Improve Telegram message deduplication

* Add pre-send message database check for deduplication
* Make dedup cache queue length configurable

example-config.yaml

@@ -136,6 +136,16 @@ bridge:
     # your own Matrix account as the Matrix puppet for your Telegram account.
     sync_with_custom_puppets: true
 
+    # Some config options related to Telegram message deduplication.
+    # The default values are usually fine, but some debug messages/warnings might recommend you
+    # change these.
+    deduplication:
+        # Whether or not to check the database if the message about to be sent is a duplicate.
+        pre_db_check: false
+        # The number of latest events to keep when checking for duplicates.
+        # You might need to increase this on high-traffic bridge instances.
+        cache_queue_length: 20
+
     # The formats to use when sending messages to Telegram via the relay bot.
     #
     # Telegram doesn't have built-in emotes, so the m.emote format is also used for non-relaybot users.

mautrix_telegram/config.py

@@ -196,6 +196,9 @@ class Config(DictWithRecursion):
         copy("bridge.catch_up")
         copy("bridge.sync_with_custom_puppets")
 
+        copy("bridge.deduplication.pre_db_check")
+        copy("bridge.deduplication.cache_queue_length")
+
         if "bridge.message_formats.m_text" in self:
             del self["bridge.message_formats"]
         copy_dict("bridge.message_formats", override_existing_map=False)

mautrix_telegram/portal.py

@@ -66,12 +66,19 @@ class Portal:
     az = None  # type: AppService
     bot = None  # type: Bot
     loop = None  # type: asyncio.AbstractEventLoop
+
     filter_mode = None  # type: str
     filter_list = None  # type: List[str]
+
     bridge_notices = False  # type: bool
+
+    dedup_pre_db_check = False  # type: bool
+    dedup_cache_queue_length = 20  # type: int
+
     alias_template = None  # type: str
     mx_alias_regex = None  # type: Pattern
     hs_domain = None  # type: str
+
     by_mxid = {}  # type: Dict[str, Portal]
     by_tgid = {}  # type: Dict[Tuple[int, int], Portal]
 
@@ -191,7 +198,7 @@ class Portal:
 
         self._dedup_action.append(evt_hash)
 
-        if len(self._dedup_action) > 20:
+        if len(self._dedup_action) > self.dedup_cache_queue_length:
             self._dedup_action.popleft()
         return False
 
@@ -221,7 +228,7 @@ class Portal:
         self._dedup_mxid[evt_hash] = mxid
         self._dedup.append(evt_hash)
 
-        if len(self._dedup) > 20:
+        if len(self._dedup) > self.dedup_cache_queue_length:
             del self._dedup_mxid[self._dedup.popleft()]
         return None
 
@@ -1330,6 +1337,8 @@ class Portal:
 
         msg = DBMessage.query.get((evt.id, tg_space))
         if not msg:
+            self.log.info(f"Didn't find edited message {evt.id}@{tg_space} (src {source.tgid}) "
+                          "in database.")
             # Oh crap
             return
         msg.mxid = mxid
@@ -1363,6 +1372,15 @@ class Portal:
                 self.db.commit()
             return
 
+        if self.dedup_pre_db_check and self.peer_type == "channel":
+            msg = DBMessage.query.get((evt.id, tg_space))
+            if msg:
+                self.log.debug(f"Ignoring message {evt.id} (src {source.tgid}) as it was already"
+                               f"handled into {msg.mxid}. This duplicate was catched in the db "
+                               "check. If you get this message often, consider increasing"
+                               "bridge.deduplication.cache_queue_length in the config.")
+                return
+
         if sender and not sender.displayname:
             self.log.debug(f"Telegram user {sender.tgid} sent a message, but doesn't have a"
                            "displayname, updating info...")
@@ -1416,10 +1434,16 @@ class Portal:
                         DBMessage.mxid == temporary_identifier) \
                 .update({"mxid": mxid})
         except FlushError as e:
-            self.log.exception(f"{e.__class__.__name__} while saving message mapping.")
+            self.log.exception(f"{e.__class__.__name__} while saving message mapping. "
+                               "This might mean that an update was handled after it left the "
+                               "dedup cache queue. You can try enabling bridge.deduplication."
+                               "pre_db_check in the config.")
             await intent.redact(self.mxid, mxid)
         except (IntegrityError, InvalidRequestError) as e:
-            self.log.exception(f"{e.__class__.__name__} while saving message mapping.")
+            self.log.exception(f"{e.__class__.__name__} while saving message mapping. "
+                               "This might mean that an update was handled after it left the "
+                               "dedup cache queue. You can try enabling bridge.deduplication."
+                               "pre_db_check in the config.")
             self.db.rollback()
             await intent.redact(self.mxid, mxid)
 
@@ -1740,6 +1764,8 @@ def init(context: Context):
     Portal.bridge_notices = config["bridge.bridge_notices"]
     Portal.filter_mode = config["bridge.filter.mode"]
     Portal.filter_list = config["bridge.filter.list"]
+    Portal.dedup_pre_db_check = config["bridge.deduplication.pre_db_check"]
+    Portal.dedup_cache_queue_length = config["bridge.deduplication.cache_queue_length"]
     Portal.alias_template = config.get("bridge.alias_template", "telegram_{groupname}")
     Portal.hs_domain = config["homeserver.domain"]
     Portal.mx_alias_regex = re.compile(