Product Documentation

Example: Caching Compressed and Uncompressed Versions of a File

Mar 16, 2012

By default, a client that can handle compression can be served uncompressed responses or compressed responses in gzip, deflate, compress, and pack200-gzip format. If the client handles compression, an Accept-Encoding:compression format header is sent in the request. The compression type accepted by the client must match the compression type of the cached object. For example, a cached .gzip file cannot be served in response to a request with an Accept-Encoding:deflate header.

A client that cannot handle compression is served a cache miss if the cached response is compressed.

For dynamic caching, you need to configure two content groups, one for compressed data and one for uncompressed versions of the same data. The following is an example of configuring the selectors, content groups, and policies for serving uncompressed files from the cache to clients that cannot handle compression, and serving compressed versions of the same files to client that can handle compression.

add cache selector uncompressed_response_selector http.req.url "http.req.header(\"Host\")" 
add cache contentGroup uncompressed_group -hitSelector uncompressed_responst_selector -invalSelector uncomp_resp_sel 
add cache policy cache_uncompressed -rule "HTTP.REQ.URL.CONTAINS(\"xyz\") && !HTTP.REQ.HEADER(\"Accept-Encoding\").EXISTS" -action CACHE -storeInGroup uncompressed_group 
bind cache global cache_uncompressed -priority 100 -gotoPriorityExpression END -type REQ_OVERRIDE 
add cache selector compressed_response_selector HTTP.REQ.URL "HTTP.REQ.HEADER(\"Host\")" "HTTP.REQ.HEADER(\"Accept-Encoding\")" 
add cache contentGroup compressed_group -hitSelector compressed_response_selector 
add cache policy cache_compressed -rule "HTTP.REQ.URL.CONTAINS(\"xyz\") && HTTP.REQ.HEADER(\"Accept-Encoding\").EXISTS" -action CACHE -storeInGroup compressed_group 
bind cache global cache_compressed -priority 200 -gotoPriorityExpression END -type REQ_OVERRIDE