Start the world's change counter, which the pass of a held backup reads (issue 1906, review round 1)

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

@@ -56,7 +56,7 @@ type parsed struct {
 }
 
 func newWorld() *world {
-	return &world{values: map[string]map[string][]byte{}, manifests: map[string]parsed{}, healthy: map[string][]string{}}
+	return &world{values: map[string]map[string][]byte{}, manifests: map[string]parsed{}, healthy: map[string][]string{}, changes: map[string]uint64{}}
 }
 
 // put takes a change of a watched bucket in: a value, or nil for a key deleted or purged.

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

@@ -111,3 +111,17 @@ func TestAManifestFallingBackToAPredefinedKeyIsReadable(t *testing.T) {
 		t.Errorf("xterm: waits %q, unreadable %q, want read", waits, ch.Unreadable["xterm"])
 	}
 }
+
+// Review round 1 (items 3 and 4): the world counts the values a key takes, so a have written again after an answer is seen.
+func TestTheWorldCountsTheValuesAKeyTakes(t *testing.T) {
+	w := newWorld()
+	w.put(delivery.HaveBucket, "ace.web", []byte(`{"v":1}`))
+	w.put(delivery.HaveBucket, "ace.web", []byte(`{"v":1}`))
+	w.put(delivery.HaveBucket, "ace.mail", []byte(`{"v":1}`))
+	if got := w.changed(delivery.HaveBucket, "ace.web"); got != 2 {
+		t.Errorf("changed = %d, want 2", got)
+	}
+	if got := w.changed(delivery.HaveBucket, "gone"); got != 0 {
+		t.Errorf("changed = %d for a key never seen", got)
+	}
+}