[checkmk-commits] Added some non blocking locking and pid_file handling code

Module: check_mk Branch: master Commit: e1e8b8ae5b019607d721598db9b6a821d65aae31 URL: http://git.mathias-kettner.de/git/?p=check_mk.git;a=commit;h=e1e8b8ae5b0196… Author: Lars Michelsen <lm(a)mathias-kettner.de> Date: Tue Jun 27 10:24:37 2017 +0200 Added some non blocking locking and pid_file handling code Change-Id: I0dc2175de6bf6a049d5425b461f47ad70ad12e6f --- lib/daemon.py | 18 ++++++++++++++++++ lib/store.py | 19 +++++++++++++++++-- 2 files changed, 35 insertions(+), 2 deletions(-) diff --git a/lib/daemon.py b/lib/daemon.py index 79ea505..b9323cf 100644 --- a/lib/daemon.py +++ b/lib/daemon.py @@ -31,6 +31,9 @@ from grp import getgrnam import ctypes import ctypes.util +import cmk.store +from .exceptions import MKGeneralException + def daemonize(user=0, group=0): # do the UNIX double-fork magic, see Stevens' "Advanced @@ -78,6 +81,21 @@ def daemonize(user=0, group=0): os.close(so) +def lock_with_pid_file(path): + """ + Use this after daemonizing or in foreground mode to ensure there is only + one process running. + """ + if not cmk.store.try_aquire_lock(path): + raise MKGeneralException("Failed to aquire PID file lock: " + "Another process is already running") + + # Now that we have the lock we are allowed to write our pid to the file. + # The pid can then be used by the init script. + with file(path, "w") as f: + f.write("%d\n" % os.getpid()) + + def set_cmdline(cmdline): """ Change the process name and process command line on of the running process diff --git a/lib/store.py b/lib/store.py index 6a5b18c..b7d1013 100644 --- a/lib/store.py +++ b/lib/store.py @@ -240,7 +240,7 @@ def save_to_mk_file(path, key, value): g_aquired_locks = [] g_locked_paths = [] -def aquire_lock(path): +def aquire_lock(path, blocking=True): if path in g_locked_paths: return True # No recursive locking @@ -252,7 +252,11 @@ def aquire_lock(path): # Handle the case where the file has been renamed in the meantime while True: - fcntl.flock(fd, fcntl.LOCK_EX) + flags = fcntl.LOCK_EX + if not blocking: + flags |= fcntl.LOCK_NB + + fcntl.flock(fd, flags) fd_new = os.open(path, os.O_RDONLY | os.O_CREAT, 0660) if os.path.sameopenfile(fd, fd_new): os.close(fd_new) @@ -265,6 +269,17 @@ def aquire_lock(path): g_locked_paths.append(path) +def try_aquire_lock(path): + try: + aquire_lock(path, blocking=False) + return True + except IOError, e: + if e.errno == 11: # Resource temporarily unavailable + return False + else: + raise + + def release_lock(path): if path not in g_locked_paths: return # no unlocking needed