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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4089) blockCache contents report
Date Wed, 10 Aug 2011 20:12:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13082640#comment-13082640
] 

stack commented on HBASE-4089:
------------------------------

I'd say the name just has to be guaranteed unique... short would be nice too.

Currently name is made in here for both v1 and v2 hfiles:

{code}
  public static String getBlockCacheKey(String hfileName, long offset) {
    return hfileName + CACHE_KEY_SEPARATOR + offset;
  }
{code}

The hfilename seems to depend on the fact storefile names are unique across hbase. They are
made here using the 'name' part of the full storefile Path (from the AbstractHFileReader constructor):

    this.name = path.getName();



> blockCache contents report
> --------------------------
>
>                 Key: HBASE-4089
>                 URL: https://issues.apache.org/jira/browse/HBASE-4089
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Doug Meil
>            Assignee: Doug Meil
>         Attachments: hbase_4089_blockcachereport.pdf
>
>
> Summarized block-cache report for a RegionServer would be helpful.  For example ...
> table1
>   cf1   100 blocks, totalBytes=yyyyy, averageTimeInCache=XXXX hours
>   cf2   200 blocks, totalBytes=zzzzz, averageTimeInCache=XXXX hours
> table2
>   cf1  75 blocks, totalBytes=yyyyy, averageTimeInCache=XXXX hours
>   cf2 150 blocks, totalBytes=zzzzz, averageTimeInCache=XXXX hours
> ... Etc.
> The current metrics list blockCacheSize and blockCacheFree, but there is no way to know
what's in there.  Any single block isn't really important, but the patterns of what CF/Table
they came from, how big are they, and how long (on average) they've been in the cache, are
important.
> No such interface exists in HRegionInterface.  But I think it would be helpful from an
operational perspective.
> Updated (7-29):  Removing suggestion for UI.  I would be happy just to get this report
on a configured interval dumped to a log file.

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