Reduce useless updates to help avoid rate limiting

src/dns_updater.rs

@@ -27,9 +27,6 @@ pub async fn dns_updater_task(
         );
     }
 
-    info!("DNS updater will start in 5 seconds");
-    tokio::time::sleep(Duration::from_secs(5)).await;
-
     info!("DNS updater starting");
 
     let mut config = Arc::new(DnsConfig::new());
@@ -42,7 +39,13 @@ pub async fn dns_updater_task(
             }
             _ = must_exit.changed() => continue,
         );
-        let new_config: Arc<DnsConfig> = rx_dns_config.borrow().clone();
+
+        // Always lag 15 seconds behind actual updates,
+        // to avoid sending too many at once and hitting rate limits
+        // TODO: retry regularly rate limits are hit
+        tokio::time::sleep(Duration::from_secs(15)).await;
+
+        let new_config: Arc<DnsConfig> = rx_dns_config.borrow_and_update().clone();
 
         for (key, value) in new_config.entries.iter() {
             // Skip entries that haven't changed