Package entropy :: Module cache :: Class EntropyCacher

Class EntropyCacher

Entropy asynchronous and synchronous cache writer and reader. This class is a Singleton and contains a thread doing the cache writes asynchronously, thus it must be stopped before your application is terminated calling the stop() method.

Sample code:

>>> # import module
>>> from entropy.cache import EntropyCacher
...
>>> # first EntropyCacher load, start it
>>> cacher = EntropyCacher()
>>> cacher.start()
...
>>> # now store something into its cache
>>> cacher.push('my_identifier1', [1, 2, 3])
>>> # now store something synchronously
>>> cacher.push('my_identifier2', [1, 2, 3], async = False)
...
>>> # now flush all the caches to disk, and make sure all
>>> # is written
>>> cacher.sync(wait = True)
...
>>> # now fetch something from the cache
>>> data = cacher.pop('my_identifier1')
[1, 2, 3]
...
>>> # now discard all the cached (async) writes
>>> cacher.discard()
...
>>> # and stop EntropyCacher
>>> cacher.stop()

Instance Methods

init_singleton(self)
Singleton overloaded method.

source code

__del__(self)

source code

start(self)
This is the method used to start the asynchronous cache writer but also the whole cacher.

source code

is_started(self)
Return whether start is called or not.

source code

stop(self)
This method stops the execution of the cacher, which won't accept cache writes anymore.

source code

None

sync(self, wait=False)
This method can be called anytime and forces the instance to flush all the cache writes queued to disk.

source code

discard(self)
This method makes buffered cache to be discarded synchronously.

source code

None

push(self, key, data, async=True)
This is the place where data is either added to the write queue or written to disk (if async == False) only and only if start() method has been called.

source code

Python object

pop(self, key)
This is the place where data is retrieved from cache.

source code

Inherited from core.Singleton: is_destroyed, is_singleton

Inherited from object: __delattr__, __getattribute__, __hash__, __init__, __reduce__, __reduce_ex__, __repr__, __setattr__, __str__

Static Methods
Inherited from `core.Singleton`: `__new__`

Properties
Inherited from `object`: `__class__`

Method Details

init_singleton(self)

source code

Singleton overloaded method. Equals to __init__. This is the place where all the properties initialization takes place.

start(self)

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This is the method used to start the asynchronous cache writer but also the whole cacher. If this method is not called, the instance will always trash and cache write request.

Returns:: None

is_started(self)

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Return whether start is called or not. This equals to checking if the cacher is running, thus is writing cache to disk.

Returns:: None

stop(self)

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This method stops the execution of the cacher, which won't accept cache writes anymore. The thread responsible of writing to disk is stopped here and the Cacher will be back to being inactive. A watchdog will avoid the thread to freeze the call if the write buffer is overloaded.

Returns:: None

sync(self, wait=False)

source code

This method can be called anytime and forces the instance to flush all the cache writes queued to disk. If wait == False a watchdog prevents this call to get stuck in case of write buffer overloads.

Parameters:

wait (bool) - indicates if waiting until done (synchronous mode) or not

Returns: None

None

discard(self)

source code

This method makes buffered cache to be discarded synchronously.

Returns:: None

push(self, key, data, async=True)

source code

This is the place where data is either added to the write queue or written to disk (if async == False) only and only if start() method has been called.

Parameters:

key (string) - cache data identifier
data (any picklable object) - picklable object
async (bool) - store cache asynchronously or not

Returns: None

None

pop(self, key)

source code

This is the place where data is retrieved from cache. You must know the cache identifier used when push() was called.

Parameters:

key (string) - cache data identifier

Returns: Python object

object stored into the stack or None (if stack is empty)