Metadata-Version: 1.0
Name: alkey
Version: 0.3
Summary: Redis backed tool for generating cache keys.
Home-page: http://github.com/thruflo/alkey
Author: James Arthur
Author-email: username: thruflo, domain: gmail.com
License: This is free and unencumbered software released into the public domain.
Description: # Alkey
        
        [Alkey][] is a [Redis][] backed tool for generating cache keys that implicitly
        update / invalidate when [SQLAlchemy][] model instances change, e.g.:
        
            from alkey.cache import get_cache_key_generator
            key_generator = get_cache_key_generator()
            
            # The `cache_key` will be invalidated when `instance1` or `instance2` change.
            cache_key = key_generator(instance1, instance2)
        
        It can be used by any [SQLAlchemy][] application that has access to [Redis][].
        Plus it has (optional) integration with the [Pyramid][] framework:
        `config.include` the package and generate keys using, e.g.:
        
            cache_key = request.cache_key(request.context)
        
        ## How it Works
        
        [Alkey][] works by binding to the SQLAlchemy session's [after_flush][] and
        [after_commit][] events to maintain a unique token, in Redis, against every
        model instance. As long as the model instance has a unique `id` property, this
        token will change whenever the instance is updated or deleted. In addition,
        Alkey maintains a global write token and a token against each database table.
        You can use these to generate cache keys that invalidate:
        
        * when an *instance* changes
        * when a *table* changes; or
        * when *anything* changes
        
        The main algorithm is to record instances as changed when they're flushed to
        the db in the session's new, dirty or deleted lists (identifiers in the format
        `alkey:tablename#row_id`, e.g.: `alkey:users#1`, are stored in a Redis set).
        Then, when the session's transaction is committed, the tokens for each recorded
        instance (plus their table and the global write token) are updated. This means
        that a cache key that contains the tokens will miss, causing the cached value
        to be regenerated.
        
        New tokens are generated when instances are looked up that are not already
        in the cache. So keys will always be invalidated if you lose / flush your
        Redis data.
        
        > Note also that changes recorded during a transaction that's
        subsequently rolled back will be discarded (i.e.: the tokens will not be updated)
        *unless* the rolled-back transaction is a sub-transaction. In that case &mdash; if
        your application code explicitly uses sub-transactions &mdash; rollbacks may lead
        to unnecessary cache-misses.
        
        ## Configuring a Redis Client
        
        [Alkey][] looks in the `os.environ` (i.e.: you need to provide
        [environment variables][]) for a values to configure a [redis client][]:
        
        * `REDIS_URL`: a connection string including any authenticaton information, e.g.:
          `redis://username:password@hostname:port`
        * `REDIS_DB`: defaults to `0`
        * `REDIS_MAX_CONNECTIONS`: the maximum number of connections for the client's
          connection pool (defaults to not set)
        
        The parsing logic is intelligent enough to pick up environment variables
        provided by popular [Heroku addons][] like `REDISTOGO_URL` and `OPENREDIS_URL`,
        etc. Read the `alkey.client.get_redis_config` docstring for the gory details.
        Alternatively, if you'd prefer to provide your own redis client, register an `alkey.interfaces.IRedisClientFactory` function or an
        `alkey.interfaces.IRedisConnectionPool` instance. Read 
        `alkey.client.get_redis_client` to see how.
        
        ## Binding to Session Events
        
        Use the `alkey.events.bind` function, e.g.:
            
            from alkey import events
            from myapp import Session # the sqlalchemy session you're using
            
            events.bind(Session)
        
        ## Generating Cache Keys
        
        You can then instantiate an `alkey.cache.CacheKeyGenerator` and call it with
        any of the following types as positional arguments to generate a cache key:
        
        * SQLAlchemy model instances
        * model instance identifiers in the format `alkey:tablename#row_id`
        * SQLAlchemy model classes
        * model class identifiers in the format `alkey:tablename#*`
        * the `alkey.constants.GLOBAL_WRITE_TOKEN`, which has the value `alkey:*#*`
        * arbitrary values that can be coerced to a unicode string
        
        E.g. using the `alkey.cache.get_cache_key_generator` factory to instantiate:
        
            from alkey.cache import get_cache_key_generator
            
            key_generator = get_cache_key_generator()
            cache_key = key_generator(instance, 'alkey:users#1', 1, 'foo', {'bar': 'baz'})
        
        Or, for example, imagine you have a `users` table, of which `user` is an instance
        with an `id` of `1`:
        
            # Invalidate when this user changes.
            cache_key = key_generator(user)
            cache_key = key_generator('alkey:users#1')
        
            # Invalidate when any user is inserted, updated or deleted.
            cache_key = key_generator(user.__class__)
            cache_key = key_generator('alkey:users#*')
        
            # Invalidate when any instance of any type is inserted, updated or deleted.
            cache_key = key_generator('alkey:*#*')
        
        Or you can directly get the instance token with `alkey.cache.get_token`, e.g.:
        
            from alkey.cache import get_token
            from alkey.client import get_redis_client
            
            redis_client = get_redis_client()
            
            token = get_token(redis_client, user)
            token = get_token(redis_client, 'alkey:users#1')
        
        ## Pyramid Integration
        
        If you're writing a [Pyramid][] application, you can bind to the session events
        by just including the package:
        
            config.include('alkey')
        
        This will, by default, use the [pyramid_basemodel][] threadlocal scoped session.
        To use a different session class, provide a dotted path to it as the
        `alkey.session_cls` in your .ini settings, e.g.:
        
            alkey.session_cls=myapp.model.Session
        
        An appropriately configured `alkey.cache.CacheKeyGenerator` instance will then
        be available as ``request.cache_key``, e.g:
        
            key = request.cache_key(instance1, instance2, 'arbitrary string')
        
        Or e.g.: in a [Mako template][]:
        
            <%page cached=True, cache_key=${request.cache_key(1, self.uri, instance)} />
        
        ## Tests
        
        [Alkey][] has been developed and tested against Python2.7. To run the tests,
        install `mock`, `nose` and `coverage` and either hack the `setUp` method in
        `alkey.tests:IntegrationTest` or have a Redis db available at
        `redis://localhost:6379`. Then, e.g.:
        
            $ nosetests alkey --with-doctest --with-coverage --cover-tests --cover-package alkey
            ..........................
            Name               Stmts   Miss  Cover   Missing
            ------------------------------------------------
            alkey                 11      0   100%   
            alkey.cache           74      0   100%   
            alkey.client          73      0   100%   
            alkey.constants        6      0   100%   
            alkey.events          12      0   100%   
            alkey.handle          76      0   100%   
            alkey.interfaces       6      0   100%   
            alkey.tests          184      0   100%   
            alkey.utils           30      0   100%   
            ------------------------------------------------
            TOTAL                472      0   100%   
            ----------------------------------------------------------------------
            Ran 26 tests in 0.566s
            
            OK
        
        [alkey]: http://github.com/thruflo/alkey
        [Redis]: http://redis.io
        [SQLAlchemy]: http://www.sqlalchemy.org/
        [redis client]: https://github.com/andymccurdy/redis-py
        [after_flush]: http://docs.sqlalchemy.org/ru/latest/orm/events.html#sqlalchemy.orm.events.SessionEvents.after_flush
        [after_commit]: http://docs.sqlalchemy.org/ru/latest/orm/events.html#sqlalchemy.orm.events.SessionEvents.after_commit
        [Pyramid]: http://docs.pylonsproject.org/projects/pyramid/en/latest
        [Mako template]: http://www.makotemplates.org/
        [pyramid_basemodel]: http://github.com/thruflo/pyramid_basemodel
        [environment variables]: http://blog.akash.im/per-project-environment-variables-with-forema
        [Heroku addons]: https://www.google.co.uk/search?q=Heroku+addons+redis
Platform: UNKNOWN
Classifier: Development Status :: 3 - Alpha
Classifier: Environment :: Web Environment
Classifier: Intended Audience :: Developers
Classifier: License :: Public Domain
Classifier: Natural Language :: English
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2.7
Classifier: Framework :: Pylons
Classifier: Topic :: Internet :: WWW/HTTP
Classifier: Topic :: Internet :: WWW/HTTP :: WSGI
Classifier: Topic :: Software Development :: Libraries :: Python Modules
