A 'dogpile' lock, typically used as a component of a larger caching solution
The dogpile.core package has been rolled into dogpile.cache directly. dogpile.core as a separate package is effectively EOL.
A "dogpile" lock, one which allows a single thread to generate an expensive resource while other threads use the "old" value, until the "new" value is ready.
Dogpile is basically the locking code extracted from the Beaker package, for simple and generic usage.
A simple example:
from dogpile.core import Dogpile # store a reference to a "resource", some # object that is expensive to create. the_resource = [None] def some_creation_function(): # create the resource here the_resource = create_some_resource() def use_the_resource(): # some function that uses # the resource. Won't reach # here until some_creation_function() # has completed at least once. the_resource.do_something() # create Dogpile with 3600 second # expiry time dogpile = Dogpile(3600) with dogpile.acquire(some_creation_function): use_the_resource()
some_creation_function() will be called
Dogpile.acquire() is first called. The
remainder of the
with block then proceeds. Concurrent threads which
Dogpile.acquire() during this initial period
will be blocked until
Once the creation function has completed successfully the first time,
new calls to
Dogpile.acquire() will call
each time the "expiretime" has been reached, allowing only a single
thread to call the function. Concurrent threads
Dogpile.acquire() during this period will
fall through, and not be blocked. It is expected that
the "stale" version of the resource remain available at this
time while the new one is generated.
dogpile.core is at the core of the dogpile.cache package which provides for a basic cache API and sample backends based on the dogpile concept.
dogpile.core has been in use in a small number of production environments for a period of months, and as of 0.3.2 has entered beta status. No issues have been reported yet with its core synchronization model, and overall the project hasn't seen many changes. Most development continues within dogpile.cache.