[HBASE-14201] hbck should not take a lock unless fixing errors

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3.0, 2.0.0
• Fix Version/s: 1.2.0, 2.0.0
• Component/s: hbck, util
• Hadoop Flags: Reviewed

Release Note

HBCK no longer takes a lock until there are changes to the cluster being made.

The old behavior can be achieved by passing the -exclusive flag.

• Flags: Patch
• Assignee: Simon Law
• Reporter: Simon Law
• Created: 10/Aug/15 18:16
• Updated: 01/Jul/22 20:49
• Resolved: 12/Aug/15 19:02

Description

By default, hbck is run in a read-only checker mode. In this case, it is
sensible to let others run. By default, the balancer is left alone,
which may cause spurious errors, but cannot leave the balancer in a bad
state. It is dangerous to leave the balancer by accident, so it is only
ever enabled after fixing, it will never be forced off because of
racing.

When hbck is run in fixer mode, it must take an exclusive lock and
disable the balancer, or all havoc will break loose.

If you want to stop hbck from running in parallel, the -exclusive flag
will create the lock file. If you want to force -disableBalancer, that
option is available too. This makes more semantic sense than -noLock and
-noSwitchBalancer, respectively.

This task is related to HBASE-14092.