CSHARP-4504: Do not perform server selection to determine sessions support (#1095)

BorisDog · web-flow · commit 726ab47cf3b9 · 2023-06-01T14:42:54.000-07:00
diff --git a/src/MongoDB.Driver.Core/Core/Bindings/CoreSession.cs b/src/MongoDB.Driver.Core/Core/Bindings/CoreSession.cs
@@ -521,11 +521,6 @@ private void EnsureTransactionsAreSupported()
 
             var connectedDataBearingServers = _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;
diff --git a/src/MongoDB.Driver.Core/Core/WireProtocol/CommandUsingCommandMessageWireProtocol.cs b/src/MongoDB.Driver.Core/Core/WireProtocol/CommandUsingCommandMessageWireProtocol.cs
@@ -334,7 +334,20 @@ private Type0CommandMessageSection<BsonDocument> CreateType0Section(ConnectionDe
 
             if (_session.Id != null)
             {
-                if (IsSessionAcknowledged())
+                var areSessionsSupported = connectionDescription.HelloResult.LogicalSessionTimeout.HasValue;
+
+                if (!areSessionsSupported)
+                {
+                    if (_session.IsImplicit)
+                    {
+                        // do not set sessionId if session is implicit and sessions are not supported
+                    }
+                    else
+                    {
+                        throw new MongoClientException("Sessions are not supported.");
+                    }
+                }
+                else if (IsSessionAcknowledged())
                 {
                     AddIfNotAlreadyAdded("lsid", _session.Id);
                 }
@@ -351,7 +364,6 @@ private Type0CommandMessageSection<BsonDocument> CreateType0Section(ConnectionDe
                 }
             }
 
-
             var snapshotReadConcernDocument = ReadConcernHelper.GetReadConcernForSnapshotSesssion(_session, connectionDescription);
             if (snapshotReadConcernDocument != null)
             {
diff --git a/src/MongoDB.Driver/Encryption/MongocryptdFactory.cs b/src/MongoDB.Driver/Encryption/MongocryptdFactory.cs
@@ -21,6 +21,7 @@
 using System.Linq;
 using System.Reflection;
 using MongoDB.Driver.Core;
+using MongoDB.Driver.Core.Events;
 using MongoDB.Driver.Core.Misc;
 
 namespace MongoDB.Driver.Encryption
@@ -74,18 +75,26 @@ public static string ExtractCryptSharedLibPath(IReadOnlyDictionary<string, objec
     internal class MongocryptdFactory
     {
         private readonly bool? _bypassQueryAnalysis;
+        private readonly IEventSubscriber _eventSubscriber;
         private readonly IReadOnlyDictionary<string, object> _extraOptions;
 
-        public MongocryptdFactory(IReadOnlyDictionary<string, object> extraOptions, bool? bypassQueryAnalysis)
+        public MongocryptdFactory(IReadOnlyDictionary<string, object> extraOptions, bool? bypassQueryAnalysis, IEventSubscriber eventSubscriber = null)
         {
             _bypassQueryAnalysis = bypassQueryAnalysis;
+            _eventSubscriber = eventSubscriber;
             _extraOptions = extraOptions ?? new Dictionary<string, object>();
         }
 
         // public methods
         public IMongoClient CreateMongocryptdClient()
         {
             var clientSettings = CreateMongocryptdClientSettings();
+
+            if (_eventSubscriber != null)
+            {
+                clientSettings.ClusterConfigurator = c => c.Subscribe(_eventSubscriber);
+            }
+
             return new MongoClient(clientSettings);
         }
 
diff --git a/src/MongoDB.Driver/MongoClient.cs b/src/MongoDB.Driver/MongoClient.cs
@@ -14,7 +14,6 @@
 */
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -24,10 +23,8 @@
 using MongoDB.Bson.Serialization.Serializers;
 using MongoDB.Driver.Core.Bindings;
 using MongoDB.Driver.Core.Clusters;
-using MongoDB.Driver.Core.Clusters.ServerSelectors;
 using MongoDB.Driver.Core.Misc;
 using MongoDB.Driver.Core.Operations;
-using MongoDB.Driver.Core.Servers;
 using MongoDB.Driver.Core.WireProtocol.Messages.Encoders;
 using MongoDB.Driver.Encryption;
 using MongoDB.Driver.Linq;
@@ -37,23 +34,6 @@ namespace MongoDB.Driver
     /// <inheritdoc/>
     public class MongoClient : MongoClientBase
     {
-        #region static
-        // private static methods
-        private static IEnumerable<ServerDescription> SelectServersThatDetermineWhetherSessionsAreSupported(ClusterDescription cluster, IEnumerable<ServerDescription> servers)
-        {
-            var connectedServers = servers.Where(s => s.State == ServerState.Connected);
-
-            if (cluster.IsDirectConnection)
-            {
-                return connectedServers;
-            }
-            else
-            {
-                return connectedServers.Where(s => s.IsDataBearing);
-            }
-        }
-        #endregion
-
         // private fields
         private readonly ICluster _cluster;
         private readonly AutoEncryptionLibMongoCryptController _libMongoCryptController;
@@ -146,9 +126,6 @@ internal void ConfigureAutoEncryptionMessageEncoderSettings(MessageEncoderSettin
             }
         }
 
-        // private static methods
-
-
         // public methods
         /// <inheritdoc/>
         public sealed override void DropDatabase(string name, CancellationToken cancellationToken = default(CancellationToken))
@@ -346,32 +323,28 @@ public sealed override Task<IAsyncCursor<BsonDocument>> ListDatabasesAsync(
         /// <returns>A session.</returns>
         internal IClientSessionHandle StartImplicitSession(CancellationToken cancellationToken)
         {
-            var areSessionsSupported = AreSessionsSupported(cancellationToken);
-            return StartImplicitSession(areSessionsSupported);
+            return StartImplicitSession();
         }
 
         /// <summary>
         /// Starts an implicit session.
         /// </summary>
         /// <returns>A Task whose result is a session.</returns>
-        internal async Task<IClientSessionHandle> StartImplicitSessionAsync(CancellationToken cancellationToken)
+        internal Task<IClientSessionHandle> StartImplicitSessionAsync(CancellationToken cancellationToken)
         {
-            var areSessionsSupported = await AreSessionsSupportedAsync(cancellationToken).ConfigureAwait(false);
-            return StartImplicitSession(areSessionsSupported);
+            return Task.FromResult(StartImplicitSession());
         }
 
         /// <inheritdoc/>
         public sealed override IClientSessionHandle StartSession(ClientSessionOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
         {
-            var areSessionsSupported = AreSessionsSupported(cancellationToken);
-            return StartSession(options, areSessionsSupported);
+            return StartSession(options);
         }
 
         /// <inheritdoc/>
-        public sealed override async Task<IClientSessionHandle> StartSessionAsync(ClientSessionOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
+        public sealed override Task<IClientSessionHandle> StartSessionAsync(ClientSessionOptions options = null, CancellationToken cancellationToken = default(CancellationToken))
         {
-            var areSessionsSupported = await AreSessionsSupportedAsync(cancellationToken).ConfigureAwait(false);
-            return StartSession(options, areSessionsSupported);
+            return Task.FromResult(StartSession(options));
         }
 
         /// <inheritdoc/>
@@ -446,52 +419,6 @@ public override IMongoClient WithWriteConcern(WriteConcern writeConcern)
         }
 
         // private methods
-        private bool AreSessionsSupported(CancellationToken cancellationToken)
-        {
-            return AreSessionsSupported(_cluster.Description) ?? AreSessionsSupportedAfterServerSelection(cancellationToken);
-        }
-
-        private async Task<bool> AreSessionsSupportedAsync(CancellationToken cancellationToken)
-        {
-            return AreSessionsSupported(_cluster.Description) ?? await AreSessionsSupportedAfterServerSelectionAsync(cancellationToken).ConfigureAwait(false);
-        }
-
-        private bool? AreSessionsSupported(ClusterDescription clusterDescription)
-        {
-            if (clusterDescription.LogicalSessionTimeout.HasValue || clusterDescription.Type == ClusterType.LoadBalanced)
-            {
-                return true;
-            }
-            else
-            {
-                var selectedServers = SelectServersThatDetermineWhetherSessionsAreSupported(clusterDescription, clusterDescription.Servers).ToList();
-                if (selectedServers.Count == 0)
-                {
-                    return null;
-                }
-                else
-                {
-                    return false;
-                }
-            }
-        }
-
-        private bool AreSessionsSupportedAfterServerSelection(CancellationToken cancellationToken)
-        {
-            var selector = new AreSessionsSupportedServerSelector();
-            var selectedServer = _cluster.SelectServer(selector, cancellationToken);
-            var clusterDescription = selector.ClusterDescription ?? _cluster.Description; // LB cluster doesn't use server selector, so clusterDescription is null for this case
-            return AreSessionsSupported(clusterDescription) ?? false;
-        }
-
-        private async Task<bool> AreSessionsSupportedAfterServerSelectionAsync(CancellationToken cancellationToken)
-        {
-            var selector = new AreSessionsSupportedServerSelector();
-            var selectedServer = await _cluster.SelectServerAsync(selector, cancellationToken).ConfigureAwait(false);
-            var clusterDescription = selector.ClusterDescription ?? _cluster.Description;  // LB cluster doesn't use server selector, so clusterDescription is null for this case
-            return AreSessionsSupported(clusterDescription) ?? false;
-        }
-
         private IAsyncCursor<string> CreateDatabaseNamesCursor(IAsyncCursor<BsonDocument> cursor)
         {
             return new BatchTransformingAsyncCursor<BsonDocument, string>(
@@ -608,15 +535,15 @@ private MessageEncoderSettings GetMessageEncoderSettings()
             return messageEncoderSettings;
         }
 
-        private IClientSessionHandle StartImplicitSession(bool areSessionsSupported)
+        private IClientSessionHandle StartImplicitSession()
         {
             var options = new ClientSessionOptions { CausalConsistency = false, Snapshot = false };
 
             ICoreSessionHandle coreSession;
 #pragma warning disable 618
             var areMultipleUsersAuthenticated = _settings.Credentials.Count() > 1;
 #pragma warning restore
-            if (areSessionsSupported && !areMultipleUsersAuthenticated)
+            if (!areMultipleUsersAuthenticated)
             {
                 coreSession = _cluster.StartSession(options.ToCore(isImplicit: true));
             }
@@ -628,13 +555,8 @@ private IClientSessionHandle StartImplicitSession(bool areSessionsSupported)
             return new ClientSessionHandle(this, options, coreSession);
         }
 
-        private IClientSessionHandle StartSession(ClientSessionOptions options, bool areSessionsSupported)
+        private IClientSessionHandle StartSession(ClientSessionOptions options)
         {
-            if (!areSessionsSupported)
-            {
-                throw new NotSupportedException("Sessions are not supported by this version of the server.");
-            }
-
             if (options != null && options.Snapshot && options.CausalConsistency == true)
             {
                 throw new NotSupportedException("Combining both causal consistency and snapshot options is not supported.");
@@ -677,17 +599,5 @@ private async Task<TResult> UsingImplicitSessionAsync<TResult>(Func<IClientSessi
                 return await funcAsync(session).ConfigureAwait(false);
             }
         }
-
-        // nested types
-        private class AreSessionsSupportedServerSelector : IServerSelector
-        {
-            public ClusterDescription ClusterDescription;
-
-            public IEnumerable<ServerDescription> SelectServers(ClusterDescription cluster, IEnumerable<ServerDescription> servers)
-            {
-                ClusterDescription = cluster;
-                return SelectServersThatDetermineWhetherSessionsAreSupported(cluster, servers);
-            }
-        }
     }
 }
diff --git a/tests/MongoDB.Driver.Core.Tests/Core/Bindings/CoreSessionTests.cs b/tests/MongoDB.Driver.Core.Tests/Core/Bindings/CoreSessionTests.cs
@@ -14,18 +14,17 @@
 */
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
 using FluentAssertions;
 using MongoDB.Bson;
 using MongoDB.Bson.TestHelpers;
-using MongoDB.TestHelpers.XunitExtensions;
 using MongoDB.Driver.Core.Clusters;
 using MongoDB.Driver.Core.Misc;
 using MongoDB.Driver.Core.Servers;
 using MongoDB.Driver.Core.TestHelpers.XunitExtensions;
+using MongoDB.TestHelpers.XunitExtensions;
 using Moq;
 using Xunit;
 
@@ -250,20 +249,6 @@ public void WasUsed_should_call_serverSession()
             Mock.Get(subject.ServerSession).Verify(m => m.WasUsed(), Times.Once);
         }
 
-        [Theory]
-        [ParameterAttributeData]
-        public void EnsureTransactionsAreSupported_should_throw_when_there_are_no_connected_servers(
-            [Values(0, 1, 2, 3)] int numberOfDisconnectedServers)
-        {
-            var clusterDescription = CreateClusterDescriptionWithDisconnectedServers(numberOfDisconnectedServers);
-            var subject = CreateSubject(clusterDescription);
-
-            var exception = Record.Exception(() => subject.EnsureTransactionsAreSupported());
-
-            var e = exception.Should().BeOfType<NotSupportedException>().Subject;
-            e.Message.Should().Be("StartTransaction cannot determine if transactions are supported because there are no connected servers.");
-        }
-
         [Theory]
         [ParameterAttributeData]
         public void EnsureTransactionsAreSupported_should_not_throw_when_there_are_no_connected_servers_with_LB(
@@ -273,7 +258,7 @@ public void EnsureTransactionsAreSupported_should_not_throw_when_there_are_no_co
             clusterDescription = clusterDescription.WithType(ClusterType.LoadBalanced);
             var subject = CreateSubject(clusterDescription);
 
-            subject.EnsureTransactionsAreSupported();       
+            subject.EnsureTransactionsAreSupported();
         }
 
         // EnsureTransactionsAreSupported scenario codes
@@ -325,7 +310,7 @@ public void EnsureTransactionsAreSupported_should_ignore_disconnected_servers(st
         [InlineData("CA,DU")]
         [InlineData("CA,CA")]
         [InlineData("CA,DL")]
-        public void EnsureTransactionsAreSupported_should_throw_when_there_are_no_connected_data_bearing_servers(string scenarios)
+        public void EnsureTransactionsAreSupported_should_ignore_no_data_bearing_servers(string scenarios)
         {
             var clusterId = new ClusterId(1);
             var servers =
@@ -342,10 +327,7 @@ public void EnsureTransactionsAreSupported_should_throw_when_there_are_no_connec
             var cluster = CreateClusterDescription(clusterId, servers: servers);
             var subject = CreateSubject(cluster);
 
-            var exception = Record.Exception(() => subject.EnsureTransactionsAreSupported());
-
-            var e = exception.Should().BeOfType<NotSupportedException>().Subject;
-            e.Message.Should().Be("StartTransaction cannot determine if transactions are supported because there are no connected servers.");
+            subject.EnsureTransactionsAreSupported();
         }
 
         [Theory]
diff --git a/tests/MongoDB.Driver.Tests/MongoClientTests.cs b/tests/MongoDB.Driver.Tests/MongoClientTests.cs
diff --git a/tests/MongoDB.Driver.Tests/Specifications/sessions/SessionsProseTests.cs b/tests/MongoDB.Driver.Tests/Specifications/sessions/SessionsProseTests.cs

Original file line number	Diff line number	Diff line change
`@@ -334,7 +334,20 @@ private Type0CommandMessageSection<BsonDocument> CreateType0Section(ConnectionDe`
`334`	`334`
`335`	`335`	`if (_session.Id != null)`
`336`	`336`	`{`
`337`		`- if (IsSessionAcknowledged())`
	`337`	`+ var areSessionsSupported = connectionDescription.HelloResult.LogicalSessionTimeout.HasValue;`
	`338`	`+`
	`339`	`+ if (!areSessionsSupported)`
	`340`	`+ {`
	`341`	`+ if (_session.IsImplicit)`
	`342`	`+ {`
	`343`	`+ // do not set sessionId if session is implicit and sessions are not supported`
	`344`	`+ }`
	`345`	`+ else`
	`346`	`+ {`
	`347`	`+ throw new MongoClientException("Sessions are not supported.");`
	`348`	`+ }`
	`349`	`+ }`
	`350`	`+ else if (IsSessionAcknowledged())`
`338`	`351`	`{`
`339`	`352`	`AddIfNotAlreadyAdded("lsid", _session.Id);`
`340`	`353`	`}`
`@@ -351,7 +364,6 @@ private Type0CommandMessageSection<BsonDocument> CreateType0Section(ConnectionDe`
`351`	`364`	`}`
`352`	`365`	`}`
`353`	`366`
`354`		`-`
`355`	`367`	`var snapshotReadConcernDocument = ReadConcernHelper.GetReadConcernForSnapshotSesssion(_session, connectionDescription);`
`356`	`368`	`if (snapshotReadConcernDocument != null)`
`357`	`369`	`{`