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From "Antony Blakey (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COUCHDB-246) allow customization of external process timeout
Date Wed, 11 Feb 2009 05:52:59 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-246?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12672520#action_12672520
] 

Antony Blakey commented on COUCHDB-246:
---------------------------------------

I have this problem with _externals that implement lazy-view update semantics. The problem
being that the amount of work required for the _external to catchup to the current update_seq
is unknown. I experimented with a solution that allows the external to return a keep-alive
message to the server, which doesn't return a value to the client but does stop the server
killing the external.

I got distracted and didn't complete that work, but I think this is a better solution than
a fixed timeout. The problem with a timeout is that it doesn't account for machine performance
or load, or the possible highly variable amount of work that the external needs to do on a
per-request basis, whereas a keep-alive more correctly captures what you want e.g. the external
process is making progress. Such a keep alive could specify a timeout value, so that the external
process could control the definition of failure according to how often it will send keep-alives,
but that might be an unnecessary complication.

> allow customization of external process timeout
> -----------------------------------------------
>
>                 Key: COUCHDB-246
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-246
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Database Core
>    Affects Versions: 0.9
>            Reporter: Robert Newson
>            Priority: Blocker
>             Fix For: 0.9
>
>
> If an external process takes too long to respond, it is killed. The timeout is quite
short (a few seconds) and is not configurable from .ini files today.
> couchdb-lucene could use this ability as the first attempt to sort on a field in a large
index is slow while it builds a cache. With the timeout, it's killed and the partial work
is lost.

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