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From "Adam Kocoloski (JIRA)" <j...@apache.org>
Subject [jira] Updated: (COUCHDB-583) adding ?compression=(gzip|deflate) optional parameter to the attachment download API
Date Tue, 22 Dec 2009 03:50:18 GMT

     [ https://issues.apache.org/jira/browse/COUCHDB-583?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Adam Kocoloski updated COUCHDB-583:
-----------------------------------


Hi Filipe, COUCHDB-437 is more about compressing the documents on disk than it is the attachments.
 To compress Erlang terms on disk, one only needs to replace

term_to_binary(Term)

with

term_to_binary(Term, [compressed])

The two issues are definitely linked, though.

> adding ?compression=(gzip|deflate) optional parameter to the attachment download API
> ------------------------------------------------------------------------------------
>
>                 Key: COUCHDB-583
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-583
>             Project: CouchDB
>          Issue Type: New Feature
>          Components: HTTP Interface
>         Environment: CouchDB trunk revision 885240
>            Reporter: Filipe Manana
>         Attachments: couchdb-583-trunk-3rd-try.patch, couchdb-583-trunk-4th-try-trunk.patch,
couchdb-583-trunk-5th-try.patch, couchdb-583-trunk-6th-try.patch, jira-couchdb-583-1st-try-trunk.patch,
jira-couchdb-583-2nd-try-trunk.patch
>
>   Original Estimate: 24h
>  Remaining Estimate: 24h
>
> The following new feature is added in the patch following this ticket creation.
> A new optional http query parameter "compression" is added to the attachments API.
> This parameter can have one of the values:  "gzip" or "deflate".
> When asking for an attachment (GET http request), if the query parameter "compression"
is found, CouchDB will send the attachment compressed to the client (and sets the header Content-Encoding
with gzip or deflate).
> Further, it adds a new config option "treshold_for_chunking_comp_responses" (httpd section)
that specifies an attachment length threshold. If an attachment has a length >= than this
threshold, the http response will be chunked (besides compressed).
> Note that using non chunked compressed  body responses requires storing all the compressed
blocks in memory and then sending each one to the client. This is a necessary "evil", as we
only know the length of the compressed body after compressing all the body, and we need to
set the "Content-Length" header for non chunked responses. By sending chunked responses, we
can send each compressed block immediately, without accumulating all of them in memory.
> Examples:
> $ curl http://localhost:5984/testdb/testdoc1/readme.txt?compression=gzip
> $ curl http://localhost:5984/testdb/testdoc1/readme.txt?compression=deflate
> $ curl http://localhost:5984/testdb/testdoc1/readme.txt   # attachment will not be compressed
> $ curl http://localhost:5984/testdb/testdoc1/readme.txt?compression=rar   # will give
a 500 error code
> Etap test case included.
> Feedback would be very welcome.
> cheers

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