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Expressions for HTTP and cache-control headers

August 12, 2024
Contributed by: 
C S C

One common method of evaluating HTTP traffic is to examine the headers in a request or a response. A header can perform a number of functions, including the following:

  • Provide cookies that contain data about the sender.
  • Identify the type of data that is being transmitted.
  • Identify the route that the data has traveled (the Via header).

Note:

If an operation is used to evaluate both header and text data, the header-based operation always overrides the text-based operation. For example, the AFTER_STR operation, when applied to a header, overrides text-based AFTER_STR operations for all instances of the current header type.

Prefixes for HTTP headers

The Prefixes for HTTP headers table for expression prefixes that extract HTTP headers.

Operations for HTTP headers

The Operations for HTTP headers table for operations that you can specify with the prefixes for HTTP headers.

Prefixes for cache-control headers

The following prefixes apply specifically to Cache-Control headers.

HTTP Header Prefix Description
HTTP.REQ.CACHE_CONTROL Returns a Cache-Control header in an HTTP request.
HTTP.RES.CACHE_CONTROL Returns a Cache-Control header in an HTTP response.

Operations for cache-control headers

You can apply any of the operations for HTTP headers to Cache-Control headers.

In addition, the following operations identify specific types of Cache-Control headers. See RFC 2616 for information about these header types.

HTTP Header Operation Description
Cache-Control header.NAME(<integer>) Returns as a text value the name of the Cache-Control header that corresponds to the nth component in a name-value list, as specified by <integer>. The index of the name-value component is 0-based. If the <integer> that is specified by the integer argument is greater than the number of components in the list, a zero-length text object is returned. Following is an example: http.req.cache_control.name(3).contains("some_text")
Cache-Control header.IS_INVALID Returns a Boolean TRUE if the Cache-Control header is not present in the request or response. Following is an example: http.req.cache_control.is_invalid
Cache-Control header.IS_PRIVATE Returns a Boolean TRUE if the Cache-Control header has the value Private. Following is an example: http.req.cache_control.is_private
Cache-Control header.IS_PUBLIC Returns a Boolean TRUE if the Cache-Control header has the value Private. Following is an example: http.req.cache_control.is_public
Cache-Control header.IS_NO_STORE Returns a Boolean TRUE if the Cache-Control header has the value No-Store. Following is an example: http.req.cache_control.is_no_store
Cache-Control header.IS_NO_CACHE Returns a Boolean TRUE if the Cache-Control header has the value No-Cache. Following is an example: http.req.cache_control.is_no_cache
Cache-Control header.IS_MAX_AGE Returns a Boolean TRUE if the Cache-Control header has the value Max-Age. Following is an example: http.req.cache_control.is_max_age
Cache-Control header.IS_MIN_FRESH Returns a Boolean TRUE if the Cache-Control header has the value Min-Fresh. Following is an example: http.req.cache_control.is_min_fresh
Cache-Control header.IS_MAX_STALE Returns a Boolean TRUE if the Cache-Control header has the value Max-Stale. Following is an example: http.req.cache_control.is_max_stale
Cache-Control header.IS_MUST_REVALIDATE Returns a Boolean TRUE if the Cache-Control header has the value Must-Revalidate. Following is an example: http.req.cache_control.is_must_revalidate
Cache-Control header.IS_NO_TRANSFORM Returns a Boolean TRUE if the Cache-Control header has the value No-Transform. Following is an example: http.req.cache_control.is_no_transform
Cache-Control header.IS_ONLY_IF_CACHED Returns a Boolean TRUE if the Cache-Control header has the value Only-If-Cached. Following is an example: http.req.cache_control.is_only_if_cached
Cache-Control header.IS_PROXY_REVALIDATE Returns a Boolean TRUE if the Cache-Control header has the value Proxy-Revalidate. Following is an example: http.req.cache_control.is_proxy_revalidate
Cache-Control header.IS_S_MAXAGE Returns a Boolean TRUE if the Cache-Control header has the value S-Maxage. Following is an example: http.req.cache_control.is_s_maxage
Cache-Control header.IS_UNKNOWN Returns a Boolean TRUE if the Cache-Control header is of an unknown type. Following is an example: http.req.cache_control.is_unknown
Cache-Control header.MAX_AGE Returns the value of the Cache-Control header Max-Age. If this header is absent or invalid, 0 is returned. Following is an example: http.req.cache_control.max_age.le(3)
Cache-Control header.MAX_STALE Returns the value of the Cache-Control header Max-Stale. If this header is absent or invalid, 0 is returned. Following is an example: http.req.cache_control.max_stale.le(3)
Cache-Control header.MIN_FRESH Returns the value of the Cache-Control header Min-Fresh. If this header is absent or invalid, 0 is returned. Following is an example: http.req.cache_control.min_fresh.le(3)
Cache-Control header.S_MAXAGE Returns the value of the Cache-Control header S-Maxage. If this header is absent or invalid, 0 is returned.Following is an example: http.req.cache_control.s_maxage.eq(2)
Expressions for HTTP and cache-control headers
August 12, 2024
Contributed by: 
C S C
August 12, 2024
Contributed by: 
C S C

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