41.9 Http trace format

The trace file of Http agents are constructed in a similar way as the SRM trace files. It consists of multiple entries, each of which occupies one line. The format of each entry is:

Time

ObjectID

Object Values

There are three types of objects: client (C), cache (E) and server (S). Following is a complete enumeration of all possible events and value types associated with these three types of objects.

Object Type	Event Type	Values
E	HIT	Prefix
E	MISS	Prefix z RequestSize
E	IMS	Prefix z Size t CacheEntryTime
E	REF	p PageID s ServerID z Size
E	UPD	p PageID m LastModifiedTime z PageSize
		s ServerID
E	GUPD	z PageSize
E	SINV	p PageID m LastModTime z PageSize
E	GINV	p PageID m LastModTime
E	SPF	p PageID c DestCache
E	RPF	p PageID c SrcCache
E	ENT	p PageID m LastModifiedTime z PageSize
		s ServerID
C	GET	p PageID s PageServerID z RequestSize
C	STA	p PageID s OrigServerID l StaleTime
C	RCV	p PageID s PageServerID l ResponseTime z PageSize
S	INV	p PageID m LastModifiedTime z Size
S	UPD	p PageID m LastModifiedTime z Size
S	SND	p PageID m LastModifiedTime z PageSize
		t Requesttype
S	MOD	p PageID n NextModifyTime

Prefix is the information common to all trace entries. It includes:

p PageID

c RequestClientID

s PageServerID

Short Explaination of event operations:

Object Type	Event Type	Explaination
E	HIT	Cache hit. PageSererID is the id of the ``owner'' of the page.
E	MISS	Cache miss. In this case the cache will send a request to the server to fetch the page.
E	IMS	If-Modified-Since. Used by TTL procotols to validate an expired page.
E	REF	Page refetch. Used by invalidation protocols to refetch an invalidated page.
E	UPD	Page update. Used by invalidation protocols to ``push'' updates
		from parent cache to children caches.
E	SINV	Send invalidation.
E	GINV	Get invalidation.
E	SPF	Send a pro forma
E	RPF	Receive a pro forma
E	ENT	Enter a page into local page cache.
C	GET	Client sends a request for a page.
C	STA	Client gets a stale hit. OrigModTime is the modification time
		in the web server, CurrModTime is the local page's modification time.
C	RCV	Client receives a page.
S	SND	Server send a response.
S	UPD	Server pushes a page update to its ``primary cache''. Used by invalidation protocol only.
S	INV	Server sends an invalidation message. Used by invalidation protocol only.
S	MOD	Server modified a page. The page will be modified next at NextModifyTime.