There are reports of disconnected participant update missing -
https://github.com/livekit/client-sdk-js/pull/2096. That results in
clients retaining disconnected participant(s) in its roster.
Two changes
1. Look for participant disconnects a little farther back than last
signal time as client app might have lost visibility earlier.
2. Look at all participants within the relaxed window above. The update
cache is LRU. So, in theory can stop when an entry is before the time
threshold above. But, theoretically it is possible that `updatedAt`
time and LRU queuing time can flip ordering although very unlikely.
I think we should do one of the following to make it more robust, but
both require client side changes
1. Send full participant list in `ReconnectResponse`. Clients can use
that to drop participants not in the list.
2. Add a sequence number to all signal responses (maybe signal requests
as well) and have client send up the last response it saw in
`SyncState` message. Server can then replay all the messages after
that. This also requires a message cache on server side.
Raja Subramanian
9d8ee5a319