Merge pull request 'Genesis registers the control plane with the manifest its build produced (hq issue 072)' (#17) from feat/one-controller-manifest into main

cmd/mesh-bootstrap/main.go

@@ -221,7 +221,7 @@ func newFlagSet(opts *bootstrap.Options, jsonOut *bool) *flag.FlagSet {
 	set.StringVar(&opts.Out, "out", opts.Out, "where the produced bundle is written")
 	set.StringVar(&opts.State, "state", opts.State, "where this node records what it has applied")
 	set.StringVar(&opts.Catalogue, "catalog", opts.Catalogue,
-		"a checkout of the mesh's catalogue; without it this stops after the foundation")
+		"a checkout of the mesh's catalogue, for the registry's and the builder's manifests and what phase two installs; without it this stops after the foundation")
 	set.StringVar(&opts.Source.Repository, "source", opts.Source.Repository,
 		"the repository the control plane is built from, on a mesh that already exists")
 	set.StringVar(&opts.Source.Ref, "source-ref", opts.Source.Ref,

internal/bootstrap/bootstrap.go

@@ -137,9 +137,11 @@ type Options struct {
 	Node string
 
 	// Catalogue is a checkout of the mesh's catalogue repository, which is where the registry's and
-	// the control plane's manifests are read from. Empty stops the installer after the foundation:
+	// the builder's manifests are read from, and everything phase two installs. Not the control
-	// there is no pivot without manifests, and pretending otherwise would leave a machine that
+	// plane's: that one comes out of the build at step 3, from the root of its own repository
-	// looks installed and cannot upgrade itself.
+	// (novox/hq ADR 0069). Empty stops the installer after the foundation: there is no pivot
+	// without manifests, and pretending otherwise would leave a machine that looks installed and
+	// cannot upgrade itself.
 	Catalogue string
 
 	// Source is where the control plane is built from — a repository on a mesh that already
@@ -585,7 +587,7 @@ func Run(ctx context.Context, o Options, d Deps, say func(string)) (Result, erro
 	// ---- 9. control plane -----------------------------------------------------------------
 	say("control plane — installed as an ordinary module, pinned to that digest")
 	permanent, err := InstallControlPlane(ctx, o, d, temporary, rewritten.Declaration,
-		published.Reference, say)
+		built, published.Reference, say)
 	result.Permanent, result.PermanentAnswered = permanent.Container, permanent.Answered
 	result.StoresDelivered = permanent.Delivered
 	if err != nil {

internal/bootstrap/build.go

@@ -1,6 +1,7 @@
 package bootstrap
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -57,13 +58,19 @@ type Built struct {
 	// Image is the artifact, named by the digest of its own configuration — the identity a machine
 	// can use with nothing serving it, and the same one the installer used for a carried image.
 	Image string
+	// Manifest is the module as the mesh should hold it: the manifest at the root of the repository
+	// that was built, its artifact resolved to Image. It is the control plane's ONE manifest
+	// (novox/hq ADR 0069) — the installer used to read a second copy out of the catalogue, and the
+	// two drifted apart the first time somebody edited one (novox/hq 04-ISSUES/072).
+	Manifest []byte
 }
 
 // builderOutput is the part of the builder's one-shot result this needs.
 type builderOutput struct {
-	Module string `json:"module"`
+	Module   string          `json:"module"`
-	Commit string `json:"commit"`
+	Commit   string          `json:"commit"`
-	Made   []struct {
+	Manifest json.RawMessage `json:"manifest"`
+	Made     []struct {
 		Name      string `json:"name"`
 		Kind      string `json:"kind"`
 		Reference string `json:"reference"`
@@ -142,8 +149,25 @@ func BuildControlPlane(ctx context.Context, run Runner, builderTag string, sourc
 			result.Module, len(images))
 	}
 
+	// The manifest is what the mesh will hold the control plane as, so a result without one is
+	// a build the installer cannot finish — refused here, beside the builder that said it, rather
+	// than at step 9 with a message about a missing file.
+	manifest := bytes.TrimSpace(result.Manifest)
+	if len(manifest) == 0 || bytes.Equal(manifest, []byte("null")) {
+		return Built{}, fmt.Errorf(
+			"%s built, and the builder reported no manifest for it. The installer registers the "+
+				"control plane with the manifest the build produced — the one at the root of its "+
+				"repository, its artifact resolved — and has no other copy to use", result.Module)
+	}
+	if !bytes.Contains(manifest, []byte(`"`+images[0]+`"`)) {
+		return Built{}, fmt.Errorf(
+			"%s built %s, and the manifest the builder reported does not name that image, so "+
+				"the installer cannot tell which of its resources runs the control plane",
+			result.Module, images[0])
+	}
+
 	say(fmt.Sprintf("  built %s from %s", result.Module, shortRef(result.Commit)))
-	return Built{Module: result.Module, Commit: result.Commit, Image: images[0]}, nil
+	return Built{Module: result.Module, Commit: result.Commit, Image: images[0], Manifest: manifest}, nil
 }
 
 func shortRef(ref string) string {

internal/bootstrap/build_test.go

@@ -1,6 +1,7 @@
 package bootstrap
 
 import (
+	"context"
 	"strings"
 	"testing"
 )
@@ -39,3 +40,56 @@ func TestARepositoryAndACommitIsEnough(t *testing.T) {
 		t.Fatalf("a repository and a commit were refused: %v", err)
 	}
 }
+
+// **The build hands over the manifest, and the installer registers that one.** The control plane
+// used to have two manifests — one at the root of its repository, which the mesh reads whenever
+// it rebuilds the control plane from source, and a copy in the catalogue, which genesis read — and
+// nothing kept them equal (novox/hq 04-ISSUES/072). The builder already reports the manifest it
+// built, artifact resolved to the image; genesis takes it from there and reads no second copy.
+func TestTheBuildHandsOverTheManifestTheMeshWillHold(t *testing.T) {
+	manifest := `{"module":"mesh-controller","version":"1","resources":[` +
+		`{"id":"server","type":"container","name":"mesh-controller","image":"` + builtImage + `"}]}`
+	runtime := &asked{answer: func(string, []string) (string, error) {
+		return `{"module":"mesh-controller","commit":"a1b2c3d4","manifest":` + manifest +
+			`,"made":[{"name":"server","kind":"image","reference":"` + builtImage + `"}]}` + "\n", nil
+	}}
+	built, err := BuildControlPlane(context.Background(), runtime.run, "mesh-builder:test",
+		Source{Repository: "https://example.invalid/mesh-controller.git", Ref: "a1b2c3d4"}, false, func(string) {})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if built.Image != builtImage {
+		t.Errorf("the built image is %q", built.Image)
+	}
+	if string(built.Manifest) != manifest {
+		t.Errorf("the manifest handed over is not the one the builder reported:\n%s", built.Manifest)
+	}
+}
+
+// A result without a manifest is a build the installer cannot finish, and it is refused beside the
+// builder that said it rather than at step 9 with a message about a missing file.
+func TestABuildReportingNoManifestIsRefused(t *testing.T) {
+	runtime := &asked{answer: func(string, []string) (string, error) {
+		return `{"module":"mesh-controller","commit":"a1b2c3d4",` +
+			`"made":[{"name":"server","kind":"image","reference":"` + builtImage + `"}]}`, nil
+	}}
+	_, err := BuildControlPlane(context.Background(), runtime.run, "mesh-builder:test",
+		Source{Repository: "https://example.invalid/mesh-controller.git", Ref: "a1b2c3d4"}, false, func(string) {})
+	if err == nil || !strings.Contains(err.Error(), "no manifest") {
+		t.Fatalf("a build reporting no manifest was accepted, or refused for another reason: %v", err)
+	}
+}
+
+// And a manifest that does not name the image the build produced describes some other build.
+func TestABuildWhoseManifestNamesAnotherImageIsRefused(t *testing.T) {
+	runtime := &asked{answer: func(string, []string) (string, error) {
+		return `{"module":"mesh-controller","commit":"a1b2c3d4","manifest":{"module":"mesh-controller",` +
+			`"resources":[{"id":"server","type":"container","image":"sha256:` + strings.Repeat("9", 64) + `"}]},` +
+			`"made":[{"name":"server","kind":"image","reference":"` + builtImage + `"}]}`, nil
+	}}
+	_, err := BuildControlPlane(context.Background(), runtime.run, "mesh-builder:test",
+		Source{Repository: "https://example.invalid/mesh-controller.git", Ref: "a1b2c3d4"}, false, func(string) {})
+	if err == nil || !strings.Contains(err.Error(), "does not name that image") {
+		t.Fatalf("a manifest naming another image was accepted, or refused for another reason: %v", err)
+	}
+}

internal/bootstrap/builder.go

@@ -53,7 +53,7 @@ func InstallBuilder(ctx context.Context, o Options, d Deps, control controlPlane
 			"This is the manifest that makes the builder an ordinary module. Without it the mesh "+
 			"has the image and no way to run it, so nothing can be built here", err)
 	}
-	pinned, places, err := pinImage(manifest, published.Reference, BuilderModule)
+	pinned, places, err := pinPlaceholder(manifest, published.Reference, BuilderModule)
 	if err != nil {
 		return out, err
 	}

internal/bootstrap/control.go

@@ -53,26 +53,33 @@ type Permanent struct {
 // exactly the path for a value the mesh must carry and could not have invented — and they are read
 // out of the bundle this installer produced rather than reconstructed, because the bundle is what
 // created them and a second opinion about what a DSN should say is a second chance to be wrong.
+//
+// **The manifest is the one the build produced** — the manifest at the root of the control plane's
+// own repository, its artifact resolved to the image built at step 3 (novox/hq ADR 0069). The
+// installer used to read a second copy out of the catalogue and pin its placeholder; the copies
+// drifted, and the first rebuild from source replaced the mesh's record with the repository's shape
+// while every later push was refused on its behalf (novox/hq 04-ISSUES/072). There is one manifest
+// now, and the only thing this step changes in it is the image's name: the id the machine built it
+// under becomes the reference the registry assigned at step 8.
 func InstallControlPlane(ctx context.Context, o Options, d Deps, control controlPlane,
-	foundation *declaration.Declaration, image string, say func(string)) (Permanent, error) {
+	foundation *declaration.Declaration, built Built, image string, say func(string)) (Permanent, error) {
 
 	out := Permanent{Image: image}
 
-	manifest, err := readManifest(o.Catalogue, ControlPlaneModule)
+	if len(built.Manifest) == 0 {
-	if err != nil {
 		return out, fmt.Errorf(
-			"%w\n"+
+			"the control plane was not built, so there is no manifest to register it with. " +
-				"This is the manifest that makes the control plane an ordinary module. Without it "+
+				"This is the manifest that makes the control plane an ordinary module. Without it " +
-				"the machine keeps the temporary control plane the foundation raised, which works "+
+				"the machine keeps the temporary control plane the foundation raised, which works " +
-				"and cannot be upgraded — so the install stops here rather than pretending to "+
+				"and cannot be upgraded — so the install stops here rather than pretending to " +
-				"have pivoted", err)
+				"have pivoted")
 	}
 
-	pinned, places, err := pinImage(manifest, image, ControlPlaneModule)
+	pinned, places, err := pinImage(built.Manifest, built.Image, image, ControlPlaneModule)
 	if err != nil {
 		return out, err
 	}
-	say(fmt.Sprintf("  pinned            %s, in %d place(s)", image, places))
+	say(fmt.Sprintf("  pinned            %s → %s, in %d place(s)", shortImage(built.Image), image, places))
 
 	container, _, err := containerIn(pinned, controlPlaneResourceIn(pinned))
 	if err != nil {
@@ -118,52 +125,34 @@ func InstallControlPlane(ctx context.Context, o Options, d Deps, control control
 	return out, nil
 }
 
-// pinImage replaces the catalogue's placeholder digest with what the registry assigned.
+// pinImage replaces the image the build named with the reference the registry assigned.
 //
 // **Textual, and every place it appears.** A manifest may name its image in more than one resource
-// — the catalogue's converted modules routinely carry a runtime container beside the application's
+// — a migrate step beside the server, a runtime beside the application — and the same reasoning
-// — and the same reasoning as the bundle rewrite applies: replacing one and not the others leaves
+// as the bundle rewrite applies: replacing one and not the others leaves something pointing at an
-// something pointing at an image nothing serves, and it fails half way through an apply rather
+// image nothing serves, and it fails half way through an apply rather than here.
-// than here.
 //
-// It refuses a manifest with no placeholder in it. That is not pedantry: a manifest already
+// The built image is named by the digest of its own configuration, `sha256:…` with no registry in
-// carrying a real digest is one somebody pinned by hand, and quietly registering it would install a
+// front, which only the machine that built it can resolve. The whole JSON string moves to the
-// control plane that is not the image this machine just published — which is the one thing this
+// registry's `<registry>/<repository>@sha256:…`, so every machine the module is later pushed to
-// step exists to guarantee.
+// pulls it from the mesh's own store.
-func pinImage(manifest []byte, reference, module string) ([]byte, int, error) {
+//
-	places := bytes.Count(manifest, []byte(placeholderDigest))
+// It refuses a manifest that does not name the built image. That is not pedantry: a manifest
+// naming some other image is one that describes some other build, and quietly registering it would
+// install a control plane that is not the image this machine just published — which is the one
+// thing this step exists to guarantee.
+func pinImage(manifest []byte, built, reference, module string) ([]byte, int, error) {
+	from := []byte(`"` + built + `"`)
+	places := bytes.Count(manifest, from)
 	if places == 0 {
 		return nil, 0, fmt.Errorf(
-			"the %s module's manifest carries no placeholder digest (%s), so there is nothing to "+
+			"the %s module's manifest does not name the image this machine built (%s), so there "+
-				"pin to the image this machine just published.\n"+
+				"is nothing to pin to the image it just published.\n"+
-				"A manifest already naming a digest was pinned by somebody else, to some other "+
+				"A manifest naming some other image describes some other build. Registering it "+
-				"build. Registering it would install a module that is not the one this "+
+				"would install a module that is not the one this installer built and pushed",
-				"installer carried and pushed", module, placeholderDigest)
+			module, built)
 	}
-	// The reference the registry gave back is `<registry>/<repository>@sha256:…`, and what the
+	pinned := bytes.ReplaceAll(manifest, from, []byte(`"`+reference+`"`))
-	// manifest holds is `<something>@sha256:0…0`. Replacing only the digest would leave the
-	// manifest's own repository name in front of it — which may be `mesh-controller` with no
-	// registry, and a runtime would then pull it from the internet. The whole reference moves.
-	var out bytes.Buffer
-	rest := manifest
-	for {
-		at := bytes.Index(rest, []byte(placeholderDigest))
-		if at < 0 {
-			out.Write(rest)
-			break
-		}
-		// Back up over the repository this digest belongs to, which runs to the opening quote.
-		start := bytes.LastIndexByte(rest[:at], '"')
-		if start < 0 {
-			return nil, 0, fmt.Errorf(
-				"the %s module's manifest has a placeholder digest that is not inside a JSON "+
-					"string, so the installer cannot tell what image it belongs to", module)
-		}
-		out.Write(rest[:start+1])
-		out.WriteString(reference)
-		rest = rest[at+len(placeholderDigest):]
-	}
-	pinned := out.Bytes()
 
 	// Read back. A substitution on text can catch more than it was aimed at, and the manifest is
 	// about to be handed to the mesh as the description of what it runs.
@@ -172,17 +161,16 @@ func pinImage(manifest []byte, reference, module string) ([]byte, int, error) {
 		return nil, 0, fmt.Errorf(
 			"pinning the %s module's image broke its manifest: %w", module, err)
 	}
-	if bytes.Contains(pinned, []byte(placeholderDigest)) {
+	if bytes.Contains(pinned, from) {
 		return nil, 0, fmt.Errorf(
-			"the %s module's manifest still carries a placeholder digest after pinning",
+			"the %s module's manifest still names the built image after pinning", module)
-			module)
 	}
 	return pinned, places, nil
 }
 
 // controlPlaneResourceIn is the id of the resource that runs the control plane.
 //
-// The manifest is written by the catalogue and the installer does not get to name its resources.
+// The manifest is the control plane's own and the installer does not get to name its resources.
 // What it can do is find the one container whose image is the one just pinned — and when a manifest
 // declares exactly one container, that is the answer without any searching at all.
 func controlPlaneResourceIn(manifest []byte) string {
@@ -410,3 +398,13 @@ func sortedKeys(m map[string]string) []string {
 	sort.Strings(keys)
 	return keys
 }
+
+// shortImage is an image id as a person reads one: the first twelve hex digits, without the
+// algorithm in front — `shortRef` would keep the prefix and show one digit of the digest.
+func shortImage(id string) string {
+	digest := strings.TrimPrefix(id, "sha256:")
+	if len(digest) > 12 {
+		return digest[:12]
+	}
+	return digest
+}

internal/bootstrap/control_test.go

@@ -11,13 +11,15 @@ import (
 // that could go wrong quietly: pinning it to the wrong image, and delivering it store connections
 // the mesh invented rather than the ones the foundation actually made.
 
-// theControlPlaneModule is the catalogue's manifest, trimmed to what this installer reads.
+// theControlPlaneModule is the manifest the build produces at step 3: the control plane's own,
+// from the root of its repository, its artifact resolved to the image the machine built — named by
+// the digest of its own configuration, with no registry in front (novox/hq ADR 0069).
 //
 // A fixture rather than the file itself, unlike the foundation example the rewrite tests use: the
-// catalogue is a different repository on a different branch, and a test that read it would pass or
+// control plane is a different repository on a different branch, and a test that read it would
-// fail according to what somebody else had checked out. What it must stay faithful to is the
+// pass or fail according to what somebody else had checked out. What it must stay faithful to is
-// SHAPE — the placeholder digest, the own-secret per context, the mount from the machine's path to
+// the SHAPE — the built image's bare id, the own-secret per context, the mount from the machine's
-// the container's, and the environment file that fills what is not a path.
+// path to the container's, and the environment file that fills what is not a path.
 const theControlPlaneModule = `{
   "module": "mesh-controller",
   "version": "1",
@@ -37,7 +39,7 @@ const theControlPlaneModule = `{
      "mode": "0600",
      "content": "MESH_BROKER_AMQP=${secret:broker}\nMESH_BROKER_MANAGEMENT=${secret:broker-management}\nMESH_BROKER_ADDRESS=${machine:at}:5671\n"},
     {"id": "server", "type": "container", "name": "mesh-controller",
-     "image": "mesh-controller@` + placeholderDigest + `",
+     "image": "` + builtImage + `",
      "network": "host", "args": ["serve"],
      "env-file": ["/var/lib/mesh/mesh-controller/broker.env"],
      "env": {
@@ -58,57 +60,62 @@ const theControlPlaneModule = `{
 const pushedReference = "127.0.0.1:5000/mesh-controller@sha256:" +
 	"eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee"
 
-// **The whole reference moves, not only the digest.** The manifest's placeholder names a
+// builtImage is what step 3 built, as the machine that built it names it.
-// repository too, and replacing sixty-four zeros inside it would leave `mesh-controller@sha256:…`
+const builtImage = "sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
-// with no registry in front — which a runtime would go to the internet for, and this mesh's
+
-// control plane exists in no public registry by design.
+// theBuild is what step 3 hands step 9.
+func theBuild(manifest string) Built {
+	return Built{Module: "mesh-controller", Commit: "a1b2c3d4", Image: builtImage, Manifest: []byte(manifest)}
+}
+
+// **The whole reference moves.** The build names its image by the bare digest of its configuration,
+// which only the machine that built it can resolve; the mesh's record must name what the registry
+// assigned, `<registry>/<repository>@sha256:…`, or every other machine the module is pushed to
+// would go looking for an image nothing serves.
 func TestTheControlPlaneIsPinnedToWhatThisMeshsRegistryAssigned(t *testing.T) {
-	pinned, places, err := pinImage([]byte(theControlPlaneModule), pushedReference, "mesh-controller")
+	pinned, places, err := pinImage([]byte(theControlPlaneModule), builtImage, pushedReference, "mesh-controller")
 	if err != nil {
 		t.Fatal(err)
 	}
 	if places != 1 {
-		t.Errorf("the placeholder was found in %d place(s)", places)
+		t.Errorf("the built image was found in %d place(s)", places)
 	}
 	if !strings.Contains(string(pinned), `"image": "`+pushedReference+`"`) {
 		t.Errorf("the manifest does not name the pushed image:\n%s", pinned)
 	}
-	if strings.Contains(string(pinned), `"mesh-controller@sha256:`) {
+	if strings.Contains(string(pinned), builtImage) {
-		t.Errorf("the digest was replaced and the manifest's own repository name was left in "+
+		t.Errorf("the built image's bare id survived, which no other machine can resolve:\n%s", pinned)
-			"front of it, so nothing says which registry serves it:\n%s", pinned)
 	}
 }
 
-// A manifest already naming a real digest was pinned by somebody else, to some other build.
+// A manifest naming some other image describes some other build. Registering it would install a
-// Registering it would install a control plane that is not the image this machine just published,
+// control plane that is not the image this machine just published, which is the one thing this
-// which is the one thing this step exists to guarantee.
+// step exists to guarantee.
-func TestAManifestAlreadyPinnedByHandIsRefused(t *testing.T) {
+func TestAManifestNamingAnotherBuildIsRefused(t *testing.T) {
-	already := strings.Replace(theControlPlaneModule, placeholderDigest,
+	other := strings.Replace(theControlPlaneModule, builtImage, "sha256:"+strings.Repeat("9", 64), 1)
-		"sha256:"+strings.Repeat("9", 64), 1)
+	if _, _, err := pinImage([]byte(other), builtImage, pushedReference, "mesh-controller"); err == nil {
-	if _, _, err := pinImage([]byte(already), pushedReference, "mesh-controller"); err == nil {
+		t.Fatal("a manifest naming some other image was accepted")
-		t.Fatal("a manifest already pinned to some other image was accepted")
 	}
 }
 
-// Every placeholder moves. A manifest naming its image in a second resource — a runtime container
+// Every place moves. A manifest naming its image in a second resource — a migrate step beside the
-// beside the application's, which the catalogue's converted modules routinely carry — would
+// server — would otherwise be left half pinned, and fail inside an apply rather than here.
-// otherwise be left half pinned, and fail inside an apply rather than here.
 func TestEveryPlaceTheManifestNamesTheImageIsPinned(t *testing.T) {
 	twice := strings.Replace(theControlPlaneModule,
 		`{"id": "mesh-state", "type": "directory", "path": "/var/lib/mesh/mesh-controller", "mode": "0700"},`,
 		`{"id": "mesh-state", "type": "directory", "path": "/var/lib/mesh/mesh-controller", "mode": "0700"},
      {"id": "migrate", "type": "container", "name": "mesh-controller-migrate", "run-once": true,
-      "image": "mesh-controller@`+placeholderDigest+`", "args": ["migrate"]},`, 1)
+      "image": "`+builtImage+`", "args": ["migrate"]},`, 1)
 
-	pinned, places, err := pinImage([]byte(twice), pushedReference, "mesh-controller")
+	pinned, places, err := pinImage([]byte(twice), builtImage, pushedReference, "mesh-controller")
 	if err != nil {
 		t.Fatal(err)
 	}
 	if places != 2 {
-		t.Errorf("the placeholder was found in %d place(s), and the manifest names it twice", places)
+		t.Errorf("the built image was found in %d place(s), and the manifest names it twice", places)
 	}
-	if strings.Contains(string(pinned), placeholderDigest) {
+	if strings.Contains(string(pinned), builtImage) {
-		t.Error("a placeholder survived the pinning")
+		t.Error("the built image's id survived the pinning")
 	}
 }
 
@@ -230,7 +237,7 @@ func TestAManifestWantingNoStoresIsRefusedWithTheShapeItShouldHave(t *testing.T)
 
 	bare := `{"module":"mesh-controller","version":"1","resources":[
 	  {"id":"container","type":"container","name":"mesh-controller",
-	   "image":"mesh-controller@` + placeholderDigest + `"}]}`
+	   "image":"` + builtImage + `"}]}`
 
 	_, err = deliverStores(context.Background(), Options{Node: "anchor"}, control,
 		[]byte(bare), rewritten.Declaration, func(string) {})
@@ -256,9 +263,11 @@ func TestThePermanentControlPlaneIsAskedTheSameQuestion(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	out, err := InstallControlPlane(context.Background(),
+	// No catalogue: the control plane's manifest is the one the build produced (novox/hq
-		installing(t, catalogueWith(t, ControlPlaneModule, theControlPlaneModule)),
+	// 04-ISSUES/072), and step 9 reads nothing from the catalogue any more.
-		Deps{Run: runtime.run}, control, rewritten.Declaration, pushedReference, func(string) {})
+	out, err := InstallControlPlane(context.Background(), installing(t, t.TempDir()),
+		Deps{Run: runtime.run}, control, rewritten.Declaration, theBuild(theControlPlaneModule),
+		pushedReference, func(string) {})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -298,3 +307,21 @@ func TestABrokerSettingReadFromAFileIsDeliveredToo(t *testing.T) {
 		t.Fatal("a plain path variable was taken for a secret")
 	}
 }
+
+// Step 9 with nothing built is a caller's fault, and it stops rather than pretending to pivot.
+func TestTheControlPlaneCannotBeInstalledWithoutABuild(t *testing.T) {
+	runtime := &asked{answer: aMeshThatAgrees(map[string]string{})}
+	control := controlPlane{container: "temp-mesh-controller", run: runtime.run, timeout: time.Second}
+	rewritten, err := Rewrite(theRealBundle(t), held)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = InstallControlPlane(context.Background(), installing(t, t.TempDir()),
+		Deps{Run: runtime.run}, control, rewritten.Declaration, Built{}, pushedReference, func(string) {})
+	if err == nil || !strings.Contains(err.Error(), "was not built") {
+		t.Fatalf("a missing build was not refused: %v", err)
+	}
+	if runtime.ran("module add") {
+		t.Error("something was registered without a manifest")
+	}
+}

internal/bootstrap/module.go

@@ -1,7 +1,9 @@
 package bootstrap
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -143,3 +145,67 @@ func pushNode(ctx context.Context, o Options, control controlPlane, say func(str
 	say("  pushed            " + o.Node)
 	return strings.TrimSpace(said), nil
 }
+
+// pinPlaceholder replaces the catalogue's placeholder digest with what the registry assigned — the
+// builder's manifest, which the catalogue still holds (the control plane's comes out of its own
+// build, see pinImage).
+//
+// **Textual, and every place it appears.** A manifest may name its image in more than one resource
+// — the catalogue's converted modules routinely carry a runtime container beside the application's
+// — and the same reasoning as the bundle rewrite applies: replacing one and not the others leaves
+// something pointing at an image nothing serves, and it fails half way through an apply rather
+// than here.
+//
+// It refuses a manifest with no placeholder in it. That is not pedantry: a manifest already
+// carrying a real digest is one somebody pinned by hand, and quietly registering it would install a
+// control plane that is not the image this machine just published — which is the one thing this
+// step exists to guarantee.
+func pinPlaceholder(manifest []byte, reference, module string) ([]byte, int, error) {
+	places := bytes.Count(manifest, []byte(placeholderDigest))
+	if places == 0 {
+		return nil, 0, fmt.Errorf(
+			"the %s module's manifest carries no placeholder digest (%s), so there is nothing to "+
+				"pin to the image this machine just published.\n"+
+				"A manifest already naming a digest was pinned by somebody else, to some other "+
+				"build. Registering it would install a module that is not the one this "+
+				"installer carried and pushed", module, placeholderDigest)
+	}
+	// The reference the registry gave back is `<registry>/<repository>@sha256:…`, and what the
+	// manifest holds is `<something>@sha256:0…0`. Replacing only the digest would leave the
+	// manifest's own repository name in front of it — which may be `mesh-controller` with no
+	// registry, and a runtime would then pull it from the internet. The whole reference moves.
+	var out bytes.Buffer
+	rest := manifest
+	for {
+		at := bytes.Index(rest, []byte(placeholderDigest))
+		if at < 0 {
+			out.Write(rest)
+			break
+		}
+		// Back up over the repository this digest belongs to, which runs to the opening quote.
+		start := bytes.LastIndexByte(rest[:at], '"')
+		if start < 0 {
+			return nil, 0, fmt.Errorf(
+				"the %s module's manifest has a placeholder digest that is not inside a JSON "+
+					"string, so the installer cannot tell what image it belongs to", module)
+		}
+		out.Write(rest[:start+1])
+		out.WriteString(reference)
+		rest = rest[at+len(placeholderDigest):]
+	}
+	pinned := out.Bytes()
+
+	// Read back. A substitution on text can catch more than it was aimed at, and the manifest is
+	// about to be handed to the mesh as the description of what it runs.
+	var checked map[string]any
+	if err := json.Unmarshal(pinned, &checked); err != nil {
+		return nil, 0, fmt.Errorf(
+			"pinning the %s module's image broke its manifest: %w", module, err)
+	}
+	if bytes.Contains(pinned, []byte(placeholderDigest)) {
+		return nil, 0, fmt.Errorf(
+			"the %s module's manifest still carries a placeholder digest after pinning",
+			module)
+	}
+	return pinned, places, nil
+}