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Filename : cc_power_state_change.py
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# Copyright (C) 2011 Canonical Ltd.
#
# Author: Scott Moser <scott.moser@canonical.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

"""Power State Change: Change power state"""

import errno
import logging
import os
import re
import subprocess
import time

from cloudinit import signal_handler, subp, util
from cloudinit.cloud import Cloud
from cloudinit.config import Config
from cloudinit.config.schema import MetaSchema
from cloudinit.distros import ALL_DISTROS
from cloudinit.settings import PER_INSTANCE

frequency = PER_INSTANCE

EXIT_FAIL = 254

meta: MetaSchema = {
    "id": "cc_power_state_change",
    "distros": [ALL_DISTROS],
    "frequency": PER_INSTANCE,
    "activate_by_schema_keys": ["power_state"],
}

LOG = logging.getLogger(__name__)


def givecmdline(pid):
    # Returns the cmdline for the given process id. In Linux we can use procfs
    # for this but on BSD there is /usr/bin/procstat.
    try:
        # Example output from procstat -c 1
        #   PID COMM             ARGS
        #     1 init             /bin/init --
        if util.is_FreeBSD():
            (output, _err) = subp.subp(["procstat", "-c", str(pid)])
            line = output.splitlines()[1]
            m = re.search(r"\d+ (\w|\.|-)+\s+(/\w.+)", line)
            return m.group(2)
        else:
            return util.load_text_file("/proc/%s/cmdline" % pid)
    except IOError:
        return None


def check_condition(cond):
    if isinstance(cond, bool):
        LOG.debug("Static Condition: %s", cond)
        return cond

    pre = "check_condition command (%s): " % cond
    try:
        proc = subprocess.Popen(cond, shell=not isinstance(cond, list))
        proc.communicate()
        ret = proc.returncode
        if ret == 0:
            LOG.debug("%sexited 0. condition met.", pre)
            return True
        elif ret == 1:
            LOG.debug("%sexited 1. condition not met.", pre)
            return False
        else:
            LOG.warning("%sunexpected exit %s. do not apply change.", pre, ret)
            return False
    except Exception as e:
        LOG.warning("%sUnexpected error: %s", pre, e)
        return False


def handle(name: str, cfg: Config, cloud: Cloud, args: list) -> None:
    try:
        (arg_list, timeout, condition) = load_power_state(cfg, cloud.distro)
        if arg_list is None:
            LOG.debug("no power_state provided. doing nothing")
            return
    except Exception as e:
        LOG.warning("%s Not performing power state change!", str(e))
        return

    if condition is False:
        LOG.debug("Condition was false. Will not perform state change.")
        return

    mypid = os.getpid()

    cmdline = givecmdline(mypid)
    if not cmdline:
        LOG.warning("power_state: failed to get cmdline of current process")
        return

    devnull_fp = open(os.devnull, "w")

    LOG.debug("After pid %s ends, will execute: %s", mypid, " ".join(arg_list))

    util.fork_cb(
        run_after_pid_gone,
        mypid,
        cmdline,
        timeout,
        condition,
        execmd,
        [arg_list, devnull_fp],
    )


def load_power_state(cfg, distro):
    # returns a tuple of shutdown_command, timeout
    # shutdown_command is None if no config found
    pstate = cfg.get("power_state")

    if pstate is None:
        return (None, None, None)

    if not isinstance(pstate, dict):
        raise TypeError("power_state is not a dict.")

    modes_ok = ["halt", "poweroff", "reboot"]
    mode = pstate.get("mode")
    if mode not in distro.shutdown_options_map:
        raise TypeError(
            "power_state[mode] required, must be one of: %s. found: '%s'."
            % (",".join(modes_ok), mode)
        )

    args = distro.shutdown_command(
        mode=mode,
        delay=pstate.get("delay", "now"),
        message=pstate.get("message"),
    )

    try:
        timeout = float(pstate.get("timeout", 30.0))
    except ValueError as e:
        raise ValueError(
            "failed to convert timeout '%s' to float." % pstate["timeout"]
        ) from e

    condition = pstate.get("condition", True)
    if not isinstance(condition, (str, list, bool)):
        raise TypeError("condition type %s invalid. must be list, bool, str")
    return (args, timeout, condition)


def doexit(sysexit):
    os._exit(sysexit)


def execmd(exe_args, output=None, data_in=None):
    ret = 1
    try:
        proc = subprocess.Popen(  # nosec B603
            exe_args,
            stdin=subprocess.PIPE,
            stdout=output,
            stderr=subprocess.STDOUT,
        )
        proc.communicate(data_in)
        ret = proc.returncode
    except Exception:
        doexit(EXIT_FAIL)
    doexit(ret)


def run_after_pid_gone(pid, pidcmdline, timeout, condition, func, args):
    # wait until pid, with /proc/pid/cmdline contents of pidcmdline
    # is no longer alive.  After it is gone, or timeout has passed
    # execute func(args)
    msg = None
    end_time = time.monotonic() + timeout

    def fatal(msg):
        LOG.warning(msg)
        doexit(EXIT_FAIL)

    known_errnos = (errno.ENOENT, errno.ESRCH)

    while True:
        if time.monotonic() > end_time:
            msg = "timeout reached before %s ended" % pid
            break

        try:
            cmdline = givecmdline(pid)
            if cmdline != pidcmdline:
                msg = "cmdline changed for %s [now: %s]" % (pid, cmdline)
                break

        except IOError as ioerr:
            if ioerr.errno in known_errnos:
                msg = "pidfile gone [%d]" % ioerr.errno
            else:
                fatal("IOError during wait: %s" % ioerr)
            break

        except Exception as e:
            fatal("Unexpected Exception: %s" % e)

        time.sleep(0.25)

    if not msg:
        fatal("Unexpected error in run_after_pid_gone")

    LOG.debug(msg)

    try:
        if not check_condition(condition):
            return
    except Exception as e:
        fatal("Unexpected Exception when checking condition: %s" % e)

    # systemd could kill this process with a signal before it exits
    # this is expected, so don't crash
    with signal_handler.suspend_crash():
        func(*args)