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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Data.Common;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using System.Transactions;
namespace System.Data.ProviderBase
{
internal abstract partial class DbConnectionInternal
{
internal static readonly StateChangeEventArgs StateChangeClosed = new StateChangeEventArgs(ConnectionState.Open, ConnectionState.Closed);
internal static readonly StateChangeEventArgs StateChangeOpen = new StateChangeEventArgs(ConnectionState.Closed, ConnectionState.Open);
private readonly bool _allowSetConnectionString;
private readonly bool _hidePassword;
private readonly ConnectionState _state;
private readonly WeakReference _owningObject = new WeakReference(null, false); // [usage must be thread safe] the owning object, when not in the pool. (both Pooled and Non-Pooled connections)
private DbConnectionPool? _connectionPool; // the pooler that the connection came from (Pooled connections only)
private DbReferenceCollection? _referenceCollection; // collection of objects that we need to notify in some way when we're being deactivated
private int _pooledCount; // [usage must be thread safe] the number of times this object has been pushed into the pool less the number of times it's been popped (0 != inPool)
private bool _connectionIsDoomed; // true when the connection should no longer be used.
private bool _cannotBePooled; // true when the connection should no longer be pooled.
private DateTime _createTime; // when the connection was created.
#if DEBUG
private int _activateCount; // debug only counter to verify activate/deactivates are in sync.
#endif //DEBUG
protected DbConnectionInternal() : this(ConnectionState.Open, true, false)
{
}
// Constructor for internal connections
internal DbConnectionInternal(ConnectionState state, bool hidePassword, bool allowSetConnectionString)
{
_allowSetConnectionString = allowSetConnectionString;
_hidePassword = hidePassword;
_state = state;
}
internal bool AllowSetConnectionString
{
get
{
return _allowSetConnectionString;
}
}
internal bool CanBePooled
{
get
{
bool flag = (!_connectionIsDoomed && !_cannotBePooled && !_owningObject.IsAlive);
return flag;
}
}
protected internal bool IsConnectionDoomed
{
get
{
return _connectionIsDoomed;
}
}
internal bool IsEmancipated
{
get
{
// NOTE: There are race conditions between PrePush, PostPop and this
// property getter -- only use this while this object is locked;
// (DbConnectionPool.Clear and ReclaimEmancipatedObjects
// do this for us)
// The functionality is as follows:
//
// _pooledCount is incremented when the connection is pushed into the pool
// _pooledCount is decremented when the connection is popped from the pool
// _pooledCount is set to -1 when the connection is not pooled (just in case...)
//
// That means that:
//
// _pooledCount > 1 connection is in the pool multiple times (This should not happen)
// _pooledCount == 1 connection is in the pool
// _pooledCount == 0 connection is out of the pool
// _pooledCount == -1 connection is not a pooled connection; we shouldn't be here for non-pooled connections.
// _pooledCount < -1 connection out of the pool multiple times
//
// Now, our job is to return TRUE when the connection is out
// of the pool and it's owning object is no longer around to
// return it.
bool value = (_pooledCount < 1) && !_owningObject.IsAlive;
return value;
}
}
internal bool IsInPool
{
get
{
Debug.Assert(_pooledCount <= 1 && _pooledCount >= -1, "Pooled count for object is invalid");
return (_pooledCount == 1);
}
}
protected internal object? Owner
{
// We use a weak reference to the owning object so we can identify when
// it has been garbage collected without throwing exceptions.
get
{
return _owningObject.Target;
}
}
internal DbConnectionPool? Pool
{
get
{
return _connectionPool;
}
}
protected internal DbReferenceCollection? ReferenceCollection
{
get
{
return _referenceCollection;
}
}
public abstract string ServerVersion
{
get;
}
// this should be abstract but until it is added to all the providers virtual will have to do
public virtual string ServerVersionNormalized
{
get
{
throw ADP.NotSupported();
}
}
public bool ShouldHidePassword
{
get
{
return _hidePassword;
}
}
public ConnectionState State
{
get
{
return _state;
}
}
internal void AddWeakReference(object value, int tag)
{
if (null == _referenceCollection)
{
_referenceCollection = CreateReferenceCollection();
if (null == _referenceCollection)
{
throw ADP.InternalError(ADP.InternalErrorCode.CreateReferenceCollectionReturnedNull);
}
}
_referenceCollection.Add(value, tag);
}
public abstract DbTransaction BeginTransaction(IsolationLevel il);
public virtual void ChangeDatabase(string value)
{
throw ADP.MethodNotImplemented();
}
internal virtual void PrepareForReplaceConnection()
{
// By default, there is no preparation required
}
protected virtual void PrepareForCloseConnection()
{
// By default, there is no preparation required
}
protected virtual object? ObtainAdditionalLocksForClose()
{
return null; // no additional locks in default implementation
}
protected virtual void ReleaseAdditionalLocksForClose(object? lockToken)
{
// no additional locks in default implementation
}
protected virtual DbReferenceCollection CreateReferenceCollection()
{
throw ADP.InternalError(ADP.InternalErrorCode.AttemptingToConstructReferenceCollectionOnStaticObject);
}
protected abstract void Deactivate();
internal void DeactivateConnection()
{
Debug.Assert(Pool != null);
// Internal method called from the connection pooler so we don't expose
// the Deactivate method publicly.
#if DEBUG
Interlocked.Decrement(ref _activateCount);
#endif // DEBUG
if (!_connectionIsDoomed && Pool.UseLoadBalancing)
{
// If we're not already doomed, check the connection's lifetime and
// doom it if it's lifetime has elapsed.
DateTime now = DateTime.UtcNow;
if ((now.Ticks - _createTime.Ticks) > Pool.LoadBalanceTimeout.Ticks)
{
DoNotPoolThisConnection();
}
}
Deactivate();
}
protected internal void DoNotPoolThisConnection()
{
_cannotBePooled = true;
}
/// <devdoc>Ensure that this connection cannot be put back into the pool.</devdoc>
protected internal void DoomThisConnection()
{
_connectionIsDoomed = true;
}
protected internal virtual DataTable GetSchema(DbConnectionFactory factory, DbConnectionPoolGroup poolGroup, DbConnection outerConnection, string collectionName, string?[]? restrictions)
{
Debug.Assert(outerConnection != null, "outerConnection may not be null.");
DbMetaDataFactory metaDataFactory = factory.GetMetaDataFactory(poolGroup, this);
Debug.Assert(metaDataFactory != null, "metaDataFactory may not be null.");
return metaDataFactory.GetSchema(outerConnection, collectionName, restrictions);
}
internal void MakeNonPooledObject(object owningObject)
{
// Used by DbConnectionFactory to indicate that this object IS NOT part of
// a connection pool.
_connectionPool = null;
_owningObject.Target = owningObject;
_pooledCount = -1;
}
internal void MakePooledConnection(DbConnectionPool connectionPool)
{
// Used by DbConnectionFactory to indicate that this object IS part of
// a connection pool.
_createTime = DateTime.UtcNow;
_connectionPool = connectionPool;
}
internal void NotifyWeakReference(int message)
{
ReferenceCollection?.Notify(message);
}
internal virtual void OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
{
if (!TryOpenConnection(outerConnection, connectionFactory, null, null))
{
throw ADP.InternalError(ADP.InternalErrorCode.SynchronousConnectReturnedPending);
}
}
/// <devdoc>The default implementation is for the open connection objects, and
/// it simply throws. Our private closed-state connection objects
/// override this and do the correct thing.</devdoc>
// User code should either override DbConnectionInternal.Activate when it comes out of the pool
// or override DbConnectionFactory.CreateConnection when the connection is created for non-pooled connections
internal virtual bool TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource<DbConnectionInternal>? retry, DbConnectionOptions? userOptions)
{
throw ADP.ConnectionAlreadyOpen(State);
}
internal virtual bool TryReplaceConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource<DbConnectionInternal>? retry, DbConnectionOptions? userOptions)
{
throw ADP.MethodNotImplemented();
}
protected bool TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource<DbConnectionInternal>? retry, DbConnectionOptions? userOptions)
{
// ?->Connecting: prevent set_ConnectionString during Open
if (connectionFactory.SetInnerConnectionFrom(outerConnection, DbConnectionClosedConnecting.SingletonInstance, this))
{
DbConnectionInternal? openConnection;
try
{
connectionFactory.PermissionDemand(outerConnection);
if (!connectionFactory.TryGetConnection(outerConnection, retry, userOptions, this, out openConnection))
{
return false;
}
}
catch
{
// This should occur for all exceptions, even ADP.UnCatchableExceptions.
connectionFactory.SetInnerConnectionTo(outerConnection, this);
throw;
}
if (null == openConnection)
{
connectionFactory.SetInnerConnectionTo(outerConnection, this);
throw ADP.InternalConnectionError(ADP.ConnectionError.GetConnectionReturnsNull);
}
connectionFactory.SetInnerConnectionEvent(outerConnection, openConnection);
}
return true;
}
internal void PrePush(object? expectedOwner)
{
// Called by DbConnectionPool when we're about to be put into it's pool, we
// take this opportunity to ensure ownership and pool counts are legit.
// IMPORTANT NOTE: You must have taken a lock on the object before
// you call this method to prevent race conditions with Clear and
// ReclaimEmancipatedObjects.
//3 // The following tests are retail assertions of things we can't allow to happen.
if (null == expectedOwner)
{
if (null != _owningObject.Target)
{
throw ADP.InternalError(ADP.InternalErrorCode.UnpooledObjectHasOwner); // new unpooled object has an owner
}
}
else if (_owningObject.Target != expectedOwner)
{
throw ADP.InternalError(ADP.InternalErrorCode.UnpooledObjectHasWrongOwner); // unpooled object has incorrect owner
}
if (0 != _pooledCount)
{
throw ADP.InternalError(ADP.InternalErrorCode.PushingObjectSecondTime); // pushing object onto stack a second time
}
_pooledCount++;
_owningObject.Target = null; // NOTE: doing this and checking for InternalError.PooledObjectHasOwner degrades the close by 2%
}
internal void PostPop(object newOwner)
{
// Called by DbConnectionPool right after it pulls this from it's pool, we
// take this opportunity to ensure ownership and pool counts are legit.
Debug.Assert(!IsEmancipated, "pooled object not in pool");
// When another thread is clearing this pool, it
// will doom all connections in this pool without prejudice which
// causes the following assert to fire, which really mucks up stress
// against checked bits. The assert is benign, so we're commenting
// it out.
//Debug.Assert(CanBePooled, "pooled object is not poolable");
// IMPORTANT NOTE: You must have taken a lock on the object before
// you call this method to prevent race conditions with Clear and
// ReclaimEmancipatedObjects.
if (null != _owningObject.Target)
{
throw ADP.InternalError(ADP.InternalErrorCode.PooledObjectHasOwner); // pooled connection already has an owner!
}
_owningObject.Target = newOwner;
_pooledCount--;
//3 // The following tests are retail assertions of things we can't allow to happen.
if (null != Pool)
{
if (0 != _pooledCount)
{
throw ADP.InternalError(ADP.InternalErrorCode.PooledObjectInPoolMoreThanOnce); // popping object off stack with multiple pooledCount
}
}
else if (-1 != _pooledCount)
{
throw ADP.InternalError(ADP.InternalErrorCode.NonPooledObjectUsedMoreThanOnce); // popping object off stack with multiple pooledCount
}
}
internal void RemoveWeakReference(object value)
{
ReferenceCollection?.Remove(value);
}
/// <summary>
/// When overridden in a derived class, will check if the underlying connection is still actually alive
/// </summary>
/// <param name="throwOnException">If true an exception will be thrown if the connection is dead instead of returning true\false
/// (this allows the caller to have the real reason that the connection is not alive (e.g. network error, etc))</param>
/// <returns>True if the connection is still alive, otherwise false (If not overridden, then always true)</returns>
internal virtual bool IsConnectionAlive(bool throwOnException = false)
{
return true;
}
}
}
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