Add keep_alive_interval config option for mqtt.

Closes #54.

Cargo.toml

@@ -22,6 +22,7 @@
   lrwn_filters = { version = "4.7", features = ["serde"] }
   serde_json = "1.0"
   serde = { version = "1.0", features = ["derive"] }
+  humantime-serde = "1.1"
   log = "0.4"
   simple_logger = "4.3"
   syslog = "6.1"

src/cmd/configfile.rs

@@ -81,6 +81,12 @@ pub fn run(config: &Configuration) {
   # a random id will be generated by ChirpStack.
   client_id="{{ mqtt.client_id }}"
 
+  # Keep alive interval.
+  #
+  # This defines the maximum time that that should pass without communication
+  # between the client and server.
+  keep_alive_interval="{{ integration.mqtt.keep_alive_interval }}"
+
   # CA certificate file (optional)
   #
   # Use this when setting up a secure connection (when server uses ssl://...)

src/config.rs

@@ -1,5 +1,6 @@
 use std::collections::HashMap;
 use std::fs;
+use std::time::Duration;
 
 use anyhow::Result;
 use serde::{Deserialize, Serialize};
@@ -52,6 +53,8 @@ pub struct Mqtt {
     pub qos: u8,
     pub clean_session: bool,
     pub client_id: String,
+    #[serde(with = "humantime_serde")]
+    pub keep_alive_interval: Duration,
     pub ca_cert: String,
     pub tls_cert: String,
     pub tls_key: String,
@@ -68,6 +71,7 @@ impl Default for Mqtt {
             qos: 0,
             clean_session: false,
             client_id: "".into(),
+            keep_alive_interval: Duration::from_secs(30),
             ca_cert: "".into(),
             tls_cert: "".into(),
             tls_key: "".into(),

src/mqtt.rs

@@ -141,6 +141,7 @@ pub async fn setup(conf: &Configuration) -> Result<()> {
 
     mqtt_opts.set_last_will(lwt_msg);
     mqtt_opts.set_clean_start(conf.mqtt.clean_session);
+    mqtt_opts.set_keep_alive(conf.mqtt.keep_alive_interval);
     if !conf.mqtt.username.is_empty() || !conf.mqtt.password.is_empty() {
         mqtt_opts.set_credentials(&conf.mqtt.username, &conf.mqtt.password);
     }