1 files changed, 148 insertions, 0 deletions
diff --git a/src/csharp/Grpc.IntegrationTesting/InterarrivalTimers.cs b/src/csharp/Grpc.IntegrationTesting/InterarrivalTimers.cs
new file mode 100644
index 0000000000..6492d34890
--- /dev/null
+++ b/src/csharp/Grpc.IntegrationTesting/InterarrivalTimers.cs
@@ -0,0 +1,148 @@
+#region Copyright notice and license
+
+// Copyright 2016, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.IO;
+using System.Linq;
+using System.Text.RegularExpressions;
+using System.Threading;
+using System.Threading.Tasks;
+using Google.Protobuf;
+using Grpc.Core;
+using Grpc.Core.Utils;
+using Grpc.Testing;
+
+namespace Grpc.IntegrationTesting
+{
+    public interface IInterarrivalTimer
+    {
+        void WaitForNext();
+
+        Task WaitForNextAsync();
+    }
+
+    /// <summary>
+    /// Interarrival timer that doesn't wait at all.
+    /// </summary>
+    public class ClosedLoopInterarrivalTimer : IInterarrivalTimer
+    {
+        public ClosedLoopInterarrivalTimer()
+        {
+        }
+
+        public void WaitForNext()
+        {
+            // NOP
+        }
+
+        public Task WaitForNextAsync()
+        {
+            return Task.FromResult<object>(null);
+        }
+    }
+
+    /// <summary>
+    /// Interarrival timer that generates Poisson process load.
+    /// </summary>
+    public class PoissonInterarrivalTimer : IInterarrivalTimer
+    {
+        readonly ExponentialDistribution exponentialDistribution;
+        DateTime? lastEventTime;
+
+        public PoissonInterarrivalTimer(double offeredLoad)
+        {
+            this.exponentialDistribution = new ExponentialDistribution(new Random(), offeredLoad);
+            this.lastEventTime = DateTime.UtcNow;
+        }
+
+        public void WaitForNext()
+        {
+            var waitDuration = GetNextWaitDuration();
+            int millisTimeout = (int) Math.Round(waitDuration.TotalMilliseconds);
+            if (millisTimeout > 0)
+            {
+                // TODO(jtattermusch): probably only works well for a relatively low interarrival rate
+                Thread.Sleep(millisTimeout);
+            }
+        }
+
+        public async Task WaitForNextAsync()
+        {
+            var waitDuration = GetNextWaitDuration();
+            int millisTimeout = (int) Math.Round(waitDuration.TotalMilliseconds);
+            if (millisTimeout > 0)
+            {
+                // TODO(jtattermusch): probably only works well for a relatively low interarrival rate
+                await Task.Delay(millisTimeout);
+            }
+        }
+
+        private TimeSpan GetNextWaitDuration()
+        {
+            if (!lastEventTime.HasValue)
+            {
+                this.lastEventTime = DateTime.Now;
+            }
+
+            var origLastEventTime = this.lastEventTime.Value;
+            this.lastEventTime = origLastEventTime + TimeSpan.FromSeconds(exponentialDistribution.Next());
+            return this.lastEventTime.Value - origLastEventTime;
+        }
+
+        /// <summary>
+        /// Exp generator.
+        /// </summary>
+        private class ExponentialDistribution
+        {
+            readonly Random random;
+            readonly double lambda;
+            readonly double lambdaReciprocal;
+
+            public ExponentialDistribution(Random random, double lambda)
+            {
+                this.random = random;
+                this.lambda = lambda;
+                this.lambdaReciprocal = 1.0 / lambda;
+            }
+
+            public double Next()
+            {
+                double uniform = random.NextDouble();
+                // Use 1.0-uni above to avoid NaN if uni is 0
+                return lambdaReciprocal * (-Math.Log(1.0 - uniform));
+            }
+        }
+    }
+}