Announce the build agent's verbs, let a waiting build hear its cancel, and retry a stopped rollout (hq ADR 0219)

The holder's verbs were served and found by nothing; it now answers discovery
with its machine's four, as a runtime announces a seat's verb, so the console
finds <node>/node-build-agent.kill. A cancel publishes no outcome, so a build
waited for also looks at the cancelled set. A plan that stopped at its first
machine is retried by sending that machine the module again, unless a newer
plan holds it.

cmd/mesh-builder/holder.go

@@ -12,7 +12,10 @@ import (
 	"sync"
 	"time"
 
+	"github.com/nats-io/nats.go/micro"
+
 	"github.com/novox/mesh-controller/internal/builder"
+	"github.com/novox/mesh-controller/internal/catalogue"
 	"github.com/novox/mesh-controller/internal/link"
 )
 
@@ -293,3 +296,41 @@ func plainRun(ctx context.Context, dir, name string, args ...string) (string, er
 	}
 	return string(out), nil
 }
+
+// announcement is what this holder answers discovery with (novox/hq ADR 0195, ADR 0197): this
+// machine's verbs of the seat, in the shape every tool runtime announces a seat's verb — kind seat,
+// the module answering, the seat, scope node, the machine, its description and argument schema — so
+// the console finds `<node>/node-build-agent.kill` by searching, as it finds any seat's verb.
+//
+// One service per machine, named for the seat and identified by the machine, so the answer is this
+// machine's four verbs and nothing more. The verbs are the compiled seat row's: a build machine has no
+// store, and what it serves is what this binary was built to serve.
+func announcement(seat, module, node string) micro.Info {
+	s, _ := catalogue.SeatNamed(seat)
+	var endpoints []micro.EndpointInfo
+	for _, v := range s.Serves {
+		schema, _ := json.Marshal(v.Input)
+		endpoints = append(endpoints, micro.EndpointInfo{
+			Name:    seat + "__" + v.Name,
+			Subject: link.NodeSeatToolSubject(seat, v.Name, node),
+			Metadata: map[string]string{
+				"kind": "seat", "module": module, "tool": v.Name, "seat": seat, "scope": "node",
+				"node": node, "interchangeable": "false", "description": v.Description, "schema": string(schema),
+			},
+		})
+	}
+	return micro.Info{
+		ServiceIdentity: micro.ServiceIdentity{Name: seat, ID: node, Version: "0.1.0",
+			Metadata: map[string]string{"seat": seat, "scope": "node", "node": node, "module": module}},
+		Description: "what the build running on " + node + " is, and ending, pausing and resuming it (novox/hq ADR 0219)",
+		Endpoints:   endpoints,
+	}
+}
+
+// moduleOf is the module a credential was issued for: its user is `<node>.<module>`.
+func moduleOf(user string) string {
+	if _, module, ok := strings.Cut(user, "."); ok && module != "" {
+		return module
+	}
+	return "build-agent"
+}

cmd/mesh-builder/holder_test.go

@@ -92,3 +92,22 @@ func TestKillEndsTheBuildRunningHereAndNoOther(t *testing.T) {
 		t.Errorf("after the kill current says %+v", c)
 	}
 }
+
+// A holder announces this machine's verbs of the seat as the console reads a seat's verb, and no more.
+func TestAHolderAnnouncesItsMachinesVerbsForTheConsole(t *testing.T) {
+	info := announcement(link.TheBuildMachine, moduleOf("ace.build-agent"), "ace")
+	if info.Name != "node-build-agent" || info.ID != "ace" || len(info.Endpoints) != 4 {
+		t.Fatalf("announced %s/%s with %d endpoints", info.Name, info.ID, len(info.Endpoints))
+	}
+	kill := info.Endpoints[1]
+	md := kill.Metadata
+	if kill.Subject != "mesh.seat.node-build-agent.tool.kill.ace" || md["kind"] != "seat" || md["seat"] != "node-build-agent" ||
+		md["scope"] != "node" || md["node"] != "ace" || md["tool"] != "kill" || md["module"] != "build-agent" ||
+		!strings.Contains(md["description"], "killed by hand") || !strings.Contains(md["schema"], `"id"`) {
+		t.Fatalf("kill is announced as %+v", kill)
+	}
+	body, err := json.Marshal(info)
+	if err != nil || len(body) > 8*1024 {
+		t.Fatalf("the answer is %d bytes (%v)", len(body), err)
+	}
+}

cmd/mesh-builder/main.go

@@ -141,6 +141,13 @@ func run() error {
 			return err
 		}
 		defer stopServing()
+		// And says so, for the console to find (novox/hq ADR 0197).
+		stopAnnouncing, err := link.OverNATS{Conn: js.Conn()}.Announce(
+			announcement(seat, moduleOf(credential.User), on), log.New(os.Stderr, "", 0))
+		if err != nil {
+			return err
+		}
+		defer stopAnnouncing()
 		go h.stateWhilePaused(ctx, time.Hour)
 	}
 

cmd/mesh-controller/plan_retry.go

@@ -156,17 +156,67 @@ func retryRefusal(p inventory.Plan, plans []inventory.Plan) error {
 	case p.Open():
 		return fmt.Errorf("%s is still %s; nothing in it failed to retry — `rebuild <module>` asks one module again", p.ID, p.State)
 	}
-	if q, found := newerOpenPlan(p, plans); found {
+	if len(failedIn(p)) > 0 {
-		return fmt.Errorf("%s supersedes it: a newer merge of %s (%s at %s) is open, and retrying %s would build "+
+		if q, found := newerOpenPlan(p, plans); found {
-			"what that one replaced", q.ID, q.Repository, q.ID, short(q.Commit), p.ID)
+			return fmt.Errorf("%s supersedes it: a newer merge of %s (%s at %s) is open, and retrying %s would build "+
+				"what that one replaced", q.ID, q.Repository, q.ID, short(q.Commit), p.ID)
+		}
+		return nil
 	}
-	if len(failedIn(p)) == 0 {
+	stopped := stoppedRollouts(p)
-		return fmt.Errorf("nothing in tier %d of %s failed to build — it stopped at: %s. Retry asks failed builds "+
+	if len(stopped) == 0 {
-			"again", p.Tier, p.ID, p.Note)
+		return fmt.Errorf("nothing in tier %d of %s failed to build or stopped rolling out — it stopped at: %s",
+			p.Tier, p.ID, p.Note)
+	}
+	// **A rollout is retried unless the module has moved on**: a newer plan holding it sends — or
+	// sent — a newer build, and sending this one again would put the older build back on its machines.
+	for _, m := range stopped {
+		if q, found := newerPlanFor(m, p, plans); found {
+			return fmt.Errorf("%s has a newer plan, %s (%s, %s at %s): sending %s's build of it again would put "+
+				"the older build back", m, q.ID, q.State, q.Repository, short(q.Commit), p.ID)
+		}
 	}
 	return nil
 }
 
+// stoppedRollouts is the modules of a plan's current tier whose rollout stopped at its first machine
+// (issue 249, ADR 0218): built, sent to the first machine, never to the rest, and why it stopped kept.
+func stoppedRollouts(p inventory.Plan) []string {
+	if p.Tier >= len(p.Tiers) {
+		return nil
+	}
+	var out []string
+	for _, m := range p.Tiers[p.Tier] {
+		if s := p.Modules[m]; s != nil && s.State == "built" && s.FirstAt != nil && s.SentAt == nil &&
+			len(s.First) > 0 && s.Why != "" {
+			out = append(out, m)
+		}
+	}
+	sort.Strings(out)
+	return out
+}
+
+// newerPlanFor is a plan made after this one that holds the module, superseded ones aside.
+func newerPlanFor(module string, p inventory.Plan, plans []inventory.Plan) (inventory.Plan, bool) {
+	for _, q := range plans {
+		if q.ID == p.ID || q.State == inventory.PlanSuperseded || !q.Created.After(p.Created) {
+			continue
+		}
+		for _, tier := range q.Tiers {
+			for _, m := range tier {
+				if m == module {
+					return q, true
+				}
+			}
+		}
+	}
+	return inventory.Plan{}, false
+}
+
+// sendRollout sends machines what the mesh would send them now, answering the ones it sent. A
+// variable so a test of a retried rollout needs no machine.
+var sendRollout = sendToEach
+
 // resumed sets a failed plan building again once nothing in its tier is failed.
 func resumed(p *inventory.Plan, why string) {
 	if p.State == inventory.PlanFailed && len(failedIn(*p)) == 0 {
@@ -192,9 +242,17 @@ func retryPlan(ctx context.Context, open *stores, id string) (string, error) {
 	if err != nil {
 		return "", err
 	}
+	recent, err := inv.RecentPlans(ctx, 50)
+	if err != nil {
+		return "", err
+	}
+	plans = append(plans, recent...)
 	if err := retryRefusal(p, plans); err != nil {
 		return "", err
 	}
+	if len(failedIn(p)) == 0 {
+		return retryRollouts(ctx, open, &p)
+	}
 	entries, err := inv.Catalogued(ctx)
 	if err != nil {
 		return "", err
@@ -306,3 +364,28 @@ func planHolding(module string, openPlans, recent []inventory.Plan) (inventory.P
 	}
 	return inventory.Plan{}, false
 }
+
+// retryRollouts sends each module whose rollout stopped to the machines it was first sent to, again,
+// records that send as the first anew, and sets the plan rolling: from there it goes on as the plan
+// would have — the rest sent once those report they applied it, the next tier after (ADR 0218).
+func retryRollouts(ctx context.Context, open *stores, p *inventory.Plan) (string, error) {
+	var said []string
+	for _, m := range stoppedRollouts(*p) {
+		s := p.Modules[m]
+		sent, err := sendRollout(ctx, open, s.First)
+		if err != nil {
+			return "", fmt.Errorf("%s could not be sent to %s again, so %s stays failed: %w",
+				m, strings.Join(s.First, ", "), p.ID, err)
+		}
+		now := time.Now().UTC()
+		s.First, s.FirstAt, s.Why = sent, &now, ""
+		said = append(said, m+" to "+strings.Join(sent, ", "))
+	}
+	p.State = inventory.PlanRolling
+	p.Note = fmt.Sprintf("tier %d retried by hand; sent %s first again", p.Tier, strings.Join(said, "; "))
+	if err := open.inventory.SavePlan(ctx, *p); err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s retried at tier %d of %d: sent %s first again; the rest follow once it reports it "+
+		"applied, as the plan would have", p.ID, p.Tier, len(p.Tiers), strings.Join(said, "; ")), nil
+}

cmd/mesh-controller/queue_test.go

@@ -580,3 +580,67 @@ func TestKillAndPauseAskTheHolderOnTheMachine(t *testing.T) {
 		t.Error("a machine nothing answers on was resumed")
 	}
 }
+
+// A plan that stopped at its first machine is retried: the module sent to that machine again, the
+// send recorded as the first anew, and the plan goes on — unless a newer plan holds the module.
+func TestAPlanStoppedAtItsFirstMachineIsRetried(t *testing.T) {
+	open := aMesh(t)
+	ctx := t.Context()
+	asked := asksRecorded(t)
+	twoTiers(t, open)
+	var sentTo [][]string
+	was := sendRollout
+	sendRollout = func(_ context.Context, _ *stores, names []string) ([]string, error) {
+		sentTo = append(sentTo, names)
+		return names, nil
+	}
+	t.Cleanup(func() { sendRollout = was })
+
+	long := time.Now().UTC().Add(-2 * time.Hour)
+	stopped := inventory.Plan{ID: "plan-rollout", Repository: "novox/a", Branch: "main", Commit: "c0ffee",
+		Created: long, State: inventory.PlanFailed, Tiers: [][]string{{"a"}, {"b"}},
+		Note: "a stopped at its first machine in tier 0: laptop refused what it was sent",
+		Modules: map[string]*inventory.PlanModule{"a": {State: "built", BuiltAt: &long, Commit: "c0ffee",
+			First: []string{"laptop"}, FirstAt: &long, Why: "laptop refused what it was sent"}}}
+	if err := open.inventory.SavePlan(ctx, stopped); err != nil {
+		t.Fatal(err)
+	}
+
+	// A newer plan holding a refuses it: sending the older build would put it back.
+	newer := inventory.Plan{ID: "plan-newer", Repository: "novox/other", Commit: "d00d", Created: long.Add(time.Hour),
+		State: inventory.PlanDone, Tiers: [][]string{{"a"}}, Modules: map[string]*inventory.PlanModule{}}
+	if err := open.inventory.SavePlan(ctx, newer); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := retryPlan(ctx, open, stopped.ID); err == nil || !strings.Contains(err.Error(), "plan-newer") {
+		t.Fatalf("retried under a newer plan: %v", err)
+	}
+	newer.State = inventory.PlanSuperseded
+	if err := open.inventory.SavePlan(ctx, newer); err != nil {
+		t.Fatal(err)
+	}
+
+	said, err := retryPlan(ctx, open, stopped.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(sentTo) != 1 || !reflect.DeepEqual(sentTo[0], []string{"laptop"}) || !strings.Contains(said, "laptop") {
+		t.Fatalf("sent %v; said %q", sentTo, said)
+	}
+	p, err := open.inventory.PlanByID(ctx, stopped.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	a := p.Modules["a"]
+	if p.State != inventory.PlanRolling || a.FirstAt == nil || !a.FirstAt.After(long) || a.Why != "" {
+		t.Fatalf("after retry the plan is %s, a %+v", p.State, a)
+	}
+	// And it goes on: a records (its policy sends nothing more), so the next tier is asked.
+	advancePlans(ctx, open)
+	if p, _ = open.inventory.PlanByID(ctx, stopped.ID); p.Tier != 1 || p.Modules["b"] == nil || p.Modules["b"].State != "asked" {
+		t.Fatalf("the retried plan did not go on: tier %d %s %+v", p.Tier, p.State, p.Modules["b"])
+	}
+	if len(*asked) != 1 {
+		t.Fatalf("asked %v", *asked)
+	}
+}

internal/link/builds_nats.go

@@ -106,7 +106,20 @@ func (b *natsBuilds) Submit(ctx context.Context, request BuildRequest,
 	waiting, cancelWait := context.WithTimeout(ctx, wait)
 	defer cancelWait()
 	for {
-		msg, err := outcomes.NextMsgWithContext(waiting)
+		// **A wait that hears a cancel** (novox/hq ADR 0219). A person cancelling an ask records its
+		// failure without publishing the role's outcome — that subject is the holders', and the
+		// controller may not speak for them — so the waiter also looks, every while, at the cancelled
+		// set the cancel wrote first. A kill needs no look: the holder announces it as any outcome.
+		slice, endSlice := context.WithTimeout(waiting, cancelLook)
+		msg, err := outcomes.NextMsgWithContext(slice)
+		endSlice()
+		if errors.Is(err, context.DeadlineExceeded) && waiting.Err() == nil {
+			if cancelled, _ := IsCancelled(b.js.Conn(), b.role(), request.ID); cancelled {
+				return BuildResult{ID: request.ID, Repository: request.Repository, Path: request.Path,
+					Ref: request.Ref, Source: request.Source, DryRun: request.DryRun, Failed: CancelledByHand}, nil
+			}
+			continue
+		}
 		switch {
 		case errors.Is(err, context.DeadlineExceeded):
 			return BuildResult{}, waitingFor(wait)
@@ -125,6 +138,9 @@ func (b *natsBuilds) Submit(ctx context.Context, request BuildRequest,
 	}
 }
 
+// cancelLook is how often a waiting asker looks whether its ask was cancelled.
+var cancelLook = 2 * time.Second
+
 // --- the machine's side ---------------------------------------------------------------------
 
 type natsMachine struct {

internal/link/queue_test.go

@@ -229,3 +229,39 @@ func TestNatsAHoldersPausedStateIsReadBack(t *testing.T) {
 		t.Fatalf("read back %+v", said)
 	}
 }
+
+// A `build` waiting on its outcome hears a cancel — which publishes no outcome — from the cancelled
+// set, and a kill from the outcome the holder announces (novox/hq ADR 0219).
+func TestNatsAWaitingAskerHearsItsAskCancelledOrKilled(t *testing.T) {
+	js := aBusWithACancelledSet(t)
+	was := cancelLook
+	cancelLook = 200 * time.Millisecond
+	t.Cleanup(func() { cancelLook = was })
+	ask := &natsBuilds{js: js, seat: TheBuildMachine}
+
+	go func() {
+		time.Sleep(500 * time.Millisecond)
+		_ = MarkCancelled(context.Background(), js, TheBuildMachine, "build-waited-cancelled")
+	}()
+	result, err := ask.Submit(context.Background(), BuildRequest{ID: "build-waited-cancelled", Repository: "/r"}, 10*time.Second)
+	if err != nil || result.Failed != CancelledByHand || result.ID != "build-waited-cancelled" {
+		t.Fatalf("the waiter heard %+v (%v)", result, err)
+	}
+
+	// Killed: the holder announces the failure as any outcome, and the waiter has it.
+	ctx, stop := context.WithCancel(context.Background())
+	defer stop()
+	machine := MachineOverNATS(js, "ace")
+	defer machine.Close()
+	go func() {
+		_ = machine.Take(ctx, func(ctx context.Context, work Build) {
+			r := work.Request()
+			_ = work.Announce(ctx, BuildResult{ID: r.ID, Repository: r.Repository, On: "ace", Failed: KilledByHand})
+			_ = work.Done()
+		})
+	}()
+	result, err = ask.Submit(context.Background(), BuildRequest{ID: "build-waited-killed", Repository: "/r"}, 10*time.Second)
+	if err != nil || result.Failed != KilledByHand || result.On != "ace" {
+		t.Fatalf("the waiter heard %+v (%v)", result, err)
+	}
+}