private static async Task Start(CancellationToken abortSignal)
{
receiveTasks = Enumerable.Range(0, 3).Select(index => DequeueTask(abortSignal)).ToArray();
var apiTasks = new OptimizedTaskQueue <bool>(log);
while (!abortSignal.IsCancellationRequested)
{
// don't inflate the list if it is already large
try
{
await WaitForAndHandleEvent(abortSignal, apiTasks);
}
catch (Exception e)
{
log.Error(e, "Error waiting for next event");
}
}
}
private static async Task WaitForAndHandleEvent(CancellationToken abortSignal, OptimizedTaskQueue <bool> apiTasks)
{
var watchDogCancelToken = new CancellationTokenSource();
var watchdogCombinedWithAbort = CancellationTokenSource.CreateLinkedTokenSource(abortSignal, watchDogCancelToken.Token);
using (watchdogCombinedWithAbort)
using (watchDogCancelToken)
{
var waitAndListenForCancelTask = Task.Delay(20000, watchdogCombinedWithAbort.Token);
var allTasks = new List <Task>();
var firstApiTask = apiTasks.Peek;
log.Debug($"awaitable is {firstApiTask?.Id}");
if (firstApiTask != null)
{
allTasks.Add(firstApiTask);
}
var receiveStart = allTasks.Count;
allTasks.AddRange(receiveTasks);
var receiveEnd = allTasks.Count;
allTasks.Add(waitAndListenForCancelTask);
log.Debug($"Waiting for tasks {string.Join(",", allTasks.Select(t => t.Id))}");
// TODO make some fault tolerance on exceptions. Best 2-level, first attempt to recover in the code and second with container recycle
var task = await Task.WhenAny(allTasks);
log.Debug($"when any returned task #{task.Id}");
var index = allTasks.IndexOf(task);
if (index < 0)
{
throw new Exception("bad index");
}
if (index < receiveEnd && index >= receiveStart)
{
// receiver fired
receiveTasks[receiveStart - index] = DequeueTask(abortSignal);
watchDogCancelToken.Cancel();
apiTasks.Enqueue(AddSomeApiCallTasks(abortSignal));
}
else if (index == 0)
{
// api fired
watchDogCancelToken.Cancel();
apiTasks.Dequeue(firstApiTask);
}
else
{
// watchdog timer fired - nothing happened last 20 seconds.
return;
}
}
}