[jira] [Created] (COUCHDB-2947) Applying limit and continuous to _changes results in odd behavior when writing documents during request

["Mike Rhodes (JIRA)" <ji...@apache.org>]

Mike Rhodes created COUCHDB-2947:
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             Summary: Applying limit and continuous to _changes results in odd behavior when writing documents during request
                 Key: COUCHDB-2947
                 URL: https://issues.apache.org/jira/browse/COUCHDB-2947
             Project: CouchDB
          Issue Type: Bug
          Components: Database Core
            Reporter: Mike Rhodes


If I have a database that is continuously receiving updates, applying continuous and limit parameters to my database query gives odd behaviour. 

Take this URL:

http://localhost:5984/database/_changes?since=0&limit=1&feed=continuous

If I call this URL while running a script writing documents to the database at a great enough rate that the continuous changes timeout is not hit, the behaviour isn't as I'd expect.

What I'd expect to happen:

1 doc is emitted, the _changes feed emits the last_seq line, then the request is terminated.

What actually happens:

Once `limit` items have been returned, entries continue being emitted until writing documents to the database stops. After writing stops, entries stop being emitted into the response. If I start writing again, the response starts to emit changes entries again. If I don't start writing again, the request eventually times out via the default setting in couch.ini and emits the last_seq line and closes.

If a timeout is applied in the URL, this overrides the default timeout as expected, but otherwise the behaviour remains the same.

Note that the _changes feed isn't catching up to the current seq, it's just continuing to emit while the documents are being written. Once writing to the database stops, the request stops emitting changes wherever it's managed to get up to. From what I can tell, the emitted entries into the changes feed are in the right sequence, so we're not missing items from the feed, just emitting too many of them.



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