Every serving principal may answer the services discovery for what it serves; the controller announces its seat (hq ADR 0197)

Grants: a principal that serves tools subscribes $SRV.PING/$SRV.INFO and those questions under
each name it serves — its own and no other's; the tool runtime and people may ask. The controller
answers discovery for the mesh-controller seat in NATS's services format, one endpoint per verb it
serves, with the seat's description and schema. module list --json says which modules declare tools,
so the console expects an announcement only from those.

cmd/mesh-controller/modules.go

@@ -151,12 +151,16 @@ func moduleCommand(ctx context.Context, args []string) error {
 		// is, where it runs, whether it is current, and what it says of itself.
 		if len(args) > 1 && args[1] == "--json" {
 			type listed struct {
-				Module       string   `json:"module"`
-				Version      string   `json:"version"`
-				Built        string   `json:"built,omitempty"`
-				Head         string   `json:"head,omitempty"`
-				Current      bool     `json:"current"`
-				Provided     bool     `json:"provided,omitempty"`
+				Module   string `json:"module"`
+				Version  string `json:"version"`
+				Built    string `json:"built,omitempty"`
+				Head     string `json:"head,omitempty"`
+				Current  bool   `json:"current"`
+				Provided bool   `json:"provided,omitempty"`
+				// Tools says whether the module answers tools anywhere it runs: a list of its own,
+				// a bundle the runtime serves, or a seat's verbs it claims (novox/hq ADR 0197) —
+				// what the console checks the bus's answers against.
+				Tools        bool     `json:"tools"`
 				On           []string `json:"on"`
 				Provides     []string `json:"provides,omitempty"`
 				Requires     []string `json:"requires,omitempty"`
@@ -169,7 +173,7 @@ func moduleCommand(ctx context.Context, args []string) error {
 				l := listed{Module: m.Module, Version: m.Version, Built: e.Source.BuiltFrom, Head: e.Source.Head,
 					Current: e.Provided || e.Source.Repository == "" || e.Source.Current(), Provided: e.Provided,
 					On: append([]string{}, e.On...), Provides: m.Offers(), Requires: m.Requires,
-					Capabilities: m.Capabilities}
+					Capabilities: m.Capabilities, Tools: declaresTools(m)}
 				for _, c := range m.Claims {
 					l.Claims = append(l.Claims, c.At()+"/"+c.Name)
 				}
@@ -763,3 +767,23 @@ func claimsFor(ctx context.Context, inv *inventory.Inventory, m catalogue.Manife
 	}
 	return out, nil
 }
+
+// declaresTools is whether a module answers tools wherever it runs (novox/hq ADR 0197): it names
+// tools of its own, its build delivers a bundle the node's runtime serves, or it claims a seat
+// whose verbs it serves. A module with none is never expected to announce anything.
+func declaresTools(m catalogue.Manifest) bool {
+	if len(m.Tools) > 0 {
+		return true
+	}
+	for _, b := range m.Bundles {
+		if len(b.Loads) > 0 {
+			return true
+		}
+	}
+	for _, c := range m.Claims {
+		if len(c.Serves) > 0 {
+			return true
+		}
+	}
+	return false
+}

cmd/mesh-controller/push.go

@@ -151,6 +151,12 @@ func serve(ctx context.Context) error {
 		return err
 	}
 	defer stopServing()
+	// And says so on the bus (novox/hq ADR 0197): what it serves, as the NATS services protocol asks.
+	stopAnnouncing, err := bus.Announce(seatAnnouncement(handlers), log.New(os.Stdout, "", log.LstdFlags))
+	if err != nil {
+		return err
+	}
+	defer stopAnnouncing()
 
 	return server.Serve(ctx)
 }

cmd/mesh-controller/seatverbs.go

@@ -6,8 +6,10 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"github.com/nats-io/nats.go/micro"
 	"os"
 	"os/exec"
+	"sort"
 	"strings"
 
 	"github.com/novox/mesh-controller/internal/catalogue"
@@ -379,3 +381,43 @@ func splitCommandLine(line string) ([]string, error) {
 	}
 	return words, nil
 }
+
+// seatAnnouncement is what the controller says it serves on the bus (novox/hq ADR 0197): the
+// mesh-controller seat, one endpoint per verb it answers, each with the seat's own description and
+// argument schema — the same facts `tools` answers from the records, as NATS's services format.
+func seatAnnouncement(handlers map[string]link.ToolHandler) micro.Info {
+	about := map[string]catalogue.Verb{}
+	for _, s := range catalogue.SeatsWithAProtocol() {
+		if s.Name == catalogue.ControllerSeatName {
+			for _, v := range s.Serves {
+				about[v.Name] = v
+			}
+		}
+	}
+	verbs := make([]string, 0, len(handlers))
+	for verb := range handlers {
+		verbs = append(verbs, verb)
+	}
+	sort.Strings(verbs)
+	var endpoints []micro.EndpointInfo
+	for _, verb := range verbs {
+		schema, _ := json.Marshal(about[verb].Input)
+		endpoints = append(endpoints, micro.EndpointInfo{
+			Name:       verb,
+			Subject:    link.SeatToolSubject(catalogue.ControllerSeatName, verb),
+			QueueGroup: "seat." + catalogue.ControllerSeatName,
+			Metadata: map[string]string{
+				"description": about[verb].Description, "schema": string(schema),
+				"seat": catalogue.ControllerSeatName, "scope": "mesh",
+			},
+		})
+	}
+	return micro.Info{
+		ServiceIdentity: micro.ServiceIdentity{
+			Name: catalogue.ControllerSeatName, ID: "controller", Version: "1.0.0",
+			Metadata: map[string]string{"seat": catalogue.ControllerSeatName, "scope": "mesh"},
+		},
+		Description: "the mesh's own verbs, answered by the holder of the mesh-controller seat",
+		Endpoints:   endpoints,
+	}
+}

cmd/mesh-controller/seatverbs_test.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"github.com/novox/mesh-controller/internal/link"
 	"strings"
 	"testing"
 
@@ -264,3 +265,30 @@ func TestTheNodesAndModulesVerbsAnswerAsJSON(t *testing.T) {
 		}
 	}
 }
+
+// novox/hq ADR 0197: the controller announces exactly the verbs it serves, each on the subject and
+// queue it serves it on, with the seat's own description and schema, in NATS's services format.
+func TestTheControllerAnnouncesTheVerbsItServes(t *testing.T) {
+	handlers, _, err := seatToolHandlers()
+	if err != nil {
+		t.Fatal(err)
+	}
+	info := seatAnnouncement(handlers)
+	if info.Name != catalogue.ControllerSeatName || info.ID == "" || info.Version == "" {
+		t.Fatalf("the service is not named for the seat: %+v", info.ServiceIdentity)
+	}
+	if len(info.Endpoints) != len(handlers) {
+		t.Fatalf("%d endpoints announced for %d verbs served", len(info.Endpoints), len(handlers))
+	}
+	for _, e := range info.Endpoints {
+		if _, served := handlers[e.Name]; !served {
+			t.Errorf("%s is announced and not served", e.Name)
+		}
+		if e.Subject != link.SeatToolSubject(catalogue.ControllerSeatName, e.Name) || e.QueueGroup != "seat."+catalogue.ControllerSeatName {
+			t.Errorf("%s is announced on %s/%s, not where it is served", e.Name, e.Subject, e.QueueGroup)
+		}
+		if e.Metadata["description"] == "" || e.Metadata["schema"] == "" || e.Metadata["scope"] != "mesh" {
+			t.Errorf("%s is announced without its description, schema or scope: %v", e.Name, e.Metadata)
+		}
+	}
+}