Add a basic metric test for multi-thread update (#2205)

* Add a basic metric test for multi-thread update

* nulklable

src/OpenTelemetry/Metrics/AggregatorStore.cs

@@ -157,6 +157,18 @@ internal List<IMetric> Collect(bool isDelta, DateTimeOffset dt)
         {
             var collectedMetrics = new List<IMetric>();
 
+            if (this.tag0Metrics != null)
+            {
+                foreach (var aggregator in this.tag0Metrics)
+                {
+                    var m = aggregator.Collect(dt, isDelta);
+                    if (m != null)
+                    {
+                        collectedMetrics.Add(m);
+                    }
+                }
+            }
+
             // Lock to prevent new time series from being added
             // until collect is done.
             lock (this.lockKeyValue2MetricAggs)

test/OpenTelemetry.Tests/Metrics/MetricAPITest.cs

@@ -14,20 +14,123 @@
 // limitations under the License.
 // </copyright>
 
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.Metrics;
-using System.Threading.Tasks;
+using System.Threading;
+using OpenTelemetry.Tests;
 using Xunit;
 
-#nullable enable
-
 namespace OpenTelemetry.Metrics.Tests
 {
     public class MetricApiTest
     {
+        private static int numberOfThreads = 10;
+        private static long deltaValueUpdatedByEachCall = 10;
+        private static int numberOfMetricUpdateByEachThread = 1000000;
+
         [Fact]
         public void SimpleTest()
         {
+            var metricItems = new List<MetricItem>();
+            var metricExporter = new TestExporter<MetricItem>(ProcessExport);
+            void ProcessExport(Batch<MetricItem> batch)
+            {
+                foreach (var metricItem in batch)
+                {
+                    metricItems.Add(metricItem);
+                }
+            }
+
+            var meter = new Meter("TestMeter");
+            var counterLong = meter.CreateCounter<long>("mycounter");
+            var meterProvider = Sdk.CreateMeterProviderBuilder()
+                .AddSource("TestMeter")
+                .AddMetricProcessor(new PushMetricProcessor(metricExporter, 100, isDelta: true))
+                .Build();
+
+            // setup args to threads.
+            var mreToBlockUpdateThreads = new ManualResetEvent(false);
+            var mreToEnsureAllThreadsStarted = new ManualResetEvent(false);
+
+            var argToThread = new UpdateThreadArguments();
+            argToThread.Counter = counterLong;
+            argToThread.ThreadsStartedCount = 0;
+            argToThread.MreToBlockUpdateThread = mreToBlockUpdateThreads;
+            argToThread.MreToEnsureAllThreadsStart = mreToEnsureAllThreadsStarted;
+
+            Thread[] t = new Thread[numberOfThreads];
+            for (int i = 0; i < numberOfThreads; i++)
+            {
+                t[i] = new Thread(CounterUpdateThread);
+                t[i].Start(argToThread);
+            }
+
+            // Block until all threads started.
+            mreToEnsureAllThreadsStarted.WaitOne();
+
+            // unblock all the threads.
+            // (i.e let them start counter.Add)
+            mreToBlockUpdateThreads.Set();
+
+            for (int i = 0; i < numberOfThreads; i++)
+            {
+                // wait for all threads to complete
+                t[i].Join();
+            }
+
+            meterProvider.Dispose();
+
+            // TODO: Once Dispose does flush, we may not need this
+            // unknown sleep below.
+            Thread.Sleep(1000);
+
+            long sumReceived = 0;
+            foreach (var metricItem in metricItems)
+            {
+                var metrics = metricItem.Metrics;
+                foreach (var metric in metrics)
+                {
+                    sumReceived += (long)(metric as ISumMetric).Sum.Value;
+                }
+            }
+
+            var expectedSum = deltaValueUpdatedByEachCall * numberOfMetricUpdateByEachThread * numberOfThreads;
+            Assert.Equal(expectedSum, sumReceived);
+        }
+
+        private static void CounterUpdateThread(object obj)
+        {
+            var arguments = obj as UpdateThreadArguments;
+            if (arguments == null)
+            {
+                throw new Exception("Invalid args");
+            }
+
+            var mre = arguments.MreToBlockUpdateThread;
+            var mreToEnsureAllThreadsStart = arguments.MreToEnsureAllThreadsStart;
+            var counter = arguments.Counter;
+
+            if (Interlocked.Increment(ref arguments.ThreadsStartedCount) == numberOfThreads)
+            {
+                mreToEnsureAllThreadsStart.Set();
+            }
+
+            // Wait until signalled to start calling update on aggregator
+            mre.WaitOne();
+
+            for (int i = 0; i < numberOfMetricUpdateByEachThread; i++)
+            {
+                counter.Add(deltaValueUpdatedByEachCall, new KeyValuePair<string, object>("verb", "GET"));
+            }
+        }
+
+        private class UpdateThreadArguments
+        {
+            public ManualResetEvent MreToBlockUpdateThread;
+            public ManualResetEvent MreToEnsureAllThreadsStart;
+            public int ThreadsStartedCount;
+            public Counter<long> Counter;
         }
     }
 }