Cache longevity detection and refresh

A web server, comprising

• a cache memory responsive for storing recently computed function results as values operable for satisfying successive invocations of the function, the cache responsive to a function invocation for storing a computed function result as a cached value in a cache;
• a cache server operable for, upon receiving a subsequent invocation of the function, examining a duration of the value in the cache, the cache server further operable for comparing, if the duration is within a staleness detection threshold, a result of a subsequent execution of the function to the cached value in response to the subsequent invocation, the comparison including comparing a hash based on the subsequent invocation of the function to find a match in a set of hash values corresponding to a plurality of cache values, the cache server operable for accepting the cached value as a function result of the subsequent invocation if the staleness detection threshold has not expired;
• a database interface for receiving function execution results;
• a logging mechanism for flagging an error if the duration exceeds the staleness detection threshold and the result of the subsequent execution differs from the cached value
• recomputing, if the duration exceeds the staleness detection threshold, a result from execution of the function for validating the cached value;
• and
• returning, if the duration of the cache value is within the staleness detection threshold, the cache value as the result of the subsequent invocation.

A computer program product having instructions encoded on a non-transitory computer readable storage medium that, when executed by a processor, perform a method of maintaining cached computational results, comprising:

• storing a computed function result as a cached value in a cache;
• upon receiving a subsequent invocation of the function, examining a duration of the value in the cache;
• comparing, based on an expiration of a staleness detection threshold, a result of a subsequent execution of the function to the cached value in response to the subsequent invocation, the comparison including comparing a hash based on the subsequent invocation of the function to find a match in a set of hash values corresponding to a plurality of cache values;
• comparing a hash based on of the function to a set of hash values corresponding to a plurality of cache values;
• identifying a matching hash value based on comparing the hash;
• comparing a duration of the cache value corresponding to the matching hash value to the staleness detection threshold, the duration defined by a previous execution of the function;
• recomputing, if the duration exceeds the staleness detection threshold, a result from execution of the function for validating the cached value;
• and
• returning, if the duration of the cache value is within the staleness detection threshold, the cache value as the result of the subsequent invocation.