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From "Paul Joseph Davis (Commented) (JIRA)" <>
Subject [jira] [Commented] (COUCHDB-1309) File descriptor leaks on design document update and view cleanup
Date Sun, 13 Nov 2011 21:01:51 GMT


Paul Joseph Davis commented on COUCHDB-1309:

So reviewing this again, my last comment still stands. There's no reason to introduce the
ddoc_changed function into the indexer API. These changes should be limited entirely to couch_index
(minus the tests anyway). This is a simple fix. Just use Mod:get(signature, Mod:init(Db, DDoc))
(or similar) in the with_db call in couch_index:handle_cast/2 call for ddoc_updated.

The other thing that occurred to me over lunch is if we might want to reimplement this by
just having couch_index close itself after a period of inactivity. At the moment there's no
limit on the number of groups that are opened like we have for databases. Some sort of mechanism
to close these things down after lack of use seems like a good idea. The patch to do this
would be pretty trivial. All you have to do is add a Timeout to each reply/noreply response
in the couch_index gen_server, and then have a handle_info(timeout) clause that returns {stop,
normal, State}.

Other than that, I've heard other people wanting the update notifications for design docs
so that could go in regardless. Another thing that we might want to think about is best practices
for commits and whether commits should span applications. I don't have super strong feelings
either way though I have heard the argument that not spanning applications decreases the chance
that code starts getting super entangled.

Good work, Filipe
> File descriptor leaks on design document update and view cleanup
> ----------------------------------------------------------------
>                 Key: COUCHDB-1309
>                 URL:
>             Project: CouchDB
>          Issue Type: Bug
>            Reporter: Filipe Manana
>            Assignee: Filipe Manana
>         Attachments: 12x-0001-Add-ddoc_updated-event.patch, 12x-0002-Shutdown-view-group-on-ddoc-update.patch,
couchdb-1309_12x.patch, couchdb-1309_trunk.patch, master-0001-Add-ddoc_updated-event.patch,
> If we add a design document with views defined in it, open the corresponding view group
(by querying one of its views for e.g.), then update the design document in such a way that
the view signature changes (changing a view's map function code for e.g), the old view group
remains open forever (unless a server restart happens) and keeps it's view file reference
counter active forever.
> If a view cleanup request comes, the old view file is not deleted since the reference
counter is not dropped by the old view group, keeping the file descriptor in use forever.
> This leakage is different from what is reported in COUCHDB-1129 but it's somehow related.
> The attached patch, simply shutdowns a view group when the design document is updated
and the new view signature changes, releasing the old view file descriptor (as soon as no
more clients are using the old view).

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