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https://issues.apache.org/jira/browse/CASSANDRA-5455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13654771#comment-13654771
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Jonathan Ellis commented on CASSANDRA-5455:
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bq. the PBS latency tracking will record both how long it took for the request
to reach a remote replica and be processed as well as how long the return trip
takes.
Hmm, I don't see that happening on the 1.2 branch. It looks to me like like
PBS was trying to measure raw message RTT (slightly incorrectly since it was
clicking Start when we enqueued the message rather than when we sent). Which,
granted, *is* different from the SP "time to complete request" metrics.
Would the latter be "close enough?" I'd rather only track one set of mostly
similar metrics, given the choice.
bq. modifying StorageProxy to log these latencies in addition to the coarser
granularity measurements it already takes
I'm fine with either "provide it as SPMBean methods" or "create a separate
MBean that we only kick off if individual data point collection is enabled."
Should we make collection be a fraction (0..1) rather than on/off? ISTM that
10% or 1% of requests could provide enough information on a busy system, and
those CLQ objects could become a contention point w/ enough cores busy.
> Remove PBSPredictor
> -------------------
>
> Key: CASSANDRA-5455
> URL: https://issues.apache.org/jira/browse/CASSANDRA-5455
> Project: Cassandra
> Issue Type: Bug
> Reporter: Jonathan Ellis
> Assignee: Jonathan Ellis
> Fix For: 2.0
>
> Attachments: 5455.txt
>
>
> It was a fun experiment, but it's unmaintained and the bar to understanding
> what is going on is high. Case in point: PBSTest has been failing
> intermittently for some time now, possibly even since it was created. Or
> possibly not and it was a regression from a refactoring we did. Who knows?
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