A build says what it does on the bus, as it happens (novox/hq ADR 0157)

The build-machine seat emits `started` and `log.<build id>` beside `built`. Every line the builder
speaks — each step, each command with its duration, and on failure the command's own output — goes
to stderr as before and onto the bus under the build's id, one subject per build, kept a week in
EVENTS with every other event. `builds --log <id>` reads it back from the stream with a consumer
that is gone when the reading is done, on the command line and as the controller's seat verb;
`builds` lists each build's id and `build` says the id it asked with.

Lines are core publishes with a sequence number, so a build is not slowed by an ack per line and a
gap is visible; `started` and `built` are awaited into the stream. The seat protocol widens
additively at the controller's next start; the holder's grant follows on the broker node's next
composition.

cmd/mesh-builder/main.go

@@ -148,20 +148,34 @@ func answer(ctx context.Context, publisher builder.Publisher, on, workspace stri
 	// it either finishes or fails is indistinguishable from one that never arrived — which cost a long
 	// diagnosis against a running mesh, chasing "the handler never fired" when the truth was only that
 	// the handler said nothing until the end.
-	fmt.Fprintf(os.Stderr, "a build request arrived for %s\n", request.Repository)
+	fmt.Fprintf(os.Stderr, "a build request arrived for %s (%s)\n", request.Repository, request.ID)
+
+	// **Everything a build says goes two ways**: to stderr, as always, and onto the bus as the
+	// role's own events under the build's id (novox/hq ADR 0157) — so whoever asked, and anybody
+	// watching, reads the same lines this container's log holds, live, and after the fact from the
+	// stream. Said first, before anything runs, so a build that hangs is one that visibly started.
+	say := func(step, message string) {
+		fmt.Fprintf(os.Stderr, "  [%s] %s\n", step, message)
+		work.Say(step, message)
+	}
+	builder.Said = say
+	defer func() { builder.Said = nil }()
+	if err := work.Began(ctx); err != nil {
+		fmt.Fprintf(os.Stderr, "cannot say a build started: %v\n", err)
+	}
 
 	result := link.BuildResult{
 		ID: request.ID, Repository: request.Repository, Path: request.Path,
 		Ref: request.Ref, On: on,
 	}
-	fmt.Fprintf(os.Stderr, "building %s", request.Repository)
+	what := "building " + request.Repository
 	if request.Path != "" {
-		fmt.Fprintf(os.Stderr, " at %s", request.Path)
+		what += " at " + request.Path
 	}
 	if request.Ref != "" {
-		fmt.Fprintf(os.Stderr, " at %s", request.Ref)
+		what += " on " + request.Ref
 	}
-	fmt.Fprintln(os.Stderr)
+	say("build", what)
 
 	npmrc, err := packagesFrom()
 	var built builder.Result
@@ -171,15 +185,13 @@ func answer(ctx context.Context, publisher builder.Publisher, on, workspace stri
 		// after a clone that then fails at npm ci.
 		built, err = builder.Build(ctx, builder.Command, publisher,
 			request.Repository, request.Path, request.Ref, workspace, request.Held, npmrc,
-			forgeFrom(), func(step, message string) {
-				fmt.Fprintf(os.Stderr, "  [%s] %s\n", step, message)
-			}, request.Seats)
+			forgeFrom(), say, request.Seats)
 	}
 	if err != nil {
 		// A failure is a result. A build that fails and says nothing is indistinguishable from a
 		// builder that is not running, and those want completely different responses.
 		result.Failed = err.Error()
-		fmt.Fprintf(os.Stderr, "  failed: %v\n", err)
+		say("failed", err.Error())
 	} else {
 		manifest, marshalErr := json.Marshal(built.Manifest)
 		if marshalErr != nil {
@@ -196,7 +208,7 @@ func answer(ctx context.Context, publisher builder.Publisher, on, workspace stri
 			for _, r := range built.Read {
 				result.Read = append(result.Read, link.ReadRepository{Repository: r.Repository, Ref: r.Ref})
 			}
-			fmt.Fprintf(os.Stderr, "  built %s from %s\n", built.Manifest.Module, short(built.Commit))
+			say("built", built.Manifest.Module+" from "+short(built.Commit))
 		}
 	}
 

cmd/mesh-controller/build.go

@@ -10,6 +10,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/nats-io/nats.go"
+
 	"github.com/novox/mesh-controller/internal/broker"
 	"github.com/novox/mesh-controller/internal/catalogue"
 	"github.com/novox/mesh-controller/internal/inventory"
@@ -175,10 +177,14 @@ func buildFrom(result link.BuildResult) inventory.Build {
 func buildsCommand(ctx context.Context, args []string) error {
 	set := flag.NewFlagSet("builds", flag.ContinueOnError)
 	limit := set.Int("n", 20, "how many to show")
+	logOf := set.String("log", "", "a build's id: print what the build machine said, line by line")
 	positionals, err := parseAround(set, args)
 	if err != nil {
 		return err
 	}
+	if *logOf != "" {
+		return buildLog(ctx, *logOf)
+	}
 	module := ""
 	if len(positionals) == 1 {
 		module = positionals[0]
@@ -219,8 +225,8 @@ func buildsCommand(ctx context.Context, args []string) error {
 		if !b.Worked() {
 			outcome = "failed"
 		}
-		fmt.Printf("%-18s %-14s %-10s %s\n",
-			what, outcome, b.On, b.At.Local().Format("2006-01-02 15:04"))
+		fmt.Printf("%-18s %-14s %-10s %s  %s\n",
+			what, outcome, b.On, b.At.Local().Format("2006-01-02 15:04"), b.ID)
 		fmt.Printf("    %s", b.Repository)
 		if b.Ref != "" {
 			fmt.Printf(" at %s", b.Ref)
@@ -414,6 +420,8 @@ func buildOne(ctx context.Context, source buildSource, path, ref string, wait ti
 	if source.Seat != "" {
 		fmt.Printf(" (%s)", repository)
 	}
+	// The id is how a person follows this build while it runs: `builds --log <id>`.
+	fmt.Printf(" as %s", request.ID)
 	if path != "" {
 		fmt.Printf(" at %s", path)
 	}
@@ -625,3 +633,57 @@ func askOver(_ *link.Server) (link.Builders, error) {
 	}
 	return link.BuildsOverNATS(address)
 }
+
+// buildLog prints everything a build machine said about one build, read back from the bus.
+//
+// **From the stream, not from a record** (novox/hq ADR 0157). A build's lines are the role's own
+// events under the build's id, retained with every other event; the mesh keeps no second copy. Read
+// with a consumer of its own that is gone when this returns, so nothing accumulates in the server
+// for the reading, and filtered by subject, so one build's lines are all that travel.
+func buildLog(ctx context.Context, id string) error {
+	address, err := broker.BusAddress()
+	if err != nil {
+		return err
+	}
+	js, err := broker.Dial(address)
+	if err != nil {
+		return fmt.Errorf("cannot reach the bus to read a build's log: %w", err)
+	}
+	defer js.Close()
+
+	sub, err := js.Context().PullSubscribe(link.BuildLog(id), "",
+		nats.BindStream(broker.EventsStream), nats.DeliverAll(), nats.AckNone())
+	if err != nil {
+		return fmt.Errorf("cannot read %s from the bus: %w", link.BuildLog(id), err)
+	}
+	defer func() { _ = sub.Unsubscribe() }()
+
+	printed := 0
+	for {
+		batch, err := sub.Fetch(200, nats.MaxWait(2*time.Second))
+		if err != nil && !errors.Is(err, nats.ErrTimeout) && !errors.Is(err, context.DeadlineExceeded) {
+			return fmt.Errorf("reading a build's log: %w", err)
+		}
+		for _, msg := range batch {
+			var line link.BuildLine
+			if err := json.Unmarshal(msg.Data, &line); err != nil {
+				fmt.Printf("  ? %s\n", string(msg.Data))
+				continue
+			}
+			at := line.At
+			if t, err := time.Parse(time.RFC3339Nano, line.At); err == nil {
+				at = t.Local().Format("15:04:05")
+			}
+			fmt.Printf("%s %4d [%s] %s\n", at, line.Seq, line.Step, line.Message)
+			printed++
+		}
+		if len(batch) < 200 {
+			break
+		}
+	}
+	if printed == 0 {
+		fmt.Printf("nothing on the bus for build %s: no build by that id in the last week, or a build "+
+			"machine older than this that said nothing while building\n", id)
+	}
+	return nil
+}

cmd/mesh-controller/seatverbs.go

@@ -62,6 +62,9 @@ func argvFor(verb string, args map[string]any) ([]string, error) {
 	case "seats":
 		return []string{"seats", "--json"}, nil
 	case "builds":
+		if id := str("log"); id != "" {
+			return []string{"builds", "--log", id}, nil
+		}
 		if m := str("module"); m != "" {
 			return []string{"builds", m}, nil
 		}

cmd/mesh-controller/seatverbs_test.go

@@ -30,6 +30,18 @@ func TestEveryDeclaredVerbHasACommandLine(t *testing.T) {
 	}
 }
 
+// `builds` given a build's id reads that build's log from the bus rather than listing builds
+// (novox/hq ADR 0157).
+func TestBuildsWithAnIdReadsThatBuildsLog(t *testing.T) {
+	argv, err := argvFor("builds", map[string]any{"log": "build-17"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.Join(argv, " ") != "builds --log build-17" {
+		t.Fatalf("builds with a log id became %q", strings.Join(argv, " "))
+	}
+}
+
 // A required argument missing is refused in the verb's own words, before anything runs.
 func TestAVerbMissingWhatItNeedsIsRefused(t *testing.T) {
 	if _, err := argvFor("node", map[string]any{}); err == nil || !strings.Contains(err.Error(), `node needs "node"`) {