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From "Robert Newson (JIRA)" <>
Subject [jira] Created: (COUCHDB-487) Pause write requests to allow compaction to complete
Date Thu, 27 Aug 2009 08:50:59 GMT
Pause write requests to allow compaction to complete

                 Key: COUCHDB-487
             Project: CouchDB
          Issue Type: Improvement
          Components: Database Core
            Reporter: Robert Newson
         Attachments: 0001-block-writes-at-completion-of-compaction-to-allow-sw.patch

Continuous writes will currently indefinitely prevent the compaction process from flipping
over to the .compact file.

Here's a small patch that adds a new db flag called 'write_available' which becomes false
the first time compaction completes but fails to flip over because of concurrent writes. Subsequent
calls to update_docs then sleep for 1/2 a second and throw retry.

I ran 'ab -p json -n 1000000 http://localhost:5984/db1' in one window. Without this patch,
I get a long sequence of;

[info] [<0.64.0>] Compaction file still behind main file (update seq=1848. compact update
seq=1845). Retrying.

and compaction never completes.

With the patch, I get this;

[info] [<0.369.0>] - - 'POST' /db1 201
[info] [<0.65.0>] Compaction file still behind main file (update seq=2140. compact update
seq=2092). Retrying.
[info] [<0.65.0>] Blocking writes to complete compaction.
[info] [<0.65.0>] Compaction for db "db1" completed.
[info] [<0.370.0>] - - 'POST' /db1 201

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