What about repairs? Can I just repair that table on a regular basis as any other?
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Wednesday, 30 October 2019 16:26, Jon Haddad <j...@jonhaddad.com> wrote: > Counters are good for things like page views, bad for money. Yes they can > under or overcount in certain situations. If your cluster is stable, you'll > see very little of it in practice. > > I've done quite a bit of tuning of counters. Here's the main takeaways: > > * They do a read before a write, so use low latency disks (SSD) > * Dial back read ahead to 4KB, this is a big deal (in fact, always do this > even if you're not using counters and you are using SSDs) > * Use 4KB compression chunk length > * Bump up you counter cache > * Some basic JVM tuning (ParNew + CMS, 16GB heap 10GB new, max tenuring > threshold 4, survivor ratio 6) > > The last 3 will give you a 10-20x perf improvement over stock Cassandra if > you've got a lot of counters. > > Jon > > On Wed, Oct 30, 2019 at 7:01 AM <advicerywo...@pm.me.invalid> wrote: > >> Hi, >> >> I would like to use counters but I am not sure I should. >> >> I read a lot of articles on the Internet how counters are bad / wrong / >> inaccurate etc etc ... >> >> Let's be honest, counters in Cassandra have quite a bad reputation. >> >> But all stuff I read about that was quite old, I know there was significant >> improvements in that area especially around 2.1 / 2.2 releases but I can not >> make my head around so I can definitely be sure if I should use them or not. >> >> The literature I read were: >> >> 1) That one elaborates about counters from node-lifecycle perspective and >> there are still some problems of over / undercounting. >> >> 2) This one explains the differences between pre and post 2.1 >> implementations and suggests that once counter caches are removed, the >> implementation will be even better and simplified - but I am not sure what >> is the outcome of this article? It says that all "wrong" implementation of >> counters (as we knew them in pre 2.x era) was corrected and we should be all >> good to use it? >> >> 3) These guys said that they have not found any bugs ... huh. >> >> So, what is the overall state of counters in 3.11.4 ? (hence 3.11.5)? Would >> you recommend to use them in production? >> >> My usecase is that I have 2 DCs with 3 nodes each and I have a table where I >> want to track number number of page visits. >> >> My perception is that "they will be inconsistent and you can not repair it >> and it is idempotent" but from what I have tested, when I put 1 node down >> and I brought it back and read it, it was just fine and numbers were good. >> >> So I am not sure if my testing is very naive but the whole mystery about >> counters and the lack of the authoritative advice what the general status is >> and where it can go wrong is imho lacking. >> >> Are the links below obsolete? Do I have strong guarantee that counters will >> "just work"? What are the downsides and why would not you use them? >> Honestly, after reading a lot about that, I am not trusting counters too >> much but I am not sure if my opinion is biased based on what I read so far. >> >> Thanks >> >> Links >> >> 1) http://datastrophic.io/evaluating-cassandra-2-1-counters-consistency/ >> >> 2) >> https://www.datastax.com/blog/2014/05/whats-new-cassandra-21-better-implementation-counters >> >> 3) https://www.datastax.com/blog/2016/01/testing-apache-cassandra-jepsen >> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org >> For additional commands, e-mail: user-h...@cassandra.apache.org
