Merge pull request #553 from darko-poljak/jobs-locking

Add file locking for -j parallel execution

cdist/config.py

@@ -39,11 +39,9 @@ import cdist.hostsource
 import cdist.exec.local
 import cdist.exec.remote
 
-from cdist import inventory
-
 import cdist.util.ipaddr as ipaddr
 
-from cdist import core
+from cdist import core, inventory
 from cdist.util.remoteutil import inspect_ssh_mux_opts
 
 

cdist/emulator.py

@@ -28,6 +28,7 @@ import sys
 
 import cdist
 from cdist import core
+from cdist import flock
 
 
 class MissingRequiredEnvironmentVariableError(cdist.Error):
@@ -94,6 +95,10 @@ class Emulator(object):
         """Emulate type commands (i.e. __file and co)"""
 
         self.commandline()
+        self.init_object()
+
+        # locking for parallel execution
+        with flock.Flock(self.flock_path) as lock:
             self.setup_object()
             self.save_stdin()
             self.record_requirements()
@@ -154,8 +159,8 @@ class Emulator(object):
         self.args = parser.parse_args(self.argv[1:])
         self.log.trace('Args: %s' % self.args)
 
-    def setup_object(self):
-        # Setup object - and ensure it is not in args
+    def init_object(self):
+        # Initialize object - and ensure it is not in args
         if self.cdist_type.is_singleton:
             self.object_id = ''
         else:
@@ -166,7 +171,13 @@ class Emulator(object):
         self.cdist_object = core.CdistObject(
                 self.cdist_type, self.object_base_path, self.object_marker,
                 self.object_id)
+        lockfname = ('.' + self.cdist_type.name +
+                     self.object_id + '_' +
+                     self.object_marker + '.lock')
+        lockfname = lockfname.replace(os.sep, '_')
+        self.flock_path = os.path.join(self.object_base_path, lockfname)
 
+    def setup_object(self):
         # Create object with given parameters
         self.parameters = {}
         for key, value in vars(self.args).items():

cdist/flock.py

@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+#
+# 2017 Darko Poljak (darko.poljak at gmail.com)
+#
+# This file is part of cdist.
+#
+# cdist is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# cdist 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with cdist. If not, see <http://www.gnu.org/licenses/>.
+#
+#
+
+import fcntl
+import logging
+import os
+
+
+log = logging.getLogger('cdist-flock')
+
+
+class Flock():
+    def __init__(self, path):
+        self.path = path
+        self.lockfd = None
+
+    def flock(self):
+        log.debug('Acquiring lock on %s', self.path)
+        self.lockfd = open(self.path, 'w+')
+        fcntl.flock(self.lockfd, fcntl.LOCK_EX)
+        log.debug('Acquired lock on %s', self.path)
+
+    def funlock(self):
+        log.debug('Releasing lock on %s', self.path)
+        fcntl.flock(self.lockfd, fcntl.LOCK_UN)
+        self.lockfd.close()
+        self.lockfd = None
+        try:
+            os.remove(self.path)
+        except FileNotFoundError:
+            pass
+        log.debug('Released lock on %s', self.path)
+
+    def __enter__(self):
+        self.flock()
+        return self
+
+    def __exit__(self, *args):
+        self.funlock()
+        return False