Exception logging for exceptions leaked to ServiceBus SDK. (#276)

Validated that nothing was broken by the change.

Author: agr

src/NuGet.Services.ServiceBus/OnMessageOptionsWrapper.cs

@@ -8,23 +8,29 @@ namespace NuGet.Services.ServiceBus
 {
     public sealed class OnMessageOptionsWrapper : IOnMessageOptions
     {
-        public OnMessageOptions OnMessageOptions { get; set; }
+        /// <summary>
+        /// Specifies whether the Service Bus message completes when message callback returns.
+        /// </summary>
+        /// <remarks>
+        /// Default value is set to the default value of the respective property of <see cref="OnMessageOptions"/>.
+        /// </remarks>
+        public bool AutoComplete { get; set; } = true;
 
-        public bool AutoComplete
-        {
-            get => OnMessageOptions.AutoComplete;
-            set => OnMessageOptions.AutoComplete = value;
-        }
-
-        public int MaxConcurrentCalls
-        {
-            get => OnMessageOptions.MaxConcurrentCalls;
-            set => OnMessageOptions.MaxConcurrentCalls = value;
-        }
+        /// <summary>
+        /// Specifies the maximum number of concurrent message callbacks.
+        /// </summary>
+        /// <remarks>
+        /// Default value is set to the default value of the respective property of <see cref="OnMessageOptions"/>.
+        /// </remarks>
+        public int MaxConcurrentCalls { get; set; } = 1;
 
-        public OnMessageOptionsWrapper(OnMessageOptions options = null)
+        public OnMessageOptions GetOptions()
         {
-            OnMessageOptions = OnMessageOptions ?? new OnMessageOptions();
+            return new OnMessageOptions
+            {
+                AutoComplete = AutoComplete,
+                MaxConcurrentCalls = MaxConcurrentCalls,
+            };
         }
     }
 }

src/NuGet.Services.ServiceBus/SubscriptionClientWrapper.cs

@@ -3,23 +3,29 @@
 
 using System;
 using System.Threading.Tasks;
+using Microsoft.Extensions.Logging;
 using Microsoft.ServiceBus.Messaging;
 
 namespace NuGet.Services.ServiceBus
 {
     public class SubscriptionClientWrapper : ISubscriptionClient
     {
         private readonly SubscriptionClient _client;
+        private readonly ILogger<SubscriptionClientWrapper> _logger;
 
-        public SubscriptionClientWrapper(string connectionString, string topicPath, string name)
+        public SubscriptionClientWrapper(string connectionString, string topicPath, string name, ILogger<SubscriptionClientWrapper> logger)
         {
             _client = SubscriptionClient.CreateFromConnectionString(connectionString, topicPath, name);
+            _logger = logger ?? throw new ArgumentNullException(nameof(logger));
         }
 
         public void OnMessageAsync(Func<IBrokeredMessage, Task> onMessageAsync)
         {
             var callback = CreateOnMessageAsyncCallback(onMessageAsync);
 
+            var onMessageOptions = new OnMessageOptions();
+            onMessageOptions.ExceptionReceived += OnMessageException;
+
             _client.OnMessageAsync(callback);
         }
 
@@ -36,9 +42,17 @@ public void OnMessageAsync(Func<IBrokeredMessage, Task> onMessageAsync, IOnMessa
                     nameof(options));
             }
 
+            var onMessageOptions = optionsWrapper.GetOptions();
+            onMessageOptions.ExceptionReceived += OnMessageException;
+
             _client.OnMessageAsync(
                 CreateOnMessageAsyncCallback(onMessageAsync),
-                optionsWrapper.OnMessageOptions);
+                onMessageOptions);
+        }
+
+        private void OnMessageException(object sender, ExceptionReceivedEventArgs e)
+        {
+            _logger.LogError(0, e.Exception, "Unhandled exception while processing ServiceBus message");
         }
 
         private Func<BrokeredMessage, Task> CreateOnMessageAsyncCallback(Func<IBrokeredMessage, Task> onMessageAsync)