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Subject: Re: Review Request 28873: ACCUMULO-3393 Follow-on work for per-table
 volume chooser.
From: "Jenna Huston" <jenna.huston22@gmail.com>
To: "Jenna Huston" <jenna.huston22@gmail.com>
Cc: "Mike Drob" <mdrob@mdrob.com>, "Sean Busbey" <sean@manvsbeard.com>,
 "accumulo" <dev@accumulo.apache.org>,
 "Christopher Tubbs" <ctubbsii-rb@apache.org>,
 "Josh Elser" <josh.elser@gmail.com>
Date: Wed, 10 Dec 2014 21:36:15 -0000
Message-ID: <20141210213615.5766.47864@reviews.apache.org>
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Sender: "Jenna Huston" <noreply@reviews.apache.org>
References: <20141210075450.26419.35187@reviews.apache.org>
In-Reply-To: <20141210075450.26419.35187@reviews.apache.org>
Reply-To: "Jenna Huston" <jenna.huston22@gmail.com>

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> On Dec. 10, 2014, 7:54 a.m., Christopher Tubbs wrote:
> > server/base/src/main/java/org/apache/accumulo/server/fs/PreferredVolumeChooser.java, line 99
> > <https://reviews.apache.org/r/28873/diff/1/?file=787889#file787889line99>
> >
> >     Do we really need an object pool for a map which holds 0 or 1 element for the duration of a single, infrequently called method? A better optimization for this case would be to add an optimized get(String key) method to AccumuloConfiguration / TableConfiguration, so we don't have to use a map at all.
> 
> Sean Busbey wrote:
>     This code path is in the critical section of tablet splitting, the frequency of which varies greatly based on system deployment. There's already a TODO for doing the refactoring you mention, which will allow us to later remove the pooling entirely.
> 
> Josh Elser wrote:
>     I really don't see the creation of a new HashMap as being critical WRT the cost of waiting for a tablet to close, performing multiple metadata table updates and then waiting for the tablets to come back online.
> 
> Sean Busbey wrote:
>     Am I correct that we currently don't have any microbenchmarks that would tell us one way or the other?
> 
> Josh Elser wrote:
>     ditto what I said down below.
> 
> Christopher Tubbs wrote:
>     As far as I know, we have not done any microbenchmarks on this. Which is why I suggested it was premature optimization.

I agree that waiting for an optimized get method would be better in the long run.


- Jenna


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On Dec. 10, 2014, 2:58 p.m., Sean Busbey wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/28873/
> -----------------------------------------------------------
> 
> (Updated Dec. 10, 2014, 2:58 p.m.)
> 
> 
> Review request for accumulo and Jenna Huston.
> 
> 
> Bugs: ACCUMULO-3393
>     https://issues.apache.org/jira/browse/ACCUMULO-3393
> 
> 
> Repository: accumulo
> 
> 
> Description
> -------
> 
> ACCUMULO-3393 Follow-on work for per-table volume chooser.
> 
> Still has TODOs for additional tickets I need to file. I'll update the review to remove once I have them all filed. I think everything marked TODO can wait for a later ticket. Please comment on relevant section if you think something needs to be done now.
> 
> * docs clean up + code guideline compliance.
> * ensure RandomVolumeChoosers are independent when used per-table.
> * make sure that per-table choosers can keep state the way that global choosers can
> * make sure that a chooser can only pick from the options it is presented.
> * avoid object creation in critical path for Tablet.split.
> 
> 
> Diffs
> -----
> 
>   core/src/main/java/org/apache/accumulo/core/conf/Property.java 4c2d0b41b3bce32449861da3ac42fa27deb2b182 
>   pom.xml 31601a1bf84e19b861e4f48b50824eeb77987b52 
>   server/base/pom.xml c21a168dec2092692f1ee6877c4703ee2d3e3977 
>   server/base/src/main/java/org/apache/accumulo/server/fs/PerTableVolumeChooser.java 7a825c796eb5a25de8c748e2aba642f483697b9a 
>   server/base/src/main/java/org/apache/accumulo/server/fs/PreferredVolumeChooser.java 7ed7bba809a4e5e4b2d472c3327b15adb37251a7 
>   server/base/src/main/java/org/apache/accumulo/server/fs/RandomVolumeChooser.java f2eb2113cb848ed58ac5f41573c6ff2cde9b0a77 
>   server/base/src/main/java/org/apache/accumulo/server/fs/VolumeChooser.java f523057b11a2dc42e82010675bb1ac8e3802f96d 
>   server/base/src/main/java/org/apache/accumulo/server/fs/VolumeManager.java 890651e92f4c34514cb839b7b9ee9d23ad55070a 
>   server/base/src/main/java/org/apache/accumulo/server/fs/VolumeManagerImpl.java dc1be739b634d91992894f8f27c2d9c184bd98cd 
>   server/base/src/main/java/org/apache/accumulo/server/fs/VolumeUtil.java 877d01c2233cca086c1ac1539eb81cc282a7ceb4 
>   server/base/src/main/java/org/apache/accumulo/server/util/TabletOperations.java c0e1a9b991d61a4dbb127c74ae297f171434e7d5 
>   server/base/src/test/java/org/apache/accumulo/server/fs/VolumeManagerImplTest.java 582822a8ccbc398925a2184eed0b9d7fa853f9b4 
> 
> Diff: https://reviews.apache.org/r/28873/diff/
> 
> 
> Testing
> -------
> 
> Ran through VolumeManagerImplTest and VolumeChooserIT 
> 
> 
> Thanks,
> 
> Sean Busbey
> 
>


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