Postgres backend allows transaction collisions to be ignored when...

...committing clenup in the sessions database

Author: Richard Jones

CHANGES.txt

@@ -47,6 +47,8 @@ Fixed:
   backends
 - Bug with name-collisions in sorted classes when sorting by Link
   properties in metakit backend fixed
+- Postgres backend allows transaction collisions to be ignored when
+  committing clenup in the sessions database
 
 2006-04-27 1.1.2
 Feature:

roundup/backends/back_anydbm.py

@@ -15,7 +15,7 @@
 # BASIS, AND THERE IS NO OBLIGATION WHATSOEVER TO PROVIDE MAINTENANCE,
 # SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 #
-#$Id: back_anydbm.py,v 1.201 2006-08-21 12:19:48 schlatterbeck Exp $
+#$Id: back_anydbm.py,v 1.202 2006-08-29 04:20:50 richard Exp $
 '''This module defines a backend that saves the hyperdatabase in a
 database chosen by anydbm. It is guaranteed to always be available in python
 versions >2.1.1 (the dumbdbm fallback in 2.1.1 and earlier has several
@@ -590,8 +590,17 @@ def pack(self, pack_before):
     #
     # Basic transaction support
     #
-    def commit(self):
+    def commit(self, fail_ok=False):
         ''' Commit the current transactions.
+
+        Save all data changed since the database was opened or since the
+        last commit() or rollback().
+
+        fail_ok indicates that the commit is allowed to fail. This is used
+        in the web interface when committing cleaning of the session
+        database. We don't care if there's a concurrency issue there.
+
+        The only backend this seems to affect is postgres.
         '''
         logging.getLogger('hyperdb').info('commit %s transactions'%(
             len(self.transactions)))

roundup/backends/back_metakit.py

@@ -1,4 +1,4 @@
-# $Id: back_metakit.py,v 1.112 2006-08-21 12:19:48 schlatterbeck Exp $
+# $Id: back_metakit.py,v 1.113 2006-08-29 04:20:50 richard Exp $
 '''Metakit backend for Roundup, originally by Gordon McMillan.
 
 Known Current Bugs:
@@ -147,8 +147,18 @@ def getclasses(self):
     # --- end of ping's spec
 
     # --- exposed methods
-    def commit(self):
-        '''commit all changes to the database'''
+    def commit(self, fail_ok=False):
+        ''' Commit the current transactions.
+
+        Save all data changed since the database was opened or since the
+        last commit() or rollback().
+
+        fail_ok indicates that the commit is allowed to fail. This is used
+        in the web interface when committing cleaning of the session
+        database. We don't care if there's a concurrency issue there.
+
+        The only backend this seems to affect is postgres.
+        '''
         if self.dirty:
             self._db.commit()
             for cl in self.classes.values():

roundup/backends/back_mysql.py

@@ -1,4 +1,4 @@
-#$Id: back_mysql.py,v 1.70 2006-07-13 10:14:56 schlatterbeck Exp $
+#$Id: back_mysql.py,v 1.71 2006-08-29 04:20:50 richard Exp $
 #
 # Copyright (c) 2003 Martynas Sklyzmantas, Andrey Lebedev <[email protected]>
 #
@@ -528,10 +528,13 @@ def create_class(self, spec):
         vals = (spec.classname, 1)
         self.sql(sql, vals)
 
-    def sql_commit(self):
+    def sql_commit(self, fail_ok=False):
         ''' Actually commit to the database.
         '''
         logging.getLogger('hyperdb').info('commit')
+
+        # MySQL commits don't seem to ever fail, the latest update winning.
+        # makes you wonder why they have transactions...
         self.conn.commit()
 
         # open a new cursor for subsequent work

roundup/backends/back_postgresql.py

@@ -1,4 +1,4 @@
-#$Id: back_postgresql.py,v 1.33 2006-08-23 12:57:10 schlatterbeck Exp $
+#$Id: back_postgresql.py,v 1.34 2006-08-29 04:20:50 richard Exp $
 #
 # Copyright (c) 2003 Martynas Sklyzmantas, Andrey Lebedev <[email protected]>
 #
@@ -181,6 +181,24 @@ def add_actor_column(self):
     def __repr__(self):
         return '<roundpsycopgsql 0x%x>' % id(self)
 
+    def sql_commit(self, fail_ok=False):
+        ''' Actually commit to the database.
+        '''
+        logging.getLogger('hyperdb').info('commit')
+
+        try:
+            self.conn.commit()
+        except psycopg.ProgrammingError, message:
+            # we've been instructed that this commit is allowed to fail
+            if fail_ok and str(message).endswith('could not serialize '
+                    'access due to concurrent update'):
+                logging.getLogger('hyperdb').info('commit FAILED, but fail_ok')
+            else:
+                raise
+
+        # open a new cursor for subsequent work
+        self.cursor = self.conn.cursor()
+
     def sql_stringquote(self, value):
         ''' psycopg.QuotedString returns a "buffer" object with the
             single-quotes around it... '''

roundup/backends/rdbms_common.py

@@ -15,7 +15,7 @@
 # BASIS, AND THERE IS NO OBLIGATION WHATSOEVER TO PROVIDE MAINTENANCE,
 # SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 #
-#$Id: rdbms_common.py,v 1.177 2006-08-23 12:57:10 schlatterbeck Exp $
+#$Id: rdbms_common.py,v 1.178 2006-08-29 04:20:50 richard Exp $
 ''' Relational database (SQL) backend common code.
 
 Basics:
@@ -1188,23 +1188,30 @@ def pack(self, pack_before):
                 "action<>'create'"%(classname, self.arg)
             self.sql(sql, (date_stamp,))
 
-    def sql_commit(self):
+    def sql_commit(self, fail_ok=False):
         ''' Actually commit to the database.
         '''
         logging.getLogger('hyperdb').info('commit')
+
         self.conn.commit()
 
         # open a new cursor for subsequent work
         self.cursor = self.conn.cursor()
 
-    def commit(self):
+    def commit(self, fail_ok=False):
         ''' Commit the current transactions.
 
         Save all data changed since the database was opened or since the
         last commit() or rollback().
+
+        fail_ok indicates that the commit is allowed to fail. This is used
+        in the web interface when committing cleaning of the session
+        database. We don't care if there's a concurrency issue there.
+
+        The only backend this seems to affect is postgres.
         '''
         # commit the database
-        self.sql_commit()
+        self.sql_commit(fail_ok)
 
         # now, do all the other transaction stuff
         for method, args in self.transactions:

roundup/cgi/client.py

@@ -1,4 +1,4 @@
-# $Id: client.py,v 1.226 2006-06-06 01:44:44 richard Exp $
+# $Id: client.py,v 1.227 2006-08-29 04:20:50 richard Exp $
 
 """WWW request handler (also used in the stand-alone server).
 """
@@ -334,7 +334,7 @@ def clean_sessions(self):
         sessions.clean(now)
         self.db.getOTKManager().clean(now)
         sessions.set('last_clean', last_use=time.time())
-        self.db.commit()
+        self.db.commit(fail_ok=True)
 
     def determine_charset(self):
         """Look for client charset in the form parameters or browser cookie.

roundup/hyperdb.py

@@ -15,7 +15,7 @@
 # BASIS, AND THERE IS NO OBLIGATION WHATSOEVER TO PROVIDE MAINTENANCE,
 # SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 #
-# $Id: hyperdb.py,v 1.125 2006-08-22 19:33:02 schlatterbeck Exp $
+# $Id: hyperdb.py,v 1.126 2006-08-29 04:20:50 richard Exp $
 
 """Hyperdatabase implementation, especially field types.
 """
@@ -728,6 +728,12 @@ def commit(self):
 
         Save all data changed since the database was opened or since the
         last commit() or rollback().
+
+        fail_ok indicates that the commit is allowed to fail. This is used
+        in the web interface when committing cleaning of the session
+        database. We don't care if there's a concurrency issue there.
+
+        The only backend this seems to affect is postgres.
         '''
         raise NotImplementedError