Merge pull request #30 from Shoobx/master

log ConflictError details, fixes #29

src/ZODB/ConflictResolution.py

@@ -236,6 +236,7 @@ _unresolvable = {}
 def tryToResolveConflict(self, oid, committedSerial, oldSerial, newpickle,
                          committedData=b''):
     # class_tuple, old, committed, newstate = ('',''), 0, 0, 0
+    klass = 'n/a'
     try:
         prfactory = PersistentReferenceFactory()
         newpickle = self._crs_untransform_record_data(newpickle)
@@ -285,15 +286,18 @@ def tryToResolveConflict(self, oid, committedSerial, oldSerial, newpickle,
         pickler.dump(meta)
         pickler.dump(resolved)
         return self._crs_transform_record_data(file.getvalue())
-    except (ConflictError, BadClassName):
-        pass
+    except (ConflictError, BadClassName) as e:
+        logger.debug(
+            "Conflict resolution on %s failed with %s: %s",
+            klass, e.__class__.__name__, str(e))
     except:
         # If anything else went wrong, catch it here and avoid passing an
         # arbitrary exception back to the client.  The error here will mask
         # the original ConflictError.  A client can recover from a
         # ConflictError, but not necessarily from other errors.  But log
         # the error so that any problems can be fixed.
-        logger.exception("Unexpected error")
+        logger.exception(
+            "Unexpected error while trying to resolve conflict on %s", klass)
 
     raise ConflictError(oid=oid, serials=(committedSerial, oldSerial),
                         data=newpickle)

src/ZODB/tests/testconflictresolution.py

@@ -39,7 +39,7 @@ def tearDown(test):
 
 class ResolveableWhenStateDoesNotChange(persistent.Persistent):
 
-    def _p_resolveConflict(old, committed, new):
+    def _p_resolveConflict(self, old, committed, new):
         raise ZODB.POSException.ConflictError
 
 class Unresolvable(persistent.Persistent):
@@ -292,6 +292,82 @@ And load the pickle:
     >>> db2.close()
     """
 
+
+class FailHard(persistent.Persistent):
+
+    def _p_resolveConflict(self, old, committed, new):
+        raise RuntimeError("epic fail")
+
+
+def show_tryToResolveConflict_log_output():
+    """
+    Verify output generated by tryToResolveConflict in the logs
+
+    >>> db = ZODB.DB('t.fs') # FileStorage!
+    >>> storage = db.storage
+    >>> conn = db.open()
+    >>> conn.root.x = FailHard()
+    >>> conn.root.x.v = 1
+    >>> transaction.commit()
+    >>> serial1 = conn.root.x._p_serial
+    >>> conn.root.x.v = 2
+    >>> transaction.commit()
+    >>> serial2 = conn.root.x._p_serial
+    >>> oid = conn.root.x._p_oid
+
+Install a log handler to be able to show log entries
+
+    >>> import logging
+    >>> from zope.testing.loggingsupport import InstalledHandler
+    >>> handler = InstalledHandler('ZODB.ConflictResolution',
+    ...     level=logging.DEBUG)
+
+Content fails hard on conflict resolution:
+
+    >>> p = storage.tryToResolveConflict(
+    ...         oid, serial2, serial1, storage.loadSerial(oid, serial2))
+    ... # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ...
+    ConflictError: database conflict error (oid 0x01, ...
+
+Content doesn't support conflict resolution:
+
+    >>> conn.root.y = Unresolvable()
+    >>> conn.root.y.v = 1
+    >>> transaction.commit()
+    >>> oid = conn.root.y._p_oid
+    >>> serial = conn.root.y._p_serial
+
+    >>> p = storage.tryToResolveConflict(
+    ...         oid, serial, serial, storage.loadSerial(oid, serial))
+    ... # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ...
+    ConflictError: database conflict error (oid 0x02, ...
+
+Let's see what went into the log:
+
+    >>> len(handler.records)
+    2
+
+    >>> import six
+
+    >>> msg = handler.records[0]
+    >>> six.print_(msg.name, msg.levelname, msg.getMessage())
+    ZODB.ConflictResolution ERROR Unexpected error while trying to resolve conflict on <class 'ZODB.tests.testconflictresolution.FailHard'>
+
+    >>> msg = handler.records[1]
+    >>> six.print_(msg.name, msg.levelname, msg.getMessage())
+    ZODB.ConflictResolution DEBUG Conflict resolution on <class 'ZODB.tests.testconflictresolution.Unresolvable'> failed with ConflictError: database conflict error
+
+Cleanup:
+
+    >>> handler.uninstall()
+    >>> db.close()
+    """
+
+
 def test_suite():
     return unittest.TestSuite([
         manuel.testing.TestSuite(
@@ -305,4 +381,3 @@ def test_suite():
             setUp=setUp, tearDown=tearDown,
             checker=ZODB.tests.util.checker),
         ])
-