdata)

        if json_warnings:
            # merge JSON junk warnings with any existing module warnings
            module_warnings = result.get('warnings', [])
            if type(module_warnings) is not list:
                module_warnings = [module_warnings]
            module_warnings.extend(json_warnings)
            result['warnings'] = module_warnings

        if stderr:
            result['stderr'] = stderr
        jobfile.write(json.dumps(result))

    except (OSError, IOError):
        e = sys.exc_info()[1]
        result = {
            "failed": 1,
            "cmd" : wrapped_cmd,
            "msg": str(e),
            "outdata": outdata, # temporary notice only
            "stderr": stderr
        }
        result['ansible_job_id'] = jid
        jobfile.write(json.dumps(result))

    except (ValueError, Exception):
        result = {
            "failed" : 1,
            "cmd" : wrapped_cmd,
            "data" : outdata, # temporary notice only
            "stderr": stderr,
            "msg" : traceback.format_exc()
        }
        result['ansible_job_id'] = jid
        jobfile.write(json.dumps(result))

    jobfile.close()
    os.rename(tmp_job_path, job_path)


####################
##      main      ##
####################
if __name__ == '__main__':

    if len(sys.argv) < 5:
        print(json.dumps({
            "failed" : True,
            "msg"    : "usage: async_wrapper <jid> <time_limit> <modulescript> <argsfile>.  Humans, do not call directly!"
        }))
        sys.exit(1)

    jid = "%s.%d" % (sys.argv[1], os.getpid())
    time_limit = sys.argv[2]
    wrapped_module = sys.argv[3]
    argsfile = sys.argv[4]
    # consider underscore as no argsfile so we can support passing of additional positional parameters
    if argsfile != '_':
        cmd = "%s %s" % (wrapped_module, argsfile)
    else:
        cmd = wrapped_module
    step = 5

    # setup job output directory
    jobdir = os.path.expanduser("~/.ansible_async")
    job_path = os.path.join(jobdir, jid)

    if not os.path.exists(jobdir):
        try:
            os.makedirs(jobdir)
        except:
            print(json.dumps({
                "failed" : 1,
                "msg" : "could not create: %s" % jobdir
            }))
    # immediately exit this process, leaving an orphaned process
    # running which immediately forks a supervisory timing process

    try:
        pid = os.fork()
        if pid:
            # Notify the overlord that the async process started

            # 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
            notice("Return async_wrapper task started.")
            print(json.dumps({ "started" : 1, "finished" : 0, "ansible_job_id" : jid, "results_file" : job_path }))
            sys.stdout.flush()
            time.sleep(1)
            sys.exit(0)
        else:
            # The actual wrapper process

            # Daemonize, so we keep on running
            daemonize_self()

            # we are now daemonized, create a supervisory process
            notice("Starting module and watcher")

            sub_pid = os.fork()
            if sub_pid:
                # the parent stops the process after the time limit
                remaining = int(time_limit)

                # set the child process group id to kill all children
                os.setpgid(sub_pid, sub_pid)

                notice("Start watching %s (%s)"%(sub_pid, remaining))
                time.sleep(step)
                while os.waitpid(sub_pid, os.WNOHANG) == (0, 0):
                    notice("%s still running (%s)"%(sub_pid, remaining))
                    time.sleep(step)
                    remaining = remaining - step
                    if remaining <= 0:
                        notice("Now killing %s"%(sub_pid))
                        os.killpg(sub_pid, signal.SIGKILL)
                        notice("Sent kill to group %s"%sub_pid)
                        time.sleep(1)
                        sys.exit(0)
                notice("Done in kid B.")
                sys.exit(0)
            else:
                # the child process runs the actual module
                notice("Start module (%s)"%os.getpid())
                _run_module(cmd, jid, job_path)
                notice("Module complete (%s)"%os.getpid())
                sys.exit(0)

    except SystemExit:
        # On python2.4, SystemExit is a subclass of Exception.
        # This block makes python2.4 behave the same as python2.5+
        raise

    except Exception:
        e = sys.exc_info()[1]
        notice("error: %s"%(e))
        print(json.dumps({
            "failed" : True,
            "msg"    : "FATAL ERROR: %s" % str(e)
        }))
        sys.exit(1)