dogpile
Dogpile consists of two subsystems, one building on top of the other.
dogpile provides the concept of a "dogpile lock", a control structure
which allows a single thread of execution to be selected as the "creator" of
some resource, while allowing other threads of execution to refer to the previous
version of this resource as the creation proceeds; if there is no previous
version, then those threads block until the object is available.
dogpile.cache is a caching API which provides a generic interface to
caching backends of any variety, and additionally provides API hooks which
integrate these cache backends with the locking mechanism of dogpile.
Overall, dogpile.cache is intended as a replacement to the Beaker <https://pypi.org/project/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.
Documentation
See dogpile.cache's full documentation at
dogpile.cache documentation <https://dogpilecache.sqlalchemy.org>_. The
sections below provide a brief synopsis of the dogpile packages.
Features
- A succinct API which encourages up-front configuration of pre-defined
"regions", each one defining a set of caching characteristics including
storage backend, configuration options, and default expiration time.
- A standard get/set/delete API as well as a function decorator API is
provided.
- The mechanics of key generation are fully customizable. The function
decorator API features a pluggable "key generator" to customize how
cache keys are made to correspond to function calls, and an optional
"key mangler" feature provides for pluggable mangling of keys
(such as encoding, SHA-1 hashing) as desired for each region.
- The dogpile lock, first developed as the core engine behind the Beaker
caching system, here vastly simplified, improved, and better tested.
Some key performance
issues that were intrinsic to Beaker's architecture, particularly that
values would frequently be "double-fetched" from the cache, have been fixed.
- Backends implement their own version of a "distributed" lock, where the
"distribution" matches the backend's storage system. For example, the
memcached backends allow all clients to coordinate creation of values
using memcached itself. The dbm file backend uses a lockfile
alongside the dbm file. New backends, such as a Redis-based backend,
can provide their own locking mechanism appropriate to the storage
engine.
- Writing new backends or hacking on the existing backends is intended to be
routine - all that's needed are basic get/set/delete methods. A distributed
lock tailored towards the backend is an optional addition, else dogpile uses
a regular thread mutex. New backends can be registered with dogpile.cache
directly or made available via setuptools entry points.
- Included backends feature three memcached backends (python-memcached, pylibmc,
bmemcached), a Redis backend, a backend based on Python's
anydbm, and a plain dictionary backend.
- Space for third party plugins, including one which provides the
dogpile.cache engine to Mako templates.
The SQLAlchemy Project
Dogpile is part of the SQLAlchemy Project <https://www.sqlalchemy.org>_ and
adheres to the same standards and conventions as the core project.
Development / Bug reporting / Pull requests
Please refer to the
SQLAlchemy Community Guide <https://www.sqlalchemy.org/develop.html>_ for
guidelines on coding and participating in this project.
Code of Conduct
Above all, SQLAlchemy places great emphasis on polite, thoughtful, and
constructive communication between users and developers.
Please see our current Code of Conduct at
Code of Conduct <https://www.sqlalchemy.org/codeofconduct.html>_.
License
Dogpile is distributed under the MIT license <https://opensource.org/licenses/MIT>_.