Add lockfile recipe

This add also dependency to inotifyx in order to have a better
mechanism for file system watching.

I choose inotifyx because the api is much more simpler.

setup.py

@@ -30,6 +30,7 @@ setup(name=name,
         'lxml', # for full blown python interpreter
         'netaddr', # to manipulate on IP addresses
         'setuptools', # namespaces
+        'inotifyx', # to watch filesystem changes (used in pidwrapper)
         'slapos.core', # uses internally
 #        'slapos.toolbox', # needed for libcloud, cloudmgr, disabled for now
         'xml_marshaller', # need to communication with slapgrid
@@ -54,6 +55,7 @@ setup(name=name,
           'kvm = slapos.recipe.kvm:Recipe',
           'libcloud = slapos.recipe.libcloud:Recipe',
           'libcloudrequest = slapos.recipe.libcloudrequest:Recipe',
+          'lockfile = slapos.recipe.lockfile:Recipe',
           'memcached = slapos.recipe.memcached:Recipe',
           'mysql = slapos.recipe.mysql:Recipe',
           'mkdirectory = slapos.recipe.mkdirectory:Recipe',

slapos/recipe/lockfile.py

+##############################################################################
+#
+# Copyright (c) 2010 Vifib SARL and Contributors. All Rights Reserved.
+#
+# WARNING: This program as such is intended to be used by professional
+# programmers who take the whole responsibility of assessing all potential
+# consequences resulting from its eventual inadequacies and bugs
+# End users who are looking for a ready-to-use solution with commercial
+# guarantees and support are strongly adviced to contract a Free Software
+# Service Company
+#
+# This program 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.
+#
+# This program 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 this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+#
+##############################################################################
+import os
+import sys
+import subprocess
+
+import inotifyx
+
+from slapos.recipe.librecipe import GenericBaseRecipe
+
+class LockFile(object):
+
+  class LockException(Exception):
+    pass
+
+  def __init__(self, filename, wait=True, exit=False):
+    self.filename = filename
+    if wait:
+      self.callback = lambda: self.waitDeletion()
+    elif not exit:
+      self.callback = lambda: self.raiseException()
+    else:
+      self.callback = lambda: sys.exit(1)
+
+  def raiseException(self):
+    raise LockFile.LockException("Not able to lock the file")
+
+  def waitDeletion(self):
+    inotify_fd = inotifyx.init()
+    try:
+      inotifyx.add_watch(inotify_fd, self.filename, inotifyx.IN_DELETE)
+      inotifyx.get_events()
+    except IOError: # add_watch failed
+      pass
+    finally:
+      os.close(inotify_fd)
+
+    self.__enter__()
+
+  def __enter__(self):
+    try:
+      # Atomic file acquisition
+      self._fd = os.open(self.filename, os.O_CREAT | os.O_EXCL)
+    except OSError:
+      self.callback()
+
+  def __exit__(self, exc_type, exc_value, traceback):
+    os.close(self._fd)
+    os.unlink(self.filename)
+
+def locked_run(args):
+  with LockFile(args['filename'], wait=args['wait'], exit=True):
+    subprocess.check_call([args['binary']])
+
+class Recipe(GenericBaseRecipe):
+
+  def install(self):
+    wrapper = self.createPythonScript(self.options['wrapper'],
+                                      __name__ + '.locked_run',
+                                      dict(
+                                        filename=self.options['lock-file'],
+                                        wait=self.optionIsTrue('wait', False),
+                                        binary=self.options['binary'],
+                                      )
+                                     )
+    return [wrapper]