couchdb-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Filipe Manana (JIRA)" <j...@apache.org>
Subject [jira] Updated: (COUCHDB-583) storing attachments in compressed form and serving them in compressed form if accepted by the client
Date Tue, 22 Dec 2009 10:04:29 GMT

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

Filipe Manana updated COUCHDB-583:
----------------------------------

           Component/s: Database Core
           Description: 
This feature allows Couch to gzip compress attachments as they are being received and store
them in compressed form.

When a client asks for downloading an attachment (e.g. GET somedb/somedoc/attachment.txt),
the attachment is sent in compressed form if the client's http request has gzip specified
as a valid transfer encoding for the response (using the http header "Accept-Encoding"). Otherwise
couch decompresses the attachment before sending it back to the client.

Attachments are compressed only if their MIME type matches one of those listed in a separate
config file. Compression level is also configurable in the default.ini file.

This follows Damien's suggestion from 30 November:

"Perhaps we need a separate user editable ini file to specify compressable or non-compressable
files (would probably be too big for the regular ini file). What do other web servers do?

Also, a potential optimization is to compress the file while writing to disk, and serve the
compressed bytes directly to clients that can handle it, and decompressed for those that can't.
For compressable types, it's a win for both disk IO for reads and writes, and CPU on read."

Patch attached.

  was:
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

           Environment: CouchDB trunk  (was: CouchDB trunk revision 885240)
    Remaining Estimate:     (was: 24h)
     Original Estimate:     (was: 24h)
               Summary: storing attachments in compressed form and serving them in compressed
form if accepted by the client  (was: adding ?compression=(gzip|deflate) optional parameter
to the attachment download API)

> storing attachments in compressed form and serving them in compressed form if accepted
by the client
> ----------------------------------------------------------------------------------------------------
>
>                 Key: COUCHDB-583
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-583
>             Project: CouchDB
>          Issue Type: New Feature
>          Components: Database Core, HTTP Interface
>         Environment: CouchDB trunk
>            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
>
>
> This feature allows Couch to gzip compress attachments as they are being received and
store them in compressed form.
> When a client asks for downloading an attachment (e.g. GET somedb/somedoc/attachment.txt),
the attachment is sent in compressed form if the client's http request has gzip specified
as a valid transfer encoding for the response (using the http header "Accept-Encoding"). Otherwise
couch decompresses the attachment before sending it back to the client.
> Attachments are compressed only if their MIME type matches one of those listed in a separate
config file. Compression level is also configurable in the default.ini file.
> This follows Damien's suggestion from 30 November:
> "Perhaps we need a separate user editable ini file to specify compressable or non-compressable
files (would probably be too big for the regular ini file). What do other web servers do?
> Also, a potential optimization is to compress the file while writing to disk, and serve
the compressed bytes directly to clients that can handle it, and decompressed for those that
can't. For compressable types, it's a win for both disk IO for reads and writes, and CPU on
read."
> Patch attached.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.


Mime
View raw message