Matrix room member lists increasingly diverge from IRC

[f0x52]

This has been an issue for a while now, where the Matrix side of portal rooms has many usernames that joined the IRC channel somewhere in the past, but left a long time ago.

I think this is partly fixed with matrix-org/node-irc#118, as that fixes a bug where the NAMES response on re-used clients would always be a superset of the previous listing, so never leaving old users unless the PART/QUIT was directly received.

The NAMES response is properly received at bridge startup at least, but that causes it to queue a gigantic amount of leave items in the MemberListSyncer, which don't retry, and which time-out after the default of 30 minutes.
In the case of my Libera bridge, around 120 thousand, which it's only able to clear a fraction of them the 30 minutes TTL.

Is there a reason to queue these with a TTL at all?
Also, I think it would be an improvement if matrix-appservice-bridge's membership queue would be smarter at cancelling out leave/join's for the same user, if there's already an entry in the queue for them, but maybe that's better directed at that repo instead.

EDIT: bridge is globally configured to do member list updates both ways, initial and incremental both true

[f0x52]

I read over this at first, but the logic here

matrix-appservice-irc/src/bridge/MemberListSyncer.ts

Lines 388 to 393 in 062f3ac

	if (this.memberLists.irc[channel] !== undefined ||
	!this.server.shouldSyncMembershipToMatrix("initial", channel)) {
	return;
	}
	const nickList = [...names.keys()];
	this.memberLists.irc[channel] = nickList;

prevents NAMES updates from ever being used after initial sync, whereas they would be very useful to keep everything in sync, especially after netsplits. Or to retry failed leave queue items, when someone joins at a later time

[jkhsjdhjs]

matrix-org/node-irc#117 may also be a cause:
If a user joins the IRC channel, their puppet joins the corresponding matrix channel. If they change their nick, this isn't recognized. Thus, if they write a message with their new nick, the irc bridge assumes it must've missed a join and has a new puppet join the matrix channel to deliver the message. If the IRC user now decides to part or quit, only the new matrix puppet leaves, the original one will stay there forever.

I still run version 0.34.0 of the bridge, as it is the most recent version where quits, parts and nick changes are bridged properly.

[f0x52]

@jkhsjdhjs ah indeed, already pulled your fix for that into my forked node-irc/matrix-appservice-irc too :)