docs(1447): add issue spec for changing connection ID error log level to WARNING

Author: josecelano

docs/issues/open/1447-change-logging-threshold-connection-id-error.md

@@ -0,0 +1,121 @@
+---
+doc-type: issue
+issue-type: task
+status: planned
+priority: p3
+github-issue: 1447
+spec-path: docs/issues/open/1447-change-logging-threshold-connection-id-error.md
+branch: "1447-change-logging-threshold-connection-id-error"
+related-pr: null
+last-updated-utc: 2026-07-13 12:00
+semantic-links:
+  skill-links:
+    - create-issue
+  related-artifacts:
+    - packages/udp-server/src/handlers/error.rs
+---
+
+# Issue #1447 - Change the logging threshold for connection ID error to `WARNING`
+
+## Goal
+
+Change the log level for UDP connection ID errors from `ERROR` to `WARNING` to reduce
+log noise in production deployments (especially the Torrust Tracker demo).
+
+## Background
+
+The UDP tracker receives a high volume of requests with invalid connection IDs from
+misconfigured or abusive peers. These produce errors like:
+
+- `cookie value is expired`
+- `cookie value is from future`
+
+These are currently logged at `ERROR` level, which floods the logs and makes it hard to
+identify other types of errors.
+
+The tracker already bans IPs that make too many such requests (tracked via the
+`udp_tracker_server_connection_id_errors_total` metric and the ban service), so the
+logging can safely be downgraded. A `WARNING` level is still appropriate because there
+is no other monitoring/analytics tool to detect unusual patterns — the log remains the
+primary observability channel for connection ID issues.
+
+This is not an application error — it is expected behaviour from bad client traffic.
+
+## Scope
+
+### In Scope
+
+- Change the `tracing::error!` call in `log_error()` in `packages/udp-server/src/handlers/error.rs` to `tracing::warn!`
+- Verify that the change does not break any tests that assert on log level or output
+- Run `linter all` and the full test suite
+
+### Out of Scope
+
+- Adding a configuration option for the log level (not configurable for now)
+- Changing log levels for other error types
+- Changing the banning behaviour (stays at `ERROR`-level events)
+- Adding separate monitoring/analytics tooling
+
+## Implementation Plan
+
+Status values: `TODO`, `IN_PROGRESS`, `BLOCKED`, `DONE`.
+
+| ID  | Status | Task                                    | Notes / Expected Output                                                                                                                         |
+| --- | ------ | --------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------- |
+| T1  | TODO   | Change log level in `handlers/error.rs` | Make `log_error()` inspect the error type: use `tracing::warn!` for `ConnectionCookie` errors, keep `tracing::error!` for all other error types |
+| T2  | TODO   | Run verification                        | `linter all`, `cargo test --workspace`, pre-commit checks                                                                                       |
+
+## Technical Details
+
+The `ServerError` type in `packages/udp-server/src/error.rs` has several variants.
+Connection cookie errors flow through two paths:
+
+- `Error::AnnounceFailed { source: UdpAnnounceError::ConnectionCookieError { .. } }`
+- `Error::ScrapeFailed { source: UdpScrapeError::ConnectionCookieError { .. } }`
+
+The current `log_error()` function in `packages/udp-server/src/handlers/error.rs` is called for **all** UDP error types, not just connection cookie errors:
+
+```rust
+fn log_error(
+    error: &Error,
+    client_socket_addr: SocketAddr,
+    server_socket_addr: SocketAddr,
+    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");
+        }
+        None => {
+            tracing::error!(target: UDP_TRACKER_LOG_TARGET, error = %error, %client_socket_addr, %server_socket_addr, %request_id, "response error");
+        }
+    }
+}
+```
+
+The implementation should inspect the error variant and use `tracing::warn!` for
+`ConnectionCookie` errors while keeping `tracing::error!` for other error types
+(invalid requests, announce/scrape errors, internal errors, etc.).
+
+The `Error` type derives `Clone` and can be pattern-matched. Matching on
+`matches!(error, Error::AnnounceFailed { source: UdpAnnounceError::ConnectionCookieError { .. } })`
+or similar approach.
+
+Note: The `ErrorKind::ConnectionCookie` variant is specifically handled by the banning
+event handler (`packages/udp-server/src/banning/event/handler.rs`) to track IP bans
+separately — this behaviour is unaffected by the log level change.
+
+## Progress Tracking
+
+### Workflow Checkpoints
+
+- [x] Spec drafted in `docs/issues/open/`
+- [ ] Spec reviewed and approved by user/maintainer
+- [ ] GitHub issue exists and issue number matches spec
+- [ ] Implementation completed
+- [ ] Automatic verification completed (`linter all`, relevant tests, and any pre-push checks)
+- [ ] Manual verification scenarios executed and recorded (status + evidence)
+- [ ] Acceptance criteria reviewed after implementation and updated with evidence
+- [ ] Reviewer validated acceptance criteria and updated checkboxes