Fixup Cache Control Headers

Problem this snippet solves:

Coalesce all instances of a header in the response into a single comma-delimited header. This is primarily used to work around a bug in RAMCache, ID360047, where it only examines the last Cache-Control response header.

Code :

when RULE_INIT {
# A list of headers; for each header, take all instances of that header and
# combine them into a single (comma-delimited) header.
#
# e.g.
# Cache-Control: private
# Cache-Control: max-age=0
#    is translated into:
# Cache-Control: private, max-age=0
#
# Headers listed here MUST be defined as a list in the HTTP RFC.
# See the definition of Cache-Control and WWW-Authenticate for examples
# (http://tools.ietf.org/html/rfc2616#section-14.9)
#set static::headers { "Cache-Control" "WWW-Authenticate" }
set static::headers { "Cache-Control" }

# Enable/disable diagnostic logging.  Set to 1 to enable, 0 to disable
set static::debug 0
}

when HTTP_RESPONSE {
foreach header $static::headers {
if {[HTTP::header exists $header]} {
# Grab the values as a list, remove the existing headers, and
# replace with the values, joined as a comma-delimited string
set from_values [HTTP::header values $header]
set to_values {}
foreach value $from_values {
set value [string trim $value]
if { $value ne ""} { lappend to_values $value }
}
set to_values [join $to_values ", "]
if { $static::debug } { log local0. "Coalescing $header from '$from_values' to '$to_values'" }

HTTP::header remove $header
HTTP::header insert "lws" $header $to_values
}
}
}