community.general/lib/ansible/module_utils/service.py

# This code is part of Ansible, but is an independent component.
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import glob
import os
import pickle
import platform
import select
import shlex
import subprocess
import traceback

from ansible.module_utils.six import PY2, b
from ansible.module_utils._text import to_bytes, to_text


def sysv_is_enabled(name):
    '''
    This function will check if the service name supplied
    is enabled in any of the sysv runlevels

    :arg name: name of the service to test for
    '''
    return bool(glob.glob('/etc/rc?.d/S??%s' % name))


def get_sysv_script(name):
    '''
    This function will return the expected path for an init script
    corresponding to the service name supplied.

    :arg name: name or path of the service to test for
    '''
    if name.startswith('/'):
        result = name
    else:
        result = '/etc/init.d/%s' % name

    return result


def sysv_exists(name):
    '''
    This function will return True or False depending on
    the existence of an init script corresponding to the service name supplied.

    :arg name: name of the service to test for
    '''
    return os.path.exists(get_sysv_script(name))


def fail_if_missing(module, found, service, msg=''):
    '''
    This function will return an error or exit gracefully depending on check mode status
    and if the service is missing or not.

    :arg module: is an  AnsibleModule object, used for it's utility methods
    :arg found: boolean indicating if services was found or not
    :arg service: name of service
    :kw msg: extra info to append to error/success msg when missing
    '''
    if not found:
        if module.check_mode:
            module.exit_json(msg="Service %s not found on %s, assuming it will exist on full run" % (service, msg), changed=True)
        else:
            module.fail_json(msg='Could not find the requested service %s: %s' % (service, msg))


def fork_process():
    '''
    This function performs the double fork process to detach from the
    parent process and execute.
    '''
    pid = os.fork()

    if pid == 0:
        # Set stdin/stdout/stderr to /dev/null
        fd = os.open(os.devnull, os.O_RDWR)

        # clone stdin/out/err
        for num in range(3):
            if fd != num:
                os.dup2(fd, num)

        # close otherwise
        if fd not in range(3):
            os.close(fd)

        # Make us a daemon
        pid = os.fork()

        # end if not in child
        if pid > 0:
            os._exit(0)

        # get new process session and detach
        sid = os.setsid()
        if sid == -1:
            raise Exception("Unable to detach session while daemonizing")

        # avoid possible problems with cwd being removed
        os.chdir("/")

        pid = os.fork()
        if pid > 0:
            os._exit(0)

    return pid


def daemonize(module, cmd):
    '''
    Execute a command while detaching as a daemon, returns rc, stdout, and stderr.

    :arg module: is an  AnsibleModule object, used for it's utility methods
    :arg cmd: is a list or string representing the command and options to run

    This is complex because daemonization is hard for people.
    What we do is daemonize a part of this module, the daemon runs the command,
    picks up the return code and output, and returns it to the main process.
    '''

    # init some vars
    chunk = 4096  # FIXME: pass in as arg?
    errors = 'surrogate_or_strict'

    # start it!
    try:
        pipe = os.pipe()
        pid = fork_process()
    except OSError:
        module.fail_json(msg="Error while attempting to fork: %s", exception=traceback.format_exc())
    except Exception as exc:
        module.fail_json(msg=to_text(exc), exception=traceback.format_exc())

    # we don't do any locking as this should be a unique module/process
    if pid == 0:
        os.close(pipe[0])

        # if command is string deal with  py2 vs py3 conversions for shlex
        if not isinstance(cmd, list):
            if PY2:
                cmd = shlex.split(to_bytes(cmd, errors=errors))
            else:
                cmd = shlex.split(to_text(cmd, errors=errors))

        # make sure we always use byte strings
        run_cmd = []
        for c in cmd:
            run_cmd.append(to_bytes(c, errors=errors))

        # execute the command in forked process
        p = subprocess.Popen(run_cmd, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE, preexec_fn=lambda: os.close(pipe[1]))
        fds = [p.stdout, p.stderr]

        # loop reading output till its done
        output = {p.stdout: b(""), p.sterr: b("")}
        while fds:
            rfd, wfd, efd = select.select(fds, [], fds, 1)
            if (rfd + wfd + efd) or p.poll():
                for out in fds:
                    if out in rfd:
                        data = os.read(out.fileno(), chunk)
                        if not data:
                            fds.remove(out)
                    output[out] += b(data)

        # even after fds close, we might want to wait for pid to die
        p.wait()

        # Return a pickled data of parent
        return_data = pickle.dumps([p.returncode, to_text(output[p.stdout]), to_text(output[p.stderr])], protocol=pickle.HIGHEST_PROTOCOL)
        os.write(pipe[1], to_bytes(return_data, errors=errors))

        # clean up
        os.close(pipe[1])
        os._exit(0)

    elif pid == -1:
        module.fail_json(msg="Unable to fork, no exception thrown, probably due to lack of resources, check logs.")

    else:
        # in parent
        os.close(pipe[1])
        os.waitpid(pid, 0)

        # Grab response data after child finishes
        return_data = b("")
        while True:
            rfd, wfd, efd = select.select([pipe[0]], [], [pipe[0]])
            if pipe[0] in rfd:
                data = os.read(pipe[0], chunk)
                if not data:
                    break
                return_data += b(data)

        # Note: no need to specify encoding on py3 as this module sends the
        # pickle to itself (thus same python interpreter so we aren't mixing
        # py2 and py3)
        return pickle.loads(to_bytes(return_data, errors=errors))


def check_ps(module, pattern):

    # Set ps flags
    if platform.system() == 'SunOS':
        psflags = '-ef'
    else:
        psflags = 'auxww'

    # Find ps binary
    psbin = module.get_bin_path('ps', True)

    (rc, out, err) = module.run_command('%s %s' % (psbin, psflags))
    # If rc is 0, set running as appropriate
    if rc == 0:
        for line in out.split('\n'):
            if pattern in line:
                return True
    return False