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Date: Fri, 3 Feb 2012 19:33:57 +0000 (UTC)
From: "Jonathan Hsieh (Commented) (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-5128) [uber hbck] Enable hbck to
 automatically repair table integrity problems as well as region consistency
 problems while online.
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    [ https://issues.apache.org/jira/browse/HBASE-5128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13199967#comment-13199967 ] 

Jonathan Hsieh commented on HBASE-5128:
---------------------------------------

Jimmy mentions this actually may be HBASE-4238.  
                
> [uber hbck] Enable hbck to automatically repair table integrity problems as well as region consistency problems while online.
> -----------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5128
>                 URL: https://issues.apache.org/jira/browse/HBASE-5128
>             Project: HBase
>          Issue Type: New Feature
>          Components: hbck
>    Affects Versions: 0.90.5, 0.92.0
>            Reporter: Jonathan Hsieh
>            Assignee: Jonathan Hsieh
>
> The current (0.90.5, 0.92.0rc2) versions of hbck detects most of region consistency and table integrity invariant violations.  However with '-fix' it can only automatically repair region consistency cases having to do with deployment problems.  This updated version should be able to handle all cases (including a new orphan regiondir case).  When complete will likely deprecate the OfflineMetaRepair tool and subsume several open META-hole related issue.
> Here's the approach (from the comment of at the top of the new version of the file).
> {code}
> /**
>  * HBaseFsck (hbck) is a tool for checking and repairing region consistency and
>  * table integrity.  
>  * 
>  * Region consistency checks verify that META, region deployment on
>  * region servers and the state of data in HDFS (.regioninfo files) all are in
>  * accordance. 
>  * 
>  * Table integrity checks verify that that all possible row keys can resolve to
>  * exactly one region of a table.  This means there are no individual degenerate
>  * or backwards regions; no holes between regions; and that there no overlapping
>  * regions. 
>  * 
>  * The general repair strategy works in these steps.
>  * 1) Repair Table Integrity on HDFS. (merge or fabricate regions)
>  * 2) Repair Region Consistency with META and assignments
>  * 
>  * For table integrity repairs, the tables their region directories are scanned
>  * for .regioninfo files.  Each table's integrity is then verified.  If there 
>  * are any orphan regions (regions with no .regioninfo files), or holes, new 
>  * regions are fabricated.  Backwards regions are sidelined as well as empty
>  * degenerate (endkey==startkey) regions.  If there are any overlapping regions,
>  * a new region is created and all data is merged into the new region.  
>  * 
>  * Table integrity repairs deal solely with HDFS and can be done offline -- the
>  * hbase region servers or master do not need to be running.  These phase can be
>  * use to completely reconstruct the META table in an offline fashion. 
>  * 
>  * Region consistency requires three conditions -- 1) valid .regioninfo file 
>  * present in an hdfs region dir,  2) valid row with .regioninfo data in META,
>  * and 3) a region is deployed only at the regionserver that is was assigned to.
>  * 
>  * Region consistency requires hbck to contact the HBase master and region
>  * servers, so the connect() must first be called successfully.  Much of the
>  * region consistency information is transient and less risky to repair.
>  */
> {code}

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