Concurrent uploads which share layers worked correctly as of #18353,
but unfortunately #18785 caused a regression. This PR removed the logic
that shares digests between different push sessions. This overlooked the
case where one session was waiting for another session to upload a
layer.
This commit adds back the ability to propagate this digest information,
using the distribution.Descriptor type because this is what is received
from stats and uploads, and also what is ultimately needed for building
the manifest.
Surprisingly, there was no test covering this case. This commit adds
one. It fails without the fix.
See recent comments on #9132.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
Currently this always uses the schema1 manifest builder. Later, it will
be changed to attempt schema2 first, and fall back when necessary.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
This commit adds a transfer manager which deduplicates and schedules
transfers, and also an upload manager and download manager that build on
top of the transfer manager to provide high-level interfaces for uploads
and downloads. The push and pull code is modified to use these building
blocks.
Some benefits of the changes:
- Simplification of push/pull code
- Pushes can upload layers concurrently
- Failed downloads and uploads are retried after backoff delays
- Cancellation is supported, but individual transfers will only be
cancelled if all pushes or pulls using them are cancelled.
- The distribution code is decoupled from Docker Engine packages and API
conventions (i.e. streamformatter), which will make it easier to split
out.
This commit also includes unit tests for the new distribution/xfer
package. The tests cover 87.8% of the statements in the package.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
