mesh-watcher: hear the self-check run the take-over key names; take the release sdk and go 1.26 (issue 1952 W1)

modules/mesh-watcher/cmd/mesh-watcher/main.go

@@ -15,6 +15,7 @@ import (
 	"time"
 
 	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/health"
 )
 
 func logf(format string, a ...any) { fmt.Fprintf(os.Stderr, format+"\n", a...) }
@@ -98,8 +99,10 @@ func run(w *Watcher, l *listening, node string) {
 			time.Sleep(10 * time.Minute)
 		}
 	}()
+	follow := newTakeover()
+	go followTakeover(follow)
 	handle := func(e stdio.Envelope) error {
-		if !isHeartbeat(e.Key) {
+		if !follow.heard(e.Key) {
 			return nil
 		}
 		b, err := DecodeBeat(e.Body)
@@ -113,6 +116,9 @@ func run(w *Watcher, l *listening, node string) {
 	time.Sleep(500 * time.Millisecond)
 	for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
 		err := stdio.Subscribe(ControllerSeat+".*", handle)
+		if err == nil {
+			err = stdio.Subscribe(health.SelfCheckModule+".*", handle)
+		}
 		if err == nil {
 			l.set("listening")
 			logf("[mesh-watcher] listening for the self-check's heartbeat; watching from %s", node)

modules/mesh-watcher/cmd/mesh-watcher/manifest_test.go

@@ -34,7 +34,7 @@ func TestTheManifestSaysWhatTheCodeDoes(t *testing.T) {
 	if err := json.Unmarshal(raw, &m); err != nil {
 		t.Fatal(err)
 	}
-	if !reflect.DeepEqual(m.Consumes, []string{ControllerSeat + "." + HeartbeatEvent}) {
+	if !reflect.DeepEqual(m.Consumes, []string{ControllerSeat + "." + HeartbeatEvent, "mesh-self-check.checked"}) {
 		t.Fatalf("consumes %v", m.Consumes)
 	}
 	if !reflect.DeepEqual(m.Invokes, []string{m.Module + ".watcher_ping", "seat:mesh-controller.seats"}) {

modules/mesh-watcher/cmd/mesh-watcher/takeover.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"sync"
+	"time"
+
+	stdio "git.novox.be/novox/mesh-sdk/go"
+	"git.novox.be/novox/mesh-sdk/go/health"
+)
+
+// takeover is which self-check run the watcher hears: the controller's `doctor-heartbeat` until the keeper's
+// take-over key names the keeper, then mesh-self-check's `checked`, whose body is the same run (novox/hq ADR 0564
+// clause 9, issue 1952 W1). An absent key follows the controller.
+type takeover struct {
+	mu sync.Mutex
+	t  health.Takeover
+}
+
+func newTakeover() *takeover {
+	return &takeover{t: health.Takeover{V: health.TakeoverVersion, Follow: health.FollowController}}
+}
+
+// heard says whether key is the followed self-check event.
+func (f *takeover) heard(key string) bool {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	seat, event := f.t.SelfCheckEvent()
+	return key == seat+"."+event
+}
+
+func (f *takeover) set(value []byte, found bool) error {
+	t, err := health.DecodeTakeover(value, found)
+	if err != nil {
+		return err
+	}
+	f.mu.Lock()
+	f.t = t
+	f.mu.Unlock()
+	return nil
+}
+
+// followTakeover watches the key for the life of the process; one it cannot read leaves the event it heard.
+func followTakeover(f *takeover) {
+	for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
+		err := stdio.State(health.KeeperModule+"."+health.TakeoverState).Watch(health.TakeoverKey, func(c stdio.StateChange) error {
+			if err := f.set(c.Value, c.Op != "delete" && len(c.Value) > 0); err != nil {
+				logf("[mesh-watcher] the take-over key is unreadable (%v); no change in what it hears", err)
+			} else {
+				logf("[mesh-watcher] the take-over key now follows %s", f.t.Follow)
+			}
+			return nil
+		})
+		if err == nil {
+			return
+		}
+		logf("[mesh-watcher] not watching the take-over key yet (%v)", err)
+		time.Sleep(wait)
+	}
+}

modules/mesh-watcher/go.mod

@@ -1,5 +1,5 @@
 module mesh-watcher
 
-go 1.22
+go 1.26.0
 
-require git.novox.be/novox/mesh-sdk/go v0.1.7
+require git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029204453-69fcb6c1c1ba

modules/mesh-watcher/go.sum

@@ -1,2 +1,2 @@
-git.novox.be/novox/mesh-sdk/go v0.1.7 h1:C0sTQmtTiyYH7bnqZb7PusXnqA37gKuT7Nqjn9gG47w=
-git.novox.be/novox/mesh-sdk/go v0.1.7/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029204453-69fcb6c1c1ba h1:uXwkcQWgbu/UthizGHFaKPiA4NBVJgqL9q2jJnnGR1o=
+git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261029204453-69fcb6c1c1ba/go.mod h1:ouERNpZizzwZ0HLEtAypsY9FR20FyUgUYRni6J7kVCY=

modules/mesh-watcher/module.json

@@ -3,7 +3,11 @@
   "version": "1",
   "slug": "watch",
   "consumes": [
-    "mesh-controller.doctor-heartbeat"
+    "mesh-controller.doctor-heartbeat",
+    "mesh-self-check.checked"
+  ],
+  "reads": [
+    "mesh-conditions.takeover"
   ],
   "invokes": [
     "mesh-watcher.watcher_ping",