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//------------------------------------------------------------------------------
// <copyright file="SqlDependencyUtils.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
// <owner current="true" primary="true">Microsoft</owner>
// <owner current="false" primary="false">Microsoft</owner>
//------------------------------------------------------------------------------
namespace System.Data.SqlClient {
using System;
using System.Collections;
using System.Collections.Generic;
using System.Data.Common;
using System.Diagnostics;
using System.Security.Principal;
using System.Security.AccessControl;
using System.Text;
using System.Threading;
// This is a singleton instance per AppDomain that acts as the notification dispatcher for
// that AppDomain. It receives calls from the SqlDependencyProcessDispatcher with an ID or a server name
// to invalidate matching dependencies in the given AppDomain.
internal class SqlDependencyPerAppDomainDispatcher : MarshalByRefObject { // MBR, since ref'ed by ProcessDispatcher.
// ----------------
// Instance members
// ----------------
internal static readonly SqlDependencyPerAppDomainDispatcher
SingletonInstance = new SqlDependencyPerAppDomainDispatcher(); // singleton object
// Dependency ID -> Dependency hashtable. 1 -> 1 mapping.
// 1) Used for ASP.Net to map from ID to dependency.
// 2) Used to enumerate dependencies to invalidate based on server.
private Dictionary<string, SqlDependency> _dependencyIdToDependencyHash;
// holds dependencies list per notification and the command hash from which this notification was generated
// command hash is needed to remove its entry from _commandHashToNotificationId when the notification is removed
sealed class DependencyList : List<SqlDependency> {
public readonly string CommandHash;
internal DependencyList(string commandHash) {
this.CommandHash = commandHash;
}
}
// notificationId -> Dependencies hashtable: 1 -> N mapping. notificationId == appDomainKey + commandHash.
// More than one dependency can be using the same command hash values resulting in a hash to the same value.
// We use this to cache mapping between command to dependencies such that we may reduce the notification
// resource effect on SQL Server. The Guid identifier is sent to the server during notification enlistment,
// and returned during the notification event. Dependencies look up existing Guids, if one exists, to ensure
// they are re-using notification ids.
private Dictionary<string, DependencyList> _notificationIdToDependenciesHash;
// CommandHash value -> notificationId associated with it: 1->1 mapping. This map is used to quickly find if we need to create
// new notification or hookup into existing one.
// CommandHash is built from connection string, command text and parameters
private Dictionary<string, string> _commandHashToNotificationId;
// TIMEOUT LOGIC DESCRIPTION
//
// Every time we add a dependency we compute the next, earlier timeout.
//
// We setup a timer to get a callback every 15 seconds. In the call back:
// - If there are no active dependencies, we just return.
// - If there are dependencies but none of them timed-out (compared to the "next timeout"),
// we just return.
// - Otherwise we Invalidate() those that timed-out.
//
// So the client-generated timeouts have a granularity of 15 seconds. This allows
// for a simple and low-resource-consumption implementation.
//
// LOCKS: don't update _nextTimeout outside of the _dependencyHash.SyncRoot lock.
private bool _SqlDependencyTimeOutTimerStarted = false;
// Next timeout for any of the dependencies in the dependency table.
private DateTime _nextTimeout;
// Timer to periodically check the dependencies in the table and see if anyone needs
// a timeout. We'll enable this only on demand.
private Timer _timeoutTimer;
// -----------
// BID members
// -----------
private readonly int _objectID = System.Threading.Interlocked.Increment(ref _objectTypeCount);
private static int _objectTypeCount; // Bid counter
internal int ObjectID {
get {
return _objectID;
}
}
private SqlDependencyPerAppDomainDispatcher() {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher|DEP> %d#", ObjectID);
try {
_dependencyIdToDependencyHash = new Dictionary<string, SqlDependency>();
_notificationIdToDependenciesHash = new Dictionary<string, DependencyList>();
_commandHashToNotificationId = new Dictionary<string, string>();
_timeoutTimer = new Timer(new TimerCallback(TimeoutTimerCallback), null, Timeout.Infinite, Timeout.Infinite);
// If rude abort - we'll leak. This is acceptable for now.
AppDomain.CurrentDomain.DomainUnload += new EventHandler(this.UnloadEventHandler);
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// SQL Hotfix 236
// When remoted across appdomains, MarshalByRefObject links by default time out if there is no activity
// within a few minutes. Add this override to prevent marshaled links from timing out.
public override object InitializeLifetimeService() {
return null;
}
// ------
// Events
// ------
private void UnloadEventHandler(object sender, EventArgs e) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.UnloadEventHandler|DEP> %d#", ObjectID);
try {
// Make non-blocking call to ProcessDispatcher to ThreadPool.QueueUserWorkItem to complete
// stopping of all start calls in this AppDomain. For containers shared among various AppDomains,
// this will just be a ref-count subtract. For non-shared containers, we will close the container
// and clean-up.
SqlDependencyProcessDispatcher dispatcher = SqlDependency.ProcessDispatcher;
if (null != dispatcher) {
dispatcher.QueueAppDomainUnloading(SqlDependency.AppDomainKey);
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// ----------------------------------------------------
// Methods for dependency hash manipulation and firing.
// ----------------------------------------------------
// This method is called upon SqlDependency constructor.
internal void AddDependencyEntry(SqlDependency dep) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.AddDependencyEntry|DEP> %d#, SqlDependency: %d#", ObjectID, dep.ObjectID);
try {
lock (this) {
_dependencyIdToDependencyHash.Add(dep.Id, dep);
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// This method is called upon Execute of a command associated with a SqlDependency object.
internal string AddCommandEntry(string commandHash, SqlDependency dep) {
IntPtr hscp;
string notificationId = string.Empty;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.AddCommandEntry|DEP> %d#, commandHash: '%ls', SqlDependency: %d#", ObjectID, commandHash, dep.ObjectID);
try {
lock (this) {
if (!_dependencyIdToDependencyHash.ContainsKey(dep.Id)) { // Determine if depId->dep hashtable contains dependency. If not, it's been invalidated.
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.AddCommandEntry|DEP> Dependency not present in depId->dep hash, must have been invalidated.\n");
}
else {
// check if we already have notification associated with given command hash
if (_commandHashToNotificationId.TryGetValue(commandHash, out notificationId)) {
// we have one or more SqlDependency instances with same command hash
DependencyList dependencyList = null;
if (!_notificationIdToDependenciesHash.TryGetValue(notificationId, out dependencyList))
{
// this should not happen since _commandHashToNotificationId and _notificationIdToDependenciesHash are always
// updated together
Debug.Assert(false, "_commandHashToNotificationId has entries that were removed from _notificationIdToDependenciesHash. Remember to keep them in sync");
throw ADP.InternalError(ADP.InternalErrorCode.SqlDependencyCommandHashIsNotAssociatedWithNotification);
}
// join the new dependency to the list
if (!dependencyList.Contains(dep)) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.AddCommandEntry|DEP> Dependency not present for commandHash, adding.\n");
dependencyList.Add(dep);
}
else {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.AddCommandEntry|DEP> Dependency already present for commandHash.\n");
}
}
else {
// we did not find notification ID with the same app domain and command hash, create a new one
// use unique guid to avoid duplicate IDs
// prepend app domain ID to the key - SqlConnectionContainer::ProcessNotificationResults (SqlDependencyListener.cs)
// uses this app domain ID to route the message back to the app domain in which this SqlDependency was created
notificationId = string.Format(System.Globalization.CultureInfo.InvariantCulture,
"{0};{1}",
SqlDependency.AppDomainKey, // must be first
Guid.NewGuid().ToString("D", System.Globalization.CultureInfo.InvariantCulture)
);
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.AddCommandEntry|DEP> Creating new Dependencies list for commandHash.\n");
DependencyList dependencyList = new DependencyList(commandHash);
dependencyList.Add(dep);
// map command hash to notification we just created to reuse it for the next client
// do it inside finally block to avoid ThreadAbort exception interrupt this operation
try {}
finally {
_commandHashToNotificationId.Add(commandHash, notificationId);
_notificationIdToDependenciesHash.Add(notificationId, dependencyList);
}
}
Debug.Assert(_notificationIdToDependenciesHash.Count == _commandHashToNotificationId.Count, "always keep these maps in sync!");
}
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
return notificationId;
}
// This method is called by the ProcessDispatcher upon a notification for this AppDomain.
internal void InvalidateCommandID(SqlNotification sqlNotification) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.InvalidateCommandID|DEP> %d#, commandHash: '%ls'", ObjectID, sqlNotification.Key);
try {
List<SqlDependency> dependencyList = null;
lock (this) {
dependencyList = LookupCommandEntryWithRemove(sqlNotification.Key);
if (null != dependencyList) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.InvalidateCommandID|DEP> commandHash found in hashtable.\n");
foreach (SqlDependency dependency in dependencyList) {
// Ensure we remove from process static app domain hash for dependency initiated invalidates.
LookupDependencyEntryWithRemove(dependency.Id);
// Completely remove Dependency from commandToDependenciesHash.
RemoveDependencyFromCommandToDependenciesHash(dependency);
}
}
else {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.InvalidateCommandID|DEP> commandHash NOT found in hashtable.\n");
}
}
if (null != dependencyList) {
// After removal from hashtables, invalidate.
foreach (SqlDependency dependency in dependencyList) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.InvalidateCommandID|DEP> Dependency found in commandHash dependency ArrayList - calling invalidate.\n");
try {
dependency.Invalidate(sqlNotification.Type, sqlNotification.Info, sqlNotification.Source);
}
catch (Exception e) {
// Since we are looping over dependencies, do not allow one Invalidate
// that results in a throw prevent us from invalidating all dependencies
// related to this server.
if (!ADP.IsCatchableExceptionType(e)) {
throw;
}
ADP.TraceExceptionWithoutRethrow(e);
}
}
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// This method is called when a connection goes down or other unknown error occurs in the ProcessDispatcher.
internal void InvalidateServer(string server, SqlNotification sqlNotification) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.Invalidate|DEP> %d#, server: '%ls'", ObjectID, server);
try {
List<SqlDependency> dependencies = new List<SqlDependency>();
lock (this) { // Copy inside of lock, but invalidate outside of lock.
foreach (KeyValuePair<string, SqlDependency> entry in _dependencyIdToDependencyHash) {
SqlDependency dependency = entry.Value;
if (dependency.ContainsServer(server)) {
dependencies.Add(dependency);
}
}
foreach (SqlDependency dependency in dependencies) { // Iterate over resulting list removing from our hashes.
// Ensure we remove from process static app domain hash for dependency initiated invalidates.
LookupDependencyEntryWithRemove(dependency.Id);
// Completely remove Dependency from commandToDependenciesHash.
RemoveDependencyFromCommandToDependenciesHash(dependency);
}
}
foreach (SqlDependency dependency in dependencies) { // Iterate and invalidate.
try {
dependency.Invalidate(sqlNotification.Type, sqlNotification.Info, sqlNotification.Source);
}
catch (Exception e) {
// Since we are looping over dependencies, do not allow one Invalidate
// that results in a throw prevent us from invalidating all dependencies
// related to this server.
if (!ADP.IsCatchableExceptionType(e)) {
throw;
}
ADP.TraceExceptionWithoutRethrow(e);
}
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// This method is called by SqlCommand to enable ASP.Net scenarios - map from ID to Dependency.
internal SqlDependency LookupDependencyEntry(string id) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.LookupDependencyEntry|DEP> %d#, Key: '%ls'", ObjectID, id);
try {
if (null == id) {
throw ADP.ArgumentNull("id");
}
if (ADP.IsEmpty(id)) {
throw SQL.SqlDependencyIdMismatch();
}
SqlDependency entry = null;
lock (this) {
if (_dependencyIdToDependencyHash.ContainsKey(id)) {
entry = _dependencyIdToDependencyHash[id];
}
else {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.LookupDependencyEntry|DEP|ERR> ERROR - dependency ID mismatch - not throwing.\n");
}
}
return entry;
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// Remove the dependency from the hashtable with the passed id.
private void LookupDependencyEntryWithRemove(string id) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.LookupDependencyEntryWithRemove|DEP> %d#, id: '%ls'", ObjectID, id);
try {
lock (this) {
if (_dependencyIdToDependencyHash.ContainsKey(id)) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.LookupDependencyEntryWithRemove|DEP> Entry found in hashtable - removing.\n");
_dependencyIdToDependencyHash.Remove(id);
// if there are no more dependencies then we can dispose the timer.
if (0 == _dependencyIdToDependencyHash.Count) {
_timeoutTimer.Change(Timeout.Infinite, Timeout.Infinite);
_SqlDependencyTimeOutTimerStarted = false;
}
}
else {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.LookupDependencyEntryWithRemove|DEP> Entry NOT found in hashtable.\n");
}
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// Find and return arraylist, and remove passed hash value.
private List<SqlDependency> LookupCommandEntryWithRemove(string notificationId) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.LookupCommandEntryWithRemove|DEP> %d#, commandHash: '%ls'", ObjectID, notificationId);
try {
DependencyList entry = null;
lock (this) {
if (_notificationIdToDependenciesHash.TryGetValue(notificationId, out entry)) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.LookupDependencyEntriesWithRemove|DEP> Entries found in hashtable - removing.\n");
// update the tables - do it inside finally block to avoid ThreadAbort exception interrupt this operation
try { }
finally {
_notificationIdToDependenciesHash.Remove(notificationId);
// VSTS 216991: cleanup the map between the command hash and associated notification ID
_commandHashToNotificationId.Remove(entry.CommandHash);
}
}
else {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.LookupDependencyEntriesWithRemove|DEP> Entries NOT found in hashtable.\n");
}
Debug.Assert(_notificationIdToDependenciesHash.Count == _commandHashToNotificationId.Count, "always keep these maps in sync!");
}
return entry; // DependencyList inherits from List<SqlDependency>
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// Remove from commandToDependenciesHash all references to the passed dependency.
private void RemoveDependencyFromCommandToDependenciesHash(SqlDependency dependency) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.RemoveDependencyFromCommandToDependenciesHash|DEP> %d#, SqlDependency: %d#", ObjectID, dependency.ObjectID);
try {
lock (this) {
List<string> notificationIdsToRemove = new List<string>();
List<string> commandHashesToRemove = new List<string>();
foreach (KeyValuePair<string, DependencyList> entry in _notificationIdToDependenciesHash) {
DependencyList dependencies = entry.Value;
if (dependencies.Remove(dependency)) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.RemoveDependencyFromCommandToDependenciesHash|DEP> Removed SqlDependency: %d#, with ID: '%ls'.\n", dependency.ObjectID, dependency.Id);
if (dependencies.Count == 0) {
// this dependency was the last associated with this notification ID, remove the entry
// note: cannot do it inside foreach over dictionary
notificationIdsToRemove.Add(entry.Key);
commandHashesToRemove.Add(entry.Value.CommandHash);
}
}
// same SqlDependency can be associated with more than one command, so we have to continue till the end...
}
Debug.Assert(commandHashesToRemove.Count == notificationIdsToRemove.Count, "maps should be kept in sync");
for (int i = 0; i < notificationIdsToRemove.Count; i++ ) {
// cleanup the entry outside of foreach
// do it inside finally block to avoid ThreadAbort exception interrupt this operation
try { }
finally {
_notificationIdToDependenciesHash.Remove(notificationIdsToRemove[i]);
// VSTS 216991: cleanup the map between the command hash and associated notification ID
_commandHashToNotificationId.Remove(commandHashesToRemove[i]);
}
}
Debug.Assert(_notificationIdToDependenciesHash.Count == _commandHashToNotificationId.Count, "always keep these maps in sync!");
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
// -----------------------------------------
// Methods for Timer maintenance and firing.
// -----------------------------------------
internal void StartTimer(SqlDependency dep) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.StartTimer|DEP> %d#, SqlDependency: %d#", ObjectID, dep.ObjectID);
try {
// If this dependency expires sooner than the current next timeout, change
// the timeout and enable timer callback as needed. Note that we change _nextTimeout
// only inside the hashtable syncroot.
lock (this) {
// Enable the timer if needed (disable when empty, enable on the first addition).
if (!_SqlDependencyTimeOutTimerStarted) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.StartTimer|DEP> Timer not yet started, starting.\n");
_timeoutTimer.Change(15000 /* 15 secs */, 15000 /* 15 secs */);
// Save this as the earlier timeout to come.
_nextTimeout = dep.ExpirationTime;
_SqlDependencyTimeOutTimerStarted = true;
}
else if(_nextTimeout > dep.ExpirationTime) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.StartTimer|DEP> Timer already started, resetting time.\n");
// Save this as the earlier timeout to come.
_nextTimeout = dep.ExpirationTime;
}
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
private static void TimeoutTimerCallback(object state) {
IntPtr hscp;
Bid.NotificationsScopeEnter(out hscp, "<sc.SqlDependencyPerAppDomainDispatcher.TimeoutTimerCallback|DEP> AppDomainKey: '%ls'", SqlDependency.AppDomainKey);
try {
SqlDependency[] dependencies;
// Only take the lock for checking whether there is work to do
// if we do have work, we'll copy the hashtable and scan it after releasing
// the lock.
lock (SingletonInstance) {
if (0 == SingletonInstance._dependencyIdToDependencyHash.Count) {
// Nothing to check.
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.TimeoutTimerCallback|DEP> No dependencies, exiting.\n");
return;
}
if (SingletonInstance._nextTimeout > DateTime.UtcNow) {
Bid.NotificationsTrace("<sc.SqlDependencyPerAppDomainDispatcher.TimeoutTimerCallback|DEP> No timeouts expired, exiting.\n");
// No dependency timed-out yet.
return;
}
// If at least one dependency timed-out do a scan of the table.
// NOTE: we could keep a shadow table sorted by expiration time, but
// given the number of typical simultaneously alive dependencies it's
// probably not worth the optimization.
dependencies = new SqlDependency[SingletonInstance._dependencyIdToDependencyHash.Count];
SingletonInstance._dependencyIdToDependencyHash.Values.CopyTo(dependencies, 0);
}
// Scan the active dependencies if needed.
DateTime now = DateTime.UtcNow;
DateTime newNextTimeout = DateTime.MaxValue;
for (int i=0; i < dependencies.Length; i++) {
// If expired fire the change notification.
if(dependencies[i].ExpirationTime <= now) {
try {
// This invokes user-code which may throw exceptions.
// NOTE: this is intentionally outside of the lock, we don't want
// to invoke user-code while holding an internal lock.
dependencies[i].Invalidate(SqlNotificationType.Change, SqlNotificationInfo.Error, SqlNotificationSource.Timeout);
}
catch(Exception e) {
if (!ADP.IsCatchableExceptionType(e)) {
throw;
}
// This is an exception in user code, and we're in a thread-pool thread
// without user's code up in the stack, no much we can do other than
// eating the exception.
ADP.TraceExceptionWithoutRethrow(e);
}
}
else {
if (dependencies[i].ExpirationTime < newNextTimeout) {
newNextTimeout = dependencies[i].ExpirationTime; // Track the next earlier timeout.
}
dependencies[i] = null; // Null means "don't remove it from the hashtable" in the loop below.
}
}
// Remove timed-out dependencies from the hashtable.
lock (SingletonInstance) {
for (int i=0; i < dependencies.Length; i++) {
if (null != dependencies[i]) {
SingletonInstance._dependencyIdToDependencyHash.Remove(dependencies[i].Id);
}
}
if (newNextTimeout < SingletonInstance._nextTimeout) {
SingletonInstance._nextTimeout = newNextTimeout; // We're inside the lock so ok to update.
}
}
}
finally {
Bid.ScopeLeave(ref hscp);
}
}
}
// Simple class used to encapsulate all data in a notification.
internal class SqlNotification : MarshalByRefObject {
// This class could be Serializable rather than MBR...
private readonly SqlNotificationInfo _info;
private readonly SqlNotificationSource _source;
private readonly SqlNotificationType _type;
private readonly string _key;
internal SqlNotification(SqlNotificationInfo info, SqlNotificationSource source, SqlNotificationType type, string key) {
_info = info;
_source = source;
_type = type;
_key = key;
}
internal SqlNotificationInfo Info {
get {
return _info;
}
}
internal string Key {
get {
return _key;
}
}
internal SqlNotificationSource Source {
get {
return _source;
}
}
internal SqlNotificationType Type {
get {
return _type;
}
}
}
}
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