[Kimchi-devel] [PATCH] [Wok] Bugfix 33: Implement a multiprocess file handler for log system

[Jose Ricardo Ziviani]

 - This commit adds a new watched file handler, used in Wok, but it uses
   a recursive lock before emitting the log register to avoid possible
   concurrency issues since multiple processes will write in the same
   log file.

Signed-off-by: Jose Ricardo Ziviani <joserz at linux.vnet.ibm.com>
---
*NOTE*: based on '[PATCH] [Wok] Bugfix 30: Duplicated log messages'

 src/wok/safewatchedfilehandler.py | 44 +++++++++++++++++++++++++++++++++++++++
 src/wok/server.py                 |  4 ++--
 2 files changed, 46 insertions(+), 2 deletions(-)
 create mode 100644 src/wok/safewatchedfilehandler.py

diff --git a/src/wok/safewatchedfilehandler.py b/src/wok/safewatchedfilehandler.py
new file mode 100644
index 0000000..c5fad85
--- /dev/null
+++ b/src/wok/safewatchedfilehandler.py
@@ -0,0 +1,44 @@
+#
+# Project Kimchi
+#
+# Copyright IBM, Corp. 2016
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
+
+from logging.handlers import WatchedFileHandler
+from multiprocessing import RLock
+
+
+class SafeWatchedFileHandler(WatchedFileHandler):
+
+    def __init__(self, filename, mode='a', encoding=None, delay=0):
+        WatchedFileHandler.__init__(self, filename, mode, encoding, delay)
+        self._lock = RLock()
+
+    def close(self):
+        self._lock.acquire(timeout=2)
+        try:
+            WatchedFileHandler.close(self)
+
+        finally:
+            self._lock.release()
+
+    def emit(self, record):
+        self._lock.acquire(timeout=2)
+        try:
+            WatchedFileHandler.emit(self, record)
+
+        finally:
+            self._lock.release()
diff --git a/src/wok/server.py b/src/wok/server.py
index 13851e8..75b41d5 100644
--- a/src/wok/server.py
+++ b/src/wok/server.py
@@ -35,6 +35,7 @@ from wok.control import sub_nodes
 from wok.model import model
 from wok.proxy import start_proxy, terminate_proxy
 from wok.root import WokRoot
+from wok.safewatchedfilehandler import SafeWatchedFileHandler
 from wok.utils import get_enabled_plugins, import_class
 
 LOGGING_LEVEL = {"debug": logging.DEBUG,
@@ -122,8 +123,7 @@ class Server(object):
         cherrypy.log.access_log.addHandler(h)
 
         # Create handler to error log file
-        h = logging.handlers.WatchedFileHandler(options.error_log, 'a',
-                                                delay=1)
+        h = SafeWatchedFileHandler(options.error_log, 'a', delay=1)
         h.setLevel(logLevel)
         h.setFormatter(cherrypy._cplogging.logfmt)
 
-- 
1.9.1