feat(udp-server): change connection ID error log level from ERROR to WARNING

Connection cookie errors (expired/from-future) are caused by bad client
traffic, not application errors. Logging them at ERROR level floods the
logs, making it hard to identify real issues.

Now  inspects the error variant:
- Connection cookie errors: logged at WARN
- All other UDP errors: remain at ERROR

Also updated the test helper log filter from ERROR to WARN so the
captured test logs include WARN messages for assertions.

Author: josecelano

packages/test-helpers/src/logging.rs

@@ -18,7 +18,7 @@ pub fn captured_logs_buffer() -> &'static Mutex<CircularBuffer> {
 
 pub fn setup() {
     INIT.call_once(|| {
-        tracing_init(LevelFilter::ERROR, &TraceStyle::Default);
+        tracing_init(LevelFilter::WARN, &TraceStyle::Default);
     });
 }
 

packages/udp-server/src/handlers/error.rs

@@ -3,6 +3,8 @@ use std::net::SocketAddr;
 use std::ops::Range;
 
 use torrust_net_primitives::service_binding::ServiceBinding;
+use torrust_tracker_udp_core::services::announce::UdpAnnounceError;
+use torrust_tracker_udp_core::services::scrape::UdpScrapeError;
 use torrust_tracker_udp_core::{self, UDP_TRACKER_LOG_TARGET};
 use torrust_tracker_udp_protocol::{ErrorResponse, Response, TransactionId};
 use tracing::{Level, instrument};
@@ -52,17 +54,40 @@ fn log_error(
     opt_transaction_id: Option<TransactionId>,
     request_id: Uuid,
 ) {
-    match opt_transaction_id {
-        Some(transaction_id) => {
-            let transaction_id = transaction_id.0.to_string();
-            tracing::error!(target: UDP_TRACKER_LOG_TARGET, error = %error, %client_socket_addr, %server_socket_addr, %request_id, %transaction_id, "response error");
+    if is_connection_cookie_error(error) {
+        match opt_transaction_id {
+            Some(transaction_id) => {
+                let transaction_id = transaction_id.0.to_string();
+                tracing::warn!(target: UDP_TRACKER_LOG_TARGET, error = %error, %client_socket_addr, %server_socket_addr, %request_id, %transaction_id, "response error");
+            }
+            None => {
+                tracing::warn!(target: UDP_TRACKER_LOG_TARGET, error = %error, %client_socket_addr, %server_socket_addr, %request_id, "response error");
+            }
         }
-        None => {
-            tracing::error!(target: UDP_TRACKER_LOG_TARGET, error = %error, %client_socket_addr, %server_socket_addr, %request_id, "response error");
+    } else {
+        match opt_transaction_id {
+            Some(transaction_id) => {
+                let transaction_id = transaction_id.0.to_string();
+                tracing::error!(target: UDP_TRACKER_LOG_TARGET, error = %error, %client_socket_addr, %server_socket_addr, %request_id, %transaction_id, "response error");
+            }
+            None => {
+                tracing::error!(target: UDP_TRACKER_LOG_TARGET, error = %error, %client_socket_addr, %server_socket_addr, %request_id, "response error");
+            }
         }
     }
 }
 
+fn is_connection_cookie_error(error: &Error) -> bool {
+    matches!(
+        error,
+        Error::AnnounceFailed {
+            source: UdpAnnounceError::ConnectionCookieError { .. }
+        } | Error::ScrapeFailed {
+            source: UdpScrapeError::ConnectionCookieError { .. }
+        }
+    )
+}
+
 async fn trigger_udp_error_event(
     error: &Error,
     client_socket_addr: SocketAddr,

packages/udp-server/tests/server/contract.rs

@@ -275,8 +275,8 @@ mod receiving_an_announce_request {
             let transaction_id = tx_id.0.to_string();
 
             assert!(
-                logs_contains_a_line_with(&["ERROR", "UDP TRACKER", &transaction_id]),
-                "Expected logs to contain: ERROR ... UDP TRACKER ... transaction_id={transaction_id}"
+                logs_contains_a_line_with(&["WARN", "UDP TRACKER", &transaction_id]),
+                "Expected logs to contain: WARN ... UDP TRACKER ... transaction_id={transaction_id}"
             );
         }