Add support for persisting event format versions

changelog.d/4437.misc

@@ -0,0 +1 @@
+Add infrastructure to support different event formats

synapse/api/constants.py

@@ -120,6 +120,19 @@ class RoomVersions(object):
     RoomVersions.STATE_V2_TEST,
 }
 
+
+class EventFormatVersions(object):
+    """This is an internal enum for tracking the version of the event format,
+    independently from the room version.
+    """
+    V1 = 1
+
+
+KNOWN_EVENT_FORMAT_VERSIONS = {
+    EventFormatVersions.V1,
+}
+
+
 ServerNoticeMsgType = "m.server_notice"
 ServerNoticeLimitReached = "m.server_notice.usage_limit_reached"
 

synapse/events/__init__.py

@@ -18,6 +18,7 @@
 
 import six
 
+from synapse.api.constants import EventFormatVersions
 from synapse.util.caches import intern_dict
 from synapse.util.frozenutils import freeze
 
@@ -179,6 +180,8 @@ def auth_event_ids(self):
 
 
 class FrozenEvent(EventBase):
+    format_version = EventFormatVersions.V1  # All events of this type are V1
+
     def __init__(self, event_dict, internal_metadata_dict={}, rejected_reason=None):
         event_dict = dict(event_dict)
 

synapse/storage/events.py

@@ -1268,6 +1268,7 @@ def event_dict(event):
                         event.internal_metadata.get_dict()
                     ),
                     "json": encode_json(event_dict(event)),
+                    "format_version": event.format_version,
                 }
                 for event, _ in events_and_contexts
             ],

synapse/storage/events_worker.py

@@ -21,10 +21,10 @@
 
 from twisted.internet import defer
 
+from synapse.api.constants import EventFormatVersions
 from synapse.api.errors import NotFoundError
-# these are only included to make the type annotations work
-from synapse.events import EventBase  # noqa: F401
 from synapse.events import FrozenEvent
+# these are only included to make the type annotations work
 from synapse.events.snapshot import EventContext  # noqa: F401
 from synapse.events.utils import prune_event
 from synapse.metrics.background_process_metrics import run_as_background_process
@@ -353,6 +353,7 @@ def _enqueue_events(self, events, check_redacted=True, allow_rejected=False):
                     self._get_event_from_row,
                     row["internal_metadata"], row["json"], row["redacts"],
                     rejected_reason=row["rejects"],
+                    format_version=row["format_version"],
                 )
                 for row in rows
             ],
@@ -377,6 +378,7 @@ def _fetch_event_rows(self, txn, events):
                 " e.event_id as event_id, "
                 " e.internal_metadata,"
                 " e.json,"
+                " e.format_version, "
                 " r.redacts as redacts,"
                 " rej.event_id as rejects "
                 " FROM event_json as e"
@@ -392,7 +394,7 @@ def _fetch_event_rows(self, txn, events):
 
     @defer.inlineCallbacks
     def _get_event_from_row(self, internal_metadata, js, redacted,
-                            rejected_reason=None):
+                            format_version, rejected_reason=None):
         with Measure(self._clock, "_get_event_from_row"):
             d = json.loads(js)
             internal_metadata = json.loads(internal_metadata)
@@ -405,8 +407,17 @@ def _get_event_from_row(self, internal_metadata, js, redacted,
                     desc="_get_event_from_row_rejected_reason",
                 )
 
+            if format_version is None:
+                # This means that we stored the event before we had the concept
+                # of a event format version, so it must be a V1 event.
+                format_version = EventFormatVersions.V1
+
+            # TODO: When we implement new event formats we'll need to use a
+            # different event python type
+            assert format_version == EventFormatVersions.V1
+
             original_ev = FrozenEvent(
-                d,
+                event_dict=d,
                 internal_metadata_dict=internal_metadata,
                 rejected_reason=rejected_reason,
             )

synapse/storage/schema/delta/53/event_format_version.sql

@@ -0,0 +1,16 @@
+/* Copyright 2019 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ALTER TABLE event_json ADD COLUMN format_version INTEGER;