fix(cache-metrics): increment/reset logic, use relaxed ordering (#109)

*Issue #, if available:*

*Description of changes:*


By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Author: ThirdEyeSqueegee

aws_secretsmanager_caching/src/lib.rs

@@ -189,18 +189,17 @@ impl SecretsManagerCachingClient {
         if refresh_now {
             #[cfg(debug_assertions)]
             {
-                let hit_rate = self.get_cache_hit_rate();
-                let miss_rate = 100.0 - hit_rate;
-
                 self.increment_counter(&self.metrics.refreshes);
 
+                let (hit_rate, miss_rate) = self.get_cache_rates();
+
                 info!(
-                    "METRICS: Bypassing GSV. Refreshing secret '{}' immediately. Total refreshes: {}. \
-                    Total hits: {}. Total misses: {}. Hit rate: {:.2}%. Miss rate: {:.2}%",
+                    "METRICS: Bypassing cache. Refreshing secret '{}' immediately. \
+                    Total hits: {}. Total misses: {}. Total refreshes: {}. Hit rate: {:.2}%. Miss rate: {:.2}%",
                     secret_id,
-                    self.get_counter_value(&self.metrics.refreshes),
                     self.get_counter_value(&self.metrics.hits),
                     self.get_counter_value(&self.metrics.misses),
+                    self.get_counter_value(&self.metrics.refreshes),
                     hit_rate,
                     miss_rate
                 );
@@ -217,11 +216,10 @@ impl SecretsManagerCachingClient {
             Ok(r) => {
                 #[cfg(debug_assertions)]
                 {
-                    let hit_rate = self.get_cache_hit_rate();
-                    let miss_rate = 100.0 - hit_rate;
-
                     self.increment_counter(&self.metrics.hits);
 
+                    let (hit_rate, miss_rate) = self.get_cache_rates();
+
                     info!(
                         "METRICS: Cache HIT for secret '{}'. Total hits: {}. Total misses: {}. \
                         Hit rate: {:.2}%. Miss rate: {:.2}%.",
@@ -238,11 +236,9 @@ impl SecretsManagerCachingClient {
             Err(SecretStoreError::ResourceNotFound) => {
                 #[cfg(debug_assertions)]
                 {
-                    let hit_rate = self.get_cache_hit_rate();
-                    let miss_rate = 100.0 - hit_rate;
-
                     self.increment_counter(&self.metrics.misses);
-                    self.increment_counter(&self.metrics.refreshes);
+
+                    let (hit_rate, miss_rate) = self.get_cache_rates();
 
                     info!(
                         "METRICS: Cache MISS for secret '{}'. Total hits: {}. Total misses: {}. \
@@ -263,18 +259,17 @@ impl SecretsManagerCachingClient {
             Err(SecretStoreError::CacheExpired(cached_value)) => {
                 #[cfg(debug_assertions)]
                 {
-                    let hit_rate = self.get_cache_hit_rate();
-                    let miss_rate = 100.0 - hit_rate;
+                    self.increment_counter(&self.metrics.misses);
 
-                    self.increment_counter(&self.metrics.refreshes);
-                    self.reset_counter(&self.metrics.hits);
-                    self.reset_counter(&self.metrics.misses);
+                    let (hit_rate, miss_rate) = self.get_cache_rates();
 
                     info!(
-                        "METRICS: Cache expired. Resetting hits and misses. Total hits: {}. Total \
-                        misses: {}. Hit rate: {:.2}%. Miss rate: {:.2}%.",
+                        "METRICS: Cache entry expired for secret '{}'. Total hits: {}. Total \
+                        misses: {}. Total refreshes: {}. Hit rate: {:.2}%. Miss rate: {:.2}%.",
+                        secret_id,
                         self.get_counter_value(&self.metrics.hits),
                         self.get_counter_value(&self.metrics.misses),
+                        self.get_counter_value(&self.metrics.refreshes),
                         hit_rate,
                         miss_rate
                     );
@@ -411,31 +406,28 @@ impl SecretsManagerCachingClient {
     }
 
     #[cfg(debug_assertions)]
-    fn get_cache_hit_rate(&self) -> f64 {
-        let hits = self.metrics.hits.load(Ordering::SeqCst);
-        let misses = self.metrics.misses.load(Ordering::SeqCst);
+    fn get_cache_rates(&self) -> (f64, f64) {
+        let hits = self.metrics.hits.load(Ordering::Relaxed);
+        let misses = self.metrics.misses.load(Ordering::Relaxed);
         let total = hits + misses;
 
         if total == 0 {
-            return 0.0;
+            return (0.0, 0.0);
         }
 
-        (hits as f64 / total as f64) * 100.0
-    }
+        let hit_rate = (hits as f64 / total as f64) * 100.0;
 
-    #[cfg(debug_assertions)]
-    fn increment_counter(&self, counter: &AtomicU32) -> () {
-        counter.fetch_add(1, Ordering::SeqCst);
+        (hit_rate, 100.0 - hit_rate)
     }
 
     #[cfg(debug_assertions)]
-    fn reset_counter(&self, counter: &AtomicU32) -> () {
-        counter.store(0, Ordering::SeqCst);
+    fn increment_counter(&self, counter: &AtomicU32) -> () {
+        counter.fetch_add(1, Ordering::Relaxed);
     }
 
     #[cfg(debug_assertions)]
     fn get_counter_value(&self, counter: &AtomicU32) -> u32 {
-        counter.load(Ordering::SeqCst)
+        counter.load(Ordering::Relaxed)
     }
 }