Update of #18

CHANGES.txt

@@ -22,12 +22,19 @@
   as a destination, not just RelStorages.
 
 - zodbconvert: The ``--incremental`` option is supported with a
-  RelStorage as a destination. See `PR 22`. With contributions by
+  RelStorage as a destination. See `PR 22`_. With contributions by
   Sylvain Viollon, Mauro Amico, and Peter Jacobs. Originally reported
   by Jan-Wijbrand Kolman.
 
 .. _`PR 22`: https://github.com/zodb/relstorage/pull/22
 
+
+- Raise a specific exception when acquiring the commit or pack locks
+  fails. See `PR 18`_.
+
+.. _`PR 18`: https://github.com/zodb/relstorage/pull/18/
+
+
 1.6.0b3 (2014-12-08)
 --------------------
 

relstorage/adapters/interfaces.py

@@ -13,6 +13,7 @@
 ##############################################################################
 """Interfaces provided by RelStorage database adapters"""
 
+from ZODB.POSException import StorageError
 from zope.interface import Attribute
 from zope.interface import Interface
 
@@ -162,7 +163,7 @@ def hold_commit_lock(cursor, ensure_current=False, nowait=False):
         If ensure_current is True, other tables may be locked as well, to
         ensure the most current data is available.
 
-        May raise StorageError if the lock can not be acquired before
+        May raise UnableToAcquireCommitLockError if the lock can not be acquired before
         some timeout.
 
         With nowait set to True, only try to obtain the lock without waiting
@@ -176,7 +177,7 @@ def release_commit_lock(cursor):
     def hold_pack_lock(cursor):
         """Try to acquire the pack lock.
 
-        Raise StorageError if packing or undo is already in progress.
+        Raise UnableToAcquirePackUndoLockError if packing or undo is already in progress.
         """
 
     def release_pack_lock(cursor):
@@ -470,3 +471,9 @@ def abort(conn, cursor, txn=None):
 
 class ReplicaClosedException(Exception):
     """The connection to the replica has been closed"""
+
+class UnableToAcquireCommitLockError(StorageError):
+    """The commit lock cannot be acquired."""
+
+class UnableToAcquirePackUndoLockError(StorageError):
+    """A pack or undo operation is in progress."""

relstorage/adapters/locker.py

@@ -14,9 +14,10 @@
 """Locker implementations.
 """
 
-from ZODB.POSException import StorageError
 from perfmetrics import metricmethod
 from relstorage.adapters.interfaces import ILocker
+from .interfaces import UnableToAcquireCommitLockError
+from .interfaces import UnableToAcquirePackUndoLockError
 from zope.interface import implements
 
 
@@ -63,7 +64,7 @@ def hold_commit_lock(self, cursor, ensure_current=False, nowait=False):
         except self.lock_exceptions:
             if nowait:
                 return False
-            raise StorageError('Acquiring a commit lock failed')
+            raise UnableToAcquireCommitLockError('Acquiring a commit lock failed')
         return True
 
     def release_commit_lock(self, cursor):
@@ -87,13 +88,13 @@ def hold_pack_lock(self, cursor):
             cursor.execute("SELECT pg_try_advisory_lock(1)")
             locked = cursor.fetchone()[0]
             if not locked:
-                raise StorageError('A pack or undo operation is in progress')
+                raise UnableToAcquirePackUndoLockError('A pack or undo operation is in progress')
         else:
             # b/w compat
             try:
                 cursor.execute("LOCK pack_lock IN EXCLUSIVE MODE NOWAIT")
             except self.lock_exceptions:  # psycopg2.DatabaseError:
-                raise StorageError('A pack or undo operation is in progress')
+                raise UnableToAcquirePackUndoLockError('A pack or undo operation is in progress')
 
     def release_pack_lock(self, cursor):
         """Release the pack lock."""
@@ -114,7 +115,7 @@ def hold_commit_lock(self, cursor, ensure_current=False, nowait=False):
         if nowait and locked in (0, 1):
             return bool(locked)
         if not locked:
-            raise StorageError("Unable to acquire commit lock")
+            raise UnableToAcquireCommitLockError("Unable to acquire commit lock")
 
     def release_commit_lock(self, cursor):
         stmt = "SELECT RELEASE_LOCK(CONCAT(DATABASE(), '.commit'))"
@@ -129,7 +130,7 @@ def hold_pack_lock(self, cursor):
         cursor.execute(stmt)
         res = cursor.fetchone()[0]
         if not res:
-            raise StorageError('A pack or undo operation is in progress')
+            raise UnableToAcquirePackUndoLockError('A pack or undo operation is in progress')
 
     def release_pack_lock(self, cursor):
         """Release the pack lock."""
@@ -166,7 +167,7 @@ def hold_commit_lock(self, cursor, ensure_current=False, nowait=False):
                     'lock already owned', 'illegal handle')[int(status)]
             else:
                 msg = str(status)
-            raise StorageError(
+            raise UnableToAcquireCommitLockError(
                 "Unable to acquire commit lock (%s)" % msg)
 
         # Alternative:
@@ -197,7 +198,7 @@ def hold_pack_lock(self, cursor):
         try:
             cursor.execute(stmt)
         except self.lock_exceptions:  # cx_Oracle.DatabaseError:
-            raise StorageError('A pack or undo operation is in progress')
+            raise UnableToAcquirePackUndoLockError('A pack or undo operation is in progress')
 
     def release_pack_lock(self, cursor):
         """Release the pack lock."""