Build
Install the openvcdiff packages.
Configure nginx like this:
./configure --add-module=/path/to/sdch_module
Directives
sdch
syntax: sdch (on|off);
default: off
context: location
on – Enable module
off – Disable module
sdch_group
syntax: sdch_group <group>
default: default
context: location, server, if
Set group of the query (see sdch_dict). group can contain variables (i.e. it is a script).
sdch_dict
syntax: sdch_dict <filename> [<group> [<priority>]]
context: location, server, if
Specify the file with the dictionary. It is possible to configure several dictionaries by specifying the directive per dictionary. If a client have several configured dictionaries, the dictionary for use is selected like this:
- A dictionary with group that equal to sdch_group of the query is preferred over a dictionary those group is not equal to the sdch_group of the query.
- If the group is equally good, lower priority is preferred over high priority.
sdch_url
syntax: sdch_url <url>
context: location, server, if
Url to suggest to the client (in the Get-Dictionary header) if it does not
have the best possible dictionary. Variables allowed.
sdch_disablecv
syntax: sdch_disablecv <script>
Disable SDCH if the value is non-empty and is not equal to 0.
sdch_min_length
syntax: sdch_min_length <length>
Minimal size of response to encode.
sdch_types
syntax: sdch_types <types>
Enable encoding responses with list of mime/types. Default is text/html, text/css, application/javascript, and application/x-sdch-dictionary.
sdch_nodict_types
syntax: sdch_nodict_types <types>
Don't announce a dictionary (with the Get-Dictionary header) if the response has Content-Type listed here. The default is application/x-sdch-dictionary, i.e. an SDCH dictionary.
sdch_fastdict
syntax: sdch_fastdict (on|off);
context: location, server, if
default: off
Enable quasi dictionaries. I.e., if client support quasi-dictionaries, store the reply in memory and allow client to use the reply as a dictionary.
If a client announces several quasi-dictionaries to the server, the one with the group that match the group of the current query is preferred. Configured dictionaries, if any, is preferred over all quasi-dictionaries.
sdch_stor_size
syntax: sdch_stor_size <memsize>
context: main
default: 10 000 000
The memory limit for quasi-dictionaries.
sdch_vary
syntax: sdch_vary (on|off)
context: main, location, server
default: on
Add Vary header
The FastDict protocol extension
To announce FastDict support, the client sends Sdch-Features: fastdict
header.
If the client support FastDicts, and server suggest that the current reply
will be used as the quasi-dictionary, it add X-Sdch-Use-As-Dictionary
header to the reply.
Then, the client may use the reply as a dictionary, i.e. announce it in the
Avail-Dictionary header etc.
(There is no headers in the quasi-dictionaries.)