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From advicerywo...@pm.me.INVALID
Subject What is the status of counters? Should I use them?
Date Wed, 30 Oct 2019 14:00:41 GMT
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


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