Simplyfied and updated the lock manager app

apps/lock_manager/admin.py

@@ -0,0 +1,10 @@
+from django.contrib import admin
+
+from lock_manager.models import Lock
+
+
+class LockAdmin(admin.ModelAdmin):
+    model = Lock
+
+
+admin.site.register(Lock, LockAdmin)

apps/lock_manager/conf/settings.py

@@ -1,5 +1,5 @@
 from django.conf import settings
 
-DEFAULT_LOCK_TIMEOUT_VALUE = 10
+DEFAULT_LOCK_TIMEOUT_VALUE = 30
 
 DEFAULT_LOCK_TIMEOUT = getattr(settings, 'LOCK_MANAGER_DEFAULT_LOCK_TIMEOUT', DEFAULT_LOCK_TIMEOUT_VALUE)

apps/lock_manager/managers.py

@@ -1,9 +1,4 @@
-try:
-    from psycopg2 import OperationalError
-except ImportError:
-    class OperationalError(Exception):
-        pass
-
+import logging
 import datetime
 
 from django.db.utils import DatabaseError
@@ -13,40 +8,33 @@ from django.db import models
 
 from lock_manager.exceptions import LockError
 
+logger = logging.getLogger(__name__)
+
 
 class LockManager(models.Manager):
-    @transaction.commit_manually
+    @transaction.commit_on_success
     def acquire_lock(self, name, timeout=None):
+        logger.debug('DEBUG: trying to acquire lock: %s' % name)
         lock = self.model(name=name, timeout=timeout)
         try:
             lock.save(force_insert=True)
+            logger.debug('DEBUG: acquired lock: %s' % name)
+            return lock
         except IntegrityError:
-            transaction.rollback()
             # There is already an existing lock
-            # Check it's expiration date and if expired, delete it and 
-            # create it again
+            # Check it's expiration date and if expired, reset it
+            try:
                 lock = self.model.objects.get(name=name)
-            transaction.rollback()
+            except self.model.DoesNotExist:
+                # Table based locking
+                logger.debug('DEBUG: lock: %s does not exist' % name)
+                raise LockError('Unable to acquire lock')
 
             if datetime.datetime.now() > lock.creation_datetime + datetime.timedelta(seconds=lock.timeout):
-                self.release_lock(name)
+                logger.debug('DEBUG: reseting deleting stale lock: %s' % name)
                 lock.timeout=timeout
+                logger.debug('DEBUG: try to reacquire stale lock: %s' % name)
                 lock.save()
-                transaction.commit()
+                return lock
             else:
                 raise LockError('Unable to acquire lock')
-        except DatabaseError:
-            transaction.rollback()
-            # Special case for ./manage.py syncdb
-        except (OperationalError, ImproperlyConfigured):
-            transaction.rollback()
-            # Special for DjangoZoom, which executes collectstatic media
-            # doing syncdb and creating the database tables
-        else:
-            transaction.commit()
-        
-    @transaction.commit_manually
-    def release_lock(self, name):
-        lock = self.model.objects.get(name=name)
-        lock.delete()
-        transaction.commit()

apps/lock_manager/models.py

@@ -10,7 +10,7 @@ from lock_manager.conf.settings import DEFAULT_LOCK_TIMEOUT
 class Lock(models.Model):
     creation_datetime = models.DateTimeField(verbose_name=_(u'creation datetime'))
     timeout = models.IntegerField(default=DEFAULT_LOCK_TIMEOUT, verbose_name=_(u'timeout'))
-    name = models.CharField(max_length=32, verbose_name=_(u'name'), unique=True)
+    name = models.CharField(max_length=48, verbose_name=_(u'name'), unique=True)
 
     objects = LockManager()
 
@@ -19,8 +19,19 @@ class Lock(models.Model):
 
     def save(self, *args, **kwargs):
         self.creation_datetime = datetime.datetime.now()
+        if not self.timeout and not kwarget.get('timeout'):
+            self.timeout = DEFAULT_LOCK_TIMEOUT
+
         super(Lock, self).save(*args, **kwargs)
 
+    def release(self):
+        try:
+            lock = Lock.objects.get(name=self.name, creation_datetime=self.creation_datetime)
+            lock.delete()
+        except Lock.DoesNotExist:
+            # Out lock expired and was reassigned
+            pass
+
     class Meta:
         verbose_name = _(u'lock')
         verbose_name_plural = _(u'locks')

apps/lock_manager/tests.py

@@ -1,10 +1,3 @@
-"""
-This file demonstrates writing tests using the unittest module. These will pass
-when you run "manage.py test".
-
-Replace this with more appropriate tests for your application.
-"""
-
 from django.test import TestCase