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32.9 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.


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2000-08-24