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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-5069) Use asynchronous refresh to provide non-blocking Phoenix Stats Client Cache
Date Sat, 15 Dec 2018 00:39:00 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-5069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16721911#comment-16721911
] 

ASF GitHub Bot commented on PHOENIX-5069:
-----------------------------------------

Github user BinShi-SecularBird commented on the issue:

    https://github.com/apache/phoenix/pull/416
  
    @karanmehta93 


> Use asynchronous refresh to provide non-blocking Phoenix Stats Client Cache
> ---------------------------------------------------------------------------
>
>                 Key: PHOENIX-5069
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-5069
>             Project: Phoenix
>          Issue Type: Improvement
>            Reporter: Bin Shi
>            Assignee: Bin Shi
>            Priority: Major
>
> The current Phoenix Stats Cache uses TTL based eviction policy. A cached entry will expire
after a given amount of time (900s by default) passed since the entry's been created. This
will lead to cache miss when Compiler/Optimizer fetches stats from cache at the next time.
As you can see from the above graph, fetching stats from the cache is a blocking operation
— when there is cache miss, it has a round trip over the wire to scan the SYSTEM.STATS Table
and to get the latest stats info, rebuild the cache and finally return the stats to the Compiler/Optimizer.
Whenever there is a cache miss, this blocking call causes significant performance penalty and
see periodic spikes.
> *This Jira suggests to use asynchronous refresh mechanism to provide a non-blocking
cache. For details, please see the linked design document below.*
> [~karanmehta93] [~twdsilva@gmail.com] [~dbwong] [~elserj] [~ankit@apache.org] [~sergey
soldatov] 



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