Online GC stage 3: Identifying and removing dangling blobs and manifests

Problem to solve

As documented in the specification, the third and last stage of online GC is to identify and remove dangling blobs and manifests.

During this stage, the garbage collector determines if a blob in the deduplicated storage or a manifest record in the database is eligible for deletion and, if so, deletes it.

Proposal

Implement the third and last stage of online GC as described in the specification.