I've been playing with mongo 3.0 rc7 and rc8 and I've discovered that mongostat doesn't show lock rate column whether I use MMAPv1 or WiredTiger engine. Similarly in MMS, "lock %" chart is unavailable for 3.0 systems
We've been using lock rate in our monitoring systems, and also as one of the measurement during performance tests (we've been running same sets of heavy load tests via Gatling or Tsung and observing if recent optimizations in our usage of DB have some real impact, and also to discover if some new features doesn't have regression in this area).
Is there a way to find this value some way in mongo 3? Now we mainly want to run comparison tests on 2.6.7 and 3.0.0-rc8 to see what the difference is, and while we of course get nice set of data from the application performance standpoint, we'd also like to compare some DB stats and lock rate was one of them. Or are we completely missing the point and collection level locks in v3 MMAPv1 or document level locks in WiredTiger are now pointless to measure or compare? If so, how can we measure, what is the DB limit at heavy load (in < 2.6.7 it was fairly easy, usually lock rate was the first thing to fire and once it got above 70-80% we knew that it's the upper limit), or test regressions/improvements in how we use DB?
Many thanks
It's not pointless to compare some kind of lock statistics for mmapv1 and WiredTiger, but I think the situation right now is that it's unclear what you should be looking at in WiredTiger for comparison. The operation of the storage engine is very different from mmapv1. Presently, I think you'll want to look at other statistics like throughput, and you can expect more statistics and more guidance on using them in future versions of MongoDB with WiredTiger.