private void AddThread(KeyValuePair <DispatchThread, Result <DispatchWorkItem> > keyvalue)
{
DispatchThread thread = keyvalue.Key;
Result <DispatchWorkItem> result = keyvalue.Value;
if (_threadVelocity >= 0)
{
lock (_syncRoot) {
_threadVelocity = 0;
// check if an item is available for dispatch
Action callback;
if (TryRequestItem(null, out callback))
{
RegisterThread("new thread", thread);
// dispatch work-item
result.Return(new DispatchWorkItem(callback, this));
return;
}
}
}
// we have no need for this thread
RemoveThread("insufficient work for new thread", thread, result);
}
private void RemoveThread(string reason, DispatchThread thread, Result <DispatchWorkItem> result)
{
if (thread == null)
{
throw new ArgumentNullException("thread");
}
if (result == null)
{
throw new ArgumentNullException("result");
}
if (thread.PendingWorkItemCount != 0)
{
throw new ArgumentException(string.Format("thread #{1} still has work-items in queue (items: {0})", thread.PendingWorkItemCount, thread.Id), "thread");
}
// remove thread from list of allocated threads
lock (_syncRoot) {
_threadVelocity = 0;
UnregisterThread(reason, thread);
}
// check if we can put thread into the reserved list
if (_reservedThreads.Count < MinReservedThreads)
{
if (!_reservedThreads.TryPush(new KeyValuePair <DispatchThread, Result <DispatchWorkItem> >(thread, result)))
{
throw new NotSupportedException("TryPush failed");
}
}
else
{
// return thread to resource manager
DispatchThreadScheduler.ReleaseThread(thread, result);
}
}
private bool TryRequestItem(DispatchThread thread, out Action callback)
{
// check if we can find a work-item in the shared queue
if (_inbox.TryDequeue(out callback))
{
return(true);
}
// try to steal a work-item from another thread; take a snapshot of all allocated threads (needed in case the array is copied for resizing)
DispatchThread[] threads = _activeThreads;
foreach (DispatchThread entry in threads)
{
// check if we can steal a work-item from this thread
if ((entry != null) && !ReferenceEquals(entry, thread) && entry.TryStealWorkItem(out callback))
{
return(true);
}
}
// check again if we can find a work-item in the shared queue since trying to steal may have overlapped with the arrival of a new item
if (_inbox.TryDequeue(out callback))
{
return(true);
}
return(false);
}
private void DispatchLoop()
{
// set thread-local self-reference
CurrentThread = this;
// begin thread loop
try {
Action callback;
while (GetNextWorkItem(out callback))
{
// execute work-item
if (callback != null)
{
try {
callback();
} catch (Exception e) {
_log.Warn("an unhandled exception occurred while executing the work-item", e);
}
}
}
} catch (Exception e) {
// something went wrong that shouldn't have!
_log.ErrorExceptionMethodCall(e, string.Format("DispatchLoop #{0}: FATAL ERROR", _id));
// TODO (steveb): tell _host about untimely exit; post items in queue to host inbox (o/w we lose them)
} finally {
CurrentThread = null;
}
}
//--- Class Methods ---
public static bool TryQueueWorkItem(IDispatchQueue queue, Action callback)
{
DispatchThread current = CurrentThread;
if ((current != null) && ReferenceEquals(AsyncUtil.CurrentDispatchQueue, queue))
{
// NOTE (steveb): next call can never fail since we're calling the queue work-item method of the current thread
current.QueueWorkItem(callback);
return(true);
}
return(false);
}
public void EvictWorkItems()
{
// clear CurrentThread to avoid having the evicted items being immediately added back again to the thread (i.e. infinite loop)
CurrentThread = null;
try {
Action item;
// remove up to 100 items from the current threads work queue
for (int i = 0; (i < 100) && _inbox.TryPop(out item); ++i)
{
_queue.QueueWorkItem(item);
}
} finally {
// restore CurrentThread before we exit
CurrentThread = this;
}
}
private void UnregisterThread(string reason, DispatchThread thread)
{
thread.Host = null;
// find thread and remove it
for (int i = 0; i < _activeThreads.Length; ++i)
{
if (ReferenceEquals(_activeThreads[i], thread))
{
--_threadCount;
_activeThreads[i] = null;
#if EXTRA_DEBUG
_log.DebugFormat("RemoveThread: {1} - {0}", this, reason);
#endif
break;
}
}
}
private bool TryQueueWorkItem(int priority, Action callback)
{
if (_disposed)
{
throw new ObjectDisposedException("ElasticThreadPool has already been disposed");
}
// check if we can enqueue work-item into current dispatch thread
IDispatchQueue queue = this[priority];
if (DispatchThread.TryQueueWorkItem(queue, callback))
{
return(true);
}
// check if there are available threads to which the work-item can be given to
KeyValuePair <DispatchThread, Result <DispatchWorkItem> > entry;
if (_reservedThreads.TryPop(out entry))
{
lock (_syncRoot) {
RegisterThread("new item", entry.Key);
}
// found an available thread, let's resume it with the work-item
entry.Value.Return(new DispatchWorkItem(callback, queue));
return(true);
}
// no threads available, keep work-item for later
if (!_inbox.TryEnqueue(priority, callback))
{
return(false);
}
// check if we need to request a thread to kick things off
if (ThreadCount == 0)
{
((IDispatchHost)this).IncreaseThreadCount("request first thread");
}
return(true);
}
public static void ReleaseThread(DispatchThread thread, Result <DispatchWorkItem> result)
{
if (thread == null)
{
throw new ArgumentNullException("thread");
}
if (result == null)
{
throw new ArgumentNullException("result");
}
// unbind thread from current host
thread.Host = null;
// add thread to list of idle threads
if (!_threadReserve.TryEnqueue(new KeyValuePair <DispatchThread, Result <DispatchWorkItem> >(thread, result)))
{
throw new NotSupportedException("TryEnqueue failed");
}
}
void IDispatchHost.RequestWorkItem(DispatchThread thread, Result <DispatchWorkItem> result)
{
if (thread == null)
{
throw new ArgumentNullException("thread");
}
if (thread.PendingWorkItemCount > 0)
{
throw new ArgumentException(string.Format("thread #{1} still has work-items in queue (items: {0})", thread.PendingWorkItemCount, thread.Id), "thread");
}
if (!ReferenceEquals(thread.Host, this))
{
throw new InvalidOperationException(string.Format("thread is allocated to another queue: received {0}, expected: {1}", thread.Host, this));
}
if (result == null)
{
throw new ArgumentNullException("result");
}
// check if we need to decommission threads without causing starvation
if (_threadVelocity < 0)
{
RemoveThread("system saturation", thread, result);
return;
}
// check if we found a work-item
int priority;
Action callback;
if (TryRequestItem(thread, out priority, out callback))
{
// dispatch work-item
result.Return(new DispatchWorkItem(callback, this[priority]));
}
else
{
// relinquich thread; it's not required anymore
RemoveThread("insufficient work", thread, result);
}
}
private void RegisterThread(string reason, DispatchThread thread)
{
++_threadCount;
thread.Host = this;
// find an empty slot in the array of all threads
int index;
for (index = 0; index < _activeThreads.Length; ++index)
{
// check if we found an empty slot
if (_activeThreads[index] == null)
{
// assign it to the found slot and stop iterating
_activeThreads[index] = thread;
break;
}
}
// check if we need to grow the array
if (index == _activeThreads.Length)
{
// make room to add a new thread by doubling the array size and copying over the existing entries
DispatchThread[] newArray = new DispatchThread[2 * _activeThreads.Length];
Array.Copy(_activeThreads, newArray, _activeThreads.Length);
// assign new thread
newArray[index] = thread;
// update instance field
_activeThreads = newArray;
}
#if EXTRA_DEBUG
_log.DebugFormat("AddThread: {1} - {0}", this, reason);
#endif
}
private void DispatchLoop()
{
// set thread-local self-reference
CurrentThread = this;
// begin thread loop
try {
while (true)
{
// check if queue has a work-item
Action callback;
if (!_inbox.TryPop(out callback))
{
var result = new Result <DispatchWorkItem>(TimeSpan.MaxValue);
// reset the dispatch queue for this thread
AsyncUtil.CurrentDispatchQueue = null;
// check if thread is associated with a host already
if (_host == null)
{
// NOTE (steveb): this is a brand new thread without a host yet
// return the thread to the dispatch scheduler
DispatchThreadScheduler.ReleaseThread(this, result);
}
else
{
// request another work-item
_host.RequestWorkItem(this, result);
}
// block until a work item is available
result.Block();
// check if we received a work item or an exception to shutdown
if (result.HasException && (result.Exception is DispatchThreadShutdownException))
{
// time to shut down
_log.DebugFormat("DispatchThread #{0} destroyed", _id);
return;
}
callback = result.Value.WorkItem;
_queue = result.Value.DispatchQueue;
// TODO (steveb): handle the weird case where _queue is null
// set the dispatch queue for this thread
AsyncUtil.CurrentDispatchQueue = _queue;
}
// execute work-item
if (callback != null)
{
try {
callback();
} catch (Exception e) {
_log.Warn("an unhandled exception occurred while executing the work-item", e);
}
}
}
} catch (Exception e) {
// something went wrong that shouldn't have!
_log.ErrorExceptionMethodCall(e, string.Format("DispatchLoop #{0}: FATAL ERROR", _id));
// TODO (steveb): tell _host about untimely exit; post items in queue to host inbox (o/w we lose them)
} finally {
CurrentThread = null;
}
}
void IDispatchHost.RequestWorkItem(DispatchThread thread, Result<DispatchWorkItem> result)
{
if(thread == null) {
throw new ArgumentNullException("thread");
}
if(thread.PendingWorkItemCount > 0) {
throw new ArgumentException(string.Format("thread #{1} still has work-items in queue (items: {0})", thread.PendingWorkItemCount, thread.Id), "thread");
}
if(!ReferenceEquals(thread.Host, this)) {
throw new InvalidOperationException(string.Format("thread is allocated to another queue: received {0}, expected: {1}", thread.Host, this));
}
if(result == null) {
throw new ArgumentNullException("result");
}
Action callback;
// check if we need to decommission threads without causing starvation
if(_threadVelocity < 0) {
RemoveThread("system saturation", thread, result);
return;
}
// check if we found a work-item
if(TryRequestItem(thread, out callback)) {
// dispatch work-item
result.Return(new DispatchWorkItem(callback, this));
} else {
// relinquich thread; it's not required anymore
RemoveThread("insufficient work", thread, result);
}
}
private void DispatchLoop()
{
// set thread-local self-reference
CurrentThread = this;
// begin thread loop
try {
Action callback;
while(GetNextWorkItem(out callback)) {
// execute work-item
if(callback != null) {
try {
callback();
} catch(Exception e) {
_log.Warn("an unhandled exception occurred while executing the work-item", e);
}
}
}
} catch(Exception e) {
// something went wrong that shouldn't have!
_log.ErrorExceptionMethodCall(e, string.Format("DispatchLoop #{0}: FATAL ERROR", _id));
// TODO (steveb): tell _host about untimely exit; post items in queue to host inbox (o/w we lose them)
} finally {
CurrentThread = null;
}
}
public static void ReleaseThread(DispatchThread thread, Result<DispatchWorkItem> result)
{
if(thread == null) {
throw new ArgumentNullException("thread");
}
if(result == null) {
throw new ArgumentNullException("result");
}
// unbind thread from current host
thread.Host = null;
// add thread to list of idle threads
if(!_threadReserve.TryEnqueue(new KeyValuePair<DispatchThread, Result<DispatchWorkItem>>(thread, result))) {
throw new NotSupportedException("TryEnqueue failed");
}
}
private void RegisterThread(string reason, DispatchThread thread)
{
++_threadCount;
thread.Host = this;
// find an empty slot in the array of all threads
int index;
for(index = 0; index < _activeThreads.Length; ++index) {
// check if we found an empty slot
if(_activeThreads[index] == null) {
// assign it to the found slot and stop iterating
_activeThreads[index] = thread;
break;
}
}
// check if we need to grow the array
if(index == _activeThreads.Length) {
// make room to add a new thread by doubling the array size and copying over the existing entries
DispatchThread[] newArray = new DispatchThread[2 * _activeThreads.Length];
Array.Copy(_activeThreads, newArray, _activeThreads.Length);
// assign new thread
newArray[index] = thread;
// update instance field
_activeThreads = newArray;
}
#if EXTRA_DEBUG
_log.DebugFormat("AddThread: {1} - {0}", this, reason);
#endif
}
private void DispatchLoop()
{
// set thread-local self-reference
CurrentThread = this;
// begin thread loop
try {
while(true) {
// check if queue has a work-item
Action callback;
if(!_inbox.TryPop(out callback)) {
var result = new Result<DispatchWorkItem>(TimeSpan.MaxValue);
// reset the dispatch queue for this thread
Async.CurrentDispatchQueue = null;
// check if thread is associated with a host already
if(_host == null) {
// NOTE (steveb): this is a brand new thread without a host yet
// return the thread to the dispatch scheduler
DispatchThreadScheduler.ReleaseThread(this, result);
} else {
// request another work-item
_host.RequestWorkItem(this, result);
}
// block until a work item is available
result.Block();
// check if we received a work item or an exception to shutdown
if(result.HasException && (result.Exception is DispatchThreadShutdownException)) {
// time to shut down
_log.DebugFormat("DispatchThread #{0} destroyed", _id);
return;
}
callback = result.Value.WorkItem;
_queue = result.Value.DispatchQueue;
// TODO (steveb): handle the weird case where _queue is null
// set the dispatch queue for this thread
Async.CurrentDispatchQueue = _queue;
}
// execute work-item
if(callback != null) {
try {
callback();
} catch(Exception e) {
_log.Warn("an unhandled exception occurred while executing the work-item", e);
}
}
}
} catch(Exception e) {
// something went wrong that shouldn't have!
_log.ErrorExceptionMethodCall(e, string.Format("DispatchLoop #{0}: FATAL ERROR", _id));
// TODO (steveb): tell _host about untimely exit; post items in queue to host inbox (o/w we lose them)
} finally {
CurrentThread = null;
}
}
public void EvictWorkItems()
{
// clear CurrentThread to avoid having the evicted items being immediately added back again to the thread (i.e. infinite loop)
CurrentThread = null;
try {
Action item;
// remove up to 100 items from the current threads work queue
for(int i = 0; (i < 100) && _inbox.TryPop(out item); ++i) {
_queue.QueueWorkItem(item);
}
} finally {
// restore CurrentThread before we exit
CurrentThread = this;
}
}
private void RemoveThread(string reason, DispatchThread thread, Result<DispatchWorkItem> result)
{
if(thread == null) {
throw new ArgumentNullException("thread");
}
if(result == null) {
throw new ArgumentNullException("result");
}
if(thread.PendingWorkItemCount != 0) {
throw new ArgumentException(string.Format("thread #{1} still has work-items in queue (items: {0})", thread.PendingWorkItemCount, thread.Id), "thread");
}
// remove thread from list of allocated threads
lock(_syncRoot) {
_threadVelocity = 0;
UnregisterThread(reason, thread);
}
// check if we can put thread into the reserved list
if(_reservedThreads.Count < MinReservedThreads) {
if(!_reservedThreads.TryPush(new KeyValuePair<DispatchThread, Result<DispatchWorkItem>>(thread, result))) {
throw new NotSupportedException("TryPush failed");
}
} else {
// return thread to resource manager
DispatchThreadScheduler.ReleaseThread(thread, result);
}
}
private bool TryRequestItem(DispatchThread thread, out Action callback)
{
// check if we can find a work-item in the shared queue
if(_inbox.TryDequeue(out callback)) {
return true;
}
// try to steal a work-item from another thread; take a snapshot of all allocated threads (needed in case the array is copied for resizing)
DispatchThread[] threads = _activeThreads;
foreach(DispatchThread entry in threads) {
// check if we can steal a work-item from this thread
if((entry != null) && !ReferenceEquals(entry, thread) && entry.TryStealWorkItem(out callback)) {
return true;
}
}
// check again if we can find a work-item in the shared queue since trying to steal may have overlapped with the arrival of a new item
if(_inbox.TryDequeue(out callback)) {
return true;
}
return false;
}
private void UnregisterThread(string reason, DispatchThread thread)
{
thread.Host = null;
// find thread and remove it
for(int i = 0; i < _activeThreads.Length; ++i) {
if(ReferenceEquals(_activeThreads[i], thread)) {
--_threadCount;
_activeThreads[i] = null;
#if EXTRA_DEBUG
_log.DebugFormat("RemoveThread: {1} - {0}", this, reason);
#endif
break;
}
}
}
