[CalendarServer-changes] [6513] CalendarServer/branches/users/glyph/sharedpool/txdav/base/datastore/ asyncsqlpool.py

[source_changes at macosforge.org]

Revision: 6513
          http://trac.macosforge.org/projects/calendarserver/changeset/6513
Author:   glyph at apple.com
Date:     2010-11-01 14:18:34 -0700 (Mon, 01 Nov 2010)
Log Message:
-----------
composition > inheritance, always, forever

Modified Paths:
--------------
    CalendarServer/branches/users/glyph/sharedpool/txdav/base/datastore/asyncsqlpool.py

Modified: CalendarServer/branches/users/glyph/sharedpool/txdav/base/datastore/asyncsqlpool.py
===================================================================
--- CalendarServer/branches/users/glyph/sharedpool/txdav/base/datastore/asyncsqlpool.py	2010-11-01 21:18:16 UTC (rev 6512)
+++ CalendarServer/branches/users/glyph/sharedpool/txdav/base/datastore/asyncsqlpool.py	2010-11-01 21:18:34 UTC (rev 6513)
@@ -37,6 +37,7 @@
 from txdav.base.datastore.threadutils import ThreadHolder
 from txdav.idav import AlreadyFinishedError
 from twisted.python import log
+from twisted.python.components import proxyForInterface
 
 
 class BaseSqlTxn(object):
@@ -112,9 +113,9 @@
 
     def abort(self):
         if not self._completed:
+            self._completed = True
             def reallyAbort():
                 self._connection.rollback()
-            self._completed = True
             result = self._holder.submit(reallyAbort)
             return result
         else:
@@ -123,7 +124,7 @@
 
     def __del__(self):
         if not self._completed:
-            print 'CommonStoreTransaction.__del__: OK'
+            print 'BaseSqlTxn.__del__: OK'
             self.abort()
 
 
@@ -136,6 +137,7 @@
         """
         if not self._completed:
             raise RuntimeError("Attempt to re-set active transaction.")
+        self._completed = False
 
 
     def stop(self):
@@ -143,49 +145,54 @@
         Release the thread and database connection associated with this
         transaction.
         """
-        if not self._completed:
-            raise RuntimeError("Un-completed task cannot be stopped.")
         self._stopped = True
         self._holder.submit(self._connection.close)
         return self._holder.stop()
 
 
 
-class PooledSqlTxn(BaseSqlTxn):
+class PooledSqlTxn(proxyForInterface(iface=IAsyncTransaction,
+                                     originalAttribute='_baseTxn')):
+    """
+    This is a temporary throw-away wrapper for the longer-lived BaseSqlTxn, so
+    that if a badly-behaved API client accidentally hangs on to one of these
+    and, for example C{.abort()}s it multiple times once another client is
+    using that connection, it will get some harmless tracebacks.
+    """
 
-    def __init__(self, pool):
-        self.pool = pool
-        super(PooledSqlTxn, self).__init__(
-            self.pool.connectionFactory,
-            self.pool.reactor
-        )
+    def __init__(self, pool, baseTxn):
+        self._pool     = pool
+        self._baseTxn  = baseTxn
+        self._complete = False
 
 
+    def execSQL(self, *a, **kw):
+        if self._complete:
+            raise AlreadyFinishedError()
+        return super(PooledSqlTxn, self).execSQL(*a, **kw)
+
+
     def commit(self):
-        return self.repoolAfter(super(PooledSqlTxn, self).commit())
+        if self._complete:
+            raise AlreadyFinishedError()
+        return self._repoolAfter(super(PooledSqlTxn, self).commit())
 
 
     def abort(self):
-        return self.repoolAfter(super(PooledSqlTxn, self).abort())
+        if self._complete:
+            raise AlreadyFinishedError()
+        return self._repoolAfter(super(PooledSqlTxn, self).abort())
 
 
-    def repoolAfter(self, d):
+    def _repoolAfter(self, d):
+        self._complete = True
         def repool(result):
-            self.pool.reclaim(self)
+            self._pool.reclaim(self)
             return result
         return d.addCallback(repool)
 
 
-    def stop(self):
-        """
-        Completely remove this transaction from the pool.
-        """
-        result = super(PooledSqlTxn, self).stop()
-        self.pool.free.remove(self)
-        return result
 
-
-
 class ConnectionPool(Service, object):
     """
     This is a central service that has a threadpool and executes SQL statements
@@ -217,22 +224,39 @@
                 yield busy.abort()
             except:
                 log.err()
-        for free in self.free[:]:
+        # all transactions should now be in the free list, since 'abort()' will
+        # have put them there.
+        for free in self.free:
             yield free.stop()
 
 
     def connection(self):
+        """
+        Find a transaction; either retrieve a free one from the list or
+        allocate a new one if no free ones are available.
+
+        @return: an L{IAsyncTransaction}
+        """
         if self.free:
-            txn = self.free.pop(0)
+            basetxn = self.free.pop(0)
         else:
-            txn = PooledSqlTxn(self)
+            basetxn = BaseSqlTxn(
+                connectionFactory=self.connectionFactory,
+                reactor=self.reactor
+            )
+        txn = PooledSqlTxn(self, basetxn)
         self.busy.append(txn)
-        return self.txn
+        return txn
 
 
     def reclaim(self, txn):
-        txn.reset()
-        self.free.append(txn)
+        """
+        Shuck the L{PooledSqlTxn} wrapper off, and put the BaseSqlTxn into the
+        free list.
+        """
+        baseTxn = txn._baseTxn
+        baseTxn.reset()
+        self.free.append(baseTxn)
         self.busy.remove(txn)
 
 
@@ -440,7 +464,7 @@
 
 class Transaction(object):
     """
-    Async transaction implementation.
+    Async protocol-based transaction implementation.
     """
 
     implements(IAsyncTransaction)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.macosforge.org/pipermail/calendarserver-changes/attachments/20101101/e61f181d/attachment-0001.html>