Fix watch error when http & https are disabled

Remove an error in watch reloading that happens when http and https
are both disabled, and use an https address for running watches if
no http addresses are present.

Fixes #3425.

agent/agent.go

@@ -515,8 +515,19 @@ func (a *Agent) serveHTTP(l net.Listener, srv *HTTPServer) error {
 // reloadWatches stops any existing watch plans and attempts to load the given
 // set of watches.
 func (a *Agent) reloadWatches(cfg *config.RuntimeConfig) error {
+	// Stop the current watches.
+	for _, wp := range a.watchPlans {
+		wp.Stop()
+	}
+	a.watchPlans = nil
+
+	// Return if there are no watches now.
+	if len(cfg.Watches) == 0 {
+		return nil
+	}
+
 	// Watches use the API to talk to this agent, so that must be enabled.
-	if len(cfg.HTTPAddrs) == 0 {
+	if len(cfg.HTTPAddrs) == 0 && len(cfg.HTTPSAddrs) == 0 {
 		return fmt.Errorf("watch plans require an HTTP or HTTPS endpoint")
 	}
 
@@ -539,16 +550,18 @@ func (a *Agent) reloadWatches(cfg *config.RuntimeConfig) error {
 		watchPlans = append(watchPlans, wp)
 	}
 
-	// Stop the current watches.
-	for _, wp := range a.watchPlans {
-		wp.Stop()
-	}
-	a.watchPlans = nil
-
-	// deterine the primary http endpoint
-	addr := cfg.HTTPAddrs[0].String()
-	if cfg.HTTPAddrs[0].Network() == "unix" {
-		addr = "unix://" + addr
+	// Determine the primary http(s) endpoint.
+	var addr string
+	if len(cfg.HTTPAddrs) > 0 {
+		addr = cfg.HTTPAddrs[0].String()
+		if cfg.HTTPAddrs[0].Network() == "unix" {
+			addr = "unix://" + addr
+		}
+	} else {
+		addr = cfg.HTTPSAddrs[0].String()
+		if cfg.HTTPSAddrs[0].Network() == "unix" {
+			addr = "unix://" + addr
+		}
 	}
 
 	// Fire off a goroutine for each new watch plan.

agent/agent_test.go

@@ -1918,3 +1918,49 @@ func TestAgent_GetCoordinate(t *testing.T) {
 	check(true)
 	check(false)
 }
+
+func TestAgent_reloadWatches(t *testing.T) {
+	t.Parallel()
+	a := NewTestAgent(t.Name(), "")
+	defer a.Shutdown()
+
+	// Normal watch with http addr set, should succeed
+	newConf := *a.config
+	newConf.Watches = []map[string]interface{}{
+		{
+			"type":    "key",
+			"key":     "asdf",
+			"handler": "ls",
+		},
+	}
+	if err := a.reloadWatches(&newConf); err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+
+	// Should still succeed with only HTTPS addresses
+	newConf.HTTPSAddrs = newConf.HTTPAddrs
+	newConf.HTTPAddrs = make([]net.Addr, 0)
+	newConf.Watches = []map[string]interface{}{
+		{
+			"type":    "key",
+			"key":     "asdf",
+			"handler": "ls",
+		},
+	}
+	if err := a.reloadWatches(&newConf); err != nil {
+		t.Fatalf("bad: %s", err)
+	}
+
+	// Should fail to reload with no http or https addrs
+	newConf.HTTPSAddrs = make([]net.Addr, 0)
+	newConf.Watches = []map[string]interface{}{
+		{
+			"type":    "key",
+			"key":     "asdf",
+			"handler": "ls",
+		},
+	}
+	if err := a.reloadWatches(&newConf); err == nil || !strings.Contains(err.Error(), "watch plans require an HTTP or HTTPS endpoint") {
+		t.Fatalf("bad: %s", err)
+	}
+}