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Posted to dev@couchdb.apache.org by "Paul Joseph Davis (JIRA)" <ji...@apache.org> on 2011/09/19 21:08:09 UTC

[jira] [Commented] (COUCHDB-1289) heartbeats skipped when continuous changes feed filter function produces no results

    [ https://issues.apache.org/jira/browse/COUCHDB-1289?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13108065#comment-13108065 ] 

Paul Joseph Davis commented on COUCHDB-1289:
--------------------------------------------

There are two aspects to this that need to be considered. We've fixed both of these in BigCouch but I'm not sure if we've the first one.

The first one is that if you have a large range of documents (ordered by update seq) that fail to pass a filter, there will be no heartbeat sent. Basically, the changes feed thinks its making process all hunky dory but nothing is being sent, and we never checked that its taking us too long to filter all these docs.

The second version of this is slightly more insidious. Basically, the timeouts we had in BigCouch were receive timeouts in two places (no db updates, and while processing in case everything is filtered). What can end up happening is that updates to the db can end up trickling in that all fail to make it through the filter function. This means that the changes loop thinks its working again but is not hitting either timeout clause to send the heartbeat.

The clustered calls in BigCouch are different enough that the patches aren't exactly applicable, but reading the code, CouchDB is at least susceptible to the second version and possible the first as well.

> heartbeats skipped when continuous changes feed filter function produces no results
> -----------------------------------------------------------------------------------
>
>                 Key: COUCHDB-1289
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1289
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Database Core
>            Reporter: Bob Dionne
>            Assignee: Bob Dionne
>            Priority: Minor
>
> if the changes feed has a filter function that produces no results, db_updated messages will still be sent and the heartbeat timeout will never be reached.

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