Initial commit

Separate project from updater-ng repository and mark is as 1.0.

README.md

+Updater-ng supervisor
+=====================
+Supervising daemon, tool and Python3 library for Updater-ng. The idea is that
+updater it self takes a long time to run and this should add simple enough layer
+on top of it to run and manage updater from some front-end. It fulfills following
+roles and features:
+* Supervises user unsupervised `pkgupdate` execution and reports fatal failures
+* Allows front-end to run updater in background
+* Provides a way to check for updater lock status (to see if updater is running)
+* Provides configuration wrapper for updater
+* Implements delayed and approved updates (generally known as updater approvals)
+* Periodic updater execution with possible random delay
+
+This tool is Turris OS specific. You can use this as a code base to write your own
+but you are going to have hard time in integrating it to other distributions.
+
+Checking for updater status
+----------------------------
+Currently only checks if updater or opkg is running and check if there is instance
+of updater running in supervisor are implemented.
+
+To check if updater or opkg is running you can use function `opkg_lock()` which
+returns boolean depending on opkg lock status.
+
+To check if there is supervised updater running then you can call
+`updater_supervised()`.
+
+Running pkgupdate with supervisor
+---------------------------------
+To run updater you can either directly run `updater-supervisor` script or you can
+use library and `run(wait_for_network, ensure_run, timeout, timeout_kill,
+hooklist)` function.
+
+Updater and updater-supervisor configuration
+---------------------------------------------
+Both updater-ng and updater-supervisor are using UCI for configuration. There are
+three primary sections of configuration: `autorun`, `l10n` and `lists`.
+
+All configuration is in UCI file `updater`.
+
+### autorun
+This is intended as a configuration for updater-supervisor. It configures
+automatic execution and approvals.
+
+`enabled()` and `set_enabled(enabled)` are getter and setter for
+`updater.autorun.enabled` config. If this is not set to `True` updater-supervisor
+won't start `pkgupdate`.
+
+`approvals()` and `set_approvals(enabled)` are getter and setter for
+`updater.autorun.approvals`. This informs updater-supervisor if `pkgupdate` should
+be run so it immediately updates system or if it should rather only generate plan
+that has to be approved.
+
+`auto_approve_time()` and `set_auto_approve_time(approve_time)` are getter and
+setter for `updater.autorun.auto_approve_time`. This is number of hours before
+approval is automatically granted. This implements update delay.
+
+### l10n
+Updater in Turris OS support multiple languages. Supported languages are provided
+by additional file provided by separate package but updater-supervisor serves as
+a bridge between that file and updater configuration (`updater.l10n`)
+
+To get current state and list of all supported languages at once you can call
+function `l10n.languages()`. This returns dictionary where keys are language codes
+and values are boolean specification if language should or should not be
+installed. You can edit this table and pass it back to
+`l10n.update_languages(langs)` to save settings. By that you are adding or
+removing lists to/from `updater.l10n.langs`.
+
+### lists
+Updater in Turris OS supports additional sets of packages called package lists.
+The definition is provided as file by package the same way as in case of l10n. The
+approach to lists is same as in case of l10n with exception that more information
+are provided by `lists.pkglists(lang)`.
+
+Approvals
+---------
+This is a feature that simulates otherwise normal package manager execution with
+user approving changes to system explicitly. This feature can also be configured
+to serve as delayed updates to just delay update by some amount of time.
+
+The implementation expects updater to be run as usual in periodic runs but
+supervisor automatically configures updater to not install update unless it was
+approved by it. This is done by providing hash of approved plan (or not providing
+any). Updater automatically only plans actions and unless those actions were
+approved (hash is same as provided by supervisor) it does not continue and instead
+dumps plan information. Front-end can receive such plan with
+`approvals.current()`. It later can either approve it by `approvals.approve(hash)`
+or deny it `approvals.approve(hash)`. If plan is denied then it won't be
+automatically approved later on if delayed updates are configured.
+
+See also `autorun` configuration section for configuration options that are
+considered in approvals.
+
+Note that for correct functionality there is `files/hook_postupdate` script that
+should be placed in `/etc/updater/hook_postupdate` to be run after `pkgupdate`
+completion. It is supporting script to handle situation when supervisor is not the
+only one running `pkgupdate`.
+
+Periodic runs
+-------------
+Cron is used to run updater periodically to check for updates. In short there is a
+cron file in `files` directory that can be used to run updater every four hours.
+
+Updater supervisor is in such case run in background which is required because
+otherwise it would hang cron execution. Another argument is `--rand-sleep`. This
+delays real `pkgupdate` execution by random amount of time. This was introduced to
+spread server load, it is highly suggested to use random delay for periodic
+updater execution.

files/cron

+MAILTO=""
+0	0-23/4	*	*	*	root	/usr/bin/updater-supervisor -d --rand-sleep

files/hook_postupdate

+#!/bin/sh
+# Updater it self is not aware of approvals. Those are completely handled in
+# updater-supervisor. But when updater does something to system it's most probable
+# that it invalidated current approval request. So this script just removes it
+# every time update proceeds.
+rm -f /usr/share/updater/approvals

files/immediate_reboot.init

+#!/bin/sh /etc/rc.common
+
+# This script handles updater-ng immediate reboot recovery. After an immediate
+# reboot there is going to be a journal and we should continue execution from it
+# as soon as possible.
+
+START=85
+
+status() {
+	return 0
+}
+
+start() {
+	# Recover updater's journal if it exists
+	if [ -e "/usr/share/updater/journal" ]; then
+		# Note: supervisor runs pkgupdate that recovers run from journal and later
+		# checks for update. This update is required because there could have been
+		# replan planned after reboot and this ensures that we do replan as soon
+		# as possible.
+		updater-supervisor
+	fi
+}
+
+stop() {
+	:
+}
+
+restart() {
+	:
+}
+
+reload() {
+	:
+}

setup.py

+#!/usr/bin/env python3
+# Copyright (c) 2018-2019, CZ.NIC, z.s.p.o. (http://www.nic.cz/)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#    * Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#    * Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in the
+#      documentation and/or other materials provided with the distribution.
+#    * Neither the name of the CZ.NIC nor the
+#      names of its contributors may be used to endorse or promote products
+#      derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL CZ.NIC BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+# OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+from setuptools import setup
+
+setup(
+    name='svupdater',
+    version='1.0',
+    description="Supervising application and library for updater-ng.",
+    url="https://gitlab.labs.nic.cz/turris/updater/supervisor",
+    author="CZ.NIC, z. s. p. o.",
+    author_email="karel.koci@nic.cz",
+    license="MIT",
+
+    packages=['svupdater'],
+    entry_points={
+        'console_scripts': [
+            'updater-supervisor=svupdater:main'
+            ]
+        }
+)

svupdater/__init__.py

+# Copyright (c) 2018, CZ.NIC, z.s.p.o. (http://www.nic.cz/)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#    * Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#    * Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in the
+#      documentation and/or other materials provided with the distribution.
+#    * Neither the name of the CZ.NIC nor the
+#      names of its contributors may be used to endorse or promote products
+#      derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL CZ.NIC BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+# OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+from . import autorun, const
+from .utils import check_exclusive_lock as _check_exclusive_lock
+from .utils import daemonize as _daemonize
+from ._pidlock import pid_locked as _pid_locked
+from .exceptions import ExceptionUpdaterDisabled
+from ._supervisor import run as _run
+from .prerun import wait_for_network as _wait_for_network
+
+
+def opkg_lock():
+    """Returns True if opkg lock is taken. It can be taken by any other
+    process. It doesn't have to be updater.
+    """
+    return _check_exclusive_lock(const.OPKG_LOCK, False)
+
+
+def updater_supervised():
+    """This returns True if there is running updater-supervisor instance.
+    (Running means as a running process not as a library in some other process)
+    """
+    # This is in reality a wrapper on top of pidlock
+    return _pid_locked()
+
+
+def run(wait_for_network=False, ensure_run=False, timeout=const.PKGUPDATE_TIMEOUT,
+        timeout_kill=const.PKGUPDATE_TIMEOUT_KILL, hooklist=None):
+    """Run updater.
+    This call will spawn daemon process and returns. But be aware that at first
+    it checks if some other supervisor is not running and it takes file lock
+    because of that. If someone messed up that lock then it won't return
+    immediately. Calling this with timeout is advised for time sensitive
+    applications.
+    If there is already running daemon then it just sends signal to it and
+    exits.
+    You can pass hooks (single line shell scripts) to be run after updater.
+    """
+    if not autorun.enabled():
+        raise ExceptionUpdaterDisabled(
+            "Can't run. Updater is configured to be disabled.")
+    # Fork to daemon
+    if _daemonize():
+        return
+    # Wait for network if configured
+    if wait_for_network:
+        if type(wait_for_network == bool):
+            wait_for_network = const.PING_TIMEOUT
+        _wait_for_network(wait_for_network)
+    # And run updater
+    _run(
+        ensure_run=ensure_run,
+        timeout=timeout,
+        timeout_kill=timeout_kill,
+        verbose=False,
+        hooklist=hooklist)
+    exit()

svupdater/__main__.py

+# Copyright (c) 2018-2019, CZ.NIC, z.s.p.o. (http://www.nic.cz/)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#    * Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#    * Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in the
+#      documentation and/or other materials provided with the distribution.
+#    * Neither the name of the CZ.NIC nor the
+#      names of its contributors may be used to endorse or promote products
+#      derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL CZ.NIC BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+# OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+import sys
+import argparse
+from svupdater import autorun
+from svupdater.prerun import random_sleep, wait_for_network
+from svupdater._supervisor import run
+from svupdater.const import PKGUPDATE_TIMEOUT, PKGUPDATE_TIMEOUT_KILL
+from svupdater.const import PING_TIMEOUT
+from svupdater.utils import daemonize
+
+HELP_DESCRIPTION = """
+    Updater-ng supervisor used for system updating.
+    """
+
+
+def parse_arguments():
+    "Parse script arguments"
+    prs = argparse.ArgumentParser(description=HELP_DESCRIPTION)
+    prs.add_argument('--daemon', '-d', action='store_true',
+                     help="""
+                     Run supervisor in background (detach from terminal).
+                     """)
+    prs.add_argument('--rand-sleep', const=7200, nargs='?', type=int,
+                     help="""
+                     Sleep random amount of the time with maximum of given
+                     number of seconds. In default two hours are used.
+                     """)
+    prs.add_argument('--wait-for-network', const=PING_TIMEOUT, type=int,
+                     nargs='?', help="""
+                     Check if Turris repository is accessible (even before
+                     going to background). You can specify timeout in seconds
+                     as an argument. 10 seconds is used if no argument is
+                     specified.
+                     """)
+    prs.add_argument('--ensure-run', action='store_true',
+                     help="""
+                     Make sure that updater runs at least once after current
+                     time. This can be used to ensure that latest changes are
+                     applied as soon as possible even if another instance of
+                     updater is already running.
+                     """)
+    prs.add_argument('--quiet', '-q', action='store_true',
+                     help="""
+                     Don't print pkgupdate's output to console. But still print
+                     supervisor output.
+                     """)
+    prs.add_argument('--timeout', default=PKGUPDATE_TIMEOUT,
+                     help="""
+                     Set time limit in seconds for updater execution. pkgupdate
+                     is gracefully exited when this timeout runs out. This is
+                     protection for pkgupdate stall. In defaut one hour is set
+                     as timeout.
+                     """)
+    prs.add_argument('--timeout-kill', default=PKGUPDATE_TIMEOUT_KILL,
+                     help="""
+                     Set time in seconds after which pkgupdate is killed. This
+                     is time from timeout. In default one minute is used.
+                     """)
+    return prs.parse_args()
+
+
+def main():
+    "Main function for updater-supervisor run as executable"
+    if not autorun.enabled():
+        print('Updater autorun disabled.')
+        sys.exit(0)
+
+    args = parse_arguments()
+
+    if args.daemon and daemonize():
+        return
+
+    random_sleep(args.rand_sleep)
+    wait_for_network(args.wait_for_network)
+
+    sys.exit(run(
+        ensure_run=args.ensure_run,
+        timeout=args.timeout,
+        timeout_kill=args.timeout_kill,
+        verbose=not args.quiet))
+
+
+if __name__ == '__main__':
+    main()

svupdater/_pidlock.py

+# Copyright (c) 2018, CZ.NIC, z.s.p.o. (http://www.nic.cz/)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#    * Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#    * Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in the
+#      documentation and/or other materials provided with the distribution.
+#    * Neither the name of the CZ.NIC nor the
+#      names of its contributors may be used to endorse or promote products
+#      derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL CZ.NIC BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+# OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""This implements updater-supervisor pid file lock.
+This ensures that only one instance of updater-supervisor is running and that
+any other just spawned instance can send signal to this instance.
+Signals are used in updater-supervisor for simple comunication between instance
+holding lock and any other spawned instance.
+"""
+import os
+import fcntl
+import errno
+import signal
+from .const import PID_FILE_PATH
+from .utils import report, check_exclusive_lock
+from .exceptions import ExceptionUpdaterPidLockFailure
+
+
+def pid_locked():
+    """Check if someone holds pid lock. It won't check if process holding the
+    lock is alive. But it can potentially also catch such situation as in that
+    case we would manage to get exclusive lock. But we can't ensure that
+    because some other instance can have shared lock at the same time because
+    it wants to read content.
+    """
+    return check_exclusive_lock(PID_FILE_PATH, True)
+
+
+def pid_lock_content():
+    """Get content of our pid lock. That is, it returns pid (as an integer).
+    If there is no lock or its content is invalid then it returns None.
+    """
+    file = None
+    try:
+        file = os.open(PID_FILE_PATH, os.O_RDONLY)
+    except IOError as excp:
+        # There is no such file
+        if excp.errno == errno.EACCES:
+            return None
+        raise
+    # TODO timeout
+    fcntl.flock(file, fcntl.LOCK_SH)  # Lock for shared read
+    # Check if we are reading existing file (if it wasn't unlinked)
+    invalid = False
+    try:
+        if os.fstat(file).st_ino != os.stat(PID_FILE_PATH).st_ino:
+            invalid = True
+    except OSError as excp:
+        if excp.errno == errno.ENOENT:
+            invalid = True
+        raise
+    if invalid:  # Otherwise try again
+        os.close(file)
+        return pid_lock_content()
+    val = None
+    with os.fdopen(file, 'r') as filed:
+        try:
+            val = int(filed.readline())
+        except ValueError:
+            pass  # Failed to convert for us means that pid is invalid (None)
+    # Note: file is closed when we leave fdopen closure
+    return val
+
+
+class PidLock():
+    """Supervisor pid file to ensure that only one instance is running and that
+    that specific instance can receive SIGUSR1 to inform it that it should run
+    pkgupdate once again. This functionality is exported using sigusr property.
+
+    Note that there should be only once PidLock object used in single process
+    because it registers signal.
+    """
+    def __init__(self):
+        self.file = None
+        self._sigusr_rec = False
+        signal.signal(signal.SIGUSR1, self._sigusr1)
+
+    def __del__(self):
+        if self.file is not None:
+            self.free()
+
+    def _sigusr1(self, *_):
+        self._sigusr_rec = True
+
+    @property
+    def sigusr1(self):
+        "If SIGUSR1 was receiver. Reading this sets it back to False"
+        val = self._sigusr_rec
+        self._sigusr_rec = False
+        return val
+
+    def _take(self, overtake):
+        "Take lock if possible"
+        flags = os.O_WRONLY | os.O_SYNC | os.O_CREAT | \
+            (os.O_EXCL if not overtake else 0)
+        while True:
+            try:
+                self.file = os.open(PID_FILE_PATH, flags)
+                fcntl.flock(self.file, fcntl.LOCK_EX | fcntl.LOCK_NB)
+            except OSError as excp:
+                # File exists or lock couldn't been acquired
+                if excp.errno == errno.EEXIST or \
+                        excp.errno == errno.EWOULDBLOCK:
+                    return False
+                raise
+            # There is possible race condition when file is removed before we
+            # lock it. This ensures that we have file that is on FS
+            invalid = False
+            try:
+                if os.fstat(self.file).st_ino == os.stat(PID_FILE_PATH).st_ino:
+                    invalid = True
+            except OSError as excp:
+                if excp.errno == errno.ENOENT:
+                    invalid = True
+                raise
+            if invalid:
+                os.ftruncate(self.file, 0)
+                os.write(self.file, str.encode(str(os.getpid())))
+                os.fsync(self.file)
+                return True
+            # File was removed before we were able to acquire lock. Try again.
+            os.close(self.file)
+
+    def acquire(self, send_signal):
+        """Try to take supervisor pid lock. Returns boolean signaling if lock
+        was taken successfully.
+        """
+        if self._take(False):
+            return True  # We have lock so return
+        pid = pid_lock_content()
+        if pid is None:
+            report("Taking lock for PID file failed but no pid loaded. Trying to lock pid again.")
+            if self._take(True):
+                return True
+            pid = pid_lock_content()  # Second attempt
+            if pid is None:
+                report("Second attempt failed too. Giving up.")
+                return False
+        # Here we have loaded pid
+        sig = signal.SIGUSR1 if send_signal else 0
+        try:
+            os.kill(pid, sig)
+        except OSError as excp:
+            if excp.errno != errno.ESRCH:
+                raise
+            # It doesn't runs
+            report("There is no running process with stored pid. Overtaking it.")
+            if self._take(True):
+                return True
+            report("Pid file overtake failed. Giving up.")
+            return False
+        # Signal sent successfully
+        if send_signal:
+            report("Another instance is already running. It was notified to run pkgupdate again.")
+        else:
+            report("Another instance of supervisor is already running.")
+        return False
+
+    def free(self):
+        """Free pid lock if we have it at the moment
+        """
+        if self.file is None:
+            raise ExceptionUpdaterPidLockFailure(
+                "Can't free not taken pidlock")
+        file = self.file
+        self.file = None
+        # TODO timeout
+        fcntl.flock(file, fcntl.LOCK_EX)
+        os.remove(PID_FILE_PATH)
+        os.close(file)
+        file = None
+
+    def block(self):
+        """Block read access to pid lock.
+        """
+        if self.file is None:
+            raise ExceptionUpdaterPidLockFailure(
+                "Can't block not taken pidlock")
+        # TODO timeout
+        fcntl.flock(self.file, fcntl.LOCK_EX)
+
+    def unblock(self):
+        """Unblock previously blocked read access. Note that in default when
+        lock is acquired it is blocking read access.
+        """
+        if self.file is None:
+            raise ExceptionUpdaterPidLockFailure(
+                "Can't block not taken pidlock")
+        # TODO timeout
+        fcntl.flock(self.file, fcntl.LOCK_SH)

svupdater/_supervisor.py

+# Copyright (c) 2018, CZ.NIC, z.s.p.o. (http://www.nic.cz/)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#    * Redistributions of source code must retain the above copyright
+#      notice, this list of conditions and the following disclaimer.
+#    * Redistributions in binary form must reproduce the above copyright
+#      notice, this list of conditions and the following disclaimer in the
+#      documentation and/or other materials provided with the distribution.
+#    * Neither the name of the CZ.NIC nor the
+#      names of its contributors may be used to endorse or promote products
+#      derived from this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL CZ.NIC BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+# OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+# LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+# EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+"""This module is core of udpdater-supervisor. It runs and supervise updater
+execution.
+"""
+from __future__ import print_function
+import os
+import sys
+import subprocess
+import atexit