[uber hbck] Enable hbck to automatically repair table integrity problems as
well as region consistency problems while online.
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Key: HBASE-5128
URL: https://issues.apache.org/jira/browse/HBASE-5128
Project: HBase
Issue Type: New Feature
Reporter: Jonathan Hsieh
Assignee: Jonathan Hsieh
The current (0.90.5, 0.92.0rc2) versions of hbck detect most of the invariant
violations (orphans is new). However with '-fix' it can only automatically
handle deployment problems with region consistency cases. This updated version
should be able to handle all cases. When complete will likely deprecate the
OfflineMetaRepair tool and subsume several META hole related problems.
{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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