refactor(actor): implement Raft consensus algorithm for cluster leader election

- Add voting mechanism with term tracking and vote persistence
- Implement election triggering logic with majority vote counting
- Add primary/replica role transition handling with state management
- Integrate health check failure detection for automatic elections
- Refactor actor messaging system for distributed coordination
- Update repository registration to query cluster for existing primary
- Add broadcast mechanism for role change notifications
- Implement proper term comparison and duplicate request filtering
- Upgrade dependency versions including tokio-util for async utilities
- Optimize code formatting and line wrapping for improved readability
- Remove redundant blank lines and improve code structure consistency
- Enhance error logging and trace information for debugging purposes

metrics.rs

@@ -15,7 +15,6 @@ use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, OnceLock};
 use std::time::{Duration, Instant};
 
-
 struct MetricsInner {
     /// Counter: total requests by (method, status_code)
     /// Key: "method:status"
@@ -61,7 +60,6 @@ fn metrics() -> &'static Arc<MetricsInner> {
     })
 }
 
-
 #[rustfmt::skip]
 const DURATION_BUCKET_MS: &[u64] = &[
     5, 10, 25, 50, 100, 250, 500, 1_000,
@@ -105,9 +103,7 @@ pub fn dec_active_requests() {
 
 /// Set the repository count.
 pub fn set_repository_count(count: u64) {
-    metrics()
-        .repository_count
-        .store(count, Ordering::Relaxed);
+    metrics().repository_count.store(count, Ordering::Relaxed);
 }
 
 /// Record a cache hit.
@@ -117,9 +113,7 @@ pub fn inc_cache_hits(count: u64) {
 
 /// Record a cache miss.
 pub fn inc_cache_misses(count: u64) {
-    metrics()
-        .cache_misses
-        .fetch_add(count, Ordering::Relaxed);
+    metrics().cache_misses.fetch_add(count, Ordering::Relaxed);
 }
 
 /// Record an error by kind (e.g., "not_found", "internal", "invalid_argument").
@@ -132,7 +126,6 @@ pub fn inc_error(kind: &str) {
         .fetch_add(1, Ordering::Relaxed);
 }
 
-
 /// Render all metrics in Prometheus text exposition format.
 pub fn render_metrics() -> String {
     let m = metrics();
@@ -163,17 +156,15 @@ pub fn render_metrics() -> String {
         let (method_and_status, count) = (entry.key(), entry.value());
         let count = count.load(Ordering::Relaxed);
         if let Some((method, status)) = method_and_status.rsplit_once(':') {
-            out.push_str(
-                &format!("gitks_requests_total{{method=\"{method}\",status=\"{status}\"}} {count}\n"),
-            );
+            out.push_str(&format!(
+                "gitks_requests_total{{method=\"{method}\",status=\"{status}\"}} {count}\n"
+            ));
         }
     }
     out.push('\n');
 
     // Duration histogram
-    out.push_str(
-        "# HELP gitks_request_duration_milliseconds Request duration histogram in ms\n",
-    );
+    out.push_str("# HELP gitks_request_duration_milliseconds Request duration histogram in ms\n");
     out.push_str("# TYPE gitks_request_duration_milliseconds histogram\n");
     for entry in &m.duration_buckets {
         let (method_and_bound, count) = (entry.key(), entry.value());
@@ -215,7 +206,6 @@ pub fn render_metrics() -> String {
     out
 }
 
-
 /// Start the metrics HTTP server on the given port.
 /// Runs in a background task; returns the JoinHandle.
 pub fn start_metrics_server(port: u16) -> tokio::task::JoinHandle<()> {
@@ -256,12 +246,14 @@ async fn handle_metrics_connection(mut socket: tokio::net::TcpStream) {
         body
     );
 
-    let _ = tokio::time::timeout(Duration::from_secs(5), socket.write_all(response.as_bytes()))
-        .await;
+    let _ = tokio::time::timeout(
+        Duration::from_secs(5),
+        socket.write_all(response.as_bytes()),
+    )
+    .await;
     let _ = socket.shutdown().await;
 }
 
-
 /// A guard that records metrics on drop.
 ///
 /// Usage in handlers: