build: read body response to check for erroneous image export to docker

[crazy-max]

• fixes --load doesn't always export the Docker image #593
• fixes load sometimes doesn't load build-push-action#321

FROM nvidia/cuda:12.1.0-cudnn8-devel-ubi9
RUN dd if=/dev/zero of=/output.dat bs=8192M count=1
RUN uname -a

#6 [2/3] RUN dd if=/dev/zero of=/output.dat bs=8192M count=1
#6 9.653 0+1 records in
#6 9.653 0+1 records out
#6 9.657 2147479552 bytes (2.1 GB, 2.0 GiB) copied, 9.53004 s, 225 MB/s
#6 DONE 12.0s

#7 [3/3] RUN uname -a
#7 0.066 Linux buildkitsandbox 5.15.0-1042-azure #49-Ubuntu SMP Tue Jul 11 17:28:46 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
#7 DONE 0.1s

#8 exporting to docker image format
#8 exporting layers
#8 exporting layers 14.1s done
#8 exporting manifest sha256:00f00d30fad0d29a48903e5bd5e62f0eb4fa3e64cc4c0c457068e2fb9580e274 done
#8 exporting config sha256:8c50355a7c7c256edf058253f8b9835766f22147d8e09e37f00012992ce1c0e0 done
#8 sending tarball
#8 sending tarball 95.6s done
#8 DONE 109.7s

#9 importing to docker
#9 ERROR: Error processing tar file(exit status 1): write /blobs/sha256/d7e3fb36b984700f58ea61a1ccb9d122cf4a1a13955c6ed82607ea370ac48a05: no space left on device
------
 > importing to docker:
------

$ docker buildx create --name foo
$ docker buildx build --load -t foo .

[crazy-max]

With the repro above, it outputs the error in the progress output as expected and w.err is returned with the error on Close():

buildx/util/dockerutil/client.go

Line 116 in b84e0e1

return w.err

but build still succeeds so it seems BuildKit discard errors on close for ExportEntry.Output.

[crazy-max]

Opened moby/buildkit#4117

[tonistiigi]

One way to possibly test this would be to load into something with LimitedWriter capabilities. The destination would accept data until some limit (eg. 100KB) and then error. Test can check if this error was detected.

[thaJeztah]

Could this also be related to some cases mentioned in this ticket?

• docker build exits successfully but no built image show up in the docker images cli#2686

[crazy-max]

Could this also be related to some cases mentioned in this ticket?

* [docker build exits successfully but no built image show up in the docker images cli#2686](https://github.com/docker/cli/issues/2686)

Yes looks to be the same issue