A caching API built around the concept of a "dogpile lock", which allows
continued access to an expiring data value while a single thread generates
a new value.
dogpile.cache builds on the dogpile.core locking system, which implements
the idea of "allow one creator to write while others read" in the abstract.
Overall, dogpile.cache is intended as a replacement to the Beaker caching
system, the internals of which are written by the same author. All the ideas
of Beaker which "work" are re-implemented in dogpile.cache in a more efficient
and succinct manner, and all the cruft (Beaker's internals were first written
in 2005) relegated to the trash heap.