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From "Tianying Chang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16030) All Regions are flushed at about same time when MEMSTORE_PERIODIC_FLUSH is on, causing flush spike
Date Mon, 20 Jun 2016 23:41:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16030?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15340691#comment-15340691

Tianying Chang commented on HBASE-16030:

[~enis] good scenario! So with the previous hard code 5 mins delay, the flush WILL NOT happen
for 5 mins. It sounds also a problem if flush is stalled for 5 mins (although not as bad as
30 mins) Feels like the right way of jittering should not be putting into a blocking queue
ahead of time. What do you think? 

> All Regions are flushed at about same time when MEMSTORE_PERIODIC_FLUSH is on, causing
flush spike
> --------------------------------------------------------------------------------------------------
>                 Key: HBASE-16030
>                 URL: https://issues.apache.org/jira/browse/HBASE-16030
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 1.2.1
>            Reporter: Tianying Chang
>            Assignee: Tianying Chang
>             Fix For: 2.0.0, 1.4.0, 1.3.1, 1.2.3
>         Attachments: Screen Shot 2016-06-15 at 11.35.42 PM.png, Screen Shot 2016-06-15
at 11.52.38 PM.png, hbase-16030-v2.patch, hbase-16030.patch
> In our production cluster, we observed that memstore flush spike every hour for all regions/RS.
(we use the default memstore periodic flush time of 1 hour). 
> This will happend when two conditions are met: 
> 1. the memstore does not have enough data to be flushed before 1 hour limit reached;
> 2. all regions are opened around the same time, (e.g. all RS are started at the same
time when start a cluster). 
> With above two conditions, all the regions will be flushed around the same time at: startTime+1hour-delay
again and again.
> We added a flush jittering time to randomize the flush time of each region, so that they
don't get flushed at around the same time. We had this feature running in our 94.7 and 94.26
cluster. Recently, we upgrade to 1.2, found this issue still there in 1.2. So we are porting
this into 1.2 branch. 

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