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From "HBase Review Board (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2937) Facilitate Timeouts In HBase Client
Date Fri, 08 Oct 2010 21:36:31 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12919387#action_12919387

HBase Review Board commented on HBASE-2937:

Message from: stack@duboce.net

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This looks great Karthik.  How does it interact with our current retry mechanism?  You replace
our old retrying Callable?  There's a few comments below.


    There is white space at the end of lines in this javadoc.  Also, its apache or hadoop
policy not to have an author tag on classes (no other classes in hbase codebase have author).


    Why not make this class immutable?  Force users to create a new one if they want to have
different settings?


    White space and author tag.


    Maybe setRegionServerTimeout is a better name fort this method?


    Timeout could be null here?


    Are there tabs in here? And we use two spaces for tabs in our code base.


    two spaces for tab spaces in hbase codebase

- stack

> Facilitate Timeouts In HBase Client
> -----------------------------------
>                 Key: HBASE-2937
>                 URL: https://issues.apache.org/jira/browse/HBASE-2937
>             Project: HBase
>          Issue Type: New Feature
>          Components: client
>    Affects Versions: 0.89.20100621
>            Reporter: Karthick Sankarachary
>             Fix For: 0.90.0
>         Attachments: HBASE-2937.patch
> Currently, there is no way to force an operation on the HBase client (viz. HTable) to
time out if a certain amount of time has elapsed.  In other words, all invocations on the
HTable class are veritable blocking calls, which will not return until a response (successful
or otherwise) is received. 
> In general, there are two ways to handle timeouts:  (a) call the operation in a separate
thread, until it returns a response or the wait on the thread times out and (b) have the underlying
socket unblock the operation if the read times out.  The downside of the former approach is
that it consumes more resources in terms of threads and callables. 
> Here, we describe a way to specify and handle timeouts on the HTable client, which relies
on the latter approach (i.e., socket timeouts). Right now, the HBaseClient sets the socket
timeout to the value of the "ipc.ping.interval" parameter, which is also how long it waits
before pinging the server in case of a failure. The goal is to allow clients to set that timeout
on the fly through HTable. Rather than adding an optional timeout argument to every HTable
operation, we chose to make it a property of HTable which effectively applies to every method
that involves a remote operation.
> In order to propagate the timeout  from HTable to HBaseClient, we replaced all occurrences
of ServerCallable in HTable with an extension called ClientCallable, which sets the timeout
on the region server interface, once it has been instantiated, through the HConnection object.
The latter, in turn, asks HBaseRPC to pass that timeout to the corresponding Invoker, so that
it may inject the timeout at the time the invocation is made on the region server proxy. Right
before the request is sent to the server, we set the timeout specified by the client on the
underlying socket.
> In conclusion, this patch will afford clients the option of performing an HBase operation
until it completes or a specified timeout elapses. Note that a timeout of zero is interpreted
as an infinite timeout.

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