build: rework build package to use only a single Build call

Signed-off-by: Justin Chadwell <me@jedevc.com>

build/build.go

@@ -653,11 +653,166 @@ func toSolveOpt(ctx context.Context, node builder.Node, multiDriver bool, opt Op
 	return &so, releaseF, nil
 }
 
+func build(ctx context.Context, c *client.Client, opt Options, so client.SolveOpt, pw progress.Writer) (*ResultContext, error) {
+	frontendInputs := make(map[string]*pb.Definition)
+	for key, st := range so.FrontendInputs {
+		def, err := st.Marshal(ctx)
+		if err != nil {
+			return nil, err
+		}
+		frontendInputs[key] = def.ToPB()
+	}
+
+	req := gateway.SolveRequest{
+		Frontend:       so.Frontend,
+		FrontendInputs: frontendInputs,
+		FrontendOpt:    make(map[string]string),
+	}
+	for k, v := range so.FrontendAttrs {
+		req.FrontendOpt[k] = v
+	}
+	so.Frontend = ""
+	so.FrontendInputs = nil
+
+	ch, chdone := progress.NewChannel(pw)
+
+	rcs := make(chan *ResultContext)
+
+	suspend := make(chan struct{})
+	suspendDone := make(chan struct{})
+
+	go func() {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		var rc *ResultContext
+
+		var printRes map[string][]byte
+		rr, err := c.Build(ctx, so, "buildx", func(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
+			var isFallback bool
+			var origErr error
+			for {
+				if opt.PrintFunc != nil {
+					if _, ok := req.FrontendOpt["frontend.caps"]; !ok {
+						req.FrontendOpt["frontend.caps"] = "moby.buildkit.frontend.subrequests+forward"
+					} else {
+						req.FrontendOpt["frontend.caps"] += ",moby.buildkit.frontend.subrequests+forward"
+					}
+					req.FrontendOpt["requestid"] = "frontend." + opt.PrintFunc.Name
+					if isFallback {
+						req.FrontendOpt["build-arg:BUILDKIT_SYNTAX"] = printFallbackImage
+					}
+				}
+				res, err := c.Solve(ctx, req)
+				if err != nil {
+					if origErr != nil {
+						return nil, err
+					}
+					var reqErr *errdefs.UnsupportedSubrequestError
+					if !isFallback {
+						if errors.As(err, &reqErr) {
+							switch reqErr.Name {
+							case "frontend.outline", "frontend.targets":
+								isFallback = true
+								origErr = err
+								continue
+							}
+							return nil, err
+						}
+						// buildkit v0.8 vendored in Docker 20.10 does not support typed errors
+						if strings.Contains(err.Error(), "unsupported request frontend.outline") || strings.Contains(err.Error(), "unsupported request frontend.targets") {
+							isFallback = true
+							origErr = err
+							continue
+						}
+					}
+				}
+
+				// TODO: would we want to compute this on demand instead of blocking?
+				eg, ctx2 := errgroup.WithContext(ctx)
+				res.EachRef(func(r gateway.Reference) error {
+					eg.Go(func() error {
+						return r.Evaluate(ctx2)
+					})
+					return nil
+				})
+				err = eg.Wait()
+
+				if opt.PrintFunc != nil {
+					printRes = res.Metadata
+				}
+
+				rc = &ResultContext{
+					gwClient:    c,
+					gwCtx:       ctx,
+					gwDone:      cancel,
+					gwRef:       res,
+					suspend:     suspend,
+					suspendDone: suspendDone,
+				}
+				var se *errdefs.SolveError
+				if errors.As(err, &se) {
+					rc.gwErr = se
+				} else if err != nil {
+					return nil, err
+				}
+				rcs <- rc
+
+				<-suspend
+				return res, err
+			}
+		}, ch)
+
+		<-chdone
+
+		if rr != nil {
+			if rr.ExporterResponse == nil {
+				rr.ExporterResponse = map[string]string{}
+			}
+			for k, v := range printRes {
+				rr.ExporterResponse[k] = string(v)
+			}
+		}
+
+		rc.resp = rr
+		rc.err = err
+		close(suspendDone)
+	}()
+
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	case rc := <-rcs:
+		return rc, nil
+	}
+}
+
 func Build(ctx context.Context, nodes []builder.Node, opt map[string]Options, docker *dockerutil.Client, configDir string, w progress.Writer) (resp map[string]*client.SolveResponse, err error) {
-	return BuildWithResultHandler(ctx, nodes, opt, docker, configDir, w, nil)
+	resp = map[string]*client.SolveResponse{}
+
+	rcs, err := BuildResults(ctx, nodes, opt, docker, configDir, w)
+	if err != nil {
+		return nil, err
+	}
+	eg, ctx := errgroup.WithContext(ctx)
+	for k, v := range rcs {
+		k, v := k, v
+		eg.Go(func() error {
+			v2, err := v.Wait(ctx)
+			if err != nil {
+				return err
+			}
+			resp[k] = v2
+			return nil
+		})
+	}
+	if err := eg.Wait(); err != nil {
+		return nil, err
+	}
+	return resp, nil
 }
 
-func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[string]Options, docker *dockerutil.Client, configDir string, w progress.Writer, resultHandleFunc func(driverIndex int, rCtx *ResultContext)) (resp map[string]*client.SolveResponse, err error) {
+func BuildResults(ctx context.Context, nodes []builder.Node, opt map[string]Options, docker *dockerutil.Client, configDir string, w progress.Writer) (resp map[string]*ResultContext, err error) {
 	if len(nodes) == 0 {
 		return nil, errors.Errorf("driver required for build")
 	}
@@ -708,8 +863,6 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 		}
 	}()
 
-	eg, ctx := errgroup.WithContext(ctx)
-
 	for k, opt := range opt {
 		multiDriver := len(m[k]) > 1
 		hasMobyDriver := false
@@ -785,8 +938,9 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 		}
 	}
 
-	resp = map[string]*client.SolveResponse{}
+	eg, ctx := errgroup.WithContext(ctx)
 	var respMu sync.Mutex
+	resp = map[string]*ResultContext{}
 	results := waitmap.New()
 
 	multiTarget := len(opt) > 1
@@ -801,15 +955,17 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 		if multiTarget {
 			span, ctx = tracing.StartSpan(ctx, k)
 		}
-		baseCtx := ctx
 
-		res := make([]*client.SolveResponse, len(dps))
+		res := make([]*ResultContext, len(dps))
-		eg2, ctx := errgroup.WithContext(ctx)
 
 		var pushNames string
 		var insecurePush bool
 
+		wg := sync.WaitGroup{}
+
 		for i, dp := range dps {
+			wg.Add(1)
+
 			i, dp, so := i, dp, *dp.so
 			if multiDriver {
 				for i, e := range so.Exports {
@@ -842,104 +998,24 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 			pw := progress.WithPrefix(w, k, multiTarget)
 
 			c := clients[dp.driverIndex]
-			eg2.Go(func() error {
+			eg.Go(func() error {
 				pw = progress.ResetTime(pw)
 
 				if err := waitContextDeps(ctx, dp.driverIndex, results, &so); err != nil {
 					return err
 				}
 
-				frontendInputs := make(map[string]*pb.Definition)
+				result, err := build(ctx, c, opt, so, pw)
-				for key, st := range so.FrontendInputs {
-					def, err := st.Marshal(ctx)
 				if err != nil {
 					return err
 				}
-					frontendInputs[key] = def.ToPB()
+				results.Set(resultKey(dp.driverIndex, k), result.gwRef)
-				}
 
-				req := gateway.SolveRequest{
+				res[i] = result
-					Frontend:       so.Frontend,
+				resp[k] = result
-					FrontendInputs: frontendInputs,
-					FrontendOpt:    make(map[string]string),
-				}
-				for k, v := range so.FrontendAttrs {
-					req.FrontendOpt[k] = v
-				}
-				so.Frontend = ""
-				so.FrontendInputs = nil
 
-				ch, done := progress.NewChannel(pw)
+				result.hook(func(ctx context.Context) error {
-				defer func() { <-done }()
+					defer wg.Done()
-
-				cc := c
-				var printRes map[string][]byte
-				rr, err := c.Build(ctx, so, "buildx", func(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
-					var isFallback bool
-					var origErr error
-					for {
-						if opt.PrintFunc != nil {
-							if _, ok := req.FrontendOpt["frontend.caps"]; !ok {
-								req.FrontendOpt["frontend.caps"] = "moby.buildkit.frontend.subrequests+forward"
-							} else {
-								req.FrontendOpt["frontend.caps"] += ",moby.buildkit.frontend.subrequests+forward"
-							}
-							req.FrontendOpt["requestid"] = "frontend." + opt.PrintFunc.Name
-							if isFallback {
-								req.FrontendOpt["build-arg:BUILDKIT_SYNTAX"] = printFallbackImage
-							}
-						}
-						res, err := c.Solve(ctx, req)
-						if err != nil {
-							if origErr != nil {
-								return nil, err
-							}
-							var reqErr *errdefs.UnsupportedSubrequestError
-							if !isFallback {
-								if errors.As(err, &reqErr) {
-									switch reqErr.Name {
-									case "frontend.outline", "frontend.targets":
-										isFallback = true
-										origErr = err
-										continue
-									}
-									return nil, err
-								}
-								// buildkit v0.8 vendored in Docker 20.10 does not support typed errors
-								if strings.Contains(err.Error(), "unsupported request frontend.outline") || strings.Contains(err.Error(), "unsupported request frontend.targets") {
-									isFallback = true
-									origErr = err
-									continue
-								}
-							}
-							return nil, err
-						}
-						if opt.PrintFunc != nil {
-							printRes = res.Metadata
-						}
-						results.Set(resultKey(dp.driverIndex, k), res)
-						if resultHandleFunc != nil {
-							resultCtx, err := NewResultContext(cc, so, res)
-							if err == nil {
-								resultHandleFunc(dp.driverIndex, resultCtx)
-							} else {
-								logrus.Warnf("failed to record result: %s", err)
-							}
-						}
-						return res, nil
-					}
-				}, ch)
-				if err != nil {
-					return err
-				}
-				res[i] = rr
-
-				if rr.ExporterResponse == nil {
-					rr.ExporterResponse = map[string]string{}
-				}
-				for k, v := range printRes {
-					rr.ExporterResponse[k] = string(v)
-				}
 
 					node := nodes[dp.driverIndex].Driver
 					if node.IsMobyDriver() {
@@ -963,12 +1039,12 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 									if err == nil && remoteDigest != "" {
 										// old daemons might not have containerimage.config.digest set
 										// in response so use containerimage.digest value for it if available
-									if _, ok := rr.ExporterResponse[exptypes.ExporterImageConfigDigestKey]; !ok {
+										if _, ok := result.resp.ExporterResponse[exptypes.ExporterImageConfigDigestKey]; !ok {
-										if v, ok := rr.ExporterResponse[exptypes.ExporterImageDigestKey]; ok {
+											if v, ok := result.resp.ExporterResponse[exptypes.ExporterImageDigestKey]; ok {
-											rr.ExporterResponse[exptypes.ExporterImageConfigDigestKey] = v
+												result.resp.ExporterResponse[exptypes.ExporterImageConfigDigestKey] = v
 											}
 										}
-									rr.ExporterResponse[exptypes.ExporterImageDigestKey] = remoteDigest
+										result.resp.ExporterResponse[exptypes.ExporterImageDigestKey] = remoteDigest
 									} else if err != nil {
 										return err
 									}
@@ -976,21 +1052,21 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 							}
 						}
 					}
+
 					return nil
 				})
-		}
 
-		eg.Go(func() (err error) {
+				if i == 0 {
-			ctx := baseCtx
+					result.hook(func(ctx context.Context) error {
+						wg.Wait()
+
 						defer func() {
 							if span != nil {
 								tracing.FinishWithError(span, err)
 							}
 						}()
+
 						pw := progress.WithPrefix(w, "default", false)
-			if err := eg2.Wait(); err != nil {
-				return err
-			}
 
 						respMu.Lock()
 						resp[k] = res[0]
@@ -998,13 +1074,15 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 						if len(res) == 1 {
 							return nil
 						}
+						if pushNames == "" {
+							return nil
+						}
 
-			if pushNames != "" {
 						progress.Write(pw, fmt.Sprintf("merging manifest list %s", pushNames), func() error {
 							descs := make([]specs.Descriptor, 0, len(res))
 
 							for _, r := range res {
-						s, ok := r.ExporterResponse[exptypes.ExporterImageDescriptorKey]
+								s, ok := r.resp.ExporterResponse[exptypes.ExporterImageDescriptorKey]
 								if ok {
 									dt, err := base64.StdEncoding.DecodeString(s)
 									if err != nil {
@@ -1021,7 +1099,7 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 								// Note that the mediatype isn't really correct as most of the time it is image manifest and
 								// not manifest list but actually both are handled because for Docker mediatypes the
 								// mediatype value in the Accpet header does not seem to matter.
-						s, ok = r.ExporterResponse[exptypes.ExporterImageDigestKey]
+								s, ok = r.resp.ExporterResponse[exptypes.ExporterImageDigestKey]
 								if ok {
 									descs = append(descs, specs.Descriptor{
 										Digest:    digest.Digest(s),
@@ -1087,7 +1165,7 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 								}
 
 								respMu.Lock()
-						resp[k] = &client.SolveResponse{
+								resp[k].resp = &client.SolveResponse{
 									ExporterResponse: map[string]string{
 										exptypes.ExporterImageDigestKey: desc.Digest.String(),
 									},
@@ -1096,10 +1174,13 @@ func BuildWithResultHandler(ctx context.Context, nodes []builder.Node, opt map[s
 							}
 							return nil
 						})
+						return nil
+					})
 				}
 				return nil
 			})
 		}
+	}
 
 	if err := eg.Wait(); err != nil {
 		return nil, err

build/result.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"io"
 	"sync"
-	"sync/atomic"
 
 	controllerapi "github.com/docker/buildx/controller/pb"
 	"github.com/moby/buildkit/client"
@@ -17,121 +16,63 @@ import (
 	specs "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/sync/errgroup"
 )
 
-func NewResultContext(c *client.Client, solveOpt client.SolveOpt, res *gateway.Result) (*ResultContext, error) {
+// ResultContext is a build result with the client that built it.
-	ctx := context.Background()
+type ResultContext struct {
-	def, err := getDefinition(ctx, res)
+	resp        *client.SolveResponse
-	if err != nil {
+	err         error
-		return nil, err
+	suspend     chan<- struct{}
-	}
+	suspendDone <-chan struct{}
-	return getResultAt(ctx, c, solveOpt, def, nil)
+
+	hooks []func(ctx context.Context) error
+
+	gwRef *gateway.Result
+	gwErr *errdefs.SolveError
+
+	gwClient   gateway.Client
+	gwCtx      context.Context
+	gwDone     func()
+	gwDoneOnce sync.Once
+
+	cleanups   []func()
+	cleanupsMu sync.Mutex
 }
 
-func getDefinition(ctx context.Context, res *gateway.Result) (*pb.Definition, error) {
+func (r *ResultContext) hook(hook func(ctx context.Context) error) {
-	ref, err := res.SingleRef()
+	r.hooks = append(r.hooks, hook)
-	if err != nil {
-		return nil, err
-	}
-	st, err := ref.ToState()
-	if err != nil {
-		return nil, err
-	}
-	def, err := st.Marshal(ctx)
-	if err != nil {
-		return nil, err
-	}
-	return def.ToPB(), nil
 }
 
-func getResultAt(ctx context.Context, c *client.Client, solveOpt client.SolveOpt, target *pb.Definition, statusChan chan *client.SolveStatus) (*ResultContext, error) {
+func (r *ResultContext) Result(ctx context.Context) (*gateway.Result, *errdefs.SolveError) {
-	ctx, cancel := context.WithCancel(ctx)
+	return r.gwRef, r.gwErr
-	defer cancel()
+}
 
-	// forward SolveStatus
+func (r *ResultContext) Wait(ctx context.Context) (*client.SolveResponse, error) {
-	done := new(atomic.Bool)
+	defer r.Close()
-	defer done.Store(true)
-	ch := make(chan *client.SolveStatus)
-	go func() {
-		for {
-			s := <-ch
-			if s == nil {
-				return
-			}
-			if done.Load() {
-				// Do not forward if the function returned because statusChan is possibly closed
-				continue
-			}
-			select {
-			case statusChan <- s:
-			case <-ctx.Done():
-			}
-		}
-	}()
 
-	// get result
+	close(r.suspend)
-	resultCtxCh := make(chan *ResultContext)
-	errCh := make(chan error)
-	go func() {
-		_, err := c.Build(context.Background(), solveOpt, "buildx", func(ctx context.Context, c gateway.Client) (*gateway.Result, error) {
-			ctx, cancel := context.WithCancel(ctx)
-			defer cancel()
-			resultCtx := ResultContext{}
-			res2, err := c.Solve(ctx, gateway.SolveRequest{
-				Evaluate:   true,
-				Definition: target,
-			})
-			if err != nil {
-				var se *errdefs.SolveError
-				if errors.As(err, &se) {
-					resultCtx.solveErr = se
-				} else {
-					return nil, err
-				}
-			}
-			// Record the client and ctx as well so that containers can be created from the SolveError.
-			resultCtx.res = res2
-			resultCtx.gwClient = c
-			resultCtx.gwCtx = ctx
-			resultCtx.gwDone = cancel
 	select {
-			case resultCtxCh <- &resultCtx:
 	case <-ctx.Done():
 		return nil, ctx.Err()
+	case <-r.suspendDone:
+		eg, ctx := errgroup.WithContext(ctx)
+		eg.Go(func() error {
+			for _, f := range r.hooks {
+				if err := f(ctx); err != nil {
+					return err
 				}
-			<-ctx.Done()
-			return nil, nil
-		}, ch)
-		if err != nil {
-			errCh <- err
 			}
-	}()
+			return nil
-
+		})
-	select {
+		if err := eg.Wait(); err != nil {
-	case resultCtx := <-resultCtxCh:
-		return resultCtx, nil
-	case err := <-errCh:
 			return nil, err
-	case <-ctx.Done():
+		}
-		return nil, ctx.Err()
+		return r.resp, r.err
 	}
 }
 
-// ResultContext is a build result with the client that built it.
+func (r *ResultContext) Close() {
-type ResultContext struct {
-	res      *gateway.Result
-	solveErr *errdefs.SolveError
-
-	gwClient   gateway.Client
-	gwCtx      context.Context
-	gwDone     func()
-	gwDoneOnce sync.Once
-
-	cleanups   []func()
-	cleanupsMu sync.Mutex
-}
-
-func (r *ResultContext) Done() {
 	r.gwDoneOnce.Do(func() {
 		r.cleanupsMu.Lock()
 		cleanups := r.cleanups
@@ -156,16 +97,16 @@ func (r *ResultContext) build(buildFunc gateway.BuildFunc) (err error) {
 }
 
 func (r *ResultContext) getContainerConfig(ctx context.Context, c gateway.Client, cfg *controllerapi.InvokeConfig) (containerCfg gateway.NewContainerRequest, _ error) {
-	if r.res != nil && r.solveErr == nil {
+	if r.gwRef != nil && r.gwErr == nil {
 		logrus.Debugf("creating container from successful build")
-		ccfg, err := containerConfigFromResult(ctx, r.res, c, *cfg)
+		ccfg, err := containerConfigFromResult(ctx, r.gwRef, c, *cfg)
 		if err != nil {
 			return containerCfg, err
 		}
 		containerCfg = *ccfg
 	} else {
 		logrus.Debugf("creating container from failed build %+v", cfg)
-		ccfg, err := containerConfigFromError(r.solveErr, *cfg)
+		ccfg, err := containerConfigFromError(r.gwErr, *cfg)
 		if err != nil {
 			return containerCfg, errors.Wrapf(err, "no result nor error is available")
 		}
@@ -176,14 +117,14 @@ func (r *ResultContext) getContainerConfig(ctx context.Context, c gateway.Client
 
 func (r *ResultContext) getProcessConfig(cfg *controllerapi.InvokeConfig, stdin io.ReadCloser, stdout io.WriteCloser, stderr io.WriteCloser) (_ gateway.StartRequest, err error) {
 	processCfg := newStartRequest(stdin, stdout, stderr)
-	if r.res != nil && r.solveErr == nil {
+	if r.gwRef != nil && r.gwErr == nil {
 		logrus.Debugf("creating container from successful build")
-		if err := populateProcessConfigFromResult(&processCfg, r.res, *cfg); err != nil {
+		if err := populateProcessConfigFromResult(&processCfg, r.gwRef, *cfg); err != nil {
 			return processCfg, err
 		}
 	} else {
 		logrus.Debugf("creating container from failed build %+v", cfg)
-		if err := populateProcessConfigFromError(&processCfg, r.solveErr, *cfg); err != nil {
+		if err := populateProcessConfigFromError(&processCfg, r.gwErr, *cfg); err != nil {
 			return processCfg, err
 		}
 	}

commands/build.go

@@ -8,11 +8,13 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"log"
 	"os"
 	"path/filepath"
 	"runtime"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/containerd/console"
 	"github.com/docker/buildx/build"
@@ -33,10 +35,14 @@ import (
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
 	dockeropts "github.com/docker/cli/opts"
+	"github.com/docker/docker/api/types/versions"
 	"github.com/docker/docker/builder/remotecontext/urlutil"
 	"github.com/docker/docker/pkg/ioutils"
 	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/exporter/containerimage/exptypes"
+	"github.com/moby/buildkit/frontend/subrequests"
+	"github.com/moby/buildkit/frontend/subrequests/outline"
+	"github.com/moby/buildkit/frontend/subrequests/targets"
 	"github.com/moby/buildkit/solver/errdefs"
 	"github.com/moby/buildkit/util/appcontext"
 	"github.com/moby/buildkit/util/grpcerrors"
@@ -106,7 +112,6 @@ func (o *buildOptions) toControllerOptions() (controllerapi.BuildOptions, error)
 		NetworkMode:    o.networkMode,
 		NoCacheFilter:  o.noCacheFilter,
 		Platforms:      o.platforms,
-		PrintFunc:      o.printFunc,
 		ShmSize:        int64(o.shmSize),
 		Tags:           o.tags,
 		Target:         o.target,
@@ -153,6 +158,11 @@ func (o *buildOptions) toControllerOptions() (controllerapi.BuildOptions, error)
 		}
 	}
 
+	opts.PrintFunc, err = parsePrintFunc(o.printFunc)
+	if err != nil {
+		return controllerapi.BuildOptions{}, err
+	}
+
 	opts.CacheFrom, err = buildflags.ParseCacheEntry(o.cacheFrom)
 	if err != nil {
 		return controllerapi.BuildOptions{}, err
@@ -231,9 +241,13 @@ func runBuild(dockerCli command.Cli, in buildOptions) error {
 			return errors.Wrap(err, "removing image ID file")
 		}
 	}
-	resp, _, err := cbuild.RunBuild(ctx, dockerCli, opts, os.Stdin, printer, false)
+	res, err := cbuild.RunBuild(ctx, dockerCli, opts, os.Stdin, printer)
-	if err1 := printer.Wait(); err == nil {
+	resp, err2 := res.Wait(ctx)
-		err = err1
+	if err == nil {
+		err = err2
+	}
+	if err2 := printer.Wait(); err == nil {
+		err = err2
 	}
 	if err != nil {
 		return err
@@ -249,6 +263,16 @@ func runBuild(dockerCli command.Cli, in buildOptions) error {
 		}
 		return os.WriteFile(in.imageIDFile, []byte(dgst), 0644)
 	}
+	if in.metadataFile != "" {
+		if err := writeMetadataFile(in.metadataFile, decodeExporterResponse(resp.ExporterResponse)); err != nil {
+			return err
+		}
+	}
+	if opts.PrintFunc != nil {
+		if err := printResult(opts.PrintFunc, resp.ExporterResponse); err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
@@ -518,7 +542,7 @@ func updateLastActivity(dockerCli command.Cli, ng *store.NodeGroup) error {
 	return txn.UpdateLastActivity(ng)
 }
 
-func launchControllerAndRunBuild(dockerCli command.Cli, options buildOptions) error {
+func launchControllerAndRunBuild(dockerCli command.Cli, options buildOptions) (err error) {
 	ctx := context.TODO()
 
 	if options.invoke != nil && (options.dockerfileName == "-" || options.contextPath == "-") {
@@ -560,6 +584,14 @@ func launchControllerAndRunBuild(dockerCli command.Cli, options buildOptions) er
 	if err != nil {
 		return err
 	}
+	printerCloseOnce := sync.Once{}
+	defer func() {
+		printerCloseOnce.Do(func() {
+			if err1 := printer.Wait(); err == nil {
+				err = err1
+			}
+		})
+	}()
 
 	// NOTE: buildx server has the current working directory different from the client
 	// so we need to resolve paths to abosolute ones in the client.
@@ -588,11 +620,7 @@ func launchControllerAndRunBuild(dockerCli command.Cli, options buildOptions) er
 			}
 		}
 
-		var resp *client.SolveResponse
+		ref, err = c.Build(ctx, opts, pr, printer)
-		ref, resp, err = c.Build(ctx, opts, pr, printer)
-		if err1 := printer.Wait(); err == nil {
-			err = err1
-		}
 		if err != nil {
 			var be *controllererrors.BuildError
 			if errors.As(err, &be) {
@@ -610,22 +638,13 @@ func launchControllerAndRunBuild(dockerCli command.Cli, options buildOptions) er
 		if err := pr.Close(); err != nil {
 			logrus.Debug("failed to close stdin pipe reader")
 		}
-
-		if options.quiet {
-			fmt.Println(resp.ExporterResponse[exptypes.ExporterImageDigestKey])
-		}
-		if options.imageIDFile != "" {
-			dgst := resp.ExporterResponse[exptypes.ExporterImageDigestKey]
-			if v, ok := resp.ExporterResponse[exptypes.ExporterImageConfigDigestKey]; ok {
-				dgst = v
-			}
-			return os.WriteFile(options.imageIDFile, []byte(dgst), 0644)
-		}
-
 	}
 
 	// post-build operations
 	if options.invoke != nil && options.invoke.needsMonitor(retErr) {
+		// HACK: pause the printer to prevent interference with monitor
+		printer.Pause(true)
+
 		pr2, pw2 := io.Pipe()
 		f.SetWriter(pw2, func() io.WriteCloser {
 			pw2.Close() // propagate EOF
@@ -646,11 +665,40 @@ func launchControllerAndRunBuild(dockerCli command.Cli, options buildOptions) er
 		if err != nil {
 			logrus.Warnf("failed to run monitor: %v", err)
 		}
-	} else {
+
-		if err := c.Disconnect(ctx, ref); err != nil {
+		printer.Pause(false)
-			logrus.Warnf("disconnect error: %v", err)
+	}
+
+	resp, err := c.Finalize(ctx, ref)
+	printerCloseOnce.Do(func() {
+		if err1 := printer.Wait(); err == nil {
+			err = err1
+		}
+	})
+	if err != nil {
+		return err
+	}
+	if options.quiet {
+		fmt.Println(resp.ExporterResponse[exptypes.ExporterImageDigestKey])
+	}
+	if options.imageIDFile != "" {
+		dgst := resp.ExporterResponse[exptypes.ExporterImageDigestKey]
+		if v, ok := resp.ExporterResponse[exptypes.ExporterImageConfigDigestKey]; ok {
+			dgst = v
+		}
+		return os.WriteFile(options.imageIDFile, []byte(dgst), 0644)
+	}
+	if options.metadataFile != "" {
+		if err := writeMetadataFile(options.metadataFile, decodeExporterResponse(resp.ExporterResponse)); err != nil {
+			return err
+		}
+	}
+	if opts.PrintFunc != nil {
+		if err := printResult(opts.PrintFunc, resp.ExporterResponse); err != nil {
+			return err
 		}
 	}
+
 	return nil
 }
 
@@ -964,3 +1012,65 @@ func printWarnings(w io.Writer, warnings []client.VertexWarning, mode string) {
 
 	}
 }
+
+func printResult(f *controllerapi.PrintFunc, res map[string]string) error {
+	switch f.Name {
+	case "outline":
+		return printValue(outline.PrintOutline, outline.SubrequestsOutlineDefinition.Version, f.Format, res)
+	case "targets":
+		return printValue(targets.PrintTargets, targets.SubrequestsTargetsDefinition.Version, f.Format, res)
+	case "subrequests.describe":
+		return printValue(subrequests.PrintDescribe, subrequests.SubrequestsDescribeDefinition.Version, f.Format, res)
+	default:
+		if dt, ok := res["result.txt"]; ok {
+			fmt.Print(dt)
+		} else {
+			log.Printf("%s %+v", f, res)
+		}
+	}
+	return nil
+}
+
+type printFunc func([]byte, io.Writer) error
+
+func printValue(printer printFunc, version string, format string, res map[string]string) error {
+	if format == "json" {
+		fmt.Fprintln(os.Stdout, res["result.json"])
+		return nil
+	}
+
+	if res["version"] != "" && versions.LessThan(version, res["version"]) && res["result.txt"] != "" {
+		// structure is too new and we don't know how to print it
+		fmt.Fprint(os.Stdout, res["result.txt"])
+		return nil
+	}
+	return printer([]byte(res["result.json"]), os.Stdout)
+}
+
+func parsePrintFunc(str string) (*controllerapi.PrintFunc, error) {
+	if str == "" {
+		return nil, nil
+	}
+	csvReader := csv.NewReader(strings.NewReader(str))
+	fields, err := csvReader.Read()
+	if err != nil {
+		return nil, err
+	}
+	f := &controllerapi.PrintFunc{}
+	for _, field := range fields {
+		parts := strings.SplitN(field, "=", 2)
+		if len(parts) == 2 {
+			if parts[0] == "format" {
+				f.Format = parts[1]
+			} else {
+				return nil, errors.Errorf("invalid print field: %s", field)
+			}
+		} else {
+			if f.Name != "" {
+				return nil, errors.Errorf("invalid print value: %s", str)
+			}
+			f.Name = field
+		}
+	}
+	return f, nil
+}

controller/build/build.go

@@ -2,14 +2,10 @@ package build
 
 import (
 	"context"
-	"encoding/base64"
-	"encoding/csv"
-	"encoding/json"
 	"io"
 	"os"
 	"path/filepath"
 	"strings"
-	"sync"
 
 	"github.com/docker/buildx/build"
 	"github.com/docker/buildx/builder"
@@ -24,7 +20,6 @@ import (
 	"github.com/docker/cli/cli/command"
 	"github.com/docker/cli/cli/config"
 	dockeropts "github.com/docker/cli/opts"
-	"github.com/docker/docker/pkg/ioutils"
 	"github.com/docker/go-units"
 	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/session/auth/authprovider"
@@ -36,13 +31,9 @@ import (
 const defaultTargetName = "default"
 
 // RunBuild runs the specified build and returns the result.
-//
+func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.BuildOptions, inStream io.Reader, progress progress.Writer) (*build.ResultContext, error) {
-// NOTE: When an error happens during the build and this function acquires the debuggable *build.ResultContext,
-// this function returns it in addition to the error (i.e. it does "return nil, res, err"). The caller can
-// inspect the result and debug the cause of that error.
-func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.BuildOptions, inStream io.Reader, progress progress.Writer, generateResult bool) (*client.SolveResponse, *build.ResultContext, error) {
 	if in.NoCache && len(in.NoCacheFilter) > 0 {
-		return nil, nil, errors.Errorf("--no-cache and --no-cache-filter cannot currently be used together")
+		return nil, errors.Errorf("--no-cache and --no-cache-filter cannot currently be used together")
 	}
 
 	contexts := map[string]build.NamedContext{}
@@ -50,11 +41,6 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 		contexts[name] = build.NamedContext{Path: path}
 	}
 
-	printFunc, err := parsePrintFunc(in.PrintFunc)
-	if err != nil {
-		return nil, nil, err
-	}
-
 	opts := build.Options{
 		Inputs: build.Inputs{
 			ContextPath:    in.ContextPath,
@@ -73,12 +59,11 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 		Tags:          in.Tags,
 		Target:        in.Target,
 		Ulimits:       controllerUlimitOpt2DockerUlimit(in.Ulimits),
-		PrintFunc:     printFunc,
 	}
 
 	platforms, err := platformutil.Parse(in.Platforms)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	opts.Platforms = platforms
 
@@ -87,7 +72,7 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 
 	secrets, err := controllerapi.CreateSecrets(in.Secrets)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	opts.Session = append(opts.Session, secrets)
 
@@ -97,17 +82,17 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 	}
 	ssh, err := controllerapi.CreateSSH(sshSpecs)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	opts.Session = append(opts.Session, ssh)
 
 	outputs, err := controllerapi.CreateExports(in.Exports)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	if in.ExportPush {
 		if in.ExportLoad {
-			return nil, nil, errors.Errorf("push and load may not be set together at the moment")
+			return nil, errors.Errorf("push and load may not be set together at the moment")
 		}
 		if len(outputs) == 0 {
 			outputs = []client.ExportEntry{{
@@ -121,7 +106,7 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 			case "image":
 				outputs[0].Attrs["push"] = "true"
 			default:
-				return nil, nil, errors.Errorf("push and %q output can't be used together", outputs[0].Type)
+				return nil, errors.Errorf("push and %q output can't be used together", outputs[0].Type)
 			}
 		}
 	}
@@ -135,12 +120,19 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 			switch outputs[0].Type {
 			case "docker":
 			default:
-				return nil, nil, errors.Errorf("load and %q output can't be used together", outputs[0].Type)
+				return nil, errors.Errorf("load and %q output can't be used together", outputs[0].Type)
 			}
 		}
 	}
 	opts.Exports = outputs
 
+	if in.PrintFunc != nil {
+		opts.PrintFunc = &build.PrintFunc{
+			Name:   in.PrintFunc.Name,
+			Format: in.PrintFunc.Format,
+		}
+	}
+
 	opts.CacheFrom = controllerapi.CreateCaches(in.CacheFrom)
 	opts.CacheTo = controllerapi.CreateCaches(in.CacheTo)
 
@@ -148,7 +140,7 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 
 	allow, err := buildflags.ParseEntitlements(in.Allow)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	opts.Allow = allow
 
@@ -164,120 +156,32 @@ func RunBuild(ctx context.Context, dockerCli command.Cli, in controllerapi.Build
 		builder.WithContextPathHash(contextPathHash),
 	)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 	if err = updateLastActivity(dockerCli, b.NodeGroup); err != nil {
-		return nil, nil, errors.Wrapf(err, "failed to update builder last activity time")
+		return nil, errors.Wrapf(err, "failed to update builder last activity time")
 	}
 	nodes, err := b.LoadNodes(ctx, false)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
 
-	resp, res, err := buildTargets(ctx, dockerCli, b.NodeGroup, nodes, map[string]build.Options{defaultTargetName: opts}, progress, in.MetadataFile, generateResult)
+	res, err := buildTargets(ctx, dockerCli, b.NodeGroup, nodes, map[string]build.Options{defaultTargetName: opts}, progress, in.MetadataFile)
 	err = wrapBuildError(err, false)
 	if err != nil {
-		// NOTE: buildTargets can return *build.ResultContext even on error.
+		return nil, err
-		return nil, res, err
 	}
-	return resp, res, nil
+	return res[defaultTargetName], nil
 }
 
 // buildTargets runs the specified build and returns the result.
-//
+func buildTargets(ctx context.Context, dockerCli command.Cli, ng *store.NodeGroup, nodes []builder.Node, opts map[string]build.Options, progress progress.Writer, metadataFile string) (map[string]*build.ResultContext, error) {
-// NOTE: When an error happens during the build and this function acquires the debuggable *build.ResultContext,
+	res, err := build.BuildResults(ctx, nodes, opts, dockerutil.NewClient(dockerCli), confutil.ConfigDir(dockerCli), progress)
-// this function returns it in addition to the error (i.e. it does "return nil, res, err"). The caller can
-// inspect the result and debug the cause of that error.
-func buildTargets(ctx context.Context, dockerCli command.Cli, ng *store.NodeGroup, nodes []builder.Node, opts map[string]build.Options, progress progress.Writer, metadataFile string, generateResult bool) (*client.SolveResponse, *build.ResultContext, error) {
-	var res *build.ResultContext
-	var resp map[string]*client.SolveResponse
-	var err error
-	if generateResult {
-		var mu sync.Mutex
-		var idx int
-		resp, err = build.BuildWithResultHandler(ctx, nodes, opts, dockerutil.NewClient(dockerCli), confutil.ConfigDir(dockerCli), progress, func(driverIndex int, gotRes *build.ResultContext) {
-			mu.Lock()
-			defer mu.Unlock()
-			if res == nil || driverIndex < idx {
-				idx, res = driverIndex, gotRes
-			}
-		})
-	} else {
-		resp, err = build.Build(ctx, nodes, opts, dockerutil.NewClient(dockerCli), confutil.ConfigDir(dockerCli), progress)
-	}
-	if err != nil {
-		return nil, res, err
-	}
-
-	if len(metadataFile) > 0 && resp != nil {
-		if err := writeMetadataFile(metadataFile, decodeExporterResponse(resp[defaultTargetName].ExporterResponse)); err != nil {
-			return nil, nil, err
-		}
-	}
-
-	for k := range resp {
-		if opts[k].PrintFunc != nil {
-			if err := printResult(opts[k].PrintFunc, resp[k].ExporterResponse); err != nil {
-				return nil, nil, err
-			}
-		}
-	}
-
-	return resp[defaultTargetName], res, err
-}
-
-func parsePrintFunc(str string) (*build.PrintFunc, error) {
-	if str == "" {
-		return nil, nil
-	}
-	csvReader := csv.NewReader(strings.NewReader(str))
-	fields, err := csvReader.Read()
 	if err != nil {
 		return nil, err
 	}
-	f := &build.PrintFunc{}
-	for _, field := range fields {
-		parts := strings.SplitN(field, "=", 2)
-		if len(parts) == 2 {
-			if parts[0] == "format" {
-				f.Format = parts[1]
-			} else {
-				return nil, errors.Errorf("invalid print field: %s", field)
-			}
-		} else {
-			if f.Name != "" {
-				return nil, errors.Errorf("invalid print value: %s", str)
-			}
-			f.Name = field
-		}
-	}
-	return f, nil
-}
 
-func writeMetadataFile(filename string, dt interface{}) error {
+	return res, err
-	b, err := json.MarshalIndent(dt, "", "  ")
-	if err != nil {
-		return err
-	}
-	return ioutils.AtomicWriteFile(filename, b, 0644)
-}
-
-func decodeExporterResponse(exporterResponse map[string]string) map[string]interface{} {
-	out := make(map[string]interface{})
-	for k, v := range exporterResponse {
-		dt, err := base64.StdEncoding.DecodeString(v)
-		if err != nil {
-			out[k] = v
-			continue
-		}
-		var raw map[string]interface{}
-		if err = json.Unmarshal(dt, &raw); err != nil || len(raw) == 0 {
-			out[k] = v
-			continue
-		}
-		out[k] = json.RawMessage(dt)
-	}
-	return out
 }
 
 func wrapBuildError(err error, bake bool) error {

controller/build/print.go

@@ -1,48 +0,0 @@
-package build
-
-import (
-	"fmt"
-	"io"
-	"log"
-	"os"
-
-	"github.com/docker/buildx/build"
-	"github.com/docker/docker/api/types/versions"
-	"github.com/moby/buildkit/frontend/subrequests"
-	"github.com/moby/buildkit/frontend/subrequests/outline"
-	"github.com/moby/buildkit/frontend/subrequests/targets"
-)
-
-func printResult(f *build.PrintFunc, res map[string]string) error {
-	switch f.Name {
-	case "outline":
-		return printValue(outline.PrintOutline, outline.SubrequestsOutlineDefinition.Version, f.Format, res)
-	case "targets":
-		return printValue(targets.PrintTargets, targets.SubrequestsTargetsDefinition.Version, f.Format, res)
-	case "subrequests.describe":
-		return printValue(subrequests.PrintDescribe, subrequests.SubrequestsDescribeDefinition.Version, f.Format, res)
-	default:
-		if dt, ok := res["result.txt"]; ok {
-			fmt.Print(dt)
-		} else {
-			log.Printf("%s %+v", f, res)
-		}
-	}
-	return nil
-}
-
-type printFunc func([]byte, io.Writer) error
-
-func printValue(printer printFunc, version string, format string, res map[string]string) error {
-	if format == "json" {
-		fmt.Fprintln(os.Stdout, res["result.json"])
-		return nil
-	}
-
-	if res["version"] != "" && versions.LessThan(version, res["version"]) && res["result.txt"] != "" {
-		// structure is too new and we don't know how to print it
-		fmt.Fprint(os.Stdout, res["result.txt"])
-		return nil
-	}
-	return printer([]byte(res["result.json"]), os.Stdout)
-}

controller/control/controller.go

@@ -10,19 +10,23 @@ import (
 )
 
 type BuildxController interface {
-	Build(ctx context.Context, options controllerapi.BuildOptions, in io.ReadCloser, progress progress.Writer) (ref string, resp *client.SolveResponse, err error)
+	Build(ctx context.Context, options controllerapi.BuildOptions, in io.ReadCloser, progress progress.Writer) (string, error)
 	// Invoke starts an IO session into the specified process.
 	// If pid doesn't matche to any running processes, it starts a new process with the specified config.
 	// If there is no container running or InvokeConfig.Rollback is speicfied, the process will start in a newly created container.
 	// NOTE: If needed, in the future, we can split this API into three APIs (NewContainer, NewProcess and Attach).
 	Invoke(ctx context.Context, ref, pid string, options controllerapi.InvokeConfig, ioIn io.ReadCloser, ioOut io.WriteCloser, ioErr io.WriteCloser) error
-	Kill(ctx context.Context) error
+	Finalize(ctx context.Context, ref string) (*client.SolveResponse, error)
-	Close() error
-	List(ctx context.Context) (refs []string, _ error)
 	Disconnect(ctx context.Context, ref string) error
-	ListProcesses(ctx context.Context, ref string) (infos []*controllerapi.ProcessInfo, retErr error)
+
-	DisconnectProcess(ctx context.Context, ref, pid string) error
 	Inspect(ctx context.Context, ref string) (*controllerapi.InspectResponse, error)
+	List(ctx context.Context) ([]string, error)
+
+	ListProcesses(ctx context.Context, ref string) ([]*controllerapi.ProcessInfo, error)
+	DisconnectProcess(ctx context.Context, ref, pid string) error
+
+	Kill(ctx context.Context) error
+	Close() error
 }
 
 type ControlOptions struct {

controller/local/controller.go

@@ -42,27 +42,27 @@ type localController struct {
 	buildOnGoing atomic.Bool
 }
 
-func (b *localController) Build(ctx context.Context, options controllerapi.BuildOptions, in io.ReadCloser, progress progress.Writer) (string, *client.SolveResponse, error) {
+func (b *localController) Build(ctx context.Context, options controllerapi.BuildOptions, in io.ReadCloser, progress progress.Writer) (string, error) {
 	if !b.buildOnGoing.CompareAndSwap(false, true) {
-		return "", nil, errors.New("build ongoing")
+		return "", errors.New("build ongoing")
 	}
 	defer b.buildOnGoing.Store(false)
 
-	resp, res, buildErr := cbuild.RunBuild(ctx, b.dockerCli, options, in, progress, true)
+	res, err := cbuild.RunBuild(ctx, b.dockerCli, options, in, progress)
-	// NOTE: RunBuild can return *build.ResultContext even on error.
+	if err != nil {
+		return "", err
+	}
 	if res != nil {
 		b.buildConfig = buildConfig{
 			resultCtx:    res,
 			buildOptions: &options,
 		}
+		_, buildErr := b.buildConfig.resultCtx.Result(ctx)
 		if buildErr != nil {
-			buildErr = controllererrors.WrapBuild(buildErr, b.ref)
+			return "", controllererrors.WrapBuild(buildErr, b.ref)
-		}
 		}
-	if buildErr != nil {
-		return "", nil, buildErr
 	}
-	return b.ref, resp, nil
+	return b.ref, nil
 }
 
 func (b *localController) ListProcesses(ctx context.Context, ref string) (infos []*controllerapi.ProcessInfo, retErr error) {
@@ -123,7 +123,7 @@ func (b *localController) Kill(context.Context) error {
 func (b *localController) Close() error {
 	b.cancelRunningProcesses()
 	if b.buildConfig.resultCtx != nil {
-		b.buildConfig.resultCtx.Done()
+		b.buildConfig.resultCtx.Close()
 	}
 	// TODO: cancel ongoing builds?
 	return nil
@@ -133,9 +133,17 @@ func (b *localController) List(ctx context.Context) (res []string, _ error) {
 	return []string{b.ref}, nil
 }
 
+func (b *localController) Finalize(ctx context.Context, key string) (*client.SolveResponse, error) {
+	b.cancelRunningProcesses()
+
+	if b.buildConfig.resultCtx != nil {
+		return b.buildConfig.resultCtx.Wait(ctx)
+	}
+	return nil, nil
+}
+
 func (b *localController) Disconnect(ctx context.Context, key string) error {
-	b.Close()
+	return b.Close()
-	return nil
 }
 
 func (b *localController) Inspect(ctx context.Context, ref string) (*controllerapi.InspectResponse, error) {

controller/pb/controller.proto

@@ -7,14 +7,19 @@ import "github.com/moby/buildkit/api/services/control/control.proto";
 option go_package = "pb";
 
 service Controller {
+  rpc Info(InfoRequest) returns (InfoResponse);
+
   rpc Build(BuildRequest) returns (BuildResponse);
-  rpc Inspect(InspectRequest) returns (InspectResponse);
+  rpc Finalize(FinalizeRequest) returns (FinalizeResponse);
-  rpc Status(StatusRequest) returns (stream StatusResponse);
-  rpc Input(stream InputMessage) returns (InputResponse);
   rpc Invoke(stream Message) returns (stream Message);
-  rpc List(ListRequest) returns (ListResponse);
   rpc Disconnect(DisconnectRequest) returns (DisconnectResponse);
-  rpc Info(InfoRequest) returns (InfoResponse);
+  rpc Status(StatusRequest) returns (stream StatusResponse);
+
+  rpc Inspect(InspectRequest) returns (InspectResponse);
+  rpc List(ListRequest) returns (ListResponse);
+
+  rpc Input(stream InputMessage) returns (InputResponse);
+
   rpc ListProcesses(ListProcessesRequest) returns (ListProcessesResponse);
   rpc DisconnectProcess(DisconnectProcessRequest) returns (DisconnectProcessResponse);
 }
@@ -48,7 +53,7 @@ message BuildRequest {
 message BuildOptions {
   string ContextPath = 1;
   string DockerfileName = 2;
-  string PrintFunc = 3;
+  PrintFunc PrintFunc = 3;
   map<string, string> NamedContexts = 4;
 
   repeated string Allow = 5;
@@ -78,6 +83,19 @@ message BuildOptions {
   bool ExportLoad = 28;
 }
 
+message FinalizeRequest {
+  string Ref = 1;
+}
+
+message FinalizeResponse {
+	map<string, string> ExporterResponse = 1;
+}
+
+message PrintFunc {
+  string Name = 1;
+  string Format = 2;
+}
+
 message ExportEntry {
   string Type = 1;
   map<string, string> Attrs = 2;
@@ -125,7 +143,6 @@ message Ulimit {
 }
 
 message BuildResponse {
-	map<string, string> ExporterResponse = 1;
 }
 
 message DisconnectRequest {

controller/remote/client.go

@@ -113,49 +113,30 @@ func (c *Client) Inspect(ctx context.Context, ref string) (*pb.InspectResponse,
 	return c.client().Inspect(ctx, &pb.InspectRequest{Ref: ref})
 }
 
-func (c *Client) Build(ctx context.Context, options pb.BuildOptions, in io.ReadCloser, progress progress.Writer) (string, *client.SolveResponse, error) {
+func (c *Client) Build(ctx context.Context, options pb.BuildOptions, in io.ReadCloser, progress progress.Writer) (string, error) {
 	ref := identity.NewID()
-	statusChan := make(chan *client.SolveStatus)
+	if err := c.build(ctx, ref, options, in, progress); err != nil {
-	eg, egCtx := errgroup.WithContext(ctx)
+		return "", err
-	var resp *client.SolveResponse
-	eg.Go(func() error {
-		defer close(statusChan)
-		var err error
-		resp, err = c.build(egCtx, ref, options, in, statusChan)
-		return err
-	})
-	eg.Go(func() error {
-		for s := range statusChan {
-			st := s
-			progress.Write(st)
 	}
-		return nil
+	return ref, nil
-	})
+}
-	return ref, resp, eg.Wait()
+
+func (c *Client) Finalize(ctx context.Context, ref string) (*client.SolveResponse, error) {
+	resp, err := c.client().Finalize(ctx, &pb.FinalizeRequest{Ref: ref})
+	if err != nil {
+		return nil, err
+	}
+	return &client.SolveResponse{
+		ExporterResponse: resp.ExporterResponse,
+	}, nil
 }
 
-func (c *Client) build(ctx context.Context, ref string, options pb.BuildOptions, in io.ReadCloser, statusChan chan *client.SolveStatus) (*client.SolveResponse, error) {
+func (c *Client) build(ctx context.Context, ref string, options pb.BuildOptions, in io.ReadCloser, writer progress.Writer) error {
 	eg, egCtx := errgroup.WithContext(ctx)
 	done := make(chan struct{})
 
-	var resp *client.SolveResponse
+	go func() error {
-
+		stream, err := c.client().Status(ctx, &pb.StatusRequest{
-	eg.Go(func() error {
-		defer close(done)
-		pbResp, err := c.client().Build(egCtx, &pb.BuildRequest{
-			Ref:     ref,
-			Options: &options,
-		})
-		if err != nil {
-			return err
-		}
-		resp = &client.SolveResponse{
-			ExporterResponse: pbResp.ExporterResponse,
-		}
-		return nil
-	})
-	eg.Go(func() error {
-		stream, err := c.client().Status(egCtx, &pb.StatusRequest{
 			Ref: ref,
 		})
 		if err != nil {
@@ -169,8 +150,20 @@ func (c *Client) build(ctx context.Context, ref string, options pb.BuildOptions,
 				}
 				return errors.Wrap(err, "failed to receive status")
 			}
-			statusChan <- pb.FromControlStatus(resp)
+			writer.Write(pb.FromControlStatus(resp))
+		}
+	}()
+
+	eg.Go(func() error {
+		defer close(done)
+		_, err := c.client().Build(egCtx, &pb.BuildRequest{
+			Ref:     ref,
+			Options: &options,
+		})
+		if err != nil {
+			return err
 		}
+		return nil
 	})
 	if in != nil {
 		eg.Go(func() error {
@@ -232,7 +225,7 @@ func (c *Client) build(ctx context.Context, ref string, options pb.BuildOptions,
 			return eg2.Wait()
 		})
 	}
-	return resp, eg.Wait()
+	return eg.Wait()
 }
 
 func (c *Client) client() pb.ControllerClient {

controller/remote/controller.go

@@ -24,7 +24,6 @@ import (
 	"github.com/docker/buildx/util/progress"
 	"github.com/docker/buildx/version"
 	"github.com/docker/cli/cli/command"
-	"github.com/moby/buildkit/client"
 	"github.com/moby/buildkit/util/grpcerrors"
 	"github.com/pelletier/go-toml"
 	"github.com/pkg/errors"
@@ -143,8 +142,8 @@ func serveCmd(dockerCli command.Cli) *cobra.Command {
 			}()
 
 			// prepare server
-			b := NewServer(func(ctx context.Context, options *controllerapi.BuildOptions, stdin io.Reader, progress progress.Writer) (*client.SolveResponse, *build.ResultContext, error) {
+			b := NewServer(func(ctx context.Context, options *controllerapi.BuildOptions, stdin io.Reader, progress progress.Writer) (*build.ResultContext, error) {
-				return cbuild.RunBuild(ctx, dockerCli, *options, stdin, progress, true)
+				return cbuild.RunBuild(ctx, dockerCli, *options, stdin, progress)
 			})
 			defer b.Close()
 

controller/remote/server.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"io"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/docker/buildx/build"
@@ -14,12 +13,11 @@ import (
 	"github.com/docker/buildx/util/ioset"
 	"github.com/docker/buildx/util/progress"
 	"github.com/docker/buildx/version"
-	"github.com/moby/buildkit/client"
 	"github.com/pkg/errors"
 	"golang.org/x/sync/errgroup"
 )
 
-type BuildFunc func(ctx context.Context, options *pb.BuildOptions, stdin io.Reader, progress progress.Writer) (resp *client.SolveResponse, res *build.ResultContext, err error)
+type BuildFunc func(ctx context.Context, options *pb.BuildOptions, stdin io.Reader, progress progress.Writer) (res *build.ResultContext, err error)
 
 func NewServer(buildFunc BuildFunc) *Server {
 	return &Server{
@@ -34,7 +32,6 @@ type Server struct {
 }
 
 type session struct {
-	buildOnGoing atomic.Bool
 	statusChan   chan *pb.StatusResponse
 	cancelBuild  func()
 	buildOptions *pb.BuildOptions
@@ -101,28 +98,6 @@ func (m *Server) List(ctx context.Context, req *pb.ListRequest) (res *pb.ListRes
 	}, nil
 }
 
-func (m *Server) Disconnect(ctx context.Context, req *pb.DisconnectRequest) (res *pb.DisconnectResponse, err error) {
-	key := req.Ref
-	if key == "" {
-		return nil, errors.New("disconnect: empty key")
-	}
-
-	m.sessionMu.Lock()
-	if s, ok := m.session[key]; ok {
-		if s.cancelBuild != nil {
-			s.cancelBuild()
-		}
-		s.cancelRunningProcesses()
-		if s.result != nil {
-			s.result.Done()
-		}
-	}
-	delete(m.session, key)
-	m.sessionMu.Unlock()
-
-	return &pb.DisconnectResponse{}, nil
-}
-
 func (m *Server) Close() error {
 	m.sessionMu.Lock()
 	for k := range m.session {
@@ -167,15 +142,10 @@ func (m *Server) Build(ctx context.Context, req *pb.BuildRequest) (*pb.BuildResp
 	}
 	s, ok := m.session[ref]
 	if ok {
-		if !s.buildOnGoing.CompareAndSwap(false, true) {
-			m.sessionMu.Unlock()
-			return &pb.BuildResponse{}, errors.New("build ongoing")
-		}
 		s.cancelRunningProcesses()
 		s.result = nil
 	} else {
 		s = &session{}
-		s.buildOnGoing.Store(true)
 	}
 
 	s.processes = processes.NewManager()
@@ -186,33 +156,24 @@ func (m *Server) Build(ctx context.Context, req *pb.BuildRequest) (*pb.BuildResp
 	s.inputPipe = inW
 	m.session[ref] = s
 	m.sessionMu.Unlock()
-	defer func() {
-		close(statusChan)
-		m.sessionMu.Lock()
-		s, ok := m.session[ref]
-		if ok {
-			s.statusChan = nil
-			s.buildOnGoing.Store(false)
-		}
-		m.sessionMu.Unlock()
-	}()
 
 	pw := pb.NewProgressWriter(statusChan)
 
 	// Build the specified request
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
-	resp, res, buildErr := m.buildFunc(ctx, req.Options, inR, pw)
+	res, err := m.buildFunc(ctx, req.Options, inR, pw)
 	m.sessionMu.Lock()
 	if s, ok := m.session[ref]; ok {
-		// NOTE: buildFunc can return *build.ResultContext even on error (e.g. when it's implemented using (github.com/docker/buildx/controller/build).RunBuild).
 		if res != nil {
 			s.result = res
 			s.cancelBuild = cancel
 			s.buildOptions = req.Options
 			m.session[ref] = s
+
+			_, buildErr := s.result.Result(ctx)
 			if buildErr != nil {
-				buildErr = controllererrors.WrapBuild(buildErr, ref)
+				err = controllererrors.WrapBuild(buildErr, ref)
 			}
 		}
 	} else {
@@ -221,18 +182,69 @@ func (m *Server) Build(ctx context.Context, req *pb.BuildRequest) (*pb.BuildResp
 	}
 	m.sessionMu.Unlock()
 
-	if buildErr != nil {
+	if err != nil {
-		return nil, buildErr
+		return nil, err
+	}
+
+	return &pb.BuildResponse{}, nil
+}
+
+func (m *Server) Finalize(ctx context.Context, req *pb.FinalizeRequest) (*pb.FinalizeResponse, error) {
+	key := req.Ref
+	if key == "" {
+		return nil, errors.New("finalize: empty key")
 	}
 
-	if resp == nil {
+	m.sessionMu.Lock()
-		resp = &client.SolveResponse{}
+	defer m.sessionMu.Unlock()
+
+	s, ok := m.session[key]
+	if !ok {
+		return nil, errors.Errorf("unknown ref %q", key)
+	}
+	if s.result == nil {
+		return nil, errors.Errorf("no build ongoing for %q", key)
 	}
-	return &pb.BuildResponse{
+	resp, err := s.result.Wait(ctx)
+	if err != nil {
+		return nil, err
+	}
+	if s.cancelBuild != nil {
+		s.cancelBuild()
+	}
+	s.cancelRunningProcesses()
+	close(s.statusChan)
+	delete(m.session, key)
+
+	return &pb.FinalizeResponse{
 		ExporterResponse: resp.ExporterResponse,
 	}, nil
 }
 
+func (m *Server) Disconnect(ctx context.Context, req *pb.DisconnectRequest) (res *pb.DisconnectResponse, err error) {
+	key := req.Ref
+	if key == "" {
+		return nil, errors.New("disconnect: empty key")
+	}
+
+	m.sessionMu.Lock()
+	defer m.sessionMu.Unlock()
+
+	if s, ok := m.session[key]; ok {
+		if s.cancelBuild != nil {
+			s.cancelBuild()
+		}
+		close(s.statusChan)
+		s.cancelRunningProcesses()
+		if s.result != nil {
+			s.result.Close()
+		}
+	}
+	delete(m.session, key)
+
+	return &pb.DisconnectResponse{}, nil
+}
+
 func (m *Server) Status(req *pb.StatusRequest, stream pb.Controller_StatusServer) error {
 	ref := req.Ref
 	if ref == "" {

monitor/monitor.go

@@ -38,11 +38,6 @@ Available commands are:
 
 // RunMonitor provides an interactive session for running and managing containers via specified IO.
 func RunMonitor(ctx context.Context, curRef string, options *controllerapi.BuildOptions, invokeConfig controllerapi.InvokeConfig, c control.BuildxController, stdin io.ReadCloser, stdout io.WriteCloser, stderr console.File, progress progress.Writer) error {
-	defer func() {
-		if err := c.Disconnect(ctx, curRef); err != nil {
-			logrus.Warnf("disconnect error: %v", err)
-		}
-	}()
 	monitorIn, monitorOut := ioset.Pipe()
 	defer func() {
 		monitorIn.Close()
@@ -146,7 +141,7 @@ func RunMonitor(ctx context.Context, curRef string, options *controllerapi.Build
 						}
 					}
 					var resultUpdated bool
-					ref, _, err := c.Build(ctx, *bo, nil, progress) // TODO: support stdin, hold build ref
+					ref, err := c.Build(ctx, *bo, nil, progress) // TODO: support stdin, hold build ref
 					if err != nil {
 						var be *controllererrors.BuildError
 						if errors.As(err, &be) {

util/progress/printer.go

@@ -29,6 +29,7 @@ type Printer struct {
 	warnings     []client.VertexWarning
 	logMu        sync.Mutex
 	logSourceMap map[digest.Digest]interface{}
+	paused       *bool
 }
 
 func (p *Printer) Wait() error {
@@ -45,6 +46,10 @@ func (p *Printer) Warnings() []client.VertexWarning {
 	return p.warnings
 }
 
+func (p *Printer) Pause(v bool) {
+	*p.paused = v
+}
+
 func (p *Printer) ValidateLogSource(dgst digest.Digest, v interface{}) bool {
 	p.logMu.Lock()
 	defer p.logMu.Unlock()
@@ -74,10 +79,12 @@ func NewPrinter(ctx context.Context, w io.Writer, out console.File, mode string,
 	statusCh := make(chan *client.SolveStatus)
 	doneCh := make(chan struct{})
 
+	paused := false
 	pw := &Printer{
 		status:       statusCh,
 		done:         doneCh,
 		logSourceMap: map[digest.Digest]interface{}{},
+		paused:       &paused,
 	}
 
 	if v := os.Getenv("BUILDKIT_PROGRESS"); v != "" && mode == PrinterModeAuto {
@@ -101,7 +108,7 @@ func NewPrinter(ctx context.Context, w io.Writer, out console.File, mode string,
 	go func() {
 		resumeLogs := logutil.Pause(logrus.StandardLogger())
 		// not using shared context to not disrupt display but let is finish reporting errors
-		pw.warnings, pw.err = progressui.DisplaySolveStatus(ctx, c, w, statusCh, solveStatusOpt...)
+		pw.warnings, pw.err = progressui.DisplaySolveStatus(ctx, c, w, statusCh, pw.paused, solveStatusOpt...)
 		resumeLogs()
 		close(doneCh)
 	}()

vendor/github.com/moby/buildkit/util/progress/progressui/display.go

@@ -42,7 +42,7 @@ func WithDesc(text string, console string) DisplaySolveStatusOpt {
 	}
 }
 
-func DisplaySolveStatus(ctx context.Context, c console.Console, w io.Writer, ch chan *client.SolveStatus, opts ...DisplaySolveStatusOpt) ([]client.VertexWarning, error) {
+func DisplaySolveStatus(ctx context.Context, c console.Console, w io.Writer, ch chan *client.SolveStatus, paused *bool, opts ...DisplaySolveStatusOpt) ([]client.VertexWarning, error) {
 	modeConsole := c != nil
 
 	dsso := &displaySolveStatusOpts{}
@@ -78,6 +78,11 @@ func DisplaySolveStatus(ctx context.Context, c console.Console, w io.Writer, ch
 
 	displayLimiter := rate.NewLimiter(rate.Every(displayTimeout), 1)
 
+	ispaused := false
+	if paused != nil {
+		ispaused = *paused
+	}
+
 	var height int
 	width, _ := disp.getSize()
 	for {
@@ -93,6 +98,10 @@ func DisplaySolveStatus(ctx context.Context, c console.Console, w io.Writer, ch
 			}
 		}
 
+		if paused != nil && *paused && ispaused {
+			continue
+		}
+
 		if modeConsole {
 			width, height = disp.getSize()
 			if done {
@@ -115,6 +124,10 @@ func DisplaySolveStatus(ctx context.Context, c console.Console, w io.Writer, ch
 				ticker = time.NewTicker(tickerTimeout)
 			}
 		}
+
+		if paused != nil {
+			ispaused = *paused
+		}
 	}
 }
 

vendor/github.com/moby/buildkit/util/progress/progresswriter/printer.go

@@ -87,7 +87,7 @@ func NewPrinter(ctx context.Context, out console.File, mode string) (Writer, err
 
 	go func() {
 		// not using shared context to not disrupt display but let is finish reporting errors
-		_, pw.err = progressui.DisplaySolveStatus(ctx, c, out, statusCh)
+		_, pw.err = progressui.DisplaySolveStatus(ctx, c, out, statusCh, nil)
 		close(doneCh)
 	}()
 	return pw, nil