Assigner: bind the seat's states at each pass and say while it waits for them, since their creation can come before this credential may hear it (ADR 0567 §1, review round 3)

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/main.go

@@ -305,6 +305,9 @@ func follow(ctx context.Context, js jetstream.JetStream, nc process.Subscriber,
 		}
 	}
 	takePlacement := func(a appeared) error {
+		if kvs[a.name] != nil {
+			return nil // bound already, by the other of its two events
+		}
 		kvs[a.name] = a.kv
 		logger.Printf("the bucket %s is open and watched", a.name)
 		return watch(a.name)
@@ -343,6 +346,23 @@ func follow(ctx context.Context, js jetstream.JetStream, nc process.Subscriber,
 			}
 		case <-dirty:
 			reopenPuts(p)
+			// The grants part makes the seat's buckets in the pass that seals the list granting them, so their creation can
+			// be said before this credential may hear it: every pass, itself started by a watched change, binds each one the
+			// bus now holds, and says the seat waits while one is missing.
+			var unbound []string
+			for _, name := range seatBuckets {
+				if kvs[name] != nil || js == nil {
+					continue
+				}
+				if kv, err := js.KeyValue(ctx, name); err == nil {
+					if err := takePlacement(appeared{name, kv}); err != nil {
+						return err
+					}
+					continue
+				}
+				unbound = append(unbound, name)
+			}
+			p.sayWaits(unbound)
 			p.pass(ctx)
 		}
 	}

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/pass.go

@@ -48,6 +48,8 @@ type passer struct {
 	seat         *seatActs
 	publish      publisher
 	saidProposed map[string]bool
+	// saidWaits is the last said of the seat's wait for its states (sayWaits).
+	saidWaits string
 	intended     map[string]map[string]map[string]bool
 }
 

modules/mesh-delivery-assigner/cmd/mesh-delivery-assigner/seat.go

@@ -15,6 +15,7 @@ import (
 	"github.com/nats-io/nats.go"
 	"github.com/nats-io/nats.go/jetstream"
 
+	"git.novox.be/novox/mesh-sdk/go/asks"
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/compose"
 	"git.novox.be/novox/mesh-sdk/go/compose/frombus"
@@ -180,6 +181,23 @@ func (p *passer) withCalls(pairs []assign.Pair) []assign.Pair {
 	return pairs
 }
 
+// sayWaits raises, once, that the seat waits for the states not yet bound, and clears it once, when all are.
+func (p *passer) sayWaits(unbound []string) {
+	c := assign.SeatWaitsCondition(unbound)
+	state := string(c.State) + c.Summary
+	if p.say == nil || p.said[c.Key] && p.saidWaits == state {
+		return
+	}
+	if c.State == asks.StateCleared && p.saidWaits == "" {
+		return // nothing was raised by this process
+	}
+	if err := p.say(c); err != nil {
+		p.logf("that the seat waits for its states could not be said, and is said at the next pass: %v", err)
+		return
+	}
+	p.said[c.Key], p.saidWaits = true, state
+}
+
 // seatPlacements is every node's placement key and its revision, as the watch holds them.
 func (p *passer) seatPlacements() (map[string]delivery.Placement, map[string]uint64) {
 	out, revs := map[string]delivery.Placement{}, map[string]uint64{}

modules/mesh-delivery-assigner/internal/assign/placement.go

@@ -2,6 +2,7 @@ package assign
 
 import (
 	"fmt"
+	"strings"
 	"sort"
 
 	"git.novox.be/novox/mesh-sdk/go/asks"
@@ -104,3 +105,17 @@ func PlacementCondition(p Pair, raised bool) asks.Condition {
 			"name a module on a node (ADR 0549 §5): the assigner writes no want for it there and leaves the one it wrote before, so "+
 			"nothing moves or is removed. This clears once both name it or neither does.", asks.NeedsYou, needs, p.Only, p.Module, p.Node)}
 }
+
+// SeatWaitsCondition is the assigner's word on the seat mesh-placement while a state of the seat is not bound (ADR 0567
+// §1): raised naming each, cleared when none is left.
+func SeatWaitsCondition(unbound []string) asks.Condition {
+	key := delivery.AssignerModule + ".seat-states"
+	subject := asks.Scope{Scope: "module", ID: delivery.AssignerModule}
+	if len(unbound) == 0 {
+		return asks.Condition{Key: key, Subject: subject, State: asks.StateCleared, Resolved: "the seat mesh-placement holds all its states."}
+	}
+	why := "the seat waits for its states: " + strings.Join(unbound, ", ") + " are not on the bus or not granted yet"
+	return asks.Condition{Key: key, Severity: asks.SeverityWarning, Subject: subject, State: asks.StateRaised,
+		Summary: "the seat waits for its states", Headline: "the seat waits for its states",
+		Explanation: asks.NothingToDo + " " + why + "; each is bound at the next pass once it is, with no restart."}
+}

modules/mesh-delivery-assigner/internal/assign/seat_test.go

@@ -82,6 +82,15 @@ func TestThePlacementSeatDecides(t *testing.T) {
 		t.Error("a proposal written whole leaves something to write")
 	}
 
+	// The seat says it waits while one of its states is not bound, naming it, and clears once all are.
+	for _, unbound := range [][]string{{delivery.PlacementPulsesBucket}, nil} {
+		c := SeatWaitsCondition(unbound)
+		if _, err := asks.EncodeCondition(c); err != nil || (len(unbound) > 0) != (c.State == asks.StateRaised) ||
+			(len(unbound) > 0 && !strings.Contains(c.Explanation, "the seat waits for its states: "+delivery.PlacementPulsesBucket)) {
+			t.Errorf("waiting for %v: %+v, %v", unbound, c, err)
+		}
+	}
+
 	writes, err := Writes(p, laid)
 	if err != nil || len(writes) != 2 || writes[0].Key != "placement.anchor" || writes[0].Base != 4 || writes[1].Base != 9 {
 		t.Fatalf("writes = %+v, %v", writes, err)