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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6423) Writes should not block reads on blocking updates to memstores
Date Fri, 30 Nov 2012 01:41:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13507028#comment-13507028
] 

Lars Hofhansl commented on HBASE-6423:
--------------------------------------

This part's a bit ugly:
{code}
+  protected Configuration createConf() {
+    Configuration conf = HBaseConfiguration.create();
+    if (busyWaitDuration != null) {
+      conf.set("hbase.busy.wait.duration", busyWaitDuration);
+    }
+    return conf;
+  }
{code}

We're using the configuration pass this information around? Why isn't it in the configuration
in the first place?
                
> Writes should not block reads on blocking updates to memstores
> --------------------------------------------------------------
>
>                 Key: HBASE-6423
>                 URL: https://issues.apache.org/jira/browse/HBASE-6423
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Karthik Ranganathan
>            Assignee: Jimmy Xiang
>         Attachments: trunk-6423.patch, trunk-6423_v2.1.patch, trunk-6423_v2.patch, trunk-6423_v3.2.patch
>
>
> We have a big data use case where we turn off WAL and have a ton of reads and writes.
We found that:
> 1. flushing a memstore takes a while (GZIP compression)
> 2. incoming writes cause the new memstore to grow in an unbounded fashion
> 3. this triggers blocking memstore updates
> 4. in turn, this causes all the RPC handler threads to block on writes to that memstore
> 5. we are not able to read during this time as RPC handlers are blocked
> At a higher level, we should not hold up the RPC threads while blocking updates, and
we should build in some sort of rate control.

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