[HBASE-16744] Procedure V2 - Lock procedures to allow clients to acquire locks on tables/namespaces/regions

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.0.0

Release Note

 Lock for HBase Entity either a Table, a Namespace, or Regions.

These are remote locks which live on master, and need periodic heartbeats to keep them alive. (Once we request the lock, internally an heartbeat thread will be started). If master doesn't receive the heartbeat in time, it'll release the lock and make it available to other users.

Use {@link LockServiceClient} to build instances. Then call {@link #requestLock()}. {@link #requestLock} will contact master to queue the lock and start the heartbeat thread which will check lock's status periodically and once the lock is acquired, it will send the heartbeats to the master.

Use {@link #await} or {@link #await(long, TimeUnit)} to wait for the lock to be acquired. Always call {@link #unlock()} irrespective of whether lock was acquired or not. If the lock was acquired, it'll be released. If it was not acquired, it is possible that master grants the lock in future and the heartbeat thread keeps it alive forever by sending heartbeats. Calling {@link #unlock()} will stop the heartbeat thread and cancel the lock queued on master.

There are 4 ways in which these remote locks may be released/can be lost:
  * Call {@link #unlock}.
  * Lock times out on master: Can happen because of network issues, GC pauses, etc. Worker thread will call the given abortable as soon as it detects such a situation. Fail to contact master: If worker thread can not contact mater and thus fails to send heartbeat before the timeout expires, it assumes that lock is lost and calls the
 * abortable.
Worker thread is interrupted.

Use example:

 EntityLock lock = lockServiceClient.*Lock(...., "exampled lock", abortable);
  lock.requestLock();
  ....
   ....can do other initializations here since lock is 'asynchronous'...
 ....
 if (lock.await(timeout)) {
    ....logic requiring mutual exclusion
  }
   lock.unlock();
 

• Assignee: Matteo Bertozzi
• Reporter: Apekshit Sharma
• Created: 01/Oct/16 00:10
• Updated: 17/Jun/22 18:07
• Resolved: 14/Jan/17 05:07

Description

Will help us get rid of ZK locks.
Will be useful for external tools like hbck, future backup manager, etc.

Issue Links

• is blocked by: HBASE-16735 Procedure v2 - Fix yield while holding locks
• is blocked by: HBASE-16871 Procedure v2 - add waiting procs back to the queue after restart
• is required by: HBASE-17067 Procedure v2 - remove tryAcquire*Lock and use wait/wake to make framework event based
• relates to: HBASE-16786 Procedure V2 - Move ZK-lock's uses to Procedure framework locks (LockProcedure)
• relates to: HBASE-16867 Procedure V2 - Check ACLs for remote HBaseLock
• relates to: HBASE-16831 Procedure V2 - Remove org.apache.hadoop.hbase.zookeeper.lock
• links to: Original RB
• links to: Review Board (master)
• links to: Review Board that supercedes the first RB link but is itself superceded by the final rb link
• links to: Reviewboard