Over in HBASE-7263 there has been some discussion about removing support for explicit RowLocks in 0.96. This would involve the following: - Remove lockRow/unlockRow functions in HTable and similar - Remove constructors for Put/Delete/Increment/Get that take RowLocks - functions in HRegion no longer take lockIds (checkAndPut, append, increment, etc). This would affect coprocessors that call directly into those functions.
I have a patch in HBASE-7315 with the details. This would violate our usual rule of deprecating a feature one release before removing. The reasoning is as follows: 1) RowLocks are broken They are only kept in the memory associated with the region, so on a split, region move, RS crash, they just disappear 2) 0.96 is special Now seems like a good time to clean things up since we've made some incompatible changes already (e.g. protobufing) and we could have a cleaner client implementation 3) RowLocks have been deprecated "in spirit" for awhile Here's a post from 2009 cautioning against their use: http://bb10.com/java-hadoop-hbase-user/2009-09/msg00239.html and a more recent example: http://permalink.gmane.org/gmane.comp.java.hadoop.hbase.user/23488 4) RowLocks are hard to use effectively Clients can deadlock or starve themselves, either by forgetting to release the RowLocks or by starving other non-contending row operations by occupying server handlers stuck waiting to acquire the locks. Thoughts? Greg
