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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8533) [REST] HBaseAdmin does not ride over cluster restart
Date Mon, 13 May 2013 02:03:16 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8533?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13655709#comment-13655709
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Andrew Purtell commented on HBASE-8533:
---------------------------------------

Option 1 seems best.

Option 3 is a REST server at every RegionServer ? I don't think that is a typical deploy.

Not sure about option 2 either. That would be an embedding of an HBase client on the server
wherever a REST servlet is deployed,  and lots of crosstalk among servers as a result. Or,
we could reboot REST semantics and do the WebHDFS thing of redirecting clients: requests for
one region's data via REST would be redirected to the other embedded REST servlet where the
region is local. Wildcards and scanners in the current API address more than one region. Would
we redirect at every region boundary? That might work for scanners but wildcards in paths
could no longer be supported (these are "mini-scans") because they have to return all the
results in one HTTP transaction, there's no place for a redirect at a boundary crossing. Anyway,
as I mention, introducing redirects is a reboot of REST, it wouldn't be backwards compatible.

                
> [REST] HBaseAdmin does not ride over cluster restart
> ----------------------------------------------------
>
>                 Key: HBASE-8533
>                 URL: https://issues.apache.org/jira/browse/HBASE-8533
>             Project: HBase
>          Issue Type: Improvement
>          Components: REST, scripts
>    Affects Versions: 0.94.3, 0.98.0
>            Reporter: Julian Zhou
>            Priority: Minor
>             Fix For: 0.94.3, 0.98.0
>
>
> For Restful servlet (org.apache.hadoop.hbase.rest.Main (0.94), org.apache.hadoop.hbase.rest.RESTServer
(trunk)) on Jetty, we need to first explicitly start the service (% ./bin/hbase-daemon.sh
start rest -p 8000 ) for application running. Here is a scenario, sometimes, HBase cluster
are stopped/started for maintanence, but rest is a seperated standalone process, which binds
the HBaseAdmin at construction method.
> HBase stop/start cause this binding lost for existing rest servlet. Rest servlet still
exist to trying on old bound HBaseAdmin until a long time duration later with an "Unavailable"
caught via an IOException caught in
> such as RootResource.
> Could we pairwise the HBase service with HBase rest service with some start/stop options?
since seems no reason to still keep the rest servlet process after HBase stopped? When HBase
restarts, original rest service could not resume to bind to the new HBase service via its
old HBaseAdmin reference?
> So may we stop the rest when hbase stopped, or even if hbase was killed by acident, restart
hbase with rest option could detect the old rest process, kill it and start to bind a new
one?
> From this point of view, application rely on rest api in previous scenario could immediately
detect it when setting up http connection session instead of wasting a long time to fail back
from IOException with "Unavailable" from rest servlet.
> Put current options from the discussion history here from Andrew, Stack and Jean-Daniel,
> 1) create an HBaseAdmin on demand in rest servlet instead of keeping singleton instance;
(another possible enhancement for HBase client: automatic reconnection of an open HBaseAdmin
handle after a cluster bounce?)
> 2) pairwise the rest webapp with hbase webui so the rest is always on with HBase serive;
> 3) add an option for rest service (such as HBASE_MANAGES_REST) in hbase-env.sh, set HBASE_MANAGES_REST
to true, the scripts will start/stop the REST server.

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