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Posted to commits@cassandra.apache.org by "Benedict (JIRA)" <ji...@apache.org> on 2014/12/01 00:18:13 UTC
[jira] [Commented] (CASSANDRA-6976) Determining replicas to query
is very slow with large numbers of nodes or vnodes
[ https://issues.apache.org/jira/browse/CASSANDRA-6976?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14229269#comment-14229269 ]
Benedict commented on CASSANDRA-6976:
-------------------------------------
On second thoughts, ignore that sentiment entirely. We don't really have any concept of a "lookup table", and we'll have to address that directly when we introduce enum types which is a better place.
I guess what really bugs me about this, and what I assumed would be related to the problem (but patently can't given the default behaviour) is that after calculating natural endpoints, we then sort them (based on a couple of hashmap lookups for each end point) for every token range, and also for every single normal query. This sort is performed over RF*DC items in either case, even for queries routed directly to the owning node with CL ONE. I was hoping we'd fix that as a result of this work, since that's a lot of duplicated effort, but that hardly seems sensible now. What we definitely _should_ do, though, is make sure we're (in general) benchmarking behaviour over common config, as our default test configuration is not at all representative.
> Determining replicas to query is very slow with large numbers of nodes or vnodes
> --------------------------------------------------------------------------------
>
> Key: CASSANDRA-6976
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6976
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Benedict
> Assignee: Ariel Weisberg
> Labels: performance
> Attachments: GetRestrictedRanges.java, jmh_output.txt, jmh_output_murmur3.txt, make_jmh_work.patch
>
>
> As described in CASSANDRA-6906, this can be ~100ms for a relatively small cluster with vnodes, which is longer than it will spend in transit on the network. This should be much faster.
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