Make Event logging more useful by default

Log messages like:

ChassisGatewayAgentEvent : Matched Chassis, create, None None

are not particularly useful. This adds a default repr to RowEvents
and also a Row stringifier (which eventually could go in the ovs
lib). Subclasses of RowEvent that rely on custom match functions
should write their own __repr__ methods.

Change-Id: Ice22858df465b37b973718be718673aab46193ce

ovsdbapp/backend/ovs_idl/event.py

@@ -40,8 +40,8 @@ class RowEvent(ovsdb_event.RowEvent):  # pylint: disable=abstract-method
             return False
         if not self.match_fn(event, row, old):
             return False
-        LOG.debug("%s : Matched %s, %s, %s %s", self.event_name, self.table,
-                  event, self.conditions, self.old_conditions)
+        LOG.debug("Matched %s: %r to row=%s old=%s", event.upper(), self,
+                  idlutils.row2str(row), idlutils.row2str(old) if old else '')
         return True
 
 

ovsdbapp/backend/ovs_idl/idlutils.py

@@ -310,3 +310,14 @@ def db_replace_record(obj):
     elif isinstance(obj, api.Command):
         obj = obj.result
     return obj
+
+
+def row2str(row):
+    """Get a string representation of a Row"""
+
+    # This is not a repr, as the Row object takes a dict of Datum objects and
+    # we don't really want to deal with those, just what the Python values are.
+    # Row foreign keys are printed as their UUID
+    return "%s(%s)" % (row._table.name, ", ".join(
+        "%s=%s" % (col, idl._row_to_uuid(getattr(row, col)))
+        for col in row._table.columns if hasattr(row, col)))

ovsdbapp/event.py

@@ -53,6 +53,11 @@ class RowEvent(object):
     def __ne__(self, other):
         return not self == other
 
+    def __repr__(self):
+        return "%s(events=%r, table=%r, conditions=%r, old_conditions=%r)" % (
+            self.__class__.__name__, self.events, self.table, self.conditions,
+            self.old_conditions)
+
     @abc.abstractmethod
     def matches(self, event, row, old=None):
         """Test that `event` on `row` matches watched events