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6.9.5 Negative caching and DNS caching

   

To reduce the costs of repeated failures (e.g., from erroneously looping clients), we implemented two forms of negative caching. First, when a DNS lookup failure occurs, we cache the negative result for one hour. Second, when an object retrieval failure occurs, we cache the negative result for a parameterized period of time, settable via the negative_ttl variable in the cached.conf file. The default value is 5 minutes.

The cache also implements a cache of successful DNS lookups. The timeout for this cache is ``hard-coded'' at one day.



Duane Wessels
Wed Jan 31 23:46:21 PST 1996