From 4f337f4fa58bcbb00526b3f73b2198952e8f008f Mon Sep 17 00:00:00 2001
From: Link Dupont <link@sub-pop.net>
Date: Fri, 15 Sep 2023 13:27:56 -0400
Subject: [PATCH] feat: new flag: mqtt-reconnect-delay

Add a new hidden flag: --mqtt-reconnect-delay. This flag will sleep for
the given duration before attempting to reconnect to the MQTT broker.
This only works if --mqtt-auto-reconnect is enabled (it is true by
default).

Signed-off-by: Link Dupont <link@sub-pop.net>
---
 cmd/yggd/main.go           |  7 +++++++
 internal/config/config.go  |  5 +++++
 internal/transport/mqtt.go | 12 ++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/cmd/yggd/main.go b/cmd/yggd/main.go
index 046d9ff7..c7dd0230 100644
--- a/cmd/yggd/main.go
+++ b/cmd/yggd/main.go
@@ -65,6 +65,7 @@ func setupDefaultConfig(c *cli.Context) {
 		MQTTConnectRetry:         c.Bool(config.FlagNameMQTTConnectRetry),
 		MQTTConnectRetryInterval: c.Duration(config.FlagNameMQTTConnectRetryInterval),
 		MQTTAutoReconnect:        c.Bool(config.FlagNameMQTTAutoReconnect),
+		MQTTReconnectDelay:       c.Duration(config.FlagNameMQTTReconnectDelay),
 	}
 }
 
@@ -508,6 +509,12 @@ func main() {
 			Value:  true,
 			Hidden: true,
 		}),
+		altsrc.NewDurationFlag(&cli.DurationFlag{
+			Name:   config.FlagNameMQTTReconnectDelay,
+			Usage:  "Sets the time to wait before attempting to reconnect to `DURATION`",
+			Value:  0 * time.Second,
+			Hidden: true,
+		}),
 	}
 
 	app.EnableBashCompletion = true
diff --git a/internal/config/config.go b/internal/config/config.go
index 5e65fff2..4f8f46a5 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -27,6 +27,7 @@ const (
 	FlagNameMQTTConnectRetry         = "mqtt-connect-retry"
 	FlagNameMQTTConnectRetryInterval = "mqtt-connect-retry-interval"
 	FlagNameMQTTAutoReconnect        = "mqtt-auto-reconnect"
+	FlagNameMQTTReconnectDelay       = "mqtt-reconnect-delay"
 )
 
 var DefaultConfig = Config{
@@ -91,6 +92,10 @@ type Config struct {
 	// MQTTAutoReconnect is the MQTT client option that enables automatic
 	// reconnection logic when the client unexpectedly disconnects.
 	MQTTAutoReconnect bool
+
+	// MQTTReconnectDelay is the duration the client with wait before attempting
+	// to reconnect to the MQTT broker.
+	MQTTReconnectDelay time.Duration
 }
 
 // CreateTLSConfig creates a tls.Config object from the current configuration.
diff --git a/internal/transport/mqtt.go b/internal/transport/mqtt.go
index 14dc8960..e8150f4e 100644
--- a/internal/transport/mqtt.go
+++ b/internal/transport/mqtt.go
@@ -99,6 +99,18 @@ func NewMQTTTransport(clientID string, brokers []string, tlsConfig *tls.Config)
 		t.events <- TransporterEventDisconnected
 	})
 
+	opts.SetReconnectingHandler(func(c mqtt.Client, co *mqtt.ClientOptions) {
+		log.Debugf("reconnecting to broker: %v", co.Servers)
+
+		if config.DefaultConfig.MQTTReconnectDelay > 0 {
+			log.Infof(
+				"delaying for %v before reconnection",
+				config.DefaultConfig.MQTTReconnectDelay,
+			)
+			time.Sleep(config.DefaultConfig.MQTTReconnectDelay)
+		}
+	})
+
 	data, err := json.Marshal(&yggdrasil.ConnectionStatus{
 		Type:      yggdrasil.MessageTypeConnectionStatus,
 		MessageID: uuid.New().String(),