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From "Christopher Tubbs (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-4078) Exclude special volumes
Date Mon, 21 Dec 2015 23:36:46 GMT


Christopher Tubbs commented on ACCUMULO-4078:

bq. What's the net benefit of keeping a static temporary directory for a tablet?

I'm not convinced there's even a benefit to having a static non-temporary directory for a
tablet (srv:dir). Personally, I'd prefer choosing on every file creation (with as much information
about the scope/environment as possible, so it can make a good decision based on current configuration
vs. a past decision)... ACCUMULO-3090

bq. My first reaction is that it seems unnecessary to provide multiple "general*" volume chooser

I agree. Some of the situations might be considered distinct "scopes" appropriate for a special
config. However, many others might be behavior dependent on a particular configured global
or per-table chooser, and it might be more appropriate to provide ACCUMULO-3384 to empower
those various implementations.

> Exclude special volumes
> -----------------------
>                 Key: ACCUMULO-4078
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.7.0
>            Reporter: Matt Peterson
>            Assignee: Matt Peterson
>            Priority: Minor
>              Labels: newbie
>             Fix For: 1.8.0
> A few improvements to the {{VolumeChooser}} are desired for a use case that seems general
enough to warrant an update to Accumulo.  
> *Use Case:*
> A new volume is added, with limited capacity, to be dedicated for a specific table. 
All other tables or files should be excluded from this new volume.
> *Suggested Improvements:*
> # Update the signature for {{VolumeManager.choose}} to take a {{VolumeChooserEnvironment}}
instead of {{Optional<String>}}.  This will allow future parameters for volume selection
without repeatedly changing the {{VolumeManager}} interface.
> # It's not currently possible to specify preferred volumes for the write-ahead logs
> # In several places including {{PreferredVolumeChooser}}, {{PerTableVolumeChooser}} and
{{VolumeManagerImpl}}, the failsafe chooser is the {{RandomVolumeChooser}} which will include
the instance volume that needs to be excluded.  It would be useful to have a configurable
failsafe in this situation.
> # The volume chooser is called in {{FileUtils}} for temp directory creation but it could
instead use the sticky dir to create the temp directory, not needing the volume chooser at
> The above suggestions could become sub-tickets.  Note that the improvements listed have
been implemented for my particular instance and I hope to submit them as a patch.

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