Attempting to resolve issues with lqos_node_manager not seeing

statistics, while lqtop still works.

1) Add warning and error logging to lqos_node_manager if any
   part of the statistics gathering process fails.
2) (Hopefully temporarily) use the non-persistent bus client,
   again logging any issues.
3) Improve the statistics gathering timer code.

src/rust/lqos_node_manager/src/tracker/cache_manager.rs

@@ -4,13 +4,13 @@
 use super::cache::*;
 use anyhow::Result;
 use lqos_bus::{
-    BusRequest, BusResponse, IpStats, BusClient,
+    BusRequest, BusResponse, IpStats, bus_request,
 };
 use lqos_config::ConfigShapedDevices;
 use rocket::tokio::{
     task::spawn_blocking,
 };
-use std::{net::IpAddr, time::Duration};
+use std::{net::IpAddr, time::{Duration, Instant}};
 
 /// Once per second, update CPU and RAM usage and ask
 /// `lqosd` for updated system statistics.
@@ -26,8 +26,9 @@ pub async fn update_tracking() {
     spawn_blocking(|| {
         let _ = watch_for_shaped_devices_changing();
     });
-    let mut bus_client = BusClient::new().await.unwrap();
+    //let mut bus_client = BusClient::new().await.unwrap();
     loop {
+        let now = Instant::now();
         //println!("Updating tracking data");
         sys.refresh_cpu();
         sys.refresh_memory();
@@ -42,8 +43,19 @@ pub async fn update_tracking() {
             mem_use[0] = sys.used_memory();
             mem_use[1] = sys.total_memory();
         }
-        let _ = get_data_from_server(&mut bus_client).await; // Ignoring errors to keep running
-        rocket::tokio::time::sleep(Duration::from_secs(1)).await;
+        let error = get_data_from_server().await; // Ignoring errors to keep running
+        if let Err(error) = error {
+            error!("Error in usage update loop: {:?}", error);
+        }
+
+        let duration = now.elapsed();
+        if duration.as_secs_f32() < 1.0 {
+            let wait_time = Duration::from_secs(1) - duration;
+            rocket::tokio::time::sleep(wait_time).await;
+        } else {
+            warn!("Gathering usage data exceeded one second, waiting for 1 second.");
+            rocket::tokio::time::sleep(Duration::from_secs(1)).await;
+        }
     }
 }
 
@@ -67,7 +79,7 @@ fn watch_for_shaped_devices_changing() -> Result<()> {
 
 /// Requests data from `lqosd` and stores it in local
 /// caches.
-async fn get_data_from_server(bus_client: &mut BusClient) -> Result<()> {
+async fn get_data_from_server() -> Result<()> {
     // Send request to lqosd
     let requests = vec![
         BusRequest::GetCurrentThroughput,
@@ -77,7 +89,7 @@ async fn get_data_from_server(bus_client: &mut BusClient) -> Result<()> {
         BusRequest::AllUnknownIps,
     ];
 
-    for r in bus_client.request(requests).await?.iter() {
+    for r in bus_request(requests).await?.iter() {
         match r {
             BusResponse::CurrentThroughput {
                 bits_per_second,