exit gracefully when MQTT server is disconnected

Cargo.lock

@@ -174,6 +174,16 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "ctrlc"
+version = "3.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "82e95fbd621905b854affdc67943b043a0fbb6ed7385fd5a25650d19a8a6cfdf"
+dependencies = [
+ "nix",
+ "windows-sys",
+]
+
 [[package]]
 name = "deranged"
 version = "0.3.8"
@@ -393,6 +403,7 @@ name = "mqtt2statsd"
 version = "0.1.0"
 dependencies = [
  "clap",
+ "ctrlc",
  "log",
  "paho-mqtt",
  "serde",
@@ -401,6 +412,17 @@ dependencies = [
  "toml",
 ]
 
+[[package]]
+name = "nix"
+version = "0.27.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2eb04e9c688eff1c89d72b407f168cf79bb9e867a9d3323ed6c01519eb9cc053"
+dependencies = [
+ "bitflags",
+ "cfg-if",
+ "libc",
+]
+
 [[package]]
 name = "num_threads"
 version = "0.1.6"

Cargo.toml

@@ -12,3 +12,4 @@ statsd = "0.16"
 toml = "0.8"
 simplelog = "0.12"
 log = "0.4"
+ctrlc = "3.4"

example.toml

@@ -2,6 +2,7 @@
 [mqtt]
 hostname = "localhost"
 #port = 1883             # optional, default: 1883
+#timeout = 60            # in seconds, optional, default: 60
 
 # Which Statsd server to send data to
 [statsd]

src/config.rs

@@ -21,8 +21,11 @@ pub struct Config {
 pub struct MqttConfig {
     pub hostname: String,
 
-    #[serde(default = "default_mqtt_port") ]
-    pub port: u32
+    #[serde(default = "default_mqtt_port")]
+    pub port: u32,
+
+    #[serde(default = "default_timeout")]
+    pub timeout: u32
 }
 
 //------------------------------------------------------------------------------
@@ -66,3 +69,9 @@ fn default_mqtt_port() -> u32 {
 fn default_statsd_port() -> u32 {
     8125
 }
+
+//------------------------------------------------------------------------------
+
+fn default_timeout() -> u32 {
+    60
+}

src/main.rs

@@ -1,18 +1,32 @@
-use std::error::Error;
-
-extern crate log;
-use log::{error, info, debug};
+use std::{thread, error::Error, time::Duration};
 
+use log::{error, warn, info, debug};
 use simplelog::{ TermLogger, LevelFilter, ConfigBuilder, TerminalMode, ColorChoice};
-
-use paho_mqtt::Message;
+use paho_mqtt as paho;
 
 mod cli_args;
 mod config;
 mod mqtt;
 
-fn handle_msg( msg: &Message )
-{
+//------------------------------------------------------------------------------
+
+fn try_reconnect( mqtt: &paho::Client, timeout: u32 ) -> bool {
+    warn!("MQTT server lost, trying to reconnect...");
+    for _ in 0..timeout {
+        thread::sleep(Duration::from_secs(1));
+        if mqtt.reconnect().is_ok() {
+            info!("MQTT server reconnected");
+            return true;
+        }
+    }
+
+    error!("MQTT server timed out");
+    false
+}
+
+//------------------------------------------------------------------------------
+
+fn handle_msg( msg: &paho::Message ) {
     info!("New message: {}", msg)
 }
 
@@ -27,12 +41,15 @@ fn main_impl( args: &cli_args::Args ) -> Result<(), Box<dyn Error>> {
     let rx = mqtt.start_consuming();
     mqtt::subscribe( &mqtt, &config.topics, args.verbose );
 
+    // handle ^C signal to quit gracefully
+    let ctrlc_mqtt = mqtt.clone();
+    ctrlc::set_handler(move || {
+        ctrlc_mqtt.stop_consuming()
+    })?;
+
     // main event loop
     for msg in rx.iter() {
-        if !mqtt.is_connected() {
-            if args.verbose {
-                println!( )
-            }
+        if !mqtt.is_connected() && !try_reconnect(&mqtt, config.mqtt.timeout) {
             break;
         }
 
@@ -41,9 +58,10 @@ fn main_impl( args: &cli_args::Args ) -> Result<(), Box<dyn Error>> {
         }
     }
 
+    // clean up before quitting
     if mqtt.is_connected() {
-        println!("Disconnecting");
-        //mqtt.unsubscribe_many(topics)
+        info!("Disconnecting");
+        mqtt.disconnect(None)?;
     }
 
     Ok(())