Performance Failure with Windows Patch: KB4074594

First off, this may be entirely Microsoft's fault. We have yet to be able to trace the specific issue. However, Couchbase is the only service impacted by this patch, of the several technologies we use.

Following an update of half of our cluster to the latest security updates, which included KB4074594, we almost immediately began noticing that a large chunk of the requests would take 6 seconds (exactly). My immediate thought was a timeout, as fibonacci TCP tries would suggest 1+2+3 = timeout.

However, the stats page showed requests coming in at a standard pace given the time of day. 20-200/sec.

As we have yet to formally identify the specific cause of the issue, we just wanted to get word out there that KB4074594 is a problem for Couchbase 5.0.0 and 5.0.1  (or vice versa)