Resolver: ensure WithSession to pass the session to the resolver

[ktock]

Currently, unlazying blobs created by the previous build seems to fail because resolver.Resolver.WithSession() doesn't propagate session to authorizer during unlazying.
This commit fixes this issue.

reproducing issue

• buildkit version: master (a640b47)

# cat <<EOF > /tmp/ctx/Dockerfile
FROM ghcr.io/stargz-containers/ubuntu:20.04-org
EOF
# buildctl build --progress=plain --frontend=dockerfile.v0 --local context=/tmp/ctx --local dockerfile=/tmp/ctx
# buildctl build --progress=plain --frontend=dockerfile.v0 --local context=/tmp/ctx --local dockerfile=/tmp/ctx \
                 --output type=oci,dest=/tmp/out.tar,oci-mediatypes=true,compression=zstd,force-compression=true

The second build in the above fails with the following error:

ERRO[2022-02-07T06:11:09Z] /moby.buildkit.v1.Control/Solve returned error: rpc error: code = Unknown desc = failed to ensure compression type of "zstd": failed to copy: httpReadSeeker: failed open: no active sessions

full log

# buildctl build --progress=plain --frontend=dockerfile.v0 --local context=/tmp/ctx --local dockerfile=/tmp/ctx
#1 [internal] load build definition from Dockerfile
#1 DONE 0.0s

#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 85B done
#1 DONE 0.0s

#2 [internal] load .dockerignore
#2 transferring context: 2B done
#2 DONE 0.1s

#3 [internal] load metadata for ghcr.io/stargz-containers/ubuntu:20.04-org
#3 DONE 0.4s

#4 [1/1] FROM ghcr.io/stargz-containers/ubuntu:20.04-org@sha256:adf73ca014822ad8237623d388cedf4d5346aa72c270c5acc01431cc93e18e2d
#4 resolve ghcr.io/stargz-containers/ubuntu:20.04-org@sha256:adf73ca014822ad8237623d388cedf4d5346aa72c270c5acc01431cc93e18e2d 0.0s done
#4 DONE 0.0s

#4 [1/1] FROM ghcr.io/stargz-containers/ubuntu:20.04-org@sha256:adf73ca014822ad8237623d388cedf4d5346aa72c270c5acc01431cc93e18e2d
#4 DONE 0.1s


# buildctl build --progress=plain --frontend=dockerfile.v0 --local context=/tmp/ctx --local dockerfile=/tmp/ctx \
                 --output type=oci,dest=/tmp/out.tar,oci-mediatypes=true,compression=zstd,force-compression=true
#1 [internal] load build definition from Dockerfile
#1 DONE 0.0s

#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 85B done
#1 DONE 0.0s

#2 [internal] load .dockerignore
#2 transferring context: 2B done
#2 DONE 0.0s

#3 [internal] load metadata for ghcr.io/stargz-containers/ubuntu:20.04-org
#3 DONE 0.7s

#4 [1/1] FROM ghcr.io/stargz-containers/ubuntu:20.04-org@sha256:adf73ca014822ad8237623d388cedf4d5346aa72c270c5acc01431cc93e18e2d
#4 resolve ghcr.io/stargz-containers/ubuntu:20.04-org@sha256:adf73ca014822ad8237623d388cedf4d5346aa72c270c5acc01431cc93e18e2d 0.0s done
#4 sha256:5e9250ddb7d0fa6d13302c7c3e6a0aa40390e42424caed1e5289077ee4054709 0B / 187B 0.2s
ERRO[2022-02-07T06:11:09Z] /moby.buildkit.v1.Control/Solve returned error: rpc error: code = Unknown desc = failed to ensure compression type of "zstd": failed to copy: httpReadSeeker: failed open: no active sessions 
#4 DONE 0.2s

#5 exporting to oci image format
#5 exporting layers 0.2s done
#5 ERROR: failed to ensure compression type of "zstd": failed to copy: httpReadSeeker: failed open: no active sessions
------
 > exporting to oci image format:
------
error: failed to solve: failed to ensure compression type of "zstd": failed to copy: httpReadSeeker: failed open: no active sessions

[tonistiigi]

Can you explain why this requires compression=zstd,force-compression=true to trigger and otherwise seems to work as is. I'm not sure I understand what the actual error case is and why r2.auth = nil is not enough here.

[ktock]

@tonistiigi

Can you explain why this requires compression=zstd,force-compression=true to trigger and otherwise seems to work as is.

The first build creates new refs for ghcr.io/stargz-containers/ubuntu:20.04-org using cache.*cacheManager.GetByBlob() but it doesn't unlazy them becuse of no export.

The second build uses these cached refs and unlazies for exporting them. Now, the session provided to an argument of cache.*immutableRef.GetRemotes() is passed to (util/pull).*PullManifests.Provider(session.Group) via lazyRefProvider. (util/pull).*PullManifests.Provider(session.Group) creates a new resolver using (util/resolver).*Resolver.WithSession() with the provided session.

However, WithSession() doesn't seem to copy (util/resolver).*Resolver.Resolver which still points to the older (util/resolver).*Resolver.g via (util/resolver).*Resolver.HostsFunc().

(BTW, *Resolver.auth doesn't seem to be used as of now? maybe I'm missing something)

[tonistiigi]

*Resolver.auth doesn't seem to be used as of now? maybe I'm missing something

Indeed. Think we can clean it up.