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From "Russell van der Walt (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COUCHDB-926) Compaction does not release file descriptors
Date Wed, 27 Oct 2010 07:36:24 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-926?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12925292#action_12925292
] 

Russell van der Walt commented on COUCHDB-926:
----------------------------------------------

Hi Adam,

Have now confirmed that it is only applicable to databases with views. No view, no problem.

I set up a test that simply kept updating a single document in a loop (and touching the view
after every update), with the following map function: 

function(doc) { if (doc.type && doc.type == 'record') { emit(doc.id, null); } }

I let that run for a bit and then when exiting the loop, compacted the database and the views.
The database and view file size goes down as expected, but "df" does not show an increase
in free size.

lsof has the following output which I reckon sums it up nicely:

root@ubuntu904:~# lsof | grep -P 'COMMAND|/var/data/couchdb/'
COMMAND     PID       USER   FD      TYPE             DEVICE      SIZE       NODE NAME
beam      21197       root   13u      REG              252,0      4185    3653752 /var/data/couchdb/_users.couch
beam      21197       root   14u      REG              252,0 191959757    3653679 /var/data/couchdb/.delete/33acca4299388cfa73e271ca6b662518
(deleted)
beam      21197       root   18u      REG              252,0      8281    3884279 /var/data/couchdb/.storage-test_design/800b1d5fe6334f272f2a8ad9feb9e0d9.view
beam      21197       root   20u      REG              252,0     36956    3654908 /var/data/couchdb/storage-test.couch

Note the deleted view file still being held open by beam.

Hope this helps.

> Compaction does not release file descriptors
> --------------------------------------------
>
>                 Key: COUCHDB-926
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-926
>             Project: CouchDB
>          Issue Type: Bug
>          Components: Database Core
>    Affects Versions: 1.0.1
>         Environment: Ubuntu 9.04/10.4
>            Reporter: Russell van der Walt
>             Fix For: 1.0.2, 1.1
>
>
> When couch compacts a database, file descriptors of the deleted files are left open,
causing the freed disk space to not be released to the system. With regular compaction, the
system eventually runs out of disk space.
> There is a conversation thread in the user mailing list titled "Couch not releasing deleted
files" that gives more insight into the problem, but I have been unable to find a bug report
for it, so please accept my apologies if this has already been dealt with.

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