Change the QUEUE_STRUCTURE to an ArcSwap, further reducing locking.

src/rust/Cargo.lock

@@ -1782,6 +1782,7 @@ name = "lqos_queue_tracker"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "arc-swap",
  "criterion",
  "dashmap",
  "lqos_bus",

src/rust/lqos_queue_tracker/Cargo.toml

@@ -17,6 +17,7 @@ tokio = { workspace = true }
 once_cell = { workspace = true}
 dashmap = { workspace = true }
 anyhow = { workspace = true }
+arc-swap = { workspace = true }
 
 [dev-dependencies]
 criterion = { version = "0", features = [ "html_reports"] }

src/rust/lqos_queue_tracker/src/queue_structure/queing_structure_json_monitor.rs

@@ -1,5 +1,5 @@
-use std::sync::RwLock;
-
+use std::sync::Arc;
+use arc_swap::ArcSwap;
 use crate::queue_structure::{
   queue_network::QueueNetwork, queue_node::QueueNode, read_queueing_structure,
 };
@@ -9,8 +9,8 @@ use once_cell::sync::Lazy;
 use thiserror::Error;
 use crate::tracking::ALL_QUEUE_SUMMARY;
 
-pub(crate) static QUEUE_STRUCTURE: Lazy<RwLock<QueueStructure>> =
-  Lazy::new(|| RwLock::new(QueueStructure::new()));
+pub(crate) static QUEUE_STRUCTURE: Lazy<ArcSwap<QueueStructure>> =
+  Lazy::new(|| ArcSwap::new(Arc::new(QueueStructure::new())));
 
 #[derive(Clone)]
 pub(crate) struct QueueStructure {
@@ -25,15 +25,6 @@ impl QueueStructure {
       Self { maybe_queues: None }
     }
   }
-
-  fn update(&mut self) {
-    ALL_QUEUE_SUMMARY.clear();
-    if let Ok(queues) = read_queueing_structure() {
-      self.maybe_queues = Some(queues);
-    } else {
-      self.maybe_queues = None;
-    }
-  }
 }
 
 /// Global file watched for `queueStructure.json`.
@@ -52,7 +43,9 @@ pub fn spawn_queue_structure_monitor() -> anyhow::Result<()> {
 
 fn update_queue_structure() {
   debug!("queueingStructure.json reloaded");
-  QUEUE_STRUCTURE.write().unwrap().update();
+  let new_queue_structure = QueueStructure::new();
+  ALL_QUEUE_SUMMARY.clear();
+  QUEUE_STRUCTURE.store(Arc::new(new_queue_structure));
 }
 
 /// Fires up a Linux file system watcher than notifies

src/rust/lqos_queue_tracker/src/tracking/mod.rs

@@ -139,7 +139,7 @@ fn connect_queues_to_circuit_up(structure: &[QueueNode], queues: &[QueueType]) -
 
 fn all_queue_reader() {
   let start = Instant::now();
-  let structure = QUEUE_STRUCTURE.read().unwrap();
+  let structure = QUEUE_STRUCTURE.load();
   if let Some(structure) = &structure.maybe_queues {
     if let Ok(config) = lqos_config::load_config() {
       // Get all the queues

src/rust/lqos_queue_tracker/src/tracking/watched_queues.rs

@@ -55,7 +55,8 @@ pub fn add_watched_queue(circuit_id: &str) {
     }
   }
 
-  if let Some(queues) = &QUEUE_STRUCTURE.read().unwrap().maybe_queues {
+  let queues = QUEUE_STRUCTURE.load();
+  if let Some(queues) = &queues.maybe_queues {
     if let Some(circuit) = queues.iter().find(|c| {
       c.circuit_id.is_some() && c.circuit_id.as_ref().unwrap() == circuit_id
     }) {