Feature 57 (config and provisioning): modules declare config and provisions, their files rendered from templates; synced with main (issues of feature 57, 874)

modules/postgres/cmd/postgres-provider/main.go

@@ -33,7 +33,32 @@ func main() {
 		return
 	}
 	var h *Harness
-	if receives := os.Getenv("MESH_RECEIVES"); receives == "" {
+	if consumers := handedConsumersFile(os.Getenv, os.Stat); consumers != "" {
+		// Handed to the provisioner (novox/hq ADR 0373): the provider helper answers the consumers its
+		// machine's client fills the file with; the grant directory is not read. Retirement is the
+		// harness's, never run, so its guards and its tools stand (issue 780).
+		h = &Harness{
+			Resource: ProvisionName,
+			Adapter:  provisioner{pg: pg, announce: announce},
+			Log:      func(format string, args ...any) { fmt.Fprintf(os.Stderr, format+"\n", args...) },
+			Announce: func(event string, body map[string]any) {
+				if err := stdio.Emit(event, body); err != nil {
+					say("emit %s failed: %v", event, err)
+				}
+			},
+			Node: os.Getenv("MESH_NODE"),
+		}
+		run, p, bus, err := moved(consumers, h)
+		if err != nil {
+			say("%v", err)
+		} else {
+			go func() {
+				if err := run.Run(context.Background(), p, bus); err != nil {
+					say("the provider helper stopped: %v", err)
+				}
+			}()
+		}
+	} else if receives := os.Getenv("MESH_RECEIVES"); receives == "" {
 		say("MESH_RECEIVES is not set — the provisioner cannot run without it")
 	} else {
 		h = &Harness{
@@ -52,6 +77,15 @@ func main() {
 		}
 		go h.Run(context.Background())
 	}
+	// Started on the grant path while the module is to be handed, it restarts itself when its client first fills
+	// the consumers' file, so the first fill moves it onto the helper without a hand restart (issue 780): `restart-on`
+	// names a service or a container, and the only one here is the database.
+	if at := os.Getenv("MESH_CONSUMERS_FILE"); at != "" && handedConsumersFile(os.Getenv, os.Stat) == "" {
+		go exitWhenFilled(at, os.Stat, 5*time.Second, func() {
+			say("%s is filled: restarting to answer from it", at)
+			os.Exit(0)
+		})
+	}
 	go audit()
 	// The store's reader is narrowed to what modules declare readable, at once and every minute, whether
 	// or not the provisioner runs: without a contributions file it is given nothing (novox/hq issue 337).
@@ -64,6 +98,31 @@ func main() {
 	}
 }
 
+// handedConsumersFile is the consumers' file when postgres is handed to the provisioner: the file MESH_CONSUMERS_FILE
+// names, which the controller places only where it hands the module. Empty, where it is not set or the file is not
+// there, and postgres then reads the grant directory exactly as it always did (issue 780).
+func handedConsumersFile(getenv func(string) string, stat func(string) (os.FileInfo, error)) string {
+	at := getenv("MESH_CONSUMERS_FILE")
+	if at == "" {
+		return ""
+	}
+	if _, err := stat(at); err != nil {
+		return ""
+	}
+	return at
+}
+
+// exitWhenFilled calls filled once the file is there, asking every so often.
+func exitWhenFilled(at string, stat func(string) (os.FileInfo, error), every time.Duration, filled func()) {
+	for {
+		if _, err := stat(at); err == nil {
+			filled()
+			return
+		}
+		time.Sleep(every)
+	}
+}
+
 // announce emits a lifecycle event without letting a broker hiccup fail the provisioning itself.
 func announce(event string, body map[string]string) {
 	if err := stdio.Emit(event, body); err != nil {