The TCP_ codes refer to requests on the HTTP port (usually 3128). The UDP_ codes refer to requests on the ICP port (usually 3130). If ICP logging was disabled using the log_icp_queries option, no ICP replies will be logged.The following result codes were taken from a Squid-2, compare with the log_tags struct in src/access_log.c:
TCP_HIT A valid copy of the requested object was in the cache.
TCP_MISS The requested object was not in the cache.
TCP_REFRESH_HIT The requested object was cached but STALE. The IMS query for the object resulted in “304 not modified”.
TCP_REF_FAIL_HIT The requested object was cached but STALE. The IMS query failed and the stale object was delivered.
TCP_REFRESH_MISS The requested object was cached but STALE. The IMS query returned the new content.
TCP_CLIENT_REFRESH_MISS The client issued a “no-cache” pragma, or some analogous cache control command along with the request. Thus, the cache has to refetch the object.
TCP_IMS_HIT The client issued an IMS request for an object which was in the cache and fresh.
TCP_SWAPFAIL_MISS The object was believed to be in the cache, but could not be accessed.
TCP_NEGATIVE_HIT Request for a negatively cached object, e.g. “404 not found”, for which the cache believes to know that it is inaccessible. Also refer to the explainations for negative_ttl in your squid.conf file.
TCP_MEM_HIT A valid copy of the requested object was in the cache and it was in memory, thus avoiding disk accesses.
TCP_DENIED Access was denied for this request.
TCP_OFFLINE_HIT The requested object was retrieved from the cache during offline mode. The offline mode never validates any object, see offline_mode in squid.conf file.
UDP_HIT A valid copy of the requested object was in the cache.
UDP_MISS The requested object is not in this cache.
UDP_DENIED Access was denied for this request.
UDP_INVALID An invalid request was received.
UDP_MISS_NOFETCH During “-Y” startup, or during frequent failures, a cache in hit only mode will return either UDP_HIT or this code. Neighbours will thus only fetch hits.
NONE Seen with errors and cachemgr requests.
The following codes are no longer available in Squid-2:
ERR_* Errors are now contained in the status code.
TCP_CLIENT_REFRESH See: TCP_CLIENT_REFRESH_MISS.
TCP_SWAPFAIL See: TCP_SWAPFAIL_MISS.
TCP_IMS_MISS Deleted, now replaced with TCP_IMS_HIT.
UDP_HIT_OBJ Refers to an old version that would send cache hits in ICP replies. No longer implemented.
UDP_RELOADING See: UDP_MISS_NOFETCH.