Forum Discussion
LarsKristensson
Altocumulus
AltocumulusCaching based on Surrogate-Control header
I want to configure a virtual server to use Web Acceleration caching based on the Surrogate-Control response header instead of the Cache-Control response header. Both headers must be preserved, so I...
Hello LarsKristensson​
Not sure if this is possible.
But you could save original Cache-Control response header in HTTP_RESPONSE in a variable, replace it with Surrogate-Control header so it can be used by Web Acceleration caching and then in HTTP_RESPONSE_RELEASE event restore the original value of Cache-Control from variable.
You could check something like this
when HTTP_RESPONSE {
# Check if Surrogate-Control header exists in the response
if { [HTTP::header exists "Surrogate-Control"] } {
set surrogate_control [HTTP::header value "Surrogate-Control"]
# Check if Cache-Control header exists in the response
if { [HTTP::header exists "Cache-Control"] } {
# Save the original Cache-Control header value in a variable
set original_cache_control [HTTP::header value "Cache-Control"]
}
# Replace Cache-Control with Surrogate-Control for Web Acceleration
HTTP::header replace "Cache-Control" $surrogate_control
}
}
when HTTP_RESPONSE_RELEASE {
# Check if we saved a Cache-Control value
if { [info exists original_cache_control] } {
# Restore the original Cache-Control header
HTTP::header replace "Cache-Control" $original_cache_control
}
}
LarsKristenssonYes, after posting my question I figured out that I could replace the Cache-Control header in HTTP_RESPONSE. However, storing it in a variable is not enough since the response may be served from the cache at a later point.
I ended up with this:
when HTTP_RESPONSE { HTTP::header insert Saved-Cache-Control [HTTP::header Cache-Control] HTTP::header replace Cache-Control [HTTP::header Surrogate-Control] } when HTTP_RESPONSE_RELEASE { if { [HTTP::header exists Saved-Cache-Control] } { HTTP::header replace Cache-Control [HTTP::header Saved-Cache-Control] HTTP::header remove Saved-Cache-Control } }
