feat(s2n-quic-core): add metrics trait

quic/s2n-quic-core/src/event.rs

@@ -4,6 +4,8 @@
 use crate::{connection, endpoint};
 use core::{ops::RangeInclusive, time::Duration};
 
+pub mod metrics;
+
 mod generated;
 pub use generated::*;
 

quic/s2n-quic-core/src/event/metrics.rs

@@ -0,0 +1,11 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+/// A Recorder should arrange to emit the properties and counters on Drop into some output.
+pub trait Recorder: 'static + Send + Sync {
+    /// Registers a counter with the recorder instance
+    fn increment_counter(&self, name: &str, amount: usize);
+
+    /// Associates a key/value pair with the recorder instance
+    fn set_value<V: core::fmt::Display>(&self, key: &str, value: V);
+}