GoXDCR: Max dcp connections(10) yields same or lesser drain rate compared to min(2)

Build

4.0.0-2134

Found during manual testing.

Pls see screenshots attached.

1. Load 3M keys on .186.
2. Start replication from .186 --> .188, source_nozzles = 2
3. At this point dcp has to stream atleast 3M keys to goxdcr. The drain-rate with 2 dcp connections streaming keys to xdcr is around 3.5K per sec. Watch for 2-3 mins.
4. Increase the source nozzle count to 10, let the drain rate stabilize. Data load continues. We have ~4M keys in dcp queue.
I saw that drain-rate was in the 3.25 - 3.5K range. I saw 10 active dcp connections.

Therefore, I do not see any difference in dcp drain rate when source_nozzles = 2 or 10.

This would mean that docs received by goxdcr from dcp will remain same and hence may not affect the rate of replication, regardless of the source nozzle count.

In another case, I saw drain rate was atleast 2.5 times slower with source nozzles = 10 compared to 2. However after a while, the drain rates looked almost equal.