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From "Jonathan Park (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-3294) Need mechanism to update iterator settings
Date Mon, 16 Nov 2015 17:56:11 GMT


Jonathan Park commented on ACCUMULO-3294:

[~elserj] thanks for the feedback! I'll apply it to the patch if the patch is still desirable.

[~ctubbsii] I agree that this can enable users shooting themselves in the foot due to the
lack of atomicity guarantees in Accumulo regarding the propagation of config. I still think
such an API call is valuable and would become safer and easier to consume if/when Accumulo
has the ability to support atomic updates to config (although if Accumulo adds transactional
support to updates, then I would admit a dedicated update call would not add much value).

The example use-case we have is 1 non-trivial iterator which is logically the composition
of a set of iterators. This iterator will at run-time read its configuration and determine
what it needs to do. The issue we're running into is that we can't afford to have a compaction
start when we're in the middle of removing/adding. We could get pretty far by re-designing
our system to disable major compactions so we can manually launch the compactions and control
the iterator settings used (we would probably need some other design around minor compactions
to handle those safely as well). 

If there's a particular direction that Accumulo is headed to support these changing configurations
for compactions, I'd love to help out where possible to help make Accumulo easier to consume
w.r.t configurations. I do admit this patch is less than ideal and doesn't address some other
issues present. 

[~kturner] Thanks for the example and explanation of the benefits. I agree that it's safer
for scans to follow such a pattern. 

> Need mechanism to update iterator settings
> ------------------------------------------
>                 Key: ACCUMULO-3294
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>            Reporter: John Vines
>            Assignee: Jonathan Park
>             Fix For: 1.8.0
>         Attachments: bug3294.patch, bug3294.patch.1
> Currently our API supports attachIterator, removeIterator, and getIteratorSettings. There
is no mechanism to directly change an iterators settings.

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