Relax SessionId validation (Azure#27924)

* Relax SessionId validation

* save

* PR fb

Author: JoshLove-msft

sdk/servicebus/Azure.Messaging.ServiceBus/src/Diagnostics/ServiceBusEventSource.cs

@@ -189,6 +189,8 @@ protected ServiceBusEventSource() : base(EventSourceName)
         internal const int ProcessorStoppingReceiveCanceledEvent = 110;
         internal const int ProcessorStoppingAcceptSessionCanceledEvent = 111;
 
+        internal const int PartitionKeyValueOverwritten = 112;
+
         #endregion
         // add new event numbers here incrementing from previous
 
@@ -1570,6 +1572,15 @@ public virtual void MaxMessagesExceedsPrefetch(string identifier, int prefetchCo
                 WriteEvent(MaxMessagesExceedsPrefetchEvent, identifier, prefetchCount, maxMessages);
             }
         }
+
+        [Event(PartitionKeyValueOverwritten, Level = EventLevel.Warning, Message = "The PartitionKey property with value '{0}' was overwritten with value '{1}' due to setting the SessionId on message with MessageId '{2}'")]
+        public virtual void PartitionKeyOverwritten(string partitionKey, string sessionId, string messageId)
+        {
+            if (IsEnabled())
+            {
+                WriteEvent(PartitionKeyValueOverwritten,partitionKey, sessionId, messageId);
+            }
+        }
         #endregion
     }
 }

sdk/servicebus/Azure.Messaging.ServiceBus/src/Primitives/ServiceBusMessage.cs

@@ -9,6 +9,7 @@
 using Azure.Core;
 using Azure.Core.Amqp;
 using Azure.Messaging.ServiceBus.Amqp;
+using Azure.Messaging.ServiceBus.Diagnostics;
 
 namespace Azure.Messaging.ServiceBus
 {
@@ -243,11 +244,14 @@ public string SessionId
             set
             {
                 Argument.AssertNotTooLong(value, Constants.MaxSessionIdLength, nameof(value));
+                AmqpMessage.Properties.GroupId = value;
+
+                // If the PartitionKey was already set to a different value, override it with the SessionId, as the SessionId takes precedence.
                 if (PartitionKey != null && PartitionKey != value)
                 {
-                    throw new ArgumentOutOfRangeException(nameof(value), $"SessionId:{value} cannot be set to a different value than PartitionKey:{PartitionKey}.");
+                    ServiceBusEventSource.Log.PartitionKeyOverwritten(PartitionKey, value, MessageId);
+                    PartitionKey = value;
                 }
-                AmqpMessage.Properties.GroupId = value;
             }
         }
 

sdk/servicebus/Azure.Messaging.ServiceBus/tests/Diagnostics/EventSourceLiveTests.cs

@@ -437,5 +437,21 @@ public async Task StoppingSessionProcessorDoesNotLogTaskCanceledExceptions()
                 Assert.True(_listener.EventsById(ServiceBusEventSource.ProcessorStoppingReceiveCanceledEvent).Any());
             }
         }
+
+        [Test]
+        public void LogsMessageEvents()
+        {
+            var message = new ServiceBusMessage()
+            {
+                SessionId = "sessionId1",
+                PartitionKey = "sessionId1",
+                MessageId = "messageId"
+            };
+            message.SessionId = "sessionId2";
+
+            _listener.SingleEventById(
+                ServiceBusEventSource.PartitionKeyValueOverwritten,
+                e => e.Payload.Contains("sessionId1") && e.Payload.Contains("sessionId2") && e.Payload.Contains("messageId"));
+        }
     }
 }

sdk/servicebus/Azure.Messaging.ServiceBus/tests/Message/MessageTests.cs

@@ -111,9 +111,9 @@ public void PartitionKeyMustMatchSessionIdIfBothSet()
             {
                 PartitionKey = "partition"
             };
-            Assert.That(
-                () => message.SessionId = "session",
-                Throws.InstanceOf<ArgumentOutOfRangeException>());
+            message.SessionId = "session";
+            Assert.AreEqual("session", message.PartitionKey);
+            Assert.AreEqual(message.SessionId, message.PartitionKey);
 
             message = new ServiceBusMessage
             {
@@ -127,33 +127,44 @@ public void PartitionKeyMustMatchSessionIdIfBothSet()
             {
                 PartitionKey = "partition"
             };
-            Assert.That(
-                () => message.SessionId = null,
-                Throws.InstanceOf<ArgumentOutOfRangeException>());
+            message.SessionId = null;
+            Assert.IsNull(message.PartitionKey);
 
             message = new ServiceBusMessage
             {
                 PartitionKey = null,
                 SessionId = "session"
             };
+            Assert.IsNull(message.PartitionKey);
 
             message = new ServiceBusMessage
             {
                 SessionId = null,
                 PartitionKey = "partition"
             };
+            Assert.IsNull(message.SessionId);
 
             message = new ServiceBusMessage
             {
                 SessionId = "partition",
                 PartitionKey = "partition"
             };
+            Assert.AreEqual(message.SessionId, message.PartitionKey);
+
+            message = new ServiceBusMessage
+            {
+                PartitionKey = "partition",
+                SessionId = "partition"
+            };
+            Assert.AreEqual(message.SessionId, message.PartitionKey);
 
             message = new ServiceBusMessage
             {
                 PartitionKey = "partition",
                 SessionId = "partition"
             };
+            message.SessionId = "session";
+            Assert.AreEqual(message.SessionId, message.PartitionKey);
         }
 
         [Test]