Report the build's own error and refuse daemons too old for BuildKit (closes #234)

A build whose output ends in Docker's error line now fails with that
error, instead of going on to inspect a tag that was never created. The
build output is written to the deployment log before the failure is
recorded, so the log ends in order. Before building, upaas compares the
daemon's API version with 1.39 (Docker Engine 18.09), the first that
builds with BuildKit without experimental mode, and fails the deploy on
an older daemon instead of letting it use the legacy builder. The
README's Compose section gives the update command and the Docker Engine
versions builds need.

Model: opus-5-5

internal/service/deploy/deploy.go

@@ -923,7 +923,6 @@ func (svc *Service) buildImage(
 
 	// Create log writer that flushes build output to deployment logs every second
 	logWriter := newDeploymentLogWriter(ctx, deployment)
-	defer logWriter.Close()
 
 	// BuildImage creates a tar archive from the local filesystem,
 	// so it needs the container path where files exist, not the host path.
@@ -933,6 +932,10 @@ func (svc *Service) buildImage(
 		Tags:           []string{imageTag},
 		LogWriter:      logWriter,
 	})
+
+	// Write the rest of the build output to the log before the result.
+	logWriter.Close()
+
 	if err != nil {
 		svc.notify.NotifyBuildFailed(ctx, app, deployment, err)
 		svc.failDeployment(

internal/service/deploy/deploy_build_test.go

@@ -0,0 +1,91 @@
+package deploy_test
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/fx/fxtest"
+
+	"sneak.berlin/go/upaas/internal/config"
+	"sneak.berlin/go/upaas/internal/database"
+	"sneak.berlin/go/upaas/internal/docker"
+	"sneak.berlin/go/upaas/internal/logger"
+	"sneak.berlin/go/upaas/internal/models"
+	"sneak.berlin/go/upaas/internal/service/deploy"
+)
+
+// TestBuildImageLogsBuildErrorBeforeDeployError runs a build that fails
+// against a fake Docker API and checks that the deploy fails with the
+// build's own error, which the deployment log shows before the deploy's.
+func TestBuildImageLogsBuildErrorBeforeDeployError(t *testing.T) {
+	t.Parallel()
+
+	srv := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			w.Header().Set("Content-Type", "application/json")
+
+			switch {
+			case strings.HasSuffix(r.URL.Path, "/containers/create"):
+				_, _ = w.Write([]byte(`{"Id":"gitcontainer"}`))
+			case strings.HasSuffix(r.URL.Path, "/version"):
+				_, _ = w.Write([]byte(`{"Version":"27.3.1","ApiVersion":"1.47"}`))
+			case strings.HasSuffix(r.URL.Path, "/build"):
+				_, _ = w.Write([]byte(`{"stream":"Step 1/1 : RUN false\n"}` + "\n" +
+					`{"errorDetail":{"message":"exit code: 1"},"error":"exit code: 1"}`))
+			default:
+				// The steps of the git clone, which succeeds.
+				_, _ = w.Write([]byte(`{}`))
+			}
+		},
+	))
+	t.Cleanup(srv.Close)
+
+	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
+	lifecycle := fxtest.NewLifecycle(t)
+
+	dockerClient, err := docker.New(lifecycle, docker.Params{
+		Logger: logger.NewForTest(log),
+		Config: &config.Config{DockerHost: "tcp://" + srv.Listener.Addr().String()},
+	})
+	require.NoError(t, err)
+
+	lifecycle.RequireStart()
+	t.Cleanup(lifecycle.RequireStop)
+
+	db := database.NewTestDatabase(t)
+	ctx := context.Background()
+
+	app := models.NewApp(db)
+	app.ID = "buildapp-id"
+	app.Name = "buildapp"
+	app.Branch = "main"
+	require.NoError(t, app.Save(ctx))
+
+	deployment := models.NewDeployment(db)
+	deployment.AppID = app.ID
+	require.NoError(t, deployment.Save(ctx))
+
+	dataDir := t.TempDir()
+	cfg := &config.Config{DataDir: dataDir, HostDataDir: dataDir}
+
+	// The service has no notify service: the app has no ntfy topic and no
+	// Slack webhook, so the build failure notification sends nothing.
+	svc := deploy.NewTestServiceWithConfig(log, cfg, dockerClient)
+
+	_, err = svc.BuildImage(ctx, app, deployment)
+	require.EqualError(t, err, "failed to build image: exit code: 1")
+
+	logs := deployment.Logs.String
+	buildError := strings.Index(logs, "ERROR: exit code: 1")
+	deployError := strings.Index(logs, "ERROR: failed to build image: exit code: 1")
+
+	require.NotEqual(t, -1, buildError, logs)
+	assert.Less(t, buildError, deployError, logs)
+}

internal/service/deploy/export_test.go

@@ -100,6 +100,15 @@ func (svc *Service) RecordDeployedImage(
 	return svc.recordDeployedImage(ctx, app, deployment, imageID)
 }
 
+// BuildImage exposes buildImage for testing.
+func (svc *Service) BuildImage(
+	ctx context.Context,
+	app *models.App,
+	deployment *models.Deployment,
+) (docker.ImageID, error) {
+	return svc.buildImage(ctx, app, deployment)
+}
+
 // BuildContainerOptionsExported exposes buildContainerOptions for testing.
 func (svc *Service) BuildContainerOptionsExported(
 	ctx context.Context,