[
https://issues.apache.org/jira/browse/COUCHDB-449?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12739942#action_12739942
]
Brian Candler commented on COUCHDB-449:
---------------------------------------
Just to be clear: _changes is supposed only to update after a commit has
taken place, not after a write?
If so, I cannot demonstrate it. If I write a document and then immediately
read _changes, it always appears. See below at (*).
Furthermore, the same is true if I run
$ curl http://127.0.0.1:5984/test/_changes?feed=continuous
in another window. As soon as I add a document in the first window, it
appears in the _changes feed.
My very rough scan of the source suggests that a delayed commit should take
place after 1 second:
Delay and (Db#db.waiting_delayed_commit == nil) ->
Db#db{waiting_delayed_commit=
erlang:send_after(1000, self(), delayed_commit)};
So if that's right, and what you say is true, then I would expect not to see
the document in _changes for this long.
OTOH, with batch=ok the commit is delayed indefinitely. I have raised this
as a separate ticket COUCHDB-454)
All tested with HEAD (git commit aebdb31001126dab6b579b8cc2e605ef7ec499c6)
and 12b5 under Jaunty.
Regards,
Brian.
(*)
$ curl -X DELETE http://127.0.0.1:5984/test
{"ok":true}
$ curl -X PUT http://127.0.0.1:5984/test
{"ok":true}
$ curl http://127.0.0.1:5984/test/_changes
{"results":[
],
"last_seq":0}
$ curl -X POST -d'{}' http://127.0.0.1:5984/test; curl
http://127.0.0.1:5984/test/_changes
{"ok":true,"id":"70708dcbc24444977b759365f9731f27","rev":"1-967a00dff5e02add41819138abb3284d"}
{"results":[
{"seq":1,"id":"70708dcbc24444977b759365f9731f27","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]}
],
"last_seq":1}
$ curl -X POST -d'{}' http://127.0.0.1:5984/test; curl
http://127.0.0.1:5984/test/_changes
{"ok":true,"id":"1d4596c1cb715c0da9f99980fea0a3a2","rev":"1-967a00dff5e02add41819138abb3284d"}
{"results":[
{"seq":1,"id":"70708dcbc24444977b759365f9731f27","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":2,"id":"1d4596c1cb715c0da9f99980fea0a3a2","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]}
],
"last_seq":2}
$ curl -X POST -d'{}' http://127.0.0.1:5984/test; curl
http://127.0.0.1:5984/test/_changes
{"ok":true,"id":"a2feeaaca391446bb7a0f24c359ff79e","rev":"1-967a00dff5e02add41819138abb3284d"}
{"results":[
{"seq":1,"id":"70708dcbc24444977b759365f9731f27","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":2,"id":"1d4596c1cb715c0da9f99980fea0a3a2","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":3,"id":"a2feeaaca391446bb7a0f24c359ff79e","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]}
],
"last_seq":3}
$ curl -X POST -d'{}' http://127.0.0.1:5984/test; curl -X POST -d'{}'
http://127.0.0.1:5984/test; curl -X POST -d'{}' http://127.0.0.1:5984/test;
curl http://127.0.0.1:5984/test/_changes
{"ok":true,"id":"a2262a5904690aec5c64bb61f44903ed","rev":"1-967a00dff5e02add41819138abb3284d"}
{"ok":true,"id":"26fdac7e139531e0f4352a089d4db7f4","rev":"1-967a00dff5e02add41819138abb3284d"}
{"ok":true,"id":"f6bb36540484788becd54391dbc6189b","rev":"1-967a00dff5e02add41819138abb3284d"}
{"results":[
{"seq":1,"id":"70708dcbc24444977b759365f9731f27","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":2,"id":"1d4596c1cb715c0da9f99980fea0a3a2","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":3,"id":"a2feeaaca391446bb7a0f24c359ff79e","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":4,"id":"a2262a5904690aec5c64bb61f44903ed","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":5,"id":"26fdac7e139531e0f4352a089d4db7f4","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]},
{"seq":6,"id":"f6bb36540484788becd54391dbc6189b","changes":[{"rev":"1-967a00dff5e02add41819138abb3284d"}]}
],
"last_seq":6}
> Turn off delayed commits by default
> -----------------------------------
>
> Key: COUCHDB-449
> URL: https://issues.apache.org/jira/browse/COUCHDB-449
> Project: CouchDB
> Issue Type: Bug
> Components: Database Core
> Affects Versions: 0.9, 0.9.1
> Reporter: Jan Lehnardt
> Priority: Blocker
> Fix For: 0.10
>
>
> Delayed commits make CouchDB significantly faster. They also open a one
> second window for data loss. In 0.9 and trunk, delayed commits are enabled by
> default and can be overridden with HTTP headers and an explicit API call to
> flush the write buffer. I suggest to turn off delayed commits by default and
> use the same overrides to enable it per request. A per-database option is
> possible, too.
> One concern is developer workflow speed. The setting affects the test suite
> performance significantly. I'd opt to change couch.js to set the appropriate
> header to enable delayed commits for tests.
> CouchDB should guarantee data safety first and speed second, with sensible
> overrides.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
