Multiplexers, observeChanges duration and OplogTailingin mongo / meteor

Question

I'm developping an app with Meteor.js. For that, I do have a cluster of mongo instances for oplog tailing. In addition, I'm using Kadira in order to trace my app perfs.

Since I've enabled oplog tailing, many of my pub/sub are slower than before. What I see is that it is way slower when the oplog "query" has its "wasMultiplexerReady" attribute set to false, which is the case on the majority of the observeChanges I see on Kadira.

The problem is there is absolutely NOTHING about it on the web. I've been looking for any resource about it and how it works, but there is literaly nothing.

Could somone give me some hint / explanation about what's going here ? Like what is this attribute "wasMultiplexerReady", how is it used, how can I reduce the oplog tailing computation time, etc...

Thanks you.

Answer 1

I know this is fairly late, and I'm not 100% on this but I think that is whether or not the subscription was already subscribed to. Meaning another client was already subscribed to that cursor, and Meteor can then just send the same results to multiple people.