Cache

cache

Classes:

Name	Description
Cache	Caching module prefetches segments of data that has long IO, for more responsive experience.
DataRequest	Object wrapping user's element of interest into a fetch request.

Cache

Caching module prefetches segments of data that has long IO, for more responsive experience.

Methods:

Name	Description
__init__	Constructor of the Cache component for long IO prefetching to mask latency behind wide bandwidth.
get_data	Request data from the cache.
join	Wait on the background cache management thread.
start	Start the background cache management thread.

__init__

__init__(fetch_fn: Callable[[Any], Dict[Any, Any]], fetch_offset: int)

Parameters:

Name	Type	Description	Default
fetch_fn	Callable[[Any], Dict[Any, Any]]	User-provided function with long IO to use for asynchronous prefetching (database operation, API call, FFmpeg decoding, etc.).	required
fetch_offset	int	How many elements before the requested to cache in case of jumping backwards during playback.	required

_fetch

_fetch(key: Any) -> Dict[Any, Any]

Fetches data from an external source using user-defined IO function.

Returns:

Type	Description
Dict[Any, Any]	Dict[Any, Any]: Mapping from a unique key to the element of interest.

_process_request

_process_request(request: DataRequest)

Process user request for the next element of interest.

Runs user-provided long-IO fetch procedure if the data is not immediately available in cache or isn't already being fetched. Updates the cache and notifies all watchers waiting for this element.

Parameters:

Name	Type	Description	Default
request	DataRequest	User-requested element of interest.	required

_run_cache_manager

_run_cache_manager()

Main loop of the background continuous cache management thread.

Processes requests from the user and prefetches most likely used next segment of elements.

get_data

get_data(key: Any) -> Any

Request data from the cache.

Checks if data is already in the cache. Adds a request to the queue for background processing. Returns immediately if requested data is cached, otherwise waits for the background task to fetch it. Stalls until the data is available in the cache for the given key.

Parameters:

Name	Type	Description	Default
key	Any	Unique key correctly identifying the element of interest in the user-provided fetch function.	required

Returns:

Name	Type	Description
Any	Any	The requested element of interest.

join

join()

Wait on the background cache management thread.

start

start()

Start the background cache management thread.

DataRequest dataclass

Object wrapping user's element of interest into a fetch request.