CSHARP-2188: Consolidate session handling in Core.

Author: rstam

src/MongoDB.Driver.Core/Core/Bindings/CoreSession.cs

@@ -24,31 +24,27 @@ namespace MongoDB.Driver.Core.Bindings
     /// Represents a session.
     /// </summary>
     /// <seealso cref="MongoDB.Driver.Core.Bindings.ICoreSession" />
-    internal sealed class CoreSession : ICoreSession
+    public sealed class CoreSession : ICoreSession
     {
         // private fields
         private readonly IClusterClock _clusterClock = new ClusterClock();
         private bool _disposed;
-        private readonly bool _isCausallyConsistent;
-        private readonly bool _isImplicit;
         private readonly IOperationClock _operationClock = new OperationClock();
+        private readonly CoreSessionOptions _options;
         private readonly ICoreServerSession _serverSession;
 
         // constructors
         /// <summary>
         /// Initializes a new instance of the <see cref="CoreSession" /> class.
         /// </summary>
         /// <param name="serverSession">The server session.</param>
-        /// <param name="isCausallyConsistent">if set to <c>true</c> [is causally consistent].</param>
-        /// <param name="isImplicit">if set to <c>true</c> [is implicit].</param>
+        /// <param name="options">The options.</param>
         public CoreSession(
             ICoreServerSession serverSession,
-            bool isCausallyConsistent = false,
-            bool isImplicit = false)
+            CoreSessionOptions options)
         {
             _serverSession = Ensure.IsNotNull(serverSession, nameof(serverSession));
-            _isCausallyConsistent = isCausallyConsistent;
-            _isImplicit = isImplicit;
+            _options = Ensure.IsNotNull(options, nameof(options));
         }
 
         // public properties
@@ -59,14 +55,20 @@ public CoreSession(
         public BsonDocument Id => _serverSession.Id;
 
         /// <inheritdoc />
-        public bool IsCausallyConsistent => _isCausallyConsistent;
+        public bool IsCausallyConsistent => _options.IsCausallyConsistent;
 
         /// <inheritdoc />
-        public bool IsImplicit => _isImplicit;
+        public bool IsImplicit => _options.IsImplicit;
 
         /// <inheritdoc />
         public BsonTimestamp OperationTime => _operationClock.OperationTime;
 
+        /// <inheritdoc />
+        public CoreSessionOptions Options => _options;
+
+        /// <inheritdoc />
+        public ICoreServerSession ServerSession => _serverSession;
+
         // public methods
         /// <inheritdoc />
         public void AdvanceClusterTime(BsonDocument newClusterTime)

src/MongoDB.Driver.Core/Core/Bindings/CoreSessionOptions.cs

@@ -0,0 +1,58 @@
+/* Copyright 2018-present MongoDB Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+namespace MongoDB.Driver.Core.Bindings
+{
+    /// <summary>
+    /// Core session options.
+    /// </summary>
+    public class CoreSessionOptions
+    {
+        // private fields
+        private readonly bool _isCausallyConsistent;
+        private readonly bool _isImplicit;
+
+        // constructors
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CoreSessionOptions"/> class.
+        /// </summary>
+        /// <param name="isCausallyConsistent">if set to <c>true</c> this session is causally consistent]</param>
+        /// <param name="isImplicit">if set to <c>true</c> this session is an implicit session.</param>
+        public CoreSessionOptions(
+            bool isCausallyConsistent = false,
+            bool isImplicit = false)
+        {
+            _isCausallyConsistent = isCausallyConsistent;
+            _isImplicit = isImplicit;
+        }
+
+        // public properties
+        /// <summary>
+        /// Gets a value indicating whether this session is causally consistent.
+        /// </summary>
+        /// <value>
+        ///   <c>true</c> if this session is causally consistent; otherwise, <c>false</c>.
+        /// </value>
+        public bool IsCausallyConsistent => _isCausallyConsistent;
+
+        /// <summary>
+        /// Gets a value indicating whether this session is an implicit session.
+        /// </summary>
+        /// <value>
+        ///   <c>true</c> if this session is an implicit session; otherwise, <c>false</c>.
+        /// </value>
+        public bool IsImplicit => _isImplicit;
+    }
+}

src/MongoDB.Driver.Core/Core/Bindings/ICoreSession.cs

@@ -15,6 +15,7 @@
 
 using System;
 using MongoDB.Bson;
+using MongoDB.Driver.Core.Clusters;
 
 namespace MongoDB.Driver.Core.Bindings
 {
@@ -64,6 +65,22 @@ public interface ICoreSession : IDisposable
         /// </value>
         BsonTimestamp OperationTime { get; }
 
+        /// <summary>
+        /// Gets the session options.
+        /// </summary>
+        /// <value>
+        /// The session options.
+        /// </value>
+        CoreSessionOptions Options { get; }
+
+        /// <summary>
+        /// Gets the server session.
+        /// </summary>
+        /// <value>
+        /// The server session.
+        /// </value>
+        ICoreServerSession ServerSession { get; }
+
         // methods
         /// <summary>
         /// Advances the cluster time.

src/MongoDB.Driver/NoServerSession.cs renamed to src/MongoDB.Driver.Core/Core/Bindings/NoCoreServerSession.cs

@@ -1,4 +1,4 @@
-/* Copyright 2017-present MongoDB Inc.
+/* Copyright 2018-present MongoDB Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -16,46 +16,31 @@
 using System;
 using MongoDB.Bson;
 
-namespace MongoDB.Driver
+namespace MongoDB.Driver.Core.Bindings
 {
-    /// <summary>
-    /// A class that represents no server session.
-    /// </summary>
-    /// <seealso cref="MongoDB.Driver.IServerSession" />
-    internal sealed class NoServerSession : IServerSession
+    internal class NoCoreServerSession : ICoreServerSession
     {
         #region static
         // private static fields
-        private static readonly IServerSession __instance = new NoServerSession();
-
-        // public static fields
-        /// <summary>
-        /// Gets the pre-created instance.
-        /// </summary>
-        /// <value>
-        /// The instance.
-        /// </value>
-        public static IServerSession Instance => __instance;
+        private static readonly ICoreServerSession __instance = new NoCoreServerSession();
+
+        // public static properties
+        public static ICoreServerSession Instance => __instance;
         #endregion
 
-        /// <inheritdoc />
         public BsonDocument Id => null;
 
-        /// <inheritdoc />
         public DateTime? LastUsedAt => null;
 
-        /// <inheritdoc />
         public long AdvanceTransactionNumber()
         {
             return -1;
         }
 
-        /// <inheritdoc />
         public void Dispose()
         {
         }
 
-        /// <inheritdoc />
         public void WasUsed()
         {
         }

src/MongoDB.Driver.Core/Core/Bindings/NoCoreSession.cs

@@ -14,6 +14,7 @@
 */
 
 using MongoDB.Bson;
+using MongoDB.Driver.Core.Clusters;
 
 namespace MongoDB.Driver.Core.Bindings
 {
@@ -63,6 +64,12 @@ public static ICoreSessionHandle NewHandle()
         /// <inheritdoc />
         public BsonTimestamp OperationTime => null;
 
+        /// <inheritdoc />
+        public CoreSessionOptions Options => null;
+
+        /// <inheritdoc />
+        public ICoreServerSession ServerSession => NoCoreServerSession.Instance;
+
         /// <inheritdoc />
         public void AdvanceClusterTime(BsonDocument newClusterTime)
         {

src/MongoDB.Driver.Core/Core/Bindings/WrappingCoreSession.cs

@@ -15,6 +15,7 @@
 
 using System;
 using MongoDB.Bson;
+using MongoDB.Driver.Core.Clusters;
 using MongoDB.Driver.Core.Misc;
 
 namespace MongoDB.Driver.Core.Bindings
@@ -93,6 +94,26 @@ public virtual BsonTimestamp OperationTime
             }
         }
 
+        /// <inheritdoc />
+        public virtual CoreSessionOptions Options
+        {
+            get
+            {
+                ThrowIfDisposed();
+                return _wrapped.Options;
+            }
+        }
+
+        /// <inheritdoc />
+        public virtual ICoreServerSession ServerSession
+        {
+            get
+            {
+                ThrowIfDisposed();
+                return _wrapped.ServerSession;
+            }
+        }
+
         /// <summary>
         /// Gets the wrapped session.
         /// </summary>

src/MongoDB.Driver.Core/Core/Clusters/Cluster.cs

@@ -21,7 +21,9 @@
 using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using MongoDB.Bson;
 using MongoDB.Driver.Core.Async;
+using MongoDB.Driver.Core.Bindings;
 using MongoDB.Driver.Core.Clusters.ServerSelectors;
 using MongoDB.Driver.Core.Configuration;
 using MongoDB.Driver.Core.Events;
@@ -281,6 +283,14 @@ public async Task<IServer> SelectServerAsync(IServerSelector selector, Cancellat
             }
         }
 
+        public ICoreSessionHandle StartSession(CoreSessionOptions options)
+        {
+            options = options ?? new CoreSessionOptions();
+            var serverSession = AcquireServerSession();
+            var session = new CoreSession(serverSession, options);
+            return new CoreSessionHandle(session);
+        }
+
         protected abstract bool TryGetServer(EndPoint endPoint, out IClusterableServer server);
 
         protected void UpdateClusterDescription(ClusterDescription newClusterDescription)

src/MongoDB.Driver.Core/Core/Clusters/ClusterClock.cs

@@ -22,7 +22,7 @@ namespace MongoDB.Driver.Core.Clusters
     /// A cluster clock.
     /// </summary>
     /// <seealso cref="MongoDB.Driver.Core.Clusters.IClusterClock" />
-    public class ClusterClock : IClusterClock
+    internal class ClusterClock : IClusterClock
     {
         #region static
         // public static methods

src/MongoDB.Driver.Core/Core/Clusters/ICluster.cs

@@ -14,15 +14,11 @@
 */
 
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Net;
-using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
+using MongoDB.Driver.Core.Bindings;
 using MongoDB.Driver.Core.Clusters.ServerSelectors;
 using MongoDB.Driver.Core.Configuration;
-using MongoDB.Driver.Core.Events;
 using MongoDB.Driver.Core.Servers;
 
 namespace MongoDB.Driver.Core.Clusters
@@ -90,5 +86,14 @@ public interface ICluster : IDisposable
         /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>A Task representing the operation. The result of the Task is the selected server.</returns>
         Task<IServer> SelectServerAsync(IServerSelector selector, CancellationToken cancellationToken);
+
+        /// <summary>
+        /// Starts a session.
+        /// </summary>
+        /// <param name="options">The options.</param>
+        /// <returns>
+        /// A session.
+        /// </returns>
+        ICoreSessionHandle StartSession(CoreSessionOptions options = null);
     }
 }

src/MongoDB.Driver.Core/Core/Operations/OperationClock.cs

@@ -22,7 +22,7 @@ namespace MongoDB.Driver.Core.Operations
     /// An operation clock.
     /// </summary>
     /// <seealso cref="MongoDB.Driver.Core.Operations.IOperationClock" />
-    public class OperationClock : IOperationClock
+    internal class OperationClock : IOperationClock
     {
         #region static
         // public static methods