mesh-self-check reads a node's presence through the watchdogs client: a part's key is no node, a refused version is an error (ADR 0634 section 4; issue 1966)

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-self-check/cmd/mesh-self-check/probes_mesh.go

@@ -10,7 +10,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	watchdogs "git.novox.be/novox/mesh-contracts/health-and-repair/go/seats/meshwatchdogs"
+	watchdogsclient "git.novox.be/novox/mesh-contracts/health-and-repair/go/clients/meshwatchdogsclient"
 	assignerclient "git.novox.be/novox/mesh-contracts/placement/go/clients/meshmoduleassignerclient"
 	placing "git.novox.be/novox/mesh-contracts/placement/go/seats/meshmoduleassigner"
 	"net"
@@ -65,16 +65,22 @@ func (c *Checker) heard() (map[string]bool, error) {
 	}
 	out := map[string]bool{}
 	for _, k := range keys {
-		node, ok := watchdogs.ParsePresenceByNodeKey(k)
-		if !ok || node == "" {
+		node, _, _, err := watchdogsclient.ParsePresenceKey(k)
+		if err != nil || node == "" { // a part's key is no node's, and a key of no form is not read
 			continue
 		}
 		raw, ok, err := c.Store.Get(PresenceRead, k)
 		if err != nil {
 			return nil, fmt.Errorf("the presence of %s cannot be read: %w", node, err)
 		}
-		var p watchdogs.PresenceByNodeValue
-		if ok && json.Unmarshal(raw, &p) == nil && p.Online {
+		if !ok {
+			continue
+		}
+		p, err := watchdogsclient.DecodeNodePresence(raw)
+		if err != nil {
+			return nil, fmt.Errorf("the presence of %s is not read: %w", node, err)
+		}
+		if p.Online {
 			out[node] = true
 		}
 	}

modules/mesh-self-check/cmd/mesh-self-check/probes_test.go

@@ -6,7 +6,7 @@ import (
 	"errors"
 	engineclient "git.novox.be/novox/mesh-contracts/go/clients/nodeengineclient"
 	nodeseat "git.novox.be/novox/mesh-contracts/go/seats/nodeengine"
-	watchdogs "git.novox.be/novox/mesh-contracts/health-and-repair/go/seats/meshwatchdogs"
+	watchdogsclient "git.novox.be/novox/mesh-contracts/health-and-repair/go/clients/meshwatchdogsclient"
 	assignerclient "git.novox.be/novox/mesh-contracts/placement/go/clients/meshmoduleassignerclient"
 	placing "git.novox.be/novox/mesh-contracts/placement/go/seats/meshmoduleassigner"
 	catalogclient "git.novox.be/novox/mesh-delivery/contracts/go/clients/meshcatalogclient"
@@ -269,7 +269,7 @@ func machines() *memStore {
 			pl.Modules = []placing.PlacedModule{{Module: "sshd"}} // a module key beside the node key
 		}
 		place(s, pl)
-		_ = s.Put(PresenceRead, p.node, watchdogs.PresenceByNodeValue{V: 1, Online: p.online})
+		_ = s.Put(PresenceRead, p.node, watchdogsclient.NodePresence{V: 1, Online: p.online})
 		key, _ := assignerclient.SeatHoldersKey(BannedSeat, p.node)
 		_ = s.Put(SeatHoldersRead, key, placing.SeatHolders{V: 1, Seat: BannedSeat, Scope: "node", Node: p.node,
 			Holders: []placing.SeatHoldersHoldersItem{{Module: "fail2ban", Node: p.node}}})
@@ -438,7 +438,7 @@ func (r *dataRig) holder(node string) {
 	key, _ := assignerclient.SeatHoldersKey("node-backup", node)
 	_ = r.s.Put(SeatHoldersRead, key, placing.SeatHolders{V: 1, Seat: "node-backup", Scope: "node", Node: node,
 		Holders: []placing.SeatHoldersHoldersItem{{Module: "restic", Node: node}}})
-	_ = r.s.Put(PresenceRead, node, watchdogs.PresenceByNodeValue{V: 1, Online: true})
+	_ = r.s.Put(PresenceRead, node, watchdogsclient.NodePresence{V: 1, Online: true})
 }
 
 // dataMesh builds the mesh: pg declares data (backed up within 48 h, written all the time within 24 h) and dumps; plex
@@ -485,3 +485,24 @@ func dataMesh(change func(*dataRig)) *memStore {
 	}
 	return r.s
 }
+
+// TestPresenceIsReadThroughTheWatchdogsClient holds the node's presence to the client's codec (ADR 0634 section 4): a
+// part's key (`part.<part>.<instance>`) is no node, and a value of a version the client refuses is a refusal, not a
+// node that is offline.
+func TestPresenceIsReadThroughTheWatchdogsClient(t *testing.T) {
+	s := newStore()
+	_ = s.Put(PresenceRead, "ace", watchdogsclient.NodePresence{V: 1, Online: true})
+	_ = s.Put(PresenceRead, "part.watchman.1", watchdogsclient.PartPresence{V: 1, Online: true})
+	c := &Checker{Store: s}
+	heard, err := c.heard()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(heard) != 1 || !heard["ace"] {
+		t.Errorf("heard %v, want only ace: a part's presence is no node's", heard)
+	}
+	_ = s.Put(PresenceRead, "g14", watchdogsclient.NodePresence{V: 99, Online: true})
+	if _, err := c.heard(); err == nil {
+		t.Error("a presence of a version the client refuses was read as a node's")
+	}
+}

modules/mesh-self-check/go.mod

@@ -5,7 +5,7 @@ go 1.26.0
 require (
 	git.novox.be/novox/mesh-delivery/contracts/go/clients/meshcatalogclient v0.0.0-00010101000000-000000000000
 	git.novox.be/novox/mesh-delivery/contracts/go/seats/meshcatalog v0.0.0-00010101000000-000000000000
-	git.novox.be/novox/mesh-contracts/health-and-repair/go/seats/meshwatchdogs v0.0.0-00010101000000-000000000000
+	git.novox.be/novox/mesh-contracts/health-and-repair/go/clients/meshwatchdogsclient v0.0.0-00010101000000-000000000000
 	git.novox.be/novox/mesh-contracts/go/seats/nodeengine v0.0.0-00010101000000-000000000000
 	git.novox.be/novox/mesh-contracts/go/clients/nodeengineclient v0.0.0-00010101000000-000000000000
 	git.novox.be/novox/mesh-contracts/placement/go/seats/meshmoduleassigner v0.0.0-00010101000000-000000000000