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From "Jonathan Hsieh (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5128) [uber hbck] Enable hbck to automatically repair table integrity problems as well as region consistency problems while online.
Date Mon, 09 Jan 2012 22:51:40 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13182898#comment-13182898
] 

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

@Ted,

For #1.  I'd ideally like the tool to be backwards compatible with existing 0.90's.  I think
this version will work for older versions in cases where the problem is table region holes.
 This problem only affects when attempting to repair overlapping regions.   If I need to modify
servers to update the unassign/close api, I'll probably put warnings on the code so that the
user is aware of potential issues if using hbck to fix older versions (or possibly ask the
user to failover to another master). 

For #2, makes sense -- I'll spend more time digging into what is "in-motion" causing the flaky
tests.


                
> [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: 0.92.0, 0.90.5
>            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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