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From "Prakash Khemani (JIRA)" <j...@apache.org>
Subject [jira] Created: (HBASE-2957) Release row lock when waiting for wal-sync
Date Fri, 03 Sep 2010 04:57:33 GMT
Release row lock when waiting for wal-sync

                 Key: HBASE-2957
                 URL: https://issues.apache.org/jira/browse/HBASE-2957
             Project: HBase
          Issue Type: Improvement
          Components: regionserver, wal
    Affects Versions: 0.20.0
            Reporter: Prakash Khemani

Is there a reason to hold on to the row-lock while waiting for the WAL-sync to be completed
by the logSyncer thread?

I think data consistency will be guaranteed even if the following happens (a) the row lock
is held while the row is updated in memory (b) the row lock is released after queuing the
KV record for WAL-syncing (c) the log-sync system guarantees that the log records for any
given row are synced in order (d) the HBase client only receives a success notification after
the sync completes (no change from the current state)

I think this should be a huge win. For my use case, and I am sure for others,  the handler
thread spends the bulk of its row-lock critical section  time waiting for sync to complete.

Even if the log-sync system cannot guarantee the orderly completion of sync records, the "Don't
hold row lock while waiting for sync" option should be available to HBase clients on a per
request basis.

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