tests: share single docker between docker-container backends

This means that we can run our docker-container tests in parallel again,
which can help speed up our test runs by a *significant* amount.

Signed-off-by: Justin Chadwell <me@jedevc.com>
(cherry picked from commit 601056f3a7)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

tests/workers/docker-container.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"os"
 	"os/exec"
+	"sync"
 
 	"github.com/moby/buildkit/identity"
 	"github.com/moby/buildkit/util/testutil/integration"
@@ -18,6 +19,11 @@ func InitDockerContainerWorker() {
 
 type containerWorker struct {
 	id string
+
+	docker      integration.Backend
+	dockerClose func() error
+	dockerErr   error
+	dockerOnce  sync.Once
 }
 
 func (w *containerWorker) Name() string {
@@ -29,9 +35,11 @@ func (w *containerWorker) Rootless() bool {
 }
 
 func (w *containerWorker) New(ctx context.Context, cfg *integration.BackendConfig) (integration.Backend, func() error, error) {
-	bk, bkclose, err := dockerWorker{id: w.id}.New(ctx, cfg)
-	if err != nil {
-		return bk, bkclose, err
+	w.dockerOnce.Do(func() {
+		w.docker, w.dockerClose, w.dockerErr = dockerWorker{id: w.id}.New(ctx, cfg)
+	})
+	if w.dockerErr != nil {
+		return w.docker, w.dockerClose, w.dockerErr
 	}
 
 	name := "integration-container-" + identity.NewID()
@@ -42,29 +50,32 @@ func (w *containerWorker) New(ctx context.Context, cfg *integration.BackendConfi
 		"--driver=docker-container",
 		"--driver-opt=network=host",
 	)
-	cmd.Env = append(os.Environ(), "DOCKER_CONTEXT="+bk.DockerAddress())
+	cmd.Env = append(os.Environ(), "DOCKER_CONTEXT="+w.docker.DockerAddress())
 	if err := cmd.Run(); err != nil {
 		return nil, nil, errors.Wrapf(err, "failed to create buildx instance %s", name)
 	}
 
 	cl := func() error {
-		var err error
-		if err1 := bkclose(); err == nil {
-			err = err1
-		}
 		cmd := exec.Command("buildx", "rm", "-f", name)
-		if err1 := cmd.Run(); err == nil {
-			err = err1
-		}
-		return err
+		return cmd.Run()
 	}
 
 	return &backend{
-		context: bk.DockerAddress(),
+		context: w.docker.DockerAddress(),
 		builder: name,
 	}, cl, nil
 }
 
 func (w *containerWorker) Close() error {
+	if close := w.dockerClose; close != nil {
+		return close()
+	}
+
+	// reset the worker to be ready to go again
+	w.docker = nil
+	w.dockerClose = nil
+	w.dockerErr = nil
+	w.dockerOnce = sync.Once{}
+
 	return nil
 }

tests/workers/docker.go

@@ -42,7 +42,7 @@ func (c dockerWorker) New(ctx context.Context, cfg *integration.BackendConfig) (
 		"--docker", "host="+bk.DockerAddress(),
 	)
 	if err := cmd.Run(); err != nil {
-		return nil, cl, errors.Wrapf(err, "failed to create buildx instance %s", name)
+		return bk, cl, errors.Wrapf(err, "failed to create buildx instance %s", name)
 	}
 
 	cl = func() error {