first_miss: HTTP 200 cache=miss
normalized_hit: HTTP 200 cache=hit
other_principal_miss: HTTP 200 cache=miss
unknown_identity: HTTP 401
collection_denied: HTTP 403
empty_bypass_first: HTTP 200 cache=bypass
empty_bypass_again: HTTP 200 cache=bypass
real_ttl_expired_miss: HTTP 200 cache=miss
tool_failure_first: HTTP 503
tool_failure_again: HTTP 503