On mån, 2007-09-17 at 11:55 -0700, Solomon Asare wrote: > Hi Amos, > I am not sure if refresh_pattern is the sole > determinant in caching an object, that is if it has > any influence at all.
It has influence, both directly by assigning freshness information when there is none, and indirectly by overriding various HTTP controls.. Requirementsto cache stale objects: a) The object must have a cache validator (Last-Modified or ETag). If there is no cache validator then the response must be fresh for at least minimum_expiry_time to get cached, this to avoid wasting disk I/O for caching content which can not be reused. b) There must not be other headers preventing it from getting cached. refresh_pattern can override most of these if needed. > I am not discussing getting a > HIT for a cached object, but rather caching an expired > object from an origin server. If this object is > expired, by say 60 seconds before being served from > the origin server, how do I cache it? Date and > Last-Modified dates are also not set. If there is no Last-Modified and no ETag then it's useless to cache an expired object, as it can not be reused on any future request and all you get is extra disk I/O for writing the object out. A cache validator (Last-Modified or ETag) is required to be able to verify with the origin server if an expired object is still valid or not. Without a cache validator there is nothing to relate to and there is no other choice than to fetch the complete object again when expired.. Regards Henrik
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