- Keep the download URLs of a batch response in memory until shortly
before they expire, so the GET that follows needs no second batch
request. A kept URL that fails is replaced by a fresh one.
- Cut off a download that isn't the object's size.
- Copy an object whose content is already stored, such as for a fork,
instead of downloading it, once the upstream has confirmed the
repository has it. Artifacts are indexed by content hash for this.
- Keep signed download URLs out of logs and the database: the fetch uses
the signed URL, everything else the URL without its query.
- Answer a batch from the cache when the upstream can't be reached or
fails, so git-lfs can use cached objects during an outage. Refusals
are still passed on.
- Answer a HEAD for an uncached object from the batch response instead
of downloading it.
git-lfs finds the LFS API under the rewritten remote, so clones through
/git/ already asked the proxy for LFS objects and got 404s. The proxy now
serves the batch API for downloads: it forwards the batch to the upstream,
which decides which objects the repository has, and points each download
at the proxy. Objects are served from the artifact cache. A miss asks the
upstream batch API for a fresh download URL, fetches it and checks it
against its sha256 object ID before caching it.
Download URLs often name another host than the Git server, such as object
storage. The proxy fetches from whatever host the upstream names, with the
usual address checks; upstream.auth credentials stay scoped to their
hosts. Objects are cached per repository. Uploads and locking are refused.
Closes#517.
