Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / Data / System / Data / SqlClient / TdsParserSessionPool.cs / 3 / TdsParserSessionPool.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //[....] //[....] //----------------------------------------------------------------------------- namespace System.Data.SqlClient { using System; using System.Collections.Generic; using System.Data.Common; using System.Data.ProviderBase; using System.Diagnostics; using System.Runtime.CompilerServices; using System.Runtime.InteropServices; using System.Threading; internal class TdsParserSessionPool { // NOTE: This is a very simplistic, lightweight pooler. It wasn't // intended to handle huge number of items, just to keep track // of the session objects to ensure that they're cleaned up in // a timely manner, to avoid holding on to an unacceptible // amount of server-side resources in the event that consumers // let their data readers be GC'd, instead of explicitly // closing or disposing of them private const int MaxInactiveCount = 10; // pick something, preferably small... private static int _objectTypeCount; // Bid counter private readonly int _objectID = System.Threading.Interlocked.Increment(ref _objectTypeCount); private readonly TdsParser _parser; // parser that owns us private readonly List_cache; // collection of all known sessions private int _cachedCount; // lock-free _cache.Count private TdsParserStateObjectListStack _freeStack; // collection of all sessions available for reuse internal TdsParserSessionPool(TdsParser parser) { _parser = parser; _cache = new List (); _freeStack = new TdsParserStateObjectListStack(); if (Bid.AdvancedOn) { Bid.Trace(" %d# created session pool for parser %d\n", ObjectID, parser.ObjectID); } } private bool IsDisposed { get { return (null == _freeStack); } } internal int ObjectID { get { return _objectID; } } internal TdsParserStateObject CreateSession() { // NOTE: In the event of a thread abort, we may lose track of // the session we create here, but since the SNI handle // contained in it is a SafeHandle, it will eventually // get reclaimed. I see no reason to go through // herculean effort to make this section of code a CER, // since the lock below will force an AppDomain unload. TdsParserStateObject session = _parser.CreateSession(); // lock (_cache) { if (Bid.AdvancedOn) { Bid.Trace(" %d# adding session %d to pool\n", ObjectID, session.ObjectID); } _cache.Add(session); _cachedCount = _cache.Count; } return session; } internal void Deactivate() { // When being deactivated, we check all the sessions in the // cache to make sure they're cleaned up and then we dispose of // sessions that are past what we want to keep around. IntPtr hscp; Bid.ScopeEnter(out hscp, " %d# deactivating cachedCount=%d\n", ObjectID, _cachedCount); try { lock(_cache) { // NOTE: The PutSession call below may choose to remove the // session from the cache, which will throw off our // enumerator. We avoid that by simply indexing backward // through the array. for (int i = _cache.Count - 1; i >= 0 ; i--) { TdsParserStateObject session = _cache[i]; if (null != session) { if (session.IsOrphaned) { // if (Bid.AdvancedOn) { Bid.Trace(" %d# reclaiming session %d\n", ObjectID, session.ObjectID); } PutSession(session); } } } // } } finally { Bid.ScopeLeave(ref hscp); } } internal void Dispose() { if (Bid.AdvancedOn) { Bid.Trace(" %d# disposing cachedCount=%d\n", ObjectID, _cachedCount); } _freeStack = null; // shutting down, dude lock(_cache) { for (int i = 0; i < _cache.Count; i++) { TdsParserStateObject session = _cache[i]; if (null != session) { session.Dispose(); } } _cache.Clear(); } } internal TdsParserStateObject GetSession(object owner) { TdsParserStateObject session = _freeStack.SynchronizedPop(); if (null == session) { session = CreateSession(); } session.Activate(owner); if (Bid.AdvancedOn) { Bid.Trace(" %d# using session %d\n", ObjectID, session.ObjectID); } return session; } internal void PutSession(TdsParserStateObject session) { Debug.Assert (null != session, "null session?"); //Debug.Assert(null != session.Owner, "session without owner?"); bool okToReuse = session.Deactivate(); if (!IsDisposed) { if (okToReuse && _cachedCount < MaxInactiveCount) { if (Bid.AdvancedOn) { Bid.Trace(" %d# keeping session %d cachedCount=%d\n", ObjectID, session.ObjectID, _cachedCount); } Debug.Assert(!session._pendingData, "pending data on a pooled session?"); _freeStack.SynchronizedPush(session); } else { if (Bid.AdvancedOn) { Bid.Trace(" %d# disposing session %d cachedCount=%d\n", ObjectID, session.ObjectID, _cachedCount); } lock (_cache) { bool removed = _cache.Remove(session); Debug.Assert(removed, "session not in pool?"); _cachedCount = _cache.Count; } session.Dispose(); } } } internal string TraceString() { return String.Format(/*IFormatProvider*/ null, "(ObjID={0}, free={1}, cached={2}, total={3})", _objectID, null == _freeStack ? "(null)" : _freeStack.CountDebugOnly.ToString((IFormatProvider) null), _cachedCount, _cache.Count); } private class TdsParserStateObjectListStack { private TdsParserStateObject _stack; #if DEBUG private int _version; private int _count; #endif internal int CountDebugOnly { get { #if DEBUG return _count; #else return -1; #endif } } internal TdsParserStateObjectListStack() { } internal TdsParserStateObject SynchronizedPop() { TdsParserStateObject value; lock(this) { value = _stack; if (null != value) { _stack = value.NextPooledObject; value.NextPooledObject = null; #if DEBUG _version++; _count--; #endif } #if DEBUG Debug.Assert((null != value || 0 == _count) && (0 <= _count), "broken SynchronizedPop"); #endif } return value; } internal void SynchronizedPush(TdsParserStateObject value) { Debug.Assert(null != value, "pushing null value"); lock(this) { #if DEBUG Debug.Assert(null == value.NextPooledObject, "pushing value with non-null NextPooledObject"); int index = 0; for(TdsParserStateObject x = _stack; null != x; x = x.NextPooledObject, ++index) { Debug.Assert(x != value, "double push: object already in stack"); } Debug.Assert(_count == index, "SynchronizedPush count is corrupt"); #endif value.NextPooledObject = _stack; _stack = value; #if DEBUG _version++; _count++; #endif } } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. 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