internal/link/enrolment.go

@@ -151,6 +151,18 @@ func (e Enrolment) Heard(ctx context.Context, report Report) error {
 	if err != nil {
 		return err
 	}
+
+	// A bare word that a node is there is not an account of what the machine did or holds: it
+	// moves last_seen and touches nothing else. This arrives every minute (link.AliveEvery),
+	// while a real report is rare, so recording it as one would overwrite the node's last real
+	// apply with an empty one — wiping the declaration digest that decides whether the node is
+	// current, the carried ports a push assigns around, and the clean-or-failed outcome — and a
+	// node that had just caught up would read as behind within the minute. The alive path calls
+	// this with only a node name; a real report always carries an account (something applied, or
+	// a refusal, or a failure), so those are the reports that get written down.
+	if report.Applied == nil && report.Refused == "" && len(report.Failed) == 0 {
+		return e.Inventory.Seen(ctx, node.ID)
+	}
 	// What it did is kept whichever way it went. Until this, a refusal or a failure moved
 	// last_seen and the reason went to a log line, so "which machine is not doing what it was
 	// told" had no answer the next morning — which is the question a mesh exists to answer.

internal/link/heard_test.go

@@ -86,6 +86,69 @@ func TestACleanApplyIsRecordedAsOne(t *testing.T) {
 	}
 }
 
+func TestABareAliveDoesNotWipeTheDeclarationThatSaysANodeIsCurrent(t *testing.T) {
+	// A node reports it is alive every minute and describes what it applied rarely. If a bare
+	// alive were written down as a report it would replace the last real apply with an empty one
+	// — clearing the declaration digest current is measured against — so a node that had just
+	// caught up would read as behind within the minute, and never converge. The lab saw exactly
+	// this: a heavy wave whose apply outran the first heartbeat never reached `current`.
+	inv := inventory.ForTest(t)
+	ctx := context.Background()
+	node, err := inv.AddNode(ctx, "anchor")
+	if err != nil {
+		t.Fatal(err)
+	}
+	// The mesh sent this node a declaration, and the node applied it and named which by digest.
+	const digest = "d640d1b6a1b2c3d4e5f60718293a4b5c6d7e8f90a1b2c3d4e5f6071829304152"
+	if err := inv.RecordSent(ctx, node.ID, digest); err != nil {
+		t.Fatal(err)
+	}
+	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{
+		Node: "anchor", Applied: []string{"a", "b"}, Declared: digest, Carried: []int{5432},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	currentOf := func(name string) bool {
+		reports, err := inv.LastReports(ctx)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, r := range reports {
+			if r.Node == name {
+				return r.Current
+			}
+		}
+		t.Fatalf("no report for %s", name)
+		return false
+	}
+	if !currentOf("anchor") {
+		t.Fatal("a node that applied exactly what it was sent does not read as current")
+	}
+
+	// Now the node says only that it is there, as it does every minute.
+	if err := (link.Enrolment{Inventory: inv}).Heard(ctx, link.Report{Node: "anchor"}); err != nil {
+		t.Fatal(err)
+	}
+	if !currentOf("anchor") {
+		t.Fatal("a bare alive wiped the declaration digest, so a current node now reads as behind")
+	}
+	// And the last real account of what it did and holds is untouched.
+	doing, said, err := inv.DoingOf(ctx, "anchor")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !said || doing.Outcome != inventory.OutcomeApplied || doing.Applied != 2 {
+		t.Fatalf("a bare alive overwrote the last real report: said=%v %+v", said, doing)
+	}
+	owned, _, err := inv.Owned(ctx, node.ID)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(owned) != 2 {
+		t.Fatalf("a bare alive replaced the account of what the machine holds: %v", owned)
+	}
+}
+
 func TestAFailureDoesNotBecomeTheAccountOfWhatTheMachineHolds(t *testing.T) {
 	// A partial list is not an account of what the machine holds. Recording one as though it
 	// were would tell a rebuilding node to remove what it still has — which is the fault that