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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1843) HBase Client Configuration -- Millisecond Pauses and very few Retries (s)
Date Fri, 18 Sep 2009 23:54:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12757538#action_12757538

stack commented on HBASE-1843:

For example, if what is wanted is 25ms maximum pause, we'd need to account for GC in client.
 We'd also need account for lookup of -ROOT- and .META. each of which could happen within
2 retries and within the 25ms but overall, the get could take 150ms though maximum asked for
was 50ms (2x25ms).

> HBase Client Configuration -- Millisecond Pauses and very few Retries (s)
> -------------------------------------------------------------------------
>                 Key: HBASE-1843
>                 URL: https://issues.apache.org/jira/browse/HBASE-1843
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: client
>    Affects Versions: 0.20.0
>            Reporter: Barney Frank
>            Priority: Critical
> The ability to set the number of retries and the pause length between them on the HBaseClient
through HBaseConfiguration.
> I am working on an application that utilizes Hbase for real-time queries.  The dependency
on Hbase is not critical so if HBase is not available for any reason the application should
continue on doing its job without the data from Hbase.  Essentially I want HBase Client to
fail quickly if the request to Hase is going to fail or take a long time to respond.  I have
tested various scenarios with Zookeeper running/not running and the master running/not running.
> Configuration:
> Hbase 0.20.0 & Hadoop 0.20.1
> Pseudo distributed mode
> Java client using HTablePool
> When ZK, Master, Regionserver and my app are running, I stop the Hbase master/regionserver.
 The HBaseClient then begins to complain:
> 16:26:51,273 INFO [HBaseClient] Retrying connect to server: / Already
tried 0 time(s).
> 16:26:53,274 INFO [HBaseClient] Retrying connect to server: / Already
tried 1 time(s).
> ...already tried 9 time(s)....
> 16:27:10,294 INFO [HbaseRPC] Server at / not available yet, Zzzzz...
> **** This is despite the fact that I set hbase.pause to be 25 ms and the retries.number
= 2.  ****
> I restart the Master and RegionServer and then send more client requests through HTablePool.
 It has the same "Retrying to connect to server:" messages.  I noticed that the port number
it is using is the old port for the region server and not the new one assigned after the restart.
 The HbaseClient does not seem to recover unless I restart the client app.  When I do not
use HTablePool and only Htable it works fine.
> Issue:
> Setting and using hbase.client.pause and hbase.client.retries.number parameters.  I have
rarely gotten them to work.  It seems to default to 2 sec and 10 retries no matter if I overwrite
the defaults on the client and the server.  Yes, I made sure my client doesn't have anything
in the classpath it might pick-up.
> <property>
> <name>hbase.client.pause</name>
> <value>20</value>
> </property>
> <property>
> <name>hbase.client.retries.number</name>
> <value>2</value>
> </property>

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