Rough sketch of session without touching currrent thread-local framew…

…ork: session-based acccess just updates existing thread-local variables to set the session for the current thread.
microsoft · Jul 11, 2019 · 2b7e24f · 2b7e24f
1 parent 3d17a2d
commit 2b7e24f
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diff --git a/cs/src/core/Epochs/LightEpoch.cs b/cs/src/core/Epochs/LightEpoch.cs
@@ -197,6 +197,8 @@ public void Release()
             (*(tableAligned + entry)).threadId = 0;
         }
 
+        internal FastThreadLocal<int> ThreadEntry => threadEntryIndex;
+
         /// <summary>
         /// Increment global current epoch
         /// </summary>

diff --git a/cs/src/core/Index/FASTER/FASTER.cs b/cs/src/core/Index/FASTER/FASTER.cs
@@ -270,6 +270,36 @@ public void Recover(Guid indexCheckpointToken, Guid hybridLogCheckpointToken)
             InternalRecover(indexCheckpointToken, hybridLogCheckpointToken);
         }
 
+
+        /// <summary>
+        /// Start shared (not thread-specific) session with FASTER
+        /// </summary>
+        /// <returns></returns>
+        public Session<Key, Value, Input, Output, Context, Functions> StartSharedSession()
+        {
+            StartSession();
+            return new Session<Key, Value, Input, Output, Context, Functions>
+                (this, prevThreadCtx.Value, threadCtx.Value, epoch.ThreadEntry.Value);
+        }
+
+        /// <summary>
+        /// Continue shared (not thread-specific) session with FASTER
+        /// </summary>
+        /// <returns></returns>
+        public Session<Key, Value, Input, Output, Context, Functions> ContinueSharedSession(Guid guid)
+        {
+            ContinueSession(guid);
+            return new Session<Key, Value, Input, Output, Context, Functions>
+                (this, prevThreadCtx.Value, threadCtx.Value, epoch.ThreadEntry.Value);
+        }
+
+        internal void SetContext(FasterExecutionContext prevThreadCtx, FasterExecutionContext threadCtx, int epochEntry)
+        {
+            this.prevThreadCtx.Value = prevThreadCtx;
+            this.threadCtx.Value = threadCtx;
+            epoch.ThreadEntry.Value = epochEntry;
+        }
+
         /// <summary>
         /// Start session with FASTER - call once per thread before using FASTER
         /// </summary>

diff --git a/cs/src/core/Index/FASTER/Session.cs b/cs/src/core/Index/FASTER/Session.cs
@@ -0,0 +1,67 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+#pragma warning disable 0162
+
+using System;
+
+namespace FASTER.core
+{
+    /// <summary>
+    /// Thread-independent session interface to FASTER
+    /// </summary>
+    /// <typeparam name="Key"></typeparam>
+    /// <typeparam name="Value"></typeparam>
+    /// <typeparam name="Input"></typeparam>
+    /// <typeparam name="Output"></typeparam>
+    /// <typeparam name="Context"></typeparam>
+    /// <typeparam name="Functions"></typeparam>
+    public class Session<Key, Value, Input, Output, Context, Functions> : IDisposable
+        where Key : new()
+        where Value : new()
+        where Functions : IFunctions<Key, Value, Input, Output, Context>
+    {
+        FasterKV<Key, Value, Input, Output, Context, Functions> fht;
+        private FasterKV<Key, Value, Input, Output, Context, Functions>.FasterExecutionContext prevThreadCtx;
+        private FasterKV<Key, Value, Input, Output, Context, Functions>.FasterExecutionContext threadCtx;
+        private int epochEntry;
+
+        internal Session(
+            FasterKV<Key, Value, Input, Output, Context, Functions> fht,
+            FasterKV<Key, Value, Input, Output, Context, Functions>.FasterExecutionContext prevThreadCtx,
+            FasterKV<Key, Value, Input, Output, Context, Functions>.FasterExecutionContext threadCtx,
+            int epochEntry)
+        {
+            this.fht = fht;
+            this.prevThreadCtx = prevThreadCtx;
+            this.threadCtx = threadCtx;
+            this.epochEntry = epochEntry;
+        }
+
+        /// <summary>
+        /// Get session Guid
+        /// </summary>
+        public Guid ID { get { return threadCtx.guid; } }
+
+        /// <summary>
+        /// Dispose session
+        /// </summary>
+        public void Dispose()
+        {
+            Resume();
+
+            fht.StopSession();
+            prevThreadCtx = threadCtx = null;
+            epochEntry = 0;
+            fht = null;
+        }
+
+        /// <summary>
+        /// Resume session on current thread
+        /// </summary>
+        public void Resume()
+        {
+            fht.SetContext(prevThreadCtx, threadCtx, epochEntry);
+        }
+    }
+}