Re: CAS operation result is unknown - proposal accepted by 1 but not a quorum

[Ralph Boehme]

On 4/12/23 15:30, Jeff Jirsa wrote:

Are you always inserting into the same partition (with contention) or
different ?

I'm actually updating the very same row. :)

Which version are you using ?

# nodetool version
ReleaseVersion: 4.1.1

The short tldr is that the failure modes of the existing paxos
implementation (under contention, under latency, under cluster
strain) can cause undefined states. I believe that a subsequent
serial read will deterministically resolve the state (look at
cassandra-12126), but that has a cost (both the extra operation and
the code complexity)

I'm definitely driving contention here in my workload. I'm basically implementing locks using LWTs on a row and I'm running lock/unlock in a tight loop *from multiple clients*. As said, this already comes to a grinding halt with just 2 clients.

The upcoming transactional rewrite will likely change this, but it’s
still WIP (CEP-15)

Thanks!
-slow

Thanks. I'm aware of Acord and can't await to get my fingers on Cassandra 5.0. :) In the meantime I was hoping I could use Cassandra's LWTs to implement locking.

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