> > Also, are you sure you couldn't use async-profiler? We use this all the > > time in our very latency-sensitive production. It has no noticeable > > overhead in my experience and doesn't need any special dependencies. > > I have to admit, I have never used async-profiler. Shame on me. > That is a fabulous hint and I'll read up on it immediately.
I now did read up on it, tried it locally, stumbled over https://issues.apache.org/jira/browse/HBASE-25685 and the fact that 2.4 fails weirdly using Java 21 only to find out (I should have read the whole docs earlier) that it's hard to run async-profiler in a container. For us, this is all running on Kubernetes, so we'll test that today. Testing i tlocally it looked very promising. > > > > On Tue, Dec 5, 2023 at 3:46 PM Lars Francke <lars.fran...@gmail.com> wrote: > > > > > Hi, > > > > > > I am debugging an issue where we see some Get requests taking 2-5s. > > > We do see "responseTooSlow" etc. and this is in an environment where I > > > cannot run a Profiler but I _can_ run modified code. > > > > > > So what I did was I added a stupid "MethodTimer"[1] which records how > > > long certain operations take at various points in the code (e.g. [2]). > > > I've been doing this a few rounds and have now arrived at the > > > StoreScanner. > > > > > > I'm wondering if anyone has better ideas on how to diagnose this? > > > I am a HBase committer but I haven't been able to keep up with the > > > changes in the last 5-6 years so I'm not too familiar with the inner > > > workings anymore and would appreciate a hint. > > > > > > I suspect it is slowness related to storage access. > > > I was not able to find any logs or tweaks to log "slow storage" > > > access, does such a thing exist? > > > And something else that'd help me: Can anyone point me (if it exists) > > > at the (vicinity of the) code that actually reads from HDFS at the > > > end? There are so many layers. > > > > > > Thank you! > > > > > > Cheers, > > > Lars > > > > > > > > > [1] < > > > https://github.com/stackabletech/docker-images/blob/8349f29f8aded8a01a8d1dbf7a90776ede1764ca/hbase/stackable/patches/2.4.12/005-STACKABLE-profiling-2.4.12.patch#L150C5-L150C5 > > > > > > > [2] < > > > https://github.com/stackabletech/docker-images/blob/8349f29f8aded8a01a8d1dbf7a90776ede1764ca/hbase/stackable/patches/2.4.12/005-STACKABLE-profiling-2.4.12.patch#L289-L297 > > > > > > >
