Don't allocate a stopwatch if it isn't going to be used. (#2608)

Co-authored-by: Cijo Thomas <cithomas@microsoft.com>

Author: CodeBlanch

src/OpenTelemetry/BatchExportProcessor.cs

@@ -130,15 +130,17 @@ protected override bool OnForceFlush(int timeoutMilliseconds)
 
             var triggers = new WaitHandle[] { this.dataExportedNotification, this.shutdownTrigger };
 
-            var sw = Stopwatch.StartNew();
+            var sw = timeoutMilliseconds == Timeout.Infinite
+                ? null
+                : Stopwatch.StartNew();
 
             // There is a chance that the export thread finished processing all the data from the queue,
             // and signaled before we enter wait here, use polling to prevent being blocked indefinitely.
             const int pollingMilliseconds = 1000;
 
             while (true)
             {
-                if (timeoutMilliseconds == Timeout.Infinite)
+                if (sw == null)
                 {
                     try
                     {

src/OpenTelemetry/CompositeProcessor.cs

@@ -83,11 +83,13 @@ public override void OnStart(T data)
         protected override bool OnForceFlush(int timeoutMilliseconds)
         {
             var result = true;
-            var sw = Stopwatch.StartNew();
+            var sw = timeoutMilliseconds == Timeout.Infinite
+                ? null
+                : Stopwatch.StartNew();
 
             for (var cur = this.head; cur != null; cur = cur.Next)
             {
-                if (timeoutMilliseconds == Timeout.Infinite)
+                if (sw == null)
                 {
                     result = cur.Value.ForceFlush(Timeout.Infinite) && result;
                 }
@@ -107,11 +109,13 @@ protected override bool OnForceFlush(int timeoutMilliseconds)
         protected override bool OnShutdown(int timeoutMilliseconds)
         {
             var result = true;
-            var sw = Stopwatch.StartNew();
+            var sw = timeoutMilliseconds == Timeout.Infinite
+                ? null
+                : Stopwatch.StartNew();
 
             for (var cur = this.head; cur != null; cur = cur.Next)
             {
-                if (timeoutMilliseconds == Timeout.Infinite)
+                if (sw == null)
                 {
                     result = cur.Value.Shutdown(Timeout.Infinite) && result;
                 }

src/OpenTelemetry/Metrics/CompositeMetricReader.cs

@@ -75,11 +75,13 @@ protected override bool ProcessMetrics(in Batch<Metric> metrics, int timeoutMill
         protected override bool OnCollect(int timeoutMilliseconds = Timeout.Infinite)
         {
             var result = true;
-            var sw = Stopwatch.StartNew();
+            var sw = timeoutMilliseconds == Timeout.Infinite
+                ? null
+                : Stopwatch.StartNew();
 
             for (var cur = this.head; cur != null; cur = cur.Next)
             {
-                if (timeoutMilliseconds == Timeout.Infinite)
+                if (sw == null)
                 {
                     result = cur.Value.Collect(Timeout.Infinite) && result;
                 }
@@ -99,11 +101,13 @@ protected override bool OnCollect(int timeoutMilliseconds = Timeout.Infinite)
         protected override bool OnShutdown(int timeoutMilliseconds)
         {
             var result = true;
-            var sw = Stopwatch.StartNew();
+            var sw = timeoutMilliseconds == Timeout.Infinite
+                ? null
+                : Stopwatch.StartNew();
 
             for (var cur = this.head; cur != null; cur = cur.Next)
             {
-                if (timeoutMilliseconds == Timeout.Infinite)
+                if (sw == null)
                 {
                     result = cur.Value.Shutdown(Timeout.Infinite) && result;
                 }

src/OpenTelemetry/Metrics/MetricReader.cs

@@ -207,12 +207,14 @@ internal virtual void SetParentProvider(BaseProvider parentProvider)
         /// </remarks>
         protected virtual bool OnCollect(int timeoutMilliseconds)
         {
-            var sw = Stopwatch.StartNew();
+            var sw = timeoutMilliseconds == Timeout.Infinite
+                ? null
+                : Stopwatch.StartNew();
 
             var collectMetric = this.ParentProvider.GetMetricCollect();
             var metrics = collectMetric();
 
-            if (timeoutMilliseconds == Timeout.Infinite)
+            if (sw == null)
             {
                 return this.ProcessMetrics(metrics, Timeout.Infinite);
             }