void IDispatchHost.IncreaseThreadCount(string reason)
{
// check if thread pool is already awaiting another thread
if (_threadVelocity > 0)
{
return;
}
lock (_syncRoot) {
_threadVelocity = 1;
// check if thread pool has enough threads
if (_threadCount >= _maxParallelThreads)
{
_threadVelocity = 0;
return;
}
#if EXTRA_DEBUG
_log.DebugFormat("IncreaseThreadCount: {1} - {0}", this, reason);
#endif
}
// check if there are threads in the reserve
KeyValuePair <DispatchThread, Result <DispatchWorkItem> > reservedThread;
if (_reservedThreads.TryPop(out reservedThread))
{
AddThread(reservedThread);
}
else
{
DispatchThreadScheduler.RequestThread(0, AddThread);
}
}
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);
}
}
/// <summary>
/// Shutdown the ElasticThreadPool instance. This method blocks until all pending items have finished processing.
/// </summary>
public void Dispose()
{
if (!_disposed)
{
_disposed = true;
_log.DebugFormat("Dispose @{0}", this);
// TODO (steveb): make dispose more reliable
// 1) we can't wait indefinitively!
// 2) we should progressively sleep longer and longer to avoid unnecessary overhead
// 3) this pattern feels useful enough to be captured into a helper method
// wait until all threads have been decommissioned
while (ThreadCount > 0)
{
AsyncUtil.Sleep(100.Milliseconds());
}
// discard all reserved threads
KeyValuePair <DispatchThread, Result <DispatchWorkItem> > reserved;
while (_reservedThreads.TryPop(out reserved))
{
DispatchThreadScheduler.ReleaseThread(reserved.Key, reserved.Value);
}
DispatchThreadScheduler.UnregisterHost(this);
}
}
//--- Constructors ---
/// <summary>
/// Creates a new ElasticThreadPool instance.
/// </summary>
/// <param name="minReservedThreads">Minium number of threads to reserve for the thread pool.</param>
/// <param name="maxParallelThreads">Maximum number of parallel threads used by the thread pool.</param>
/// <exception cref="InsufficientResourcesException">The ElasticThreadPool instance was unable to obtain the minimum reserved threads.</exception>
public ElasticThreadPool(int minReservedThreads, int maxParallelThreads)
{
_minReservedThreads = Math.Max(0, Math.Min(minReservedThreads, MAX_RESERVED_THREADS));
_maxParallelThreads = Math.Max(Math.Max(1, minReservedThreads), Math.Min(maxParallelThreads, int.MaxValue));
// initialize reserved threads
_activeThreads = new DispatchThread[Math.Min(_maxParallelThreads, Math.Max(_minReservedThreads, Math.Min(16, _maxParallelThreads)))];
if (_minReservedThreads > 0)
{
DispatchThreadScheduler.RequestThread(_minReservedThreads, AddThread);
}
DispatchThreadScheduler.RegisterHost(this);
_log.DebugFormat("Create @{0}", this);
}
// (yurig): This method has been intentionally split from DispatchLoop()
// result.Block() inside causes Result<DispatchWorkItem> to never be disposed.
// By moving it into its own method we ensure its garbage collection as it is
// popped off the stack. Do NOT inline this method into DispatchLoop().
private bool GetNextWorkItem(out Action callback)
{
if (!_inbox.TryPop(out callback))
{
var result = new Result <DispatchWorkItem>(TimeSpan.MaxValue);
// reset the dispatch queue for this thread
AsyncUtil.CurrentDispatchQueue = null;
_queue = 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(false);
}
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;
}
return(true);
}
//--- Constructors ---
/// <summary>
/// Creates a new ElasticPriorityThreadPool instance.
/// </summary>
/// <param name="minReservedThreads">Minium number of threads to reserve for the thread pool.</param>
/// <param name="maxParallelThreads">Maximum number of parallel threads used by the thread pool.</param>
/// <param name="maxPriority">Maximum priority number (inclusive upper bound).</param>
/// <exception cref="InsufficientResourcesException">The ElasticPriorityThreadPool instance was unable to obtain the minimum reserved threads.</exception>
public ElasticPriorityThreadPool(int minReservedThreads, int maxParallelThreads, int maxPriority)
{
_minReservedThreads = Math.Max(0, Math.Min(minReservedThreads, MAX_RESERVED_THREADS));
_maxParallelThreads = Math.Max(Math.Max(1, minReservedThreads), Math.Min(maxParallelThreads, int.MaxValue));
_inbox = new LockFreePriorityQueue <Action>(maxPriority);
_prioritizedInbox = new PrioritizedThreadPool[maxPriority];
for (int i = 0; i < maxPriority; ++i)
{
_prioritizedInbox[i] = new PrioritizedThreadPool(i, this);
}
// initialize reserved threads
_activeThreads = new DispatchThread[Math.Min(_maxParallelThreads, Math.Max(_minReservedThreads, Math.Min(16, _maxParallelThreads)))];
if (_minReservedThreads > 0)
{
DispatchThreadScheduler.RequestThread(_minReservedThreads, AddThread);
}
DispatchThreadScheduler.RegisterHost(this);
_log.DebugFormat("Create @{0}", this);
}
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;
}
}
