Do not retry when there's an ambient transaction (#621)

* Do not retry when there's an ambient transaction
Fixes #615

src/Microsoft.Azure.ServiceBus/RetryExponential.cs

@@ -8,7 +8,8 @@ namespace Microsoft.Azure.ServiceBus
 
     /// <summary>
     /// RetryPolicy implementation where the delay between retries will grow in a staggered exponential manner.
-    /// RetryIntervals will be computed using a retryFactor which is a function of deltaBackOff (MaximumBackoff - MinimumBackoff) and MaximumRetryCount
+    /// RetryIntervals will be computed using a retryFactor which is a function of deltaBackOff (MaximumBackoff - MinimumBackoff) and MaximumRetryCount.
+    /// <remarks>RetryPolicy will not be applied when an ambient transaction is found.</remarks>
     /// </summary>
     public sealed class RetryExponential : RetryPolicy
     {

src/Microsoft.Azure.ServiceBus/RetryPolicy.cs

@@ -6,11 +6,13 @@ namespace Microsoft.Azure.ServiceBus
     using System;
     using System.Collections.Generic;
     using System.Threading.Tasks;
+    using System.Transactions;
     using Primitives;
 
     /// <summary>
     /// Represents an abstraction for retrying messaging operations. Users should not
     /// implement this class, and instead should use one of the provided implementations.
+    /// <remarks>RetryPolicy will not be applied when an ambient transaction is found.</remarks>
     /// </summary>
     public abstract class RetryPolicy
     {
@@ -124,9 +126,9 @@ namespace Microsoft.Azure.ServiceBus
 
         internal bool ShouldRetry(TimeSpan remainingTime, int currentRetryCount, Exception lastException, out TimeSpan retryInterval)
         {
-            if (lastException == null)
+            // There is no exception information or there's there's an ambient transaction - should not retry
+            if (lastException == null || Transaction.Current != null)
             {
-                // there are no exceptions.
                 retryInterval = TimeSpan.Zero;
                 return false;
             }

test/Microsoft.Azure.ServiceBus.UnitTests/RetryPolicyTests.cs

@@ -0,0 +1,59 @@
+namespace Microsoft.Azure.ServiceBus.UnitTests
+{
+    using System;
+    using System.Threading.Tasks;
+    using System.Transactions;
+    using Xunit;
+
+    public class RetryPolicyTests
+    {
+        [Fact]
+        [DisplayTestMethodName]
+        public async Task Should_retry_when_throttled_and_no_ambient_transaction_is_detected()
+        {
+            var retryPolicy = RetryPolicy.Default;
+
+            var numberOfExecutions = 0;
+
+            await retryPolicy.RunOperation(() =>
+            {
+                if (numberOfExecutions > 1)
+                {
+                    return Task.CompletedTask;
+                }
+
+                numberOfExecutions++;
+
+                throw new ServerBusyException("Rico KABOOM!");
+            }, TimeSpan.FromSeconds(30));
+
+            Assert.Equal(2, numberOfExecutions);
+        }
+
+        [Fact]
+        [DisplayTestMethodName]
+        public async Task Should_not_retry_when_throttled_and_ambient_transaction_is_detected()
+        {
+            var retryPolicy = RetryPolicy.Default;
+            var numberOfExecutions = 0;
+
+            using (var tx = new TransactionScope(TransactionScopeOption.RequiresNew, TransactionScopeAsyncFlowOption.Enabled))
+            {
+                await Assert.ThrowsAsync<ServerBusyException>(() =>
+                    retryPolicy.RunOperation(() =>
+                    {
+                        if (numberOfExecutions > 1)
+                        {
+                            return Task.CompletedTask;
+                        }
+
+                        numberOfExecutions++;
+
+                        throw new ServerBusyException("Rico KABOOM!");
+                    }, TimeSpan.FromSeconds(30)));
+            }
+
+            Assert.Equal(1, numberOfExecutions);
+        }
+    }
+}

test/Microsoft.Azure.ServiceBus.UnitTests/SenderReceiverClientTestBase.cs

@@ -25,8 +25,8 @@ namespace Microsoft.Azure.ServiceBus.UnitTests
         internal async Task ReceiveDeleteTestCase(IMessageSender messageSender, IMessageReceiver messageReceiver, int messageCount)
         {
             await TestUtility.SendMessagesAsync(messageSender, messageCount);
-            var receivedMessages = await TestUtility.ReceiveMessagesAsync(messageReceiver, messageCount);
+            var receivedMessages = await TestUtility.ReceiveMessagesAsync(messageReceiver, messageCount, TimeSpan.FromSeconds(10));
-            Assert.True(messageCount == receivedMessages.Count);
+            Assert.Equal(receivedMessages.Count, messageCount);
         }
 
         internal async Task PeekLockWithAbandonTestCase(IMessageSender messageSender, IMessageReceiver messageReceiver, int messageCount)

test/Microsoft.Azure.ServiceBus.UnitTests/TestConstants.cs

@@ -3,9 +3,12 @@
 
 namespace Microsoft.Azure.ServiceBus.UnitTests
 {
+    using System;
+
     static class TestConstants
     {
         internal const int MaxAttemptsCount = 5;
+        internal readonly static TimeSpan WaitTimeBetweenAttempts = TimeSpan.FromSeconds(1);
 
         internal const string ConnectionStringEnvironmentVariable = "azure-service-bus-dotnet/connectionstring";
 

test/Microsoft.Azure.ServiceBus.UnitTests/TestUtility.cs

@@ -67,18 +67,27 @@ namespace Microsoft.Azure.ServiceBus.UnitTests
             Log($"Sent {messageCount} messages");
         }
 
-        internal static async Task<IList<Message>> ReceiveMessagesAsync(IMessageReceiver messageReceiver, int messageCount)
+        internal static async Task<IList<Message>> ReceiveMessagesAsync(IMessageReceiver messageReceiver, int messageCount, TimeSpan timeout = default)
         {
             var receiveAttempts = 0;
             var messagesToReturn = new List<Message>();
+            var stopwatch = Stopwatch.StartNew();
 
-            while (receiveAttempts++ < TestConstants.MaxAttemptsCount && messagesToReturn.Count < messageCount)
+            if (timeout == default)
+            {
+                timeout = TimeSpan.Zero;
+            }
+
+            while (messagesToReturn.Count < messageCount && (receiveAttempts++ < TestConstants.MaxAttemptsCount || stopwatch.Elapsed < timeout))
             {
                 var messages = await messageReceiver.ReceiveAsync(messageCount - messagesToReturn.Count);
-                if (messages != null)
+                if (messages == null)
                 {
-                    messagesToReturn.AddRange(messages);
+                    await Task.Delay(TestConstants.WaitTimeBetweenAttempts);
+                    continue;
                 }
+
+                messagesToReturn.AddRange(messages);
             }
 
             VerifyUniqueMessages(messagesToReturn);
@@ -98,7 +107,7 @@ namespace Microsoft.Azure.ServiceBus.UnitTests
                 var msg = await messageReceiver.ReceiveDeferredMessageAsync(sequenceNumber);
                 if (msg != null)
                 {
-                    messagesToReturn.Add(msg); 
+                    messagesToReturn.Add(msg);
                 }
             }