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From "kulkarni.swarnim@gmail.com" <kulkarni.swar...@gmail.com>
Subject Question about RPC queues
Date Fri, 04 Sep 2015 14:12:01 GMT
Hello all,

So I am trying to play around with de-prioritizing long running scanners
feature added with HBASE-10993. Essentially I wanted to see how "deadline"
queue prevents contention. This is what my did for my setup. Changed the
callqueue type to "fifo" and reduced the number of RPC handlers to 1 to
ensure that I have only one RPC queue in place. I am also testing on a
cluster with only one RS to again make sure that there is only one RPC
handler working. I confirmed that my settings are properly in place with
the following message in the hmaster logs after I restarted my cluster.

"INFO org.apache.hadoop.hbase.ipc.SimpleRpcScheduler: Using fifo as user
call queue, count=1"

I now kicked off a long running "scan" first and while the scan was running
kicked off another "get". My hope was that with fifo, we should see a
contention and the "get" would essentially hang until the "scan" finished
as it would be placed behind the "scan" request in the RPC queue. But I see
the gets still return quickly irrespective of whether the scan is running
or not.

Is there something obvious that I am missing here to be able to reproduce
the contention?

Thanks,
Swarnim

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