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From "Jean-Daniel Cryans (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2087) The wait on compaction because "Too many store files" holds up all flushing
Date Mon, 04 Jan 2010 04:51:04 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2087?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796078#action_12796078

Jean-Daniel Cryans commented on HBASE-2087:

bq. And this issue is about something else anyway, never holding up flushes

As I said in my first comment, it's either too much WALs or too much store files. If we let
all flushes go then we are overrun by store files. If we force flush memstores to be able
to roll WALs then we easily create too much store files. We have seen stores that needed to
compact 100 files and this is why we have a limit.

So, I question the feasibility of this jira.

In the particular case of WALs waiting on flushes waiting on too many store files, what I
said is that it's by setting a very low number of WALs that we easily hit the limit. Setting
it to a higher number means less chance of hitting this jira's problem, hence making it invalid?

> The wait on compaction because "Too many store files" holds up all flushing
> ---------------------------------------------------------------------------
>                 Key: HBASE-2087
>                 URL: https://issues.apache.org/jira/browse/HBASE-2087
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
> The method MemStoreFlusher#checkStoreFileCount is called from flushRegion.  flushRegion
is called by MemStoreFlusher#run thread.  If the checkStoreFileCount finds too many store
files, it'll stick around waiting on a compaction to happen.  While its hanging, the MemStoreFlusher#run
is held up.  No other region can flush.  Meantime WALs will be rolling and memory will be
accumulating writes.

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