ansible/library/cron

#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# (c) 2012, Dane Summers <dsummers@pinedesk.biz>
#
# 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/>.

# Cron Plugin: The goal of this plugin is to provide an indempotent method for
# setting up cron jobs on a host. The script will play well with other manually
# entered crons. Each cron job entered will be preceded with a comment
# describing the job so that it can be found later, which is required to be
# present in order for this plugin to find/modify the job.

DOCUMENTATION = '''
---
module: cron
short_description: Manage crontab entries.
description:
     - Use this module to manage crontab entries. This module allows you to create named
       crontab entries, update, or delete them.
     - The module include one line with the description of the crontab entry "#Ansible: <name>" 
       corresponding to the 'name' passed to the module, which is used by future ansible/module calls
       to find/check the state.
version_added: "0.9"
options:
  name:
    description:
      - Description of a crontab entry.
    required: true
    default:
    aliases: []
  user:
    description:
      - The specific user who's crontab should be modified.
    required: false
    default: root
    aliases: []
  job:
    description:
      - The command to execute.
      - Required if state=present.
    required: false
    default: 
    aliases: []
  state:
    description:
      - Whether to ensure the job is present or absent.
    required: false
    default: present
    aliases: []
  backup:
    description:
      - If set, then create a backup of the crontab before it is modified.
      - The location of the backup is returned in the 'backup' variable by this module.
    required: false
    default: false
    aliases: []
  minute:
    description:
      - Minute when the job should run ( 0-59, *, */2, etc )
    required: false
    default: *
    aliases: []
  hour:
    description:
      - Hour when the job should run ( 0-23, *, */2, etc )
    required: false
    default: *
    aliases: []
  day:
    description:
      - Day of the month the job should run ( 1-31, *, */2, etc )
    required: false
    default: *
    aliases: []
  month:
    description:
      - Month of the year the job should run ( 1-12, *, */2, etc )
    required: false
    default: *
    aliases: []
  weekday:
    description:
      - Day of the week that the job should run ( 0-7 for Sunday - Saturday, or mon, tue, * etc )
    required: false
    default: *
    aliases: []
examples:
   - code: cron name="check dirs" hour="5,2" job="ls -alh > /dev/null"
     description: Ensure a job that runs at 2 and 5 exists. Creates an entry like "* 5,2 * * ls -alh > /dev/null"
   - code: name="an old job" cron job="/some/dir/job.sh" state=absent
     description: Ensure an old job is no longer present. Removes any job that is preceded by "#Ansible: an old job" in the crontab
requirements: cron
author: Dane Summers
'''

import re
import tempfile

def get_jobs_file(user,tmpfile):
    cmd = "crontab -l %s > %s" % (user,tmpfile)
    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    (out, err) = cmd.communicate()
    rc = cmd.returncode
    return (rc, out, err)

def install_jobs(user,tmpfile):
    cmd = "crontab %s %s" % (user,tmpfile)
    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    (out, err) = cmd.communicate()
    rc = cmd.returncode
    return (rc, out, err)

def get_jobs(tmpfile):
    lines = open(tmpfile).read().splitlines()
    comment = None
    jobs = []
    for l in lines:
        if comment is not None:
            jobs.append([comment,l])
            comment = None
        elif re.match( r'#Ansible: ',l):
            comment = re.sub( r'#Ansible: ', '', l)
    return jobs

def find_job(name,tmpfile):
    jobs = get_jobs(tmpfile)
    for j in jobs:
        if j[0] == name:
            return j
    return []

def add_job(name,job,tmpfile):
    cmd = "echo \"#Ansible: %s\n%s\" >> %s" % (name,job,tmpfile)
    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    (out, err) = cmd.communicate()
    rc = cmd.returncode
    return (rc, out, err)


def update_job(name,job,tmpfile):
    return _update_job(name,job,tmpfile,do_add_job)

def do_add_job (lines, comment, job):
    lines.append(comment)
    lines.append(job)

def remove_job(name,tmpfile):
    return _update_job(name,"",tmpfile,do_remove_job)

def do_remove_job(lines,comment,job):
    return None

def _update_job(name,job,tmpfile,addlinesfunction):
    ansiblename="#Ansible: %s" % (name)
    f = open(tmpfile)
    lines = f.read().splitlines()
    newlines = []
    comment = None
    for l in lines:
        if comment is not None:
            addlinesfunction(newlines,comment,job)
            comment = None
        elif l == ansiblename:
            comment = l
        else:
            newlines.append(l)
    f.close()
    f = open(tmpfile,'w')
    for l in newlines:
        f.write(l)
        f.write('\n')
    f.close()
    return (0,"","") # TODO add some more error testing 

def main():
    # The following example playbooks:
    # - action: cron name="check dirs" hour="5,2" job="ls -alh > /dev/null"
    # - name: do the job
    #   action: name="do the job" cron hour="5,2" job="/some/dir/job.sh"
    # - name: no job
    #   action: name="an old job" cron job="/some/dir/job.sh" state=absent
    #
    # Would produce:
    # # Ansible: check dirs
    # * * 5,2 * * ls -alh > /dev/null
    # # Ansible: do the job
    # * * 5,2 * * /some/dir/job.sh

    # Function:
    # 1. dump the existing cron:
    #    crontab -l -u <user> > /tmp/tmpfile
    # 2. search for comment "^# Ansible: <name>" followed by a cron.
    # 3. if absent: remove if present (and say modified), otherwise return with no mod.
    # 4. if present: if the same return no mod, if not present add (and say mod), if different add (and say mod)
    # 5. Install new cron (if mod):
    #    crontab -u <user> /tmp/tmpfile
    # 6. return mod

    module = AnsibleModule(
        argument_spec = dict(
            name=dict(required=True),
            user=dict(required=False),
            job=dict(required=False),
            state=dict(default='present', choices=['present', 'absent']),
            backup=dict(default=False, choices=BOOLEANS),
            minute=dict(default='*'),
            hour=dict(default='*'),
            day=dict(default='*'),
            month=dict(default='*'),
            weekday=dict(default='*')
        )
    )

    backup     = module.boolean(module.params.get('backup', False))
    name       = module.params['name']
    user       = module.params['user']
    job        = module.params['job']
    minute     = module.params['minute']
    hour       = module.params['hour']
    day        = module.params['day']
    month      = module.params['month']
    weekday    = module.params['weekday']
    do_install = module.params['state'] == 'present'
    changed    = False
    job = "%s %s %s %s %s %s" % (minute,hour,day,month,weekday,job)

    if not user:
        user = ""
    else:
        user = "-u %s" % (user)

    rc, out, err, status = (0, None, None, None)

    if job is None and do_install:
        module.fail_json(msg="You must specify 'job' to install a new cron job")
    tmpfile = tempfile.NamedTemporaryFile()
    (rc, out, err) = get_jobs_file(user,tmpfile.name)
    if rc != 0 and rc != 1: # 1 can mean that there are no jobs.
        module.fail_json(msg=err)
    backupfile = tempfile.NamedTemporaryFile(prefix='crontab',delete=False)
    (rc, out, err) = get_jobs_file(user,backupfile.name)
    if rc != 0 and rc != 1:
        module.fail_json(msg=err)
    old_job = find_job(name,backupfile.name)
    if do_install:
        if len(old_job) == 0:
            (rc, out, err) = add_job(name,job,tmpfile.name)
            changed = True
        if len(old_job) > 0 and old_job[1] != job:
            (rc, out, err) = update_job(name,job,tmpfile.name)
            changed = True
    else:
        if len(old_job) > 0:
            (rc, out, err) = remove_job(name,tmpfile.name)
            changed = True
    if (rc != 0):
        module.fail_json(msg=err)
    if changed:
        if backup:
            module.backup_local(backupfile.name)
        (rc, out, err) = install_jobs(user,tmpfile.name)
        if (rc != 0):
            module.fail_json(msg=err)

    jobnames = []
    for j in get_jobs(tmpfile.name):
        jobnames.append(j[0])
    tmpfile.close()
    backupfile.close()
    if not backup:
        module.exit_json(changed=changed,jobs=jobnames)
    else:
        module.exit_json(changed=changed,jobs=jobnames,backup=backupfile.name)

# include magic from lib/ansible/module_common.py
#<<INCLUDE_ANSIBLE_MODULE_COMMON>>
main()