public async Task IncreaseConcurrency()
{
int count = 0;
var waitForFirstTwoItems = TaskSourceSlim.Create <object>();
// Event that will hold first two workers.
var mre = new ManualResetEventSlim(false);
var actionBlock = new ActionBlockSlim <int>(
2,
n =>
{
var currentCount = Interlocked.Increment(ref count);
if (currentCount == 2)
{
// Notify the test that 2 items are processed.
waitForFirstTwoItems.SetResult(null);
}
if (currentCount <= 2)
{
// This is the first or the second thread that should be blocked before we increase the number of threads.
mre.Wait(TimeSpan.FromSeconds(100));
}
Thread.Sleep(1);
});
// Schedule work
actionBlock.Post(1);
actionBlock.Post(2);
await waitForFirstTwoItems.Task;
// The first 2 threads should be blocked in the callback in the action block,
// but the count should be incremented
Assert.Equal(2, count);
var task = actionBlock.CompletionAsync();
// The task should not be completed yet!
Assert.NotEqual(TaskStatus.RanToCompletion, task.Status);
// This will cause another thread to spawn
actionBlock.IncreaseConcurrencyTo(3);
// Add more work
actionBlock.Post(3);
actionBlock.Complete();
// Release the first 2 threads
mre.Set();
// Waiting for completion
await task;
// The new thread should run and increment the count
Assert.Equal(3, count);
}
/// <summary>
/// Changes the concurrency level.
/// </summary>
public void IncreaseConcurrencyTo(int maxDegreeOfParallelism)
{
Contract.Requires(maxDegreeOfParallelism >= -1);
maxDegreeOfParallelism = maxDegreeOfParallelism == -1 ? Environment.ProcessorCount : maxDegreeOfParallelism;
if (maxDegreeOfParallelism > m_serializationQueue.DegreeOfParallelism)
{
m_serializationQueue.IncreaseConcurrencyTo(maxDegreeOfParallelism);
}
}