TODO.md

@@ -20,6 +20,15 @@ regress.
 
 # Completed Steps
 
+- 2026-09-29: Built images are tagged `upaas-<app>:<short hash>`, git's short
+  form of the commit built, instead of the deployment number. A redeploy of a
+  commit gives its tag to the new image; the old one is kept while the app runs
+  it or Rollback would start it, then removed by its ID, found among the images
+  the app's deployments recorded. The removal of old images now keeps every
+  image any app runs or would roll back to. The clone now reads the commit from
+  git's output, which Docker's log headers had hidden, so manual deploys record
+  their commit too (#239).
+
 - 2026-09-29: The app page is 50% wider on large screens (84rem instead of
   56rem), its build log and container log boxes are twice as tall, the build log
   sits between the webhook URL and the environment variables, and the container

internal/docker/client.go

@@ -25,6 +25,7 @@ import (
 	"github.com/docker/docker/client"
 	"github.com/docker/docker/pkg/archive"
 	"github.com/docker/docker/pkg/jsonmessage"
+	"github.com/docker/docker/pkg/stdcopy"
 	"github.com/docker/go-connections/nat"
 	controlapi "github.com/moby/buildkit/api/services/control"
 	buildkitclient "github.com/moby/buildkit/client"
@@ -491,6 +492,7 @@ type cloneConfig struct {
 type CloneResult struct {
 	Output    string // Combined stdout/stderr from git clone
 	CommitSHA string // The HEAD commit SHA after clone/checkout
+	ShortSHA  string // git's short form of CommitSHA (git rev-parse --short)
 }
 
 // CloneRepo clones a git repository using SSH and optionally checks out a
@@ -553,7 +555,7 @@ func (c *Client) RemoveImage(ctx context.Context, imageID ImageID) error {
 }
 
 // ListImageTags returns the tags in the given repository, such as
-// "upaas-myapp:12" in "upaas-myapp", each with the ID of its image.
+// "upaas-myapp:1a2b3c4" in "upaas-myapp", each with the ID of its image.
 // Tags the same image has in other repositories are left out.
 func (c *Client) ListImageTags(
 	ctx context.Context,
@@ -583,19 +585,44 @@ func (c *Client) ListImageTags(
 	return tags, nil
 }
 
-// RemoveImageTag removes a tag such as "upaas-myapp:12", without force.
+// ListUntaggedImages returns the IDs of the images that have no tag, such
-// Docker then deletes the image, and the untagged images it was built on,
+// as one whose tag a later build gave to the image it built.
-// only if no other tag and no container still uses it.
+func (c *Client) ListUntaggedImages(ctx context.Context) ([]ImageID, error) {
-func (c *Client) RemoveImageTag(ctx context.Context, tag string) error {
+	if c.docker == nil {
+		return nil, ErrNotConnected
+	}
+
+	images, err := c.docker.ImageList(ctx, image.ListOptions{
+		Filters: filters.NewArgs(filters.Arg("dangling", "true")),
+	})
+	if err != nil {
+		return nil, fmt.Errorf("failed to list untagged images: %w", err)
+	}
+
+	imageIDs := make([]ImageID, 0, len(images))
+
+	for _, img := range images {
+		imageIDs = append(imageIDs, ImageID(img.ID))
+	}
+
+	return imageIDs, nil
+}
+
+// RemoveImageTag removes the tag name, such as "upaas-myapp:1a2b3c4",
+// without force. Docker then deletes the image, and the untagged images it
+// was built on, only if no other tag and no container still uses it. If name
+// is instead the ID of an untagged image, it removes that image unless a
+// container uses it.
+func (c *Client) RemoveImageTag(ctx context.Context, name string) error {
 	if c.docker == nil {
 		return ErrNotConnected
 	}
 
-	_, err := c.docker.ImageRemove(ctx, tag, image.RemoveOptions{
+	_, err := c.docker.ImageRemove(ctx, name, image.RemoveOptions{
 		PruneChildren: true,
 	})
 	if err != nil && !client.IsErrNotFound(err) {
-		return fmt.Errorf("failed to remove image tag %s: %w", tag, err)
+		return fmt.Errorf("failed to remove image %s: %w", name, err)
 	}
 
 	return nil
@@ -850,11 +877,13 @@ func (c *Client) createGitContainer(
 		// Clone without depth limit so we can checkout any commit, then checkout specific SHA
 		script = `git clone --branch "$CLONE_BRANCH" "$CLONE_URL" /repo` +
 			` && cd /repo && git checkout "$CLONE_SHA"` +
-			` && echo COMMIT:$(git rev-parse HEAD)`
+			` && echo COMMIT:$(git rev-parse HEAD)` +
+			` && echo SHORT_SHA:$(git rev-parse --short HEAD)`
 	} else {
 		// Shallow clone of branch HEAD, then output commit SHA
 		script = `git clone --depth 1 --branch "$CLONE_BRANCH" "$CLONE_URL" /repo` +
-			` && cd /repo && echo COMMIT:$(git rev-parse HEAD)`
+			` && cd /repo && echo COMMIT:$(git rev-parse HEAD)` +
+			` && echo SHORT_SHA:$(git rev-parse --short HEAD)`
 	}
 
 	env := []string{
@@ -921,7 +950,7 @@ func (c *Client) runGitClone(
 		return nil, fmt.Errorf("error waiting for git container: %w", err)
 	case status := <-statusCh:
 		// Always capture logs for the result
-		logs, _ := c.ContainerLogs(ctx, containerID, "100")
+		logs := c.gitContainerOutput(ctx, containerID)
 
 		if status.StatusCode != 0 {
 			return nil, fmt.Errorf(
@@ -932,23 +961,62 @@ func (c *Client) runGitClone(
 			)
 		}
 
-		// Parse commit SHA from output (looks for "COMMIT:<sha>" line)
+		// Parse the commit from the "COMMIT:" and "SHORT_SHA:" lines.
-		commitSHA := parseCommitSHA(logs)
+		result := &CloneResult{
+			Output:    logs,
+			CommitSHA: parseCommitSHA(logs, commitMarker),
+			ShortSHA:  parseCommitSHA(logs, shortSHAMarker),
+		}
 
-		return &CloneResult{Output: logs, CommitSHA: commitSHA}, nil
+		// The short hash names the image the deploy builds.
+		if result.ShortSHA == "" {
+			return nil, fmt.Errorf("%w: no short commit hash in its output: %s",
+				ErrGitCloneFailed, logs)
+		}
+
+		return result, nil
 	}
 }
 
-// commitMarker is the prefix used to identify commit SHA in clone output.
+// gitContainerOutput returns the last 100 lines the git container wrote.
-const commitMarker = "COMMIT:"
+// Docker puts a header before each line a container without a terminal
+// writes; stdcopy removes them so that the lines can be parsed.
+func (c *Client) gitContainerOutput(
+	ctx context.Context,
+	containerID ContainerID,
+) string {
+	reader, err := c.docker.ContainerLogs(ctx, containerID.String(), container.LogsOptions{
+		ShowStdout: true,
+		ShowStderr: true,
+		Tail:       "100",
+	})
+	if err != nil {
+		return ""
+	}
 
-// parseCommitSHA extracts the commit SHA from git clone output.
+	defer func() { _ = reader.Close() }()
-// It looks for a line starting with "COMMIT:" and returns the SHA after it.
+
-func parseCommitSHA(output string) string {
+	var output strings.Builder
+
+	_, _ = stdcopy.StdCopy(&output, &output, reader)
+
+	return output.String()
+}
+
+// Prefixes of the lines in the clone output that carry the commit checked
+// out, in full and in git's short form.
+const (
+	commitMarker   = "COMMIT:"
+	shortSHAMarker = "SHORT_SHA:"
+)
+
+// parseCommitSHA extracts a commit SHA from git clone output.
+// It looks for a line starting with marker and returns the SHA after it.
+func parseCommitSHA(output, marker string) string {
 	for line := range strings.SplitSeq(output, "\n") {
 		line = strings.TrimSpace(line)
 
-		sha, found := strings.CutPrefix(line, commitMarker)
+		sha, found := strings.CutPrefix(line, marker)
 		if found {
 			return strings.TrimSpace(sha)
 		}

internal/docker/validation_test.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"log/slog"
 	"net/http"
 	"net/http/httptest"
@@ -16,6 +17,7 @@ import (
 	"time"
 
 	"github.com/docker/docker/client"
+	"github.com/docker/docker/pkg/stdcopy"
 	controlapi "github.com/moby/buildkit/api/services/control"
 )
 
@@ -203,6 +205,8 @@ func TestPerformCloneRemovesContainerVolumes(t *testing.T) {
 						<-r.Context().Done()
 					case strings.HasSuffix(r.URL.Path, "/wait"):
 						_, _ = fmt.Fprintf(w, `{"StatusCode":%d}`, tt.exitCode)
+					case strings.HasSuffix(r.URL.Path, "/logs"):
+						writeCloneOutput(w)
 					default:
 						_, _ = w.Write([]byte(`{}`))
 					}
@@ -244,6 +248,62 @@ func TestPerformCloneRemovesContainerVolumes(t *testing.T) {
 	}
 }
 
+// cloneCommit is the commit the fake clones in these tests check out.
+const cloneCommit = "1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b"
+
+// writeCloneOutput writes the output of a git clone of cloneCommit as
+// Docker sends a container's log: each line after a header.
+func writeCloneOutput(w io.Writer) {
+	stdout := stdcopy.NewStdWriter(w, stdcopy.Stdout)
+	stderr := stdcopy.NewStdWriter(w, stdcopy.Stderr)
+
+	_, _ = stderr.Write([]byte("Cloning into '/repo'...\n"))
+	_, _ = stdout.Write([]byte("COMMIT:" + cloneCommit + "\n"))
+	_, _ = stdout.Write([]byte("SHORT_SHA:1a2b3c4\n"))
+}
+
+// TestCloneRepoReadsCommit runs a clone against a fake Docker API and
+// checks that the commit checked out is read from the clone's output, in
+// full and in git's short form.
+func TestCloneRepoReadsCommit(t *testing.T) {
+	t.Parallel()
+
+	srv := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			switch {
+			case strings.HasSuffix(r.URL.Path, "/containers/create"):
+				_, _ = w.Write([]byte(`{"Id":"gitcontainer"}`))
+			case strings.HasSuffix(r.URL.Path, "/logs"):
+				writeCloneOutput(w)
+			default:
+				_, _ = w.Write([]byte(`{}`))
+			}
+		},
+	))
+	t.Cleanup(srv.Close)
+
+	dockerAPI, err := client.NewClientWithOpts(
+		client.WithHost("tcp://" + srv.Listener.Addr().String()),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	c := &Client{docker: dockerAPI, log: slog.Default()}
+
+	result, err := c.CloneRepo(
+		t.Context(), "git@example.com:repo.git", mainBranch, "", "fake-key",
+		t.TempDir(), t.TempDir(),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if result.CommitSHA != cloneCommit || result.ShortSHA != "1a2b3c4" {
+		t.Errorf("got commit %q, short %q", result.CommitSHA, result.ShortSHA)
+	}
+}
+
 // TestPerformBuildUsesBuildKit runs a build against a fake Docker API and
 // checks that it asks for BuildKit and that BuildKit's progress reaches the
 // build log as plain text.

internal/models/deployment.go

@@ -203,11 +203,12 @@ func (d *Deployment) insert(ctx context.Context) error {
 func (d *Deployment) update(ctx context.Context) error {
 	query := `
 		UPDATE deployments SET
-			image_id = ?, container_id = ?, status = ?, logs = ?, finished_at = ?
+			commit_sha = ?, image_id = ?, container_id = ?, status = ?, logs = ?,
+			finished_at = ?
 		WHERE id = ?`
 
 	_, err := d.db.Exec(ctx, query,
-		d.ImageID, d.ContainerID, d.Status, d.Logs, d.FinishedAt, d.ID,
+		d.CommitSHA, d.ImageID, d.ContainerID, d.Status, d.Logs, d.FinishedAt, d.ID,
 	)
 
 	return err
@@ -295,6 +296,45 @@ func FindDeploymentsByAppID(
 	return deployments, nil
 }
 
+// FindDeploymentImageIDs returns the IDs of the images an app's
+// deployments built or rolled back to.
+func FindDeploymentImageIDs(
+	ctx context.Context,
+	deployDB *database.Database,
+	appID string,
+) ([]string, error) {
+	rows, err := deployDB.Query(ctx, `
+		SELECT DISTINCT image_id FROM deployments
+		WHERE app_id = ? AND image_id IS NOT NULL`,
+		appID,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("querying deployment image IDs: %w", err)
+	}
+
+	defer func() { _ = rows.Close() }()
+
+	var imageIDs []string
+
+	for rows.Next() {
+		var imageID string
+
+		scanErr := rows.Scan(&imageID)
+		if scanErr != nil {
+			return nil, fmt.Errorf("scanning deployment image ID: %w", scanErr)
+		}
+
+		imageIDs = append(imageIDs, imageID)
+	}
+
+	rowsErr := rows.Err()
+	if rowsErr != nil {
+		return nil, fmt.Errorf("iterating deployment image IDs: %w", rowsErr)
+	}
+
+	return imageIDs, nil
+}
+
 // LatestDeploymentForApp finds the most recent deployment for an app.
 //
 //nolint:nilnil // returning nil,nil is idiomatic for "not found" in Active Record

internal/service/deploy/deploy.go

@@ -735,44 +735,103 @@ func (svc *Service) recordDeployedImage(
 	return nil
 }
 
-// removeUnusedImages removes the app's tags (upaas-<app>:<deployment>, set by
+// removeUnusedImages removes the app's images except those an app's running
-// buildImage) except those of the image the running container uses and the
+// container uses or its Rollback would start. Docker deletes a tagged image
-// one Rollback would start. Docker deletes an image only once no other tag,
+// only once no other tag, such as another app's, and no container still
-// such as another app's, and no container still uses it.
+// uses it.
 func (svc *Service) removeUnusedImages(
 	ctx context.Context,
 	app *models.App,
 	deployment *models.Deployment,
 ) {
-	tags, err := svc.docker.ListImageTags(ctx, "upaas-"+app.Name)
+	images, err := svc.findAppImages(ctx, app)
 	if err != nil {
 		svc.log.Error("failed to list app images", "error", err, "app", app.Name)
 
 		return
 	}
 
-	for _, tag := range slices.Sorted(maps.Keys(tags)) {
+	keep, err := svc.imagesToKeep(ctx)
-		imageID := tags[tag].String()
+	if err != nil {
-		if imageID == app.ImageID.String || imageID == app.PreviousImageID.String {
+		svc.log.Error("failed to list the images apps use", "error", err, "app", app.Name)
+
+		return
+	}
+
+	for _, name := range slices.Sorted(maps.Keys(images)) {
+		if keep[images[name].String()] {
 			continue
 		}
 
-		removeErr := svc.docker.RemoveImageTag(ctx, tag)
+		removeErr := svc.docker.RemoveImageTag(ctx, name)
 		if removeErr != nil {
 			svc.log.Error("failed to remove old image",
-				"error", removeErr, "app", app.Name, "tag", tag)
+				"error", removeErr, "app", app.Name, "image", name)
 			_ = deployment.AppendLog(
 				ctx,
-				"WARNING: failed to remove old image "+tag+": "+removeErr.Error(),
+				"WARNING: failed to remove old image "+name+": "+removeErr.Error(),
 			)
 
 			continue
 		}
 
-		_ = deployment.AppendLog(ctx, "Removed old image: "+tag)
+		_ = deployment.AppendLog(ctx, "Removed old image: "+name)
 	}
 }
 
+// findAppImages returns the app's images, each under the name it is removed
+// by: its tag, upaas-<app>:<short hash> as set by buildImage, or its ID if
+// it has none. A redeploy of a commit gives the commit's tag to the new
+// image, so the old one is found among the images the app's deployments
+// recorded.
+func (svc *Service) findAppImages(
+	ctx context.Context,
+	app *models.App,
+) (map[string]docker.ImageID, error) {
+	images, err := svc.docker.ListImageTags(ctx, "upaas-"+app.Name)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list image tags: %w", err)
+	}
+
+	untagged, err := svc.docker.ListUntaggedImages(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list untagged images: %w", err)
+	}
+
+	recorded, err := models.FindDeploymentImageIDs(ctx, svc.db, app.ID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to find deployment images: %w", err)
+	}
+
+	for _, imageID := range untagged {
+		if slices.Contains(recorded, imageID.String()) {
+			images[imageID.String()] = imageID
+		}
+	}
+
+	return images, nil
+}
+
+// imagesToKeep returns the IDs of the image each app's running container
+// uses and the one its Rollback would start. It covers every app because
+// apps that build the same commit can share an image, and a redeploy can
+// take the tag that kept the image for one of them.
+func (svc *Service) imagesToKeep(ctx context.Context) (map[string]bool, error) {
+	apps, err := models.AllApps(ctx, svc.db)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list apps: %w", err)
+	}
+
+	keep := make(map[string]bool)
+
+	for _, app := range apps {
+		keep[app.ImageID.String] = true
+		keep[app.PreviousImageID.String] = true
+	}
+
+	return keep, nil
+}
+
 // cleanupCancelledDeploy removes orphan resources left by a cancelled deployment.
 func (svc *Service) cleanupCancelledDeploy(
 	ctx context.Context,
@@ -912,14 +971,14 @@ func (svc *Service) buildImage(
 	app *models.App,
 	deployment *models.Deployment,
 ) (docker.ImageID, error) {
-	workDir, cleanup, err := svc.cloneRepository(ctx, app, deployment)
+	workDir, shortSHA, cleanup, err := svc.cloneRepository(ctx, app, deployment)
 	if err != nil {
 		return "", err
 	}
 
 	defer cleanup()
 
-	imageTag := fmt.Sprintf("upaas-%s:%d", app.Name, deployment.ID)
+	imageTag := "upaas-" + app.Name + ":" + shortSHA
 
 	// Create log writer that flushes build output to deployment logs every second
 	logWriter := newDeploymentLogWriter(ctx, deployment)
@@ -954,11 +1013,14 @@ func (svc *Service) buildImage(
 	return imageID, nil
 }
 
+// cloneRepository clones the app's repository for a build. It returns the
+// directory of the clone, git's short form of the commit checked out, and a
+// function that removes the clone.
 func (svc *Service) cloneRepository(
 	ctx context.Context,
 	app *models.App,
 	deployment *models.Deployment,
-) (string, func(), error) {
+) (string, string, func(), error) {
 	// Use a subdirectory of DataDir for builds since it's mounted from the host
 	// and accessible to Docker for bind mounts (unlike /tmp inside the container).
 	// Structure: builds/<appname>/<deployment-id>-<random>/
@@ -975,7 +1037,7 @@ func (svc *Service) cloneRepository(
 			fmt.Errorf("failed to create builds dir: %w", err),
 		)
 
-		return "", nil, fmt.Errorf("failed to create builds dir: %w", err)
+		return "", "", nil, fmt.Errorf("failed to create builds dir: %w", err)
 	}
 
 	buildDir, err := os.MkdirTemp(appBuildsDir, fmt.Sprintf("%d-*", deployment.ID))
@@ -987,7 +1049,7 @@ func (svc *Service) cloneRepository(
 			fmt.Errorf("failed to create temp dir: %w", err),
 		)
 
-		return "", nil, fmt.Errorf("failed to create temp dir: %w", err)
+		return "", "", nil, fmt.Errorf("failed to create temp dir: %w", err)
 	}
 
 	cleanup := func() { _ = os.RemoveAll(buildDir) }
@@ -1023,7 +1085,7 @@ func (svc *Service) cloneRepository(
 			fmt.Errorf("failed to clone repo: %w", cloneErr),
 		)
 
-		return "", nil, fmt.Errorf("failed to clone repo: %w", cloneErr)
+		return "", "", nil, fmt.Errorf("failed to clone repo: %w", cloneErr)
 	}
 
 	svc.processCloneResult(ctx, app, deployment, cloneResult, commitSHA)
@@ -1031,7 +1093,7 @@ func (svc *Service) cloneRepository(
 	// Return the 'work' subdirectory where the repo was cloned
 	workDir := filepath.Join(buildDir, "work")
 
-	return workDir, cleanup, nil
+	return workDir, cloneResult.ShortSHA, cleanup, nil
 }
 
 // processCloneResult handles the result of a git clone operation.

internal/service/deploy/deploy_build_test.go

@@ -34,6 +34,8 @@ func TestBuildImageLogsBuildErrorBeforeDeployError(t *testing.T) {
 			switch {
 			case strings.HasSuffix(r.URL.Path, "/containers/create"):
 				_, _ = w.Write([]byte(`{"Id":"gitcontainer"}`))
+			case strings.HasSuffix(r.URL.Path, "/logs"):
+				writeCloneOutput(w, "abc1234")
 			case strings.HasSuffix(r.URL.Path, "/version"):
 				_, _ = w.Write([]byte(`{"Version":"27.3.1","ApiVersion":"1.47"}`))
 			case strings.HasSuffix(r.URL.Path, "/build"):
@@ -77,7 +79,7 @@ func TestBuildImageLogsBuildErrorBeforeDeployError(t *testing.T) {
 
 	// 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)
+	svc := deploy.NewTestServiceWithConfig(log, cfg, db, dockerClient)
 
 	_, err = svc.BuildImage(ctx, app, deployment)
 	require.EqualError(t, err, "failed to build image: exit code: 1")

internal/service/deploy/deploy_cleanup_test.go

@@ -20,7 +20,7 @@ func TestCleanupCancelledDeploy_RemovesBuildDir(t *testing.T) {
 	tmpDir := t.TempDir()
 	cfg := &config.Config{DataDir: tmpDir}
 
-	svc := deploy.NewTestServiceWithConfig(slog.Default(), cfg, nil)
+	svc := deploy.NewTestServiceWithConfig(slog.Default(), cfg, nil, nil)
 
 	// Create a fake build directory matching the deployment pattern
 	appName := "test-app"
@@ -59,7 +59,7 @@ func TestCleanupCancelledDeploy_NoBuildDir(t *testing.T) {
 	tmpDir := t.TempDir()
 	cfg := &config.Config{DataDir: tmpDir}
 
-	svc := deploy.NewTestServiceWithConfig(slog.Default(), cfg, nil)
+	svc := deploy.NewTestServiceWithConfig(slog.Default(), cfg, nil, nil)
 
 	// Should not panic when build dir doesn't exist
 	svc.CleanupCancelledDeploy(context.Background(), "nonexistent-app", 1, "")

internal/service/deploy/deploy_images_test.go

@@ -3,14 +3,21 @@ package deploy_test
 import (
 	"context"
 	"database/sql"
+	"encoding/json"
+	"fmt"
+	"io"
 	"log/slog"
+	"maps"
 	"net/http"
 	"net/http/httptest"
 	"os"
+	"slices"
 	"strings"
 	"sync"
 	"testing"
 
+	"github.com/docker/docker/api/types/image"
+	"github.com/docker/docker/pkg/stdcopy"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/fx/fxtest"
@@ -23,45 +30,139 @@ import (
 	"sneak.berlin/go/upaas/internal/service/deploy"
 )
 
-// TestRecordDeployedImageRemovesOldImages runs the step after a deploy
+// fakeImageAPI is a fake Docker API that keeps images and their tags as
-// against a fake Docker API. Image one is also tagged for another app,
+// Docker does: a build gives its tag to the image it builds, and removing
-// image two was the previous image, three the current one, four is new.
+// an image's last tag, or an untagged image by its ID, deletes the image.
-func TestRecordDeployedImageRemovesOldImages(t *testing.T) {
+// It also answers the steps of a git clone that reports shortSHA.
-	t.Parallel()
+type fakeImageAPI struct {
-
-	var (
 	mu       sync.Mutex
-		removed []string
+	images   map[string][]string // image ID -> tags
-		forced  bool
+	shortSHA string              // the commit's short hash the clone reports
-	)
+	nextID   string              // ID of the image the next build creates
+	removed  []string            // each tag or ID removed
+	forced   bool                // whether a removal was forced
+}
+
+func (api *fakeImageAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	api.mu.Lock()
+	defer api.mu.Unlock()
 
-	srv := httptest.NewServer(http.HandlerFunc(
-		func(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 
+	_, name, isImage := strings.Cut(r.URL.Path, "/images/")
+
 	switch {
-			case r.Method == http.MethodDelete:
-				_, name, _ := strings.Cut(r.URL.Path, "/images/")
-
-				mu.Lock()
-
-				removed = append(removed, name)
-				forced = forced || r.URL.Query().Get("force") != ""
-				mu.Unlock()
-
-				_, _ = w.Write([]byte(`[]`))
 	case strings.HasSuffix(r.URL.Path, "/images/json"):
-				_, _ = w.Write([]byte(`[
+		dangling := strings.Contains(r.URL.Query().Get("filters"), "dangling")
-					{"Id":"sha256:one","RepoTags":["upaas-myapp:1","upaas-otherapp:7"]},
+		api.listImages(w, dangling)
-					{"Id":"sha256:two","RepoTags":["upaas-myapp:2"]},
+	case isImage && r.Method == http.MethodDelete:
-					{"Id":"sha256:three","RepoTags":["upaas-myapp:3"]},
+		api.forced = api.forced || r.URL.Query().Get("force") != ""
-					{"Id":"sha256:four","RepoTags":["upaas-myapp:4"]}
+		api.removeImage(w, name)
-				]`))
+	case isImage && strings.HasSuffix(name, "/json"):
+		api.inspectImage(w, strings.TrimSuffix(name, "/json"))
+	case strings.HasSuffix(r.URL.Path, "/build"):
+		tag := r.URL.Query().Get("t")
+		api.untag(tag)
+		api.images[api.nextID] = append(api.images[api.nextID], tag)
+	case strings.HasSuffix(r.URL.Path, "/version"):
+		_, _ = w.Write([]byte(`{"Version":"27.3.1","ApiVersion":"1.47"}`))
+	case strings.HasSuffix(r.URL.Path, "/containers/create"):
+		_, _ = w.Write([]byte(`{"Id":"gitcontainer"}`))
+	case strings.HasSuffix(r.URL.Path, "/logs"):
+		writeCloneOutput(w, api.shortSHA)
 	default:
+		// The other steps of the git clone, which succeeds.
 		_, _ = w.Write([]byte(`{}`))
 	}
-		},
+}
-	))
+
+// listImages lists the untagged images, or else the tagged ones.
+func (api *fakeImageAPI) listImages(w http.ResponseWriter, dangling bool) {
+	list := []image.Summary{}
+
+	for _, id := range slices.Sorted(maps.Keys(api.images)) {
+		if (len(api.images[id]) == 0) == dangling {
+			list = append(list, image.Summary{ID: id, RepoTags: api.images[id]})
+		}
+	}
+
+	data, err := json.Marshal(list)
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+
+		return
+	}
+
+	_, _ = w.Write(data)
+}
+
+func (api *fakeImageAPI) inspectImage(w http.ResponseWriter, name string) {
+	for id, tags := range api.images {
+		if id == name || slices.Contains(tags, name) {
+			_, _ = fmt.Fprintf(w, `{"Id":%q}`, id)
+
+			return
+		}
+	}
+
+	w.WriteHeader(http.StatusNotFound)
+	_, _ = w.Write([]byte(`{"message":"No such image"}`))
+}
+
+func (api *fakeImageAPI) removeImage(w http.ResponseWriter, name string) {
+	api.removed = append(api.removed, name)
+
+	id := name
+	if _, isID := api.images[name]; !isID {
+		id = api.untag(name)
+	}
+
+	if len(api.images[id]) == 0 {
+		delete(api.images, id)
+	}
+
+	_, _ = w.Write([]byte(`[]`))
+}
+
+// untag removes tag from the image that has it, leaving the image, and
+// returns the image's ID.
+func (api *fakeImageAPI) untag(tag string) string {
+	for id, tags := range api.images {
+		if slices.Contains(tags, tag) {
+			api.images[id] = slices.DeleteFunc(tags, func(t string) bool { return t == tag })
+
+			return id
+		}
+	}
+
+	return ""
+}
+
+// state returns each image's tags and each tag or ID removed.
+func (api *fakeImageAPI) state() (map[string][]string, []string) {
+	api.mu.Lock()
+	defer api.mu.Unlock()
+
+	return maps.Clone(api.images), slices.Clone(api.removed)
+}
+
+// writeCloneOutput writes the line of a git clone's output that gives the
+// commit's short hash, as Docker sends a container's log: after a header.
+func writeCloneOutput(w io.Writer, shortSHA string) {
+	out := stdcopy.NewStdWriter(w, stdcopy.Stdout)
+
+	_, _ = fmt.Fprintf(out, "SHORT_SHA:%s\n", shortSHA)
+}
+
+// newImageTestService returns a deploy service that uses api as its
+// Docker API, and its database.
+func newImageTestService(
+	t *testing.T,
+	api *fakeImageAPI,
+) (*deploy.Service, *database.Database) {
+	t.Helper()
+
+	srv := httptest.NewServer(api)
 	t.Cleanup(srv.Close)
 
 	log := slog.New(slog.NewTextHandler(os.Stderr, nil))
@@ -77,30 +178,155 @@ func TestRecordDeployedImageRemovesOldImages(t *testing.T) {
 	t.Cleanup(lifecycle.RequireStop)
 
 	db := database.NewTestDatabase(t)
-	ctx := context.Background()
+	dataDir := t.TempDir()
+	cfg := &config.Config{DataDir: dataDir, HostDataDir: dataDir}
+
+	return deploy.NewTestServiceWithConfig(log, cfg, db, dockerClient), db
+}
+
+// saveApp saves an app with the given current and previous image.
+func saveApp(
+	t *testing.T,
+	db *database.Database,
+	name, imageID, previousImageID string,
+) *models.App {
+	t.Helper()
 
 	app := models.NewApp(db)
-	app.ID = "myapp-id"
+	app.ID = name + "-id"
-	app.Name = "myapp"
+	app.Name = name
-	app.ImageID = sql.NullString{String: "sha256:three", Valid: true}
+	app.ImageID = sql.NullString{String: imageID, Valid: true}
-	app.PreviousImageID = sql.NullString{String: "sha256:two", Valid: true}
+	app.PreviousImageID = sql.NullString{String: previousImageID, Valid: true}
-	require.NoError(t, app.Save(ctx))
+	require.NoError(t, app.Save(context.Background()))
+
+	return app
+}
+
+// TestRecordDeployedImageRemovesOldImages runs the step after a deploy
+// against a fake Docker API. Image one has a tag from before images were
+// tagged with their commit, and is also tagged for another app. Image two
+// was the previous image, three the current one, four is new. Image five is
+// the other app's previous image, which a redeploy of its commit left
+// without the other app's tag.
+func TestRecordDeployedImageRemovesOldImages(t *testing.T) {
+	t.Parallel()
+
+	api := &fakeImageAPI{images: map[string][]string{
+		"sha256:one":   {"upaas-myapp:140", "upaas-otherapp:1a2b3c4"},
+		"sha256:two":   {"upaas-myapp:2b3c4d5"},
+		"sha256:three": {"upaas-myapp:3c4d5e6"},
+		"sha256:four":  {"upaas-myapp:4d5e6f7"},
+		"sha256:five":  {"upaas-myapp:5e6f7a8"},
+	}}
+	svc, db := newImageTestService(t, api)
+	ctx := context.Background()
+
+	app := saveApp(t, db, "myapp", "sha256:three", "sha256:two")
+	saveApp(t, db, "otherapp", "sha256:other", "sha256:five")
 
 	deployment := models.NewDeployment(db)
 	deployment.AppID = app.ID
 	require.NoError(t, deployment.Save(ctx))
 
-	svc := deploy.NewTestServiceWithConfig(log, &config.Config{}, dockerClient)
+	err := svc.RecordDeployedImage(ctx, app, deployment, "sha256:four")
-
-	err = svc.RecordDeployedImage(ctx, app, deployment, "sha256:four")
 	require.NoError(t, err)
 
 	assert.Equal(t, "sha256:four", app.ImageID.String)
 	assert.Equal(t, "sha256:three", app.PreviousImageID.String)
 
-	mu.Lock()
+	images, removed := api.state()
-	defer mu.Unlock()
 
-	assert.Equal(t, []string{"upaas-myapp:1", "upaas-myapp:2"}, removed)
+	assert.Equal(t, []string{"upaas-myapp:140", "upaas-myapp:2b3c4d5"}, removed)
-	assert.False(t, forced, "old image tags must be removed without force")
+	assert.Equal(t, map[string][]string{
+		"sha256:one":   {"upaas-otherapp:1a2b3c4"},
+		"sha256:three": {"upaas-myapp:3c4d5e6"},
+		"sha256:four":  {"upaas-myapp:4d5e6f7"},
+		"sha256:five":  {"upaas-myapp:5e6f7a8"},
+	}, images)
+	assert.False(t, api.forced, "old images must be removed without force")
+}
+
+// TestRedeployRemovesImagesLeftWithoutTag deploys commits against a fake
+// Docker API, some of them again. A build takes the commit's tag from the
+// image an earlier build of it made. That image is kept, without a tag,
+// while the app runs it or Rollback would start it, and is removed by its
+// ID once neither does.
+func TestRedeployRemovesImagesLeftWithoutTag(t *testing.T) {
+	t.Parallel()
+
+	const (
+		tagABC1234   = "upaas-myapp:abc1234"
+		tag0123ABC   = "upaas-myapp:0123abc"
+		retriedImage = "sha256:retried-0123abc"
+	)
+
+	// The app runs commit abc1234 and would roll back to def5678. The last
+	// deploy, of commit 0123abc, failed after its build.
+	api := &fakeImageAPI{images: map[string][]string{
+		"sha256:built-abc1234":  {tagABC1234},
+		"sha256:built-def5678":  {"upaas-myapp:def5678"},
+		"sha256:failed-0123abc": {tag0123ABC},
+	}}
+	svc, db := newImageTestService(t, api)
+	ctx := context.Background()
+
+	app := saveApp(t, db, "myapp", "sha256:built-abc1234", "sha256:built-def5678")
+
+	for imageID := range api.images {
+		deployment := models.NewDeployment(db)
+		deployment.AppID = app.ID
+		deployment.ImageID = sql.NullString{String: imageID, Valid: true}
+		require.NoError(t, deployment.Save(ctx))
+	}
+
+	deployCommit := func(shortSHA, imageID string) {
+		t.Helper()
+
+		api.mu.Lock()
+		api.shortSHA = shortSHA
+		api.nextID = imageID
+		api.mu.Unlock()
+
+		deployment := models.NewDeployment(db)
+		deployment.AppID = app.ID
+		require.NoError(t, deployment.Save(ctx))
+
+		built, err := svc.BuildImage(ctx, app, deployment)
+		require.NoError(t, err)
+		require.NoError(t, svc.RecordDeployedImage(ctx, app, deployment, built))
+	}
+
+	// The failed deploy's image loses its tag, and nothing uses it.
+	deployCommit("0123abc", retriedImage)
+
+	images, _ := api.state()
+	assert.Equal(t, map[string][]string{
+		"sha256:built-abc1234": {tagABC1234},
+		retriedImage:           {tag0123ABC},
+	}, images)
+
+	// The running image loses its tag and becomes the one Rollback starts.
+	deployCommit("0123abc", "sha256:rebuilt-0123abc")
+
+	images, _ = api.state()
+	assert.Equal(t, map[string][]string{
+		"sha256:rebuilt-0123abc": {tag0123ABC},
+		retriedImage:             {},
+	}, images)
+	assert.Equal(t, retriedImage, app.PreviousImageID.String)
+
+	// Once Rollback no longer needs it, the untagged image is removed.
+	deployCommit("4567def", "sha256:built-4567def")
+
+	images, removed := api.state()
+	assert.Equal(t, map[string][]string{
+		"sha256:built-4567def":   {"upaas-myapp:4567def"},
+		"sha256:rebuilt-0123abc": {tag0123ABC},
+	}, images)
+	assert.Equal(t, []string{
+		"sha256:failed-0123abc", "upaas-myapp:def5678", // first deploy
+		tagABC1234,   // second deploy
+		retriedImage, // third deploy
+	}, removed)
+	assert.False(t, api.forced, "old images must be removed without force")
 }

internal/service/deploy/export_test.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"sneak.berlin/go/upaas/internal/config"
+	"sneak.berlin/go/upaas/internal/database"
 	"sneak.berlin/go/upaas/internal/docker"
 	"sneak.berlin/go/upaas/internal/models"
 )
@@ -44,15 +45,18 @@ func (svc *Service) UnlockApp(appID string) {
 	svc.unlockApp(appID)
 }
 
-// NewTestServiceWithConfig creates a Service with config and docker client for testing.
+// NewTestServiceWithConfig creates a Service with config, database and
+// docker client for testing.
 func NewTestServiceWithConfig(
 	log *slog.Logger,
 	cfg *config.Config,
+	db *database.Database,
 	dockerClient *docker.Client,
 ) *Service {
 	return &Service{
 		log:    log,
 		config: cfg,
+		db:     db,
 		docker: dockerClient,
 	}
 }