/// <summary>
/// Runs an asynchronous task synchronously, using just the current thread to execute continuations.
/// </summary>
internal static void Run(Func <Task> func)
{
if (func == null)
{
throw new ArgumentNullException(nameof(func));
}
var prevCtx = SynchronizationContext.Current;
try
{
var syncCtx = SingleThreadedSynchronizationContext.New();
SynchronizationContext.SetSynchronizationContext(syncCtx);
var t = func();
if (t == null)
{
throw new InvalidOperationException();
}
var frame = SingleThreadedSynchronizationContext.NewFrame();
t.ContinueWith(_ => { frame.Continue = false; }, TaskScheduler.Default);
SingleThreadedSynchronizationContext.PushFrame(syncCtx, frame);
t.GetAwaiter().GetResult();
}
finally
{
SynchronizationContext.SetSynchronizationContext(prevCtx);
}
}
/// <summary>
/// Runs a given scenario many times to observe memory characteristics and assert that they can satisfy given conditions.
/// </summary>
/// <param name="scenario">The delegate to invoke.</param>
/// <param name="maxBytesAllocated">The maximum number of bytes allowed to be allocated by one run of the scenario. Use -1 to indicate no limit.</param>
/// <param name="iterations">The number of times to invoke <paramref name="scenario"/> in a row before measuring average memory impact.</param>
/// <param name="allowedAttempts">The number of times the (scenario * iterations) loop repeats with a failing result before ultimately giving up.</param>
protected void CheckGCPressure(Action scenario, int maxBytesAllocated, int iterations = 100, int allowedAttempts = GCAllocationAttempts)
{
// prime the pump
for (int i = 0; i < iterations; i++)
{
scenario();
}
// This test is rather rough. So we're willing to try it a few times in order to observe the desired value.
bool passingAttemptObserved = false;
for (int attempt = 1; attempt <= allowedAttempts; attempt++)
{
this.Logger?.WriteLine("Iteration {0}", attempt);
long initialMemory = GC.GetTotalMemory(true);
for (int i = 0; i < iterations; i++)
{
scenario();
}
long allocated = (GC.GetTotalMemory(false) - initialMemory) / iterations;
// If there is a dispatcher sync context, let it run for a bit.
// This allows any posted messages that are now obsolete to be released.
if (SingleThreadedSynchronizationContext.IsSingleThreadedSyncContext(SynchronizationContext.Current))
{
var frame = SingleThreadedSynchronizationContext.NewFrame();
SynchronizationContext.Current.Post(state => frame.Continue = false, null);
SingleThreadedSynchronizationContext.PushFrame(SynchronizationContext.Current, frame);
}
long leaked = (GC.GetTotalMemory(true) - initialMemory) / iterations;
this.Logger?.WriteLine("{0} bytes leaked per iteration.", leaked);
this.Logger?.WriteLine("{0} bytes allocated per iteration ({1} allowed).", allocated, maxBytesAllocated);
if (leaked <= 0 && (maxBytesAllocated == -1 || allocated <= maxBytesAllocated))
{
passingAttemptObserved = true;
}
if (!passingAttemptObserved)
{
// give the system a bit of cool down time to increase the odds we'll pass next time.
GC.Collect();
Thread.Sleep(250);
}
}
Assert.True(passingAttemptObserved);
}
protected JoinableTaskTestBase(ITestOutputHelper logger)
: base(logger)
{
this.dispatcherContext = SingleThreadedSynchronizationContext.New();
SynchronizationContext.SetSynchronizationContext(this.dispatcherContext);
this.context = this.CreateJoinableTaskContext();
this.joinableCollection = this.context.CreateCollection();
this.asyncPump = this.context.CreateFactory(this.joinableCollection);
this.originalThread = Thread.CurrentThread;
this.testFrame = SingleThreadedSynchronizationContext.NewFrame();
// Suppress the assert dialog that appears and causes test runs to hang.
Trace.Listeners.OfType <DefaultTraceListener>().Single().AssertUiEnabled = false;
}
protected void ExecuteOnDispatcher(Func <Task> action)
{
Action worker = delegate
{
var frame = SingleThreadedSynchronizationContext.NewFrame();
Exception failure = null;
SynchronizationContext.Current.Post(
async _ =>
{
try
{
await action();
}
catch (Exception ex)
{
failure = ex;
}
finally
{
frame.Continue = false;
}
},
null);
SingleThreadedSynchronizationContext.PushFrame(SynchronizationContext.Current, frame);
if (failure != null)
{
ExceptionDispatchInfo.Capture(failure).Throw();
}
};
if (Thread.CurrentThread.GetApartmentState() == ApartmentState.STA &&
SingleThreadedSynchronizationContext.IsSingleThreadedSyncContext(SynchronizationContext.Current))
{
worker();
}
else
{
this.ExecuteOnSTA(() =>
{
if (!SingleThreadedSynchronizationContext.IsSingleThreadedSyncContext(SynchronizationContext.Current))
{
SynchronizationContext.SetSynchronizationContext(SingleThreadedSynchronizationContext.New());
}
worker();
});
}
}
public void ValueFactoryRequiresMainThreadHeldByOtherSync(bool passJtfToLazyCtor)
{
var ctxt = SingleThreadedSynchronizationContext.New();
SynchronizationContext.SetSynchronizationContext(ctxt);
var context = new JoinableTaskContext();
var asyncPump = context.Factory;
var originalThread = Thread.CurrentThread;
var evt = new AsyncManualResetEvent();
var lazy = new AsyncLazy <object>(
async delegate
{
// It is important that no await appear before this JTF.Run call, since
// we're testing that the value factory is not invoked while the AsyncLazy
// holds a private lock that would deadlock when called from another thread.
asyncPump.Run(async delegate
{
await asyncPump.SwitchToMainThreadAsync(this.TimeoutToken);
});
await Task.Yield();
return(new object());
},
passJtfToLazyCtor ? asyncPump : null); // mix it up to exercise all the code paths in the ctor.
var backgroundRequest = Task.Run(async delegate
{
return(await lazy.GetValueAsync());
});
Thread.Sleep(AsyncDelay); // Give the background thread time to call GetValueAsync(), but it doesn't yield (when the test was written).
var foregroundRequest = lazy.GetValueAsync();
var frame = SingleThreadedSynchronizationContext.NewFrame();
var combinedTask = Task.WhenAll(foregroundRequest, backgroundRequest);
combinedTask.WithTimeout(UnexpectedTimeout).ContinueWith(_ => frame.Continue = false, TaskScheduler.Default);
SingleThreadedSynchronizationContext.PushFrame(ctxt, frame);
// Ensure that the test didn't simply timeout, and that the individual tasks did not throw.
Assert.True(foregroundRequest.IsCompleted);
Assert.True(backgroundRequest.IsCompleted);
Assert.Same(foregroundRequest.GetAwaiter().GetResult(), backgroundRequest.GetAwaiter().GetResult());
}
/// <summary>
/// Runs a given scenario many times to observe memory characteristics and assert that they can satisfy given conditions.
/// </summary>
/// <param name="scenario">The delegate to invoke.</param>
/// <param name="maxBytesAllocated">The maximum number of bytes allowed to be allocated by one run of the scenario. Use -1 to indicate no limit.</param>
/// <param name="iterations">The number of times to invoke <paramref name="scenario"/> in a row before measuring average memory impact.</param>
/// <param name="allowedAttempts">The number of times the (scenario * iterations) loop repeats with a failing result before ultimately giving up.</param>
/// <param name="completeSynchronously"><c>true</c> to synchronously complete instead of yielding.</param>
/// <returns>A task that captures the result of the operation.</returns>
protected async Task CheckGCPressureAsync(Func <Task> scenario, int maxBytesAllocated, int iterations = 100, int allowedAttempts = GCAllocationAttempts, bool completeSynchronously = false)
{
const int quietPeriodMaxAttempts = 3;
const int shortDelayDuration = 250;
const int quietThreshold = 1200;
// prime the pump
for (int i = 0; i < 2; i++)
{
await MaybeShouldBeComplete(scenario(), completeSynchronously);
}
long waitForQuietMemory1, waitForQuietMemory2, waitPeriodAllocations, waitForQuietAttemptCount = 0;
do
{
waitForQuietMemory1 = GC.GetTotalMemory(true);
await MaybeShouldBlock(Task.Delay(shortDelayDuration), completeSynchronously);
waitForQuietMemory2 = GC.GetTotalMemory(true);
waitPeriodAllocations = Math.Abs(waitForQuietMemory2 - waitForQuietMemory1);
this.Logger.WriteLine("Bytes allocated during quiet wait period: {0}", waitPeriodAllocations);
}while (waitPeriodAllocations > quietThreshold || ++waitForQuietAttemptCount >= quietPeriodMaxAttempts);
if (waitPeriodAllocations > quietThreshold)
{
this.Logger.WriteLine("WARNING: Unable to establish a quiet period.");
}
// This test is rather rough. So we're willing to try it a few times in order to observe the desired value.
bool attemptWithNoLeakObserved = false;
bool attemptWithinMemoryLimitsObserved = false;
for (int attempt = 1; attempt <= allowedAttempts; attempt++)
{
this.Logger?.WriteLine("Iteration {0}", attempt);
long initialMemory = GC.GetTotalMemory(true);
for (int i = 0; i < iterations; i++)
{
await MaybeShouldBeComplete(scenario(), completeSynchronously);
}
long allocated = (GC.GetTotalMemory(false) - initialMemory) / iterations;
attemptWithinMemoryLimitsObserved |= maxBytesAllocated == -1 || allocated <= maxBytesAllocated;
long leaked = long.MaxValue;
for (int leakCheck = 0; leakCheck < 3; leakCheck++)
{
// Allow the message queue to drain.
if (completeSynchronously)
{
// If there is a dispatcher sync context, let it run for a bit.
// This allows any posted messages that are now obsolete to be released.
if (SingleThreadedSynchronizationContext.IsSingleThreadedSyncContext(SynchronizationContext.Current))
{
var frame = SingleThreadedSynchronizationContext.NewFrame();
SynchronizationContext.Current.Post(state => frame.Continue = false, null);
SingleThreadedSynchronizationContext.PushFrame(SynchronizationContext.Current, frame);
}
}
else
{
await Task.Yield();
}
leaked = (GC.GetTotalMemory(true) - initialMemory) / iterations;
attemptWithNoLeakObserved |= leaked <= 3 * IntPtr.Size; // any real leak would be an object, which is at least this size.
if (attemptWithNoLeakObserved)
{
break;
}
await MaybeShouldBlock(Task.Delay(shortDelayDuration), completeSynchronously);
}
this.Logger?.WriteLine("{0} bytes leaked per iteration.", leaked);
this.Logger?.WriteLine("{0} bytes allocated per iteration ({1} allowed).", allocated, maxBytesAllocated);
if (attemptWithNoLeakObserved && attemptWithinMemoryLimitsObserved)
{
// Don't keep looping. We got what we needed.
break;
}
// give the system a bit of cool down time to increase the odds we'll pass next time.
GC.Collect();
await MaybeShouldBlock(Task.Delay(shortDelayDuration), completeSynchronously);
}
Assert.True(attemptWithNoLeakObserved, "Leaks observed in every iteration.");
Assert.True(attemptWithinMemoryLimitsObserved, "Excess memory allocations in every iteration.");
}
protected void ExecuteOnDispatcher(Func <Task> action, bool staRequired = true)
{
Action worker = delegate
{
var frame = SingleThreadedSynchronizationContext.NewFrame();
Exception failure = null;
SynchronizationContext.Current.Post(
async _ =>
{
try
{
await action();
}
catch (Exception ex)
{
failure = ex;
}
finally
{
frame.Continue = false;
}
},
null);
SingleThreadedSynchronizationContext.PushFrame(SynchronizationContext.Current, frame);
if (failure != null)
{
ExceptionDispatchInfo.Capture(failure).Throw();
}
};
#if DESKTOP || NETCOREAPP2_0
if ((!staRequired || Thread.CurrentThread.GetApartmentState() == ApartmentState.STA) &&
SingleThreadedSynchronizationContext.IsSingleThreadedSyncContext(SynchronizationContext.Current))
{
worker();
}
else
{
this.ExecuteOnSTA(() =>
{
if (!SingleThreadedSynchronizationContext.IsSingleThreadedSyncContext(SynchronizationContext.Current))
{
SynchronizationContext.SetSynchronizationContext(SingleThreadedSynchronizationContext.New());
}
worker();
});
}
#else
if (SingleThreadedSynchronizationContext.IsSingleThreadedSyncContext(SynchronizationContext.Current))
{
worker();
}
else
{
Task.Run(delegate
{
SynchronizationContext.SetSynchronizationContext(SingleThreadedSynchronizationContext.New());
worker();
}).GetAwaiter().GetResult();
}
#endif
}
