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Posted to issues@lucene.apache.org by "Michael McCandless (Jira)" <ji...@apache.org> on 2020/09/02 16:14:00 UTC
[jira] [Commented] (LUCENE-8319) A Time-limiting collector that
works with CollectorManagers
[ https://issues.apache.org/jira/browse/LUCENE-8319?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17189352#comment-17189352 ]
Michael McCandless commented on LUCENE-8319:
--------------------------------------------
{quote}Timeout handling seems to be a frequent need so maybe we should add support for it directly on IndexSearcher where we could more easily do the right thing?
{quote}
+1 to implement this in {{IndexSearcher}}, carefully. The exponential backoff sounds like a great approach!
> A Time-limiting collector that works with CollectorManagers
> -----------------------------------------------------------
>
> Key: LUCENE-8319
> URL: https://issues.apache.org/jira/browse/LUCENE-8319
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/search
> Reporter: Tony Xu
> Priority: Minor
>
> Currently Lucene has *TimeLimitingCollector* to support time-bound collection and it will throw
> *TimeExceededException* if timeout happens. This only works nicely with the single-thread low-level API from the IndexSearcher. The method signature is --
> *void search(List<LeafReaderContext> leaves, Weight weight, Collector collector)*
> The intended use is to always enclose the searcher.search(query, collector) call with a try ... catch and handle the timeout exception. Unfortunately when working with a *CollectorManager* in the multi-thread search context, the *TimeExceededException* thrown during collecting one leaf slice will be re-thrown by *IndexSearcher* without calling *CollectorManager*'s reduce(), even if other slices are successfully collected. The signature
> of the search api with *CollectorManager* is --
> *<C extends Collector, T> T search(Query query, CollectorManager<C, T> collectorManager)*
>
> The good news is that IndexSearcher handles *CollectionTerminatedException* gracefully by ignoring it. We can either wrap TimeLimitingCollector and throw *CollectionTerminatedException* when timeout happens or simply replace *TimeExceededException* with *CollectionTerminatedException*. In either way, we also need to maintain a flag that indicates if timeout occurred so that the user know it's a partial collection.
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