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Jason Brown commented on CASSANDRA-13289:
-----------------------------------------
I'm pretty much +1 on the patch, except for the
{{AbstractWriteResponseHandler#responsesAndExpirations}} extra garbage and two
trivial nits, which you can feel free to completely ignore:
- maybe use the javacdoc comment style on {{Config#ideal_consistency_level}}
rather than the line comment style?
- {{StorageProxy#setIdealConsistencyLevel}} returns the previous value of the
{{ideal_consistency_level}}. Would that be confusing to operators who execute
the JMX command? maybe return "updating setIdealConsistencyLevel, previous
value was <VALUE>"?
The last thing is testing: i think it's possible to add unit tests to confirm
most of the behaviors here. Can you take a look into that?
> Make it possible to monitor an ideal consistency level separate from actual
> consistency level
> ---------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-13289
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13289
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: Ariel Weisberg
> Assignee: Ariel Weisberg
> Fix For: 4.0
>
>
> As an operator there are several issues related to multi-datacenter
> replication and consistency you may want to have more information on from
> your production database.
> For instance. If your application writes at LOCAL_QUORUM how often are those
> writes failing to achieve EACH_QUORUM at other data centers. If you failed
> your application over to one of those data centers roughly how inconsistent
> might it be given the number of writes that didn't propagate since the last
> incremental repair?
> You might also want to know roughly what the latency of writes would be if
> you switched to a different consistency level. For instance you are writing
> at LOCAL_QUORUM and want to know what would happen if you switched to
> EACH_QUORUM.
> The proposed change is to allow an ideal_consistency_level to be specified in
> cassandra.yaml as well as get/set via JMX. If no ideal consistency level is
> specified no additional tracking is done.
> if an ideal consistency level is specified then the
> {{AbstractWriteResponesHandler}} will contain a delegate WriteResponseHandler
> that tracks whether the ideal consistency level is met before a write times
> out. It also tracks the latency for achieving the ideal CL of successful
> writes.
> These two metrics would be reported on a per keyspace basis.
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