What is deflatemod?
Deflatemod is a module for Ocsigen that allows you to deflate content, using HTTP/1.1 mechanism. It supports gzip as well as deflate.
What do I need to use deflatemod?
You need the camlzip library by Xavier Leroy and a working Ocsigen installation.
How do I use deflatemod?
First, load the extension in the configuration file:
<extension findlib-package="ocsigenserver.ext.deflatemod" />
Alternatively, if you do not want to use findlib, you need to:
- load camlzip
<extension module="/path/to/camlzip.cma" />
- then load deflatemod
<extension module="/path/to/deflatemod.cmo" />
How do I configure deflatemod?
Again, the options are in ocsigen.conf. You can set a few options globally, in the extension tag:
- the compress level: from 0 (no compression) to 9. The higher, the better compression rate you achieve. Conversely, the lower, the faster it is. Default is 6.
- the buffer size: default is 1024. You shouldn't need to change this one, but you can still try a few other values (any feedback welcomed).
<extension module="/home/gabriel/ocsigen/extensions/deflatemod.cmo"> <compress level="6" /> <buffer size="1024" /> </extension>
Next, you '''have to''' specify which pages you whish to deflate, in which host/site (otherwise, deflatemod won't compress anything). See next question to do that.
I want to deflate only some files. Is it possible?
To some extent, yes. You can '''exclude''' some files and deflate every other, according to their mime-type or extension (''ie.'' the end of the '''url''' in fact, not really the file name on the disk).
Here is an example:
<host> <site> <!-- ... --> </site> <deflate compress="allbut"> <!-- deflate everything but *.tar.gz files and image/* files --> <extension>.tar.gz</extension> <type>image/*</type> </deflate> </host>
As you can see, you must put the <deflate> tag at the very end of the <host> element. Indeed, Ocsigen deals with extensions sequentially, so if you put <site> or other elements '''after''' <deflatemod>, they won't be compressed.
Conversely, you can choose to deflate '''only''' some files, based on their mime-types or extension:
<host> <site> <!-- ... --> </site> <deflate compress="only"> <!-- deflate only text/html files --> <type>text/html</type> </deflate> </host>
Warning: you can use only one contenttype tag! So you must choose, either the "only" or the "allbut" way.
Limitations: you cannot filter by directory or by filename extension (remember extension is the url's extension). If you really need it, please fill a bug report or send a patch.
How can I choose the content-encoding (gzip or deflate)?
You can't. Deflatemod follows the RFC and chooses automatically the right encoding, based upon Accept-encoding header sent by the client.
Does deflatemod support transfert-encoding?
No, it doesn't. Content-encoding is definitely a better solution, providing end to end compression at the content-level.
How does deflatemod deal with the content-length header?
As it cannot compute the new content-length, deflatemod uses chunked-encoding. This is the recommended way to go.
Page written by Gabriel Kerneis