glance.image_cache package

Module contents

LRU Cache for Image Data

class glance.image_cache.ImageCache[source]

Bases: object

Provides an LRU cache for image data.

cache_image_file(image_id, image_file)[source]

Cache an image file.

Parameters
  • image_id – Image ID

  • image_file – Image file to cache

Returns

True if image file was cached, False otherwise

cache_image_iter(image_id, image_iter, image_checksum=None)[source]

Cache an image with supplied iterator.

Parameters
  • image_id – Image ID

  • image_file – Iterator retrieving image chunks

  • image_checksum – Checksum of image

Returns

True if image file was cached, False otherwise

cache_tee_iter(image_id, image_iter, image_checksum)[source]
clean(stall_time=None)[source]

Cleans up any invalid or incomplete cached images. The cache driver decides what that means…

configure_driver()[source]

Configure the driver for the cache and, if it fails to configure, fall back to using the SQLite driver which has no odd dependencies

delete_all_cached_images()[source]

Removes all cached image files and any attributes about the images and returns the number of cached image files that were deleted.

delete_all_queued_images()[source]

Removes all queued image files and any attributes about the images and returns the number of queued image files that were deleted.

delete_cached_image(image_id)[source]

Removes a specific cached image file and any attributes about the image

Parameters

image_id – Image ID

delete_queued_image(image_id)[source]

Removes a specific queued image file and any attributes about the image

Parameters

image_id – Image ID

get_cache_size()[source]

Returns the total size in bytes of the image cache.

get_cached_images()[source]

Returns a list of records about cached images.

get_caching_iter(image_id, image_checksum, image_iter)[source]

Returns an iterator that caches the contents of an image while the image contents are read through the supplied iterator.

Parameters
  • image_id – Image ID

  • image_checksum – checksum expected to be generated while iterating over image data

  • image_iter – Iterator that will read image contents

get_hit_count(image_id)[source]

Return the number of hits that an image has

Parameters

image_id – Opaque image identifier

get_image_size(image_id)[source]

Return the size of the image file for an image with supplied identifier.

Parameters

image_id – Image ID

get_queued_images()[source]

Returns a list of image IDs that are in the queue. The list should be sorted by the time the image ID was inserted into the queue.

init_driver()[source]

Create the driver for the cache

is_cached(image_id)[source]

Returns True if the image with the supplied ID has its image file cached.

Parameters

image_id – Image ID

is_queued(image_id)[source]

Returns True if the image identifier is in our cache queue.

Parameters

image_id – Image ID

open_for_read(image_id)[source]

Open and yield file for reading the image file for an image with supplied identifier.

:note Upon successful reading of the image file, the image’s

hit count will be incremented.

Parameters

image_id – Image ID

prune()[source]

Removes all cached image files above the cache’s maximum size. Returns a tuple containing the total number of cached files removed and the total size of all pruned image files.

queue_image(image_id)[source]

This adds a image to be cache to the queue.

If the image already exists in the queue or has already been cached, we return False, True otherwise

Parameters

image_id – Image ID