Log errors and rollback if the current MongoDB does not support transactions.

framework/src/Volo.Abp.MongoDB/Volo/Abp/Uow/MongoDB/UnitOfWorkMongoDbContextProvider.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.DependencyInjection;
@@ -7,6 +8,8 @@ using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 using MongoDB.Bson;
 using MongoDB.Driver;
+using MongoDB.Driver.Core.Misc;
+using MongoDB.Driver.Core.Servers;
 using Volo.Abp.Data;
 using Volo.Abp.MongoDB;
 using Volo.Abp.MultiTenancy;
@@ -127,7 +130,7 @@ namespace Volo.Abp.Uow.MongoDB
             var client = CreateMongoClient(mongoUrl);
             var database = client.GetDatabase(databaseName);
 
-            if (unitOfWork.Options.IsTransactional)
+            if (unitOfWork.Options.IsTransactional && IsSupportedTransactions(client))
             {
                 return CreateDbContextWithTransaction(unitOfWork, mongoUrl, client, database);
             }
@@ -147,7 +150,7 @@ namespace Volo.Abp.Uow.MongoDB
             var client = CreateMongoClient(mongoUrl);
             var database = client.GetDatabase(databaseName);
 
-            if (unitOfWork.Options.IsTransactional)
+            if (unitOfWork.Options.IsTransactional && IsSupportedTransactions(client))
             {
                 return await CreateDbContextWithTransactionAsync(
                     unitOfWork,
@@ -285,5 +288,55 @@ namespace Volo.Abp.Uow.MongoDB
         {
             return _cancellationTokenProvider.FallbackToProvider(preferredValue);
         }
+
+        /// <summary>
+        /// https://github.com/mongodb/mongo-csharp-driver/blob/master/src/MongoDB.Driver.Core/Core/Bindings/CoreSession.cs#L495
+        /// </summary>
+        /// <param name="client"></param>
+        /// <returns></returns>
+        /// <exception cref="NotSupportedException"></exception>
+        protected virtual bool IsSupportedTransactions(MongoClient client)
+        {
+            try
+            {
+                var connectedDataBearingServers = client.Cluster.Description.Servers.Where(s => s.State == ServerState.Connected && s.IsDataBearing).ToList();
+            
+                if (connectedDataBearingServers.Count == 0)
+                {
+                    throw new NotSupportedException("StartTransaction cannot determine if transactions are supported because there are no connected servers.");
+                }
+
+                foreach (var connectedDataBearingServer in connectedDataBearingServers)
+                {
+                    var serverType = connectedDataBearingServer.Type;
+
+                    switch (serverType)
+                    {
+                        case ServerType.Standalone:
+                            throw new NotSupportedException("Standalone servers do not support transactions.");
+                        case ServerType.ShardRouter:
+                            Feature.ShardedTransactions.ThrowIfNotSupported(connectedDataBearingServer.Version);
+                            break;
+                        case ServerType.LoadBalanced:
+                            // do nothing, load balancing always supports transactions
+                            break;
+                        default:
+                            Feature.Transactions.ThrowIfNotSupported(connectedDataBearingServer.Version);
+                            break;
+                    }
+                }
+            }
+            catch (Exception e)
+            {
+                Logger.LogError("The current MongoDB database does not support transactions, " +
+                                "All operations will be performed in non-transactions. " +
+                                "This may cause errors, " +
+                                "Please make your database support transactions.");
+                Logger.LogException(e);
+                return false;
+            }
+
+            return true;
+        }
     }
 }