Leave an announced move to the plan rolling the module out (hq issue 249)

The catalogue's upgrade announcement sent every machine one after another
without waiting for any to apply, beside the plan that now sends one
machine first. A module an open plan has not finished sending is the
plan's to roll out.

cmd/mesh-controller/rollout_first_test.go

@@ -82,3 +82,22 @@ func TestAPlanSendsOneMachineFirstAndTheRestAfterItsReport(t *testing.T) {
 		t.Fatalf("a module on one machine waited for more: %+v", step)
 	}
 }
+
+// An announced move of a module an open plan is still rolling out is left to the plan: sending it
+// here as well put the bundle on every machine at once (novox/hq issue 249).
+func TestAnAnnouncedMoveIsLeftToThePlanRollingItOut(t *testing.T) {
+	sent := time.Now()
+	plans := []inventory.Plan{
+		{ID: "plan-done", State: inventory.PlanDone, Modules: map[string]*inventory.PlanModule{"agent": {}}},
+		{ID: "plan-1", State: inventory.PlanRolling, Modules: map[string]*inventory.PlanModule{
+			"agent": {State: "built", First: []string{"ace"}, FirstAt: &sent}, "gitea": {State: "built", SentAt: &sent}}},
+	}
+	if got := rolledOutByAPlan(plans, "agent"); got != "plan-1" {
+		t.Fatalf("a module the plan is rolling out was not left to it: %q", got)
+	}
+	for _, m := range []string{"gitea", "keycloak"} {
+		if got := rolledOutByAPlan(plans, m); got != "" {
+			t.Errorf("%s, which no plan will send, was left to %s", m, got)
+		}
+	}
+}

cmd/mesh-controller/upgrades.go

@@ -56,6 +56,18 @@ func (f following) Upgraded(ctx context.Context, u link.Upgraded) error {
 		return nil
 	}
 
+	// **A plan that holds the module rolls it out, and this does not** (novox/hq issue 249, ADR
+	// 0218). A merge's plan builds the module and sends it one machine first, the rest once that one
+	// has applied it; this announcement arrives as the build registers, and sending here too — one
+	// machine after another without waiting for any to apply — put the new bundle on every machine in
+	// the same minute, whatever the plan was waiting for. A move no plan answers (a build asked by
+	// hand) is still this handler's.
+	if plans, err := inv.OpenPlans(ctx); err != nil {
+		return notNow(err)
+	} else if id := rolledOutByAPlan(plans, u.Module); id != "" {
+		fmt.Printf("%s moved to %s; %s rolls it out to %s\n", u.Module, shortCommit(u.Commit), id, readableList(on))
+		return nil
+	}
 	if decision.Together {
 		fmt.Printf("%s moved to %s; sending %s together\n",
 			u.Module, shortCommit(u.Commit), readableList(on))
@@ -77,6 +89,17 @@ func (f following) Upgraded(ctx context.Context, u link.Upgraded) error {
 	return nil
 }
 
+// rolledOutByAPlan is the open plan that will send a module's machines its new build — one holding
+// the module that has not finished sending it — or empty when none will (novox/hq issue 249).
+func rolledOutByAPlan(plans []inventory.Plan, module string) string {
+	for _, p := range plans {
+		if s, holds := p.Modules[module]; p.Open() && holds && (s == nil || s.SentAt == nil) {
+			return p.ID
+		}
+	}
+	return ""
+}
+
 // readableList names machines the way a sentence does, because this is read by a person deciding
 // whether an upgrade went where they expected.
 func readableList(names []string) string {