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https://issues.apache.org/jira/browse/COUCHDB-1289?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13158020#comment-13158020
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Filipe Manana commented on COUCHDB-1289:
----------------------------------------
Bob, looks good.
I was testing this against a very large database
(http://fdmanana.iriscouch.com/many_docs) by querying _changes without an
heartbeat parameter and with a filter that returned false for the first half of
the changes of the db.
It turns out that about 1 minute after the feed terminated without folding the
entire seq tree (last_seq in the response was not the current db's seq number).
So what happens is that when no heartbeat is given, a default TimeoutFun which
returns {stop, Acc} (always) is used:
https://github.com/fdmanana/couchdb/blob/c574d29bb92f2b61688b52e2e03548b05cc4a163/src/couchdb/couch_changes.erl#L239
So we have 2 distinct concepts in the changes feed: heartbeat and timeout.
I think renaming "maybe_timeout" to "maybe_heartbeat" makes it more clear, and
call the function only if no heartbeat was specified. I made quick code change
to test this:
https://github.com/fdmanana/couchdb/commit/c574d29bb92f2b61688b52e2e03548b05cc4a163
Makes sense?
thanks :)
> 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
> Attachments: 0001-Ensure-heartbeats-are-not-skipped.patch,
> 0002-Failing-etap-for-heartbeats-skipped.patch
>
>
> 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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