Implement the delete API by implementing soft delete for layers
and blobs by removing link files and updating the blob descriptor
cache. Deletion is configurable - if it is disabled API calls
will return an unsupported error.
We invalidate the blob descriptor cache by changing the linkedBlobStore's
blobStatter to a blobDescriptorService and naming it blobAccessController.
Delete() is added throughout the relevant API to support this functionality.
Signed-off-by: Richard Scothern <richard.scothern@gmail.com>
After consideration, we've changed the main descriptor field name to for number
of bytes to "size" to match convention. While this may be a subjective
argument, commonly we refer to files by their "size" rather than their
"length". This will match other conventions, like `(FileInfo).Size()` and
methods on `io.SizeReaderAt`. Under more broad analysis, this argument doesn't
necessarily hold up. If anything, "size" is shorter than "length".
Signed-off-by: Stephen J Day <stephen.day@docker.com>
Ensure that clients can use the blob descriptor cache provider without needing
the redis package.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
