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#region Copyright notice and license
// Copyright 2015 gRPC authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#endregion
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Grpc.Core.Logging;
using Grpc.Core.Profiling;
using Grpc.Core.Utils;
namespace Grpc.Core.Internal
{
/// <summary>
/// Pool of threads polling on a set of completions queues.
/// </summary>
internal class GrpcThreadPool
{
static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<GrpcThreadPool>();
const int FinishContinuationsSleepMillis = 10;
const int MaxFinishContinuationsSleepTotalMillis = 10000;
readonly GrpcEnvironment environment;
readonly object myLock = new object();
readonly List<Thread> threads = new List<Thread>();
readonly int poolSize;
readonly int completionQueueCount;
readonly bool inlineHandlers;
readonly WaitCallback runCompletionQueueEventCallbackSuccess;
readonly WaitCallback runCompletionQueueEventCallbackFailure;
readonly AtomicCounter queuedContinuationCounter = new AtomicCounter();
readonly List<BasicProfiler> threadProfilers = new List<BasicProfiler>(); // profilers assigned to threadpool threads
bool stopRequested;
IReadOnlyCollection<CompletionQueueSafeHandle> completionQueues;
/// <summary>
/// Creates a thread pool threads polling on a set of completions queues.
/// </summary>
/// <param name="environment">Environment.</param>
/// <param name="poolSize">Pool size.</param>
/// <param name="completionQueueCount">Completion queue count.</param>
/// <param name="inlineHandlers">Handler inlining.</param>
public GrpcThreadPool(GrpcEnvironment environment, int poolSize, int completionQueueCount, bool inlineHandlers)
{
this.environment = environment;
this.poolSize = poolSize;
this.completionQueueCount = completionQueueCount;
this.inlineHandlers = inlineHandlers;
GrpcPreconditions.CheckArgument(poolSize >= completionQueueCount,
"Thread pool size cannot be smaller than the number of completion queues used.");
this.runCompletionQueueEventCallbackSuccess = new WaitCallback((callback) => RunCompletionQueueEventCallback((IOpCompletionCallback) callback, true));
this.runCompletionQueueEventCallbackFailure = new WaitCallback((callback) => RunCompletionQueueEventCallback((IOpCompletionCallback) callback, false));
}
public void Start()
{
lock (myLock)
{
GrpcPreconditions.CheckState(completionQueues == null, "Already started.");
completionQueues = CreateCompletionQueueList(environment, completionQueueCount);
for (int i = 0; i < poolSize; i++)
{
var optionalProfiler = i < threadProfilers.Count ? threadProfilers[i] : null;
threads.Add(CreateAndStartThread(i, optionalProfiler));
}
}
}
public Task StopAsync()
{
lock (myLock)
{
GrpcPreconditions.CheckState(!stopRequested, "Stop already requested.");
stopRequested = true;
foreach (var cq in completionQueues)
{
cq.Shutdown();
}
}
return Task.Run(() =>
{
foreach (var thread in threads)
{
thread.Join();
}
foreach (var cq in completionQueues)
{
cq.Dispose();
}
for (int i = 0; i < threadProfilers.Count; i++)
{
threadProfilers[i].Dump(string.Format("grpc_trace_thread_{0}.txt", i));
}
});
}
/// <summary>
/// Returns true if there is at least one thread pool thread that hasn't
/// already stopped.
/// Threads can either stop because all completion queues shut down or
/// because all foreground threads have already shutdown and process is
/// going to exit.
/// </summary>
internal bool IsAlive
{
get
{
return threads.Any(t => t.ThreadState != ThreadState.Stopped);
}
}
internal IReadOnlyCollection<CompletionQueueSafeHandle> CompletionQueues
{
get
{
return completionQueues;
}
}
private Thread CreateAndStartThread(int threadIndex, IProfiler optionalProfiler)
{
var cqIndex = threadIndex % completionQueues.Count;
var cq = completionQueues.ElementAt(cqIndex);
var thread = new Thread(new ThreadStart(() => RunHandlerLoop(cq, optionalProfiler)));
thread.IsBackground = true;
thread.Name = string.Format("grpc {0} (cq {1})", threadIndex, cqIndex);
thread.Start();
return thread;
}
/// <summary>
/// Body of the polling thread.
/// </summary>
private void RunHandlerLoop(CompletionQueueSafeHandle cq, IProfiler optionalProfiler)
{
if (optionalProfiler != null)
{
Profilers.SetForCurrentThread(optionalProfiler);
}
CompletionQueueEvent ev;
do
{
ev = cq.Next();
if (ev.type == CompletionQueueEvent.CompletionType.OpComplete)
{
bool success = (ev.success != 0);
IntPtr tag = ev.tag;
try
{
var callback = cq.CompletionRegistry.Extract(tag);
queuedContinuationCounter.Increment();
if (!inlineHandlers)
{
// Use cached delegates to avoid unnecessary allocations
ThreadPool.QueueUserWorkItem(success ? runCompletionQueueEventCallbackSuccess : runCompletionQueueEventCallbackFailure, callback);
}
else
{
RunCompletionQueueEventCallback(callback, success);
}
}
catch (Exception e)
{
Logger.Error(e, "Exception occured while extracting event from completion registry.");
}
}
}
while (ev.type != CompletionQueueEvent.CompletionType.Shutdown);
// Continuations are running on default threadpool that consists of background threads.
// GrpcThreadPool thread (a foreground thread) will not exit unless all queued work had
// been finished to prevent terminating the continuations queued prematurely.
int sleepIterations = 0;
while (queuedContinuationCounter.Count != 0)
{
// Only happens on shutdown and having pending continuations shouldn't very common,
// so sleeping here for a little bit is fine.
if (sleepIterations >= MaxFinishContinuationsSleepTotalMillis / FinishContinuationsSleepMillis)
{
Logger.Warning("Shutting down gRPC thread [{0}] with unfinished callbacks (Timed out waiting for callbacks to finish).",
Thread.CurrentThread.Name);
break;
}
Thread.Sleep(FinishContinuationsSleepMillis);
sleepIterations ++;
}
}
private static IReadOnlyCollection<CompletionQueueSafeHandle> CreateCompletionQueueList(GrpcEnvironment environment, int completionQueueCount)
{
var list = new List<CompletionQueueSafeHandle>();
for (int i = 0; i < completionQueueCount; i++)
{
var completionRegistry = new CompletionRegistry(environment, () => environment.BatchContextPool.Lease());
list.Add(CompletionQueueSafeHandle.CreateAsync(completionRegistry));
}
return list.AsReadOnly();
}
private void RunCompletionQueueEventCallback(IOpCompletionCallback callback, bool success)
{
try
{
callback.OnComplete(success);
}
catch (Exception e)
{
Logger.Error(e, "Exception occured while invoking completion delegate");
}
finally
{
queuedContinuationCounter.Decrement();
}
}
}
}
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