Overview
Akamai provides debug data for content hosted by their CDN service. This data is useful when trying to assess issues with Akamai services.
Accessing Data
To access this data, the Pragma in the request header must be set to the following:
akamai-x-cache-on, akamai-x-cache-remote-on, akamai-x-check-cacheable, akamai-x-get-cache-key, akamai-x-get-extracted-values, akamai-x-get-nonces, akamai-x-get-ssl-client-session-id, akamai-x-get-true-cache-key, akamai-x-serial-no
Capture Response Headers
The server will respond with the debug data in its response header. Below is an example of an Akamai debug response header:
HTTP/1.x 200 OK
Content-Type: text/html
Etag: W/"26100-124692218130400"
Cache-Control: max-age=120
Date: Tue, 14 Jul 2009 18:01:27 GMT
X-Cache: TCP_MEM_HIT from a69-174-50-208 (AkamaiGHost/5.7.2-5726413) (-)
X-Cache-Key: S/L/2649/75069/6h/www.example.com/common/global.html
X-True-Cache-Key: /L/www.example.com/common/global.html
X-Serial: 2649
Connection: keep-alive
Vary: Accept-Encoding
X-Check-Cacheable: YES
This response can be captured by Catchpoint by enabling the header capture options.
Debug Data Values and Information
The parameters in the request header with the prefix ** X-** are the debug data provided from Akamai. Below are possible return values for the debug data and their meanings:
TCP_HIT: The object was fresh in cache and object from the disk cache.
TCP_MISS: The object was not in the cache, the server fetched it from the origin.
TCP_REFRESH_HIT: The object was stale in the cache and successfully refreshed with the origin on an If-Modified-Since request.
TCP_REFRESH_MISS: Object was stale in the cache and refresh obtained a new object from the origin in response to our IF-Modified-Since request.
TCP_REFRESH_FAIL_HIT: Object was stale in the cache and we failed on refresh (couldn't reach origin) so stale object was served.
TCP_IMS_HIT: IF-Modified-Since request from client and object was fresh in the cache and served.
TCP_NEGATIVE_HIT: Object previously returned "not found" (or any other negatively cacheable response) and that cached response was a hit for this new request.
TCP_MEM_HIT: Object was on disk and in the memory cache. The server served it without hitting the disk.
TCP_DENIED: Denied access to the client
TCP_COOKIE_DENY: Denied access on cookie authentication (if centralized or decentralized authorization feature is being used in a configuration)
X-Cache-Key: the internal cache key for the page or object on the Akamai server
Additional reference may be found at Understanding Akamai Headers