[checkmk-commits] Add context manager for PID file locking

Module: check_mk Branch: master Commit: 91cc92e7eee858c6aedaef614772ceaad69fd5c2 URL: http://git.mathias-kettner.de/git/?p=check_mk.git;a=commit;h=91cc92e7eee858… Author: Lars Michelsen <lm(a)mathias-kettner.de> Date: Mon Nov 5 08:42:10 2018 +0100 Add context manager for PID file locking * Added tests to verify PID locking mechanism Change-Id: Id8c69cf894e6c1b34b76798af76882c97a1e4c6d --- cmk/daemon.py | 32 +++++++++++++++++++++++- tests/unit/cmk/test_daemon.py | 58 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 89 insertions(+), 1 deletion(-) diff --git a/cmk/daemon.py b/cmk/daemon.py index aac0e95..20faeb9 100644 --- a/cmk/daemon.py +++ b/cmk/daemon.py @@ -30,9 +30,11 @@ from pwd import getpwnam from grp import getgrnam import ctypes import ctypes.util +from pathlib2 import Path # pylint: disable=unused-import +from contextlib import contextmanager import cmk.store -from .exceptions import MKGeneralException +from cmk.exceptions import MKGeneralException def daemonize(user=0, group=0): @@ -99,7 +101,9 @@ def closefrom(lowfd): os.closerange(lowfd, highfd) +# TODO: Change API and call sites to work with Path() objects def lock_with_pid_file(path): + # type: (str) -> None """ Use this after daemonizing or in foreground mode to ensure there is only one process running. @@ -114,6 +118,32 @@ def lock_with_pid_file(path): f.write("%d\n" % os.getpid()) +# TODO: Change API and call sites to work with Path() objects +def _cleanup_locked_pid_file(path): + # type: (str) -> None + """Cleanup the lock + file acquired by the function above""" + if not cmk.store.have_lock(path): + return + + cmk.store.release_lock(path) + + try: + os.remove(path) + except OSError: + pass + + +@contextmanager +def pid_file_lock(path): + # type: (Path) -> None + """Context manager for PID file based locking""" + lock_with_pid_file("%s" % path) + try: + yield + finally: + _cleanup_locked_pid_file("%s" % path) + + def set_cmdline(cmdline): """ Change the process name and process command line on of the running process diff --git a/tests/unit/cmk/test_daemon.py b/tests/unit/cmk/test_daemon.py new file mode 100644 index 0000000..7ca5599 --- /dev/null +++ b/tests/unit/cmk/test_daemon.py @@ -0,0 +1,58 @@ +import pytest +from pathlib2 import Path +import os + +import cmk.store as store +import cmk.daemon as daemon +from cmk.exceptions import MKGeneralException + +(a)pytest.fixture(autouse=True) +def cleanup_locks(): + yield + store.release_all_locks() + + +def test_lock_with_pid_file(tmpdir): + pid_file = Path(tmpdir) / "test.pid" + + daemon.lock_with_pid_file("%s" % pid_file) + + assert store.have_lock("%s" % pid_file) + + with pid_file.open() as f: + assert int(f.read()) == os.getpid() + + +def test_cleanup_locked_pid_file(tmpdir): + pid_file = Path(tmpdir) / "test.pid" + + assert not store.have_lock("%s" % pid_file) + daemon.lock_with_pid_file("%s" % pid_file) + assert store.have_lock("%s" % pid_file) + + daemon._cleanup_locked_pid_file("%s" % pid_file) + + assert not store.have_lock("%s" % pid_file) + + +def test_pid_file_lock_context_manager(tmpdir): + pid_file = Path(tmpdir) / "test.pid" + + assert not store.have_lock("%s" % pid_file) + + with daemon.pid_file_lock(pid_file): + assert store.have_lock("%s" % pid_file) + + +def test_pid_file_lock_context_manager_exception(tmpdir): + pid_file = Path(tmpdir) / "test.pid" + + assert not store.have_lock("%s" % pid_file) + try: + with daemon.pid_file_lock(pid_file): + assert store.have_lock("%s" % pid_file) + raise MKGeneralException("bla") + except MKGeneralException: + pass + + assert not store.have_lock("%s" % pid_file)