We have 6 Meteor instances in production that runs behind nginx on one server. And MongoDB that is running on the other server. The issues occur when a lot of changes (about 5000 per second) happen to the MongoDB. All meteor instances start to receive a huge amount of data by the network (speed up to 300 Mbps). CPU raises up to 100% and meteor dies until changes to MongoDB stop happening. That happens even when there are no active publications/subscriptions. Looks like it’s happening just because of DB updates. Also, we have 2 other meteor apps and they are connected to the same DB. What’s interesting, they also receive some unknown data with the enormous speed.
As far, as we understand it happens because of reading oplog. We are looking for a workaround because every time it happens it causes DDOS.