Commits on Jan 17, 2022

1. ⚡️ Remove server-side Presence transformations …

   This change addresses a performance issue with Presence, whereby every
   single Presence update will cause a Database call to fetch the latest
   ops, and transform Presence up.
   
   This can be quite costly if there are a lot of Presence updates, and
   adversely impact the "normal" operation of ShareDB. This is particularly
   strange for the "happy case", where two clients are exchanging Presence
   on the same version of a document (where there should be no need to
   query the database at all for Presence).
   
   We already have mechanisms in the client to transform presence, as well
   as re-request stale presence, so we can remove the server-side Presence
   transformations all together.
   
   This alleviates pressure on the server, at the cost of decreased
   performance in edge cases, where clients need to re-request Presence
   from other clients, or catch up on cached ops. However, this should be a
   sensible change to make, since we're trying to optimise for the happy
   path, rather than edge cases.
   
   Note that this changes a test case: we have to resubscribe `doc1` in
   this test case, otherwise it's never up-to-date, and `presence2`
   continues to throw out its presence updates. This could happen in a
   real-world situation (where `doc1` stays offline), but it's arguable
   that this is uninteresting presence anyway, since that client is not
   "live".

   

   alecgibson committed Jan 17, 2022
   Configuration menu

   • View commit details
   • Copy full SHA for febb54f
   • Browse repository at this point

   Copy the full SHA

   febb54f View commit details

   Browse the repository at this point in the history