/// <summary>
/// Gets the full path to the next file to be received or null if no files
/// </summary>
/// <param name="cancellationToken"></param>
/// <returns></returns>
public string Dequeue(CancellationToken cancellationToken)
{
string fullPath = null;
if (!this._TryDequeue(out fullPath))
{
// allow only one thread at a time to fill the cache (it is done without locking)
if (Interlocked.CompareExchange(ref _accessCounter, 1, 0) > 0)
{
return(null);
}
try
{
// try again, maybe another thread already added items to the queue
if (!this._TryDequeue(out fullPath))
{
TimeSpan lastNoMessage = TimeSpan.FromTicks(DateTime.Now.Ticks - this._lastNoMessage);
if (lastNoMessage.TotalMilliseconds > BACKOFF_NOMSG_MSEC)
{
var dirName = _queueRegister.EnsureQueueInitialized(this._inputQueue);
List <string> tempStore = new List <string>();
// Don't check for defered too often
TimeSpan lastNoDefered = TimeSpan.FromTicks(DateTime.Now.Ticks - this._lastNoDefered);
if (lastNoDefered.TotalMilliseconds > BACKOFF_DEFERED_MSEC)
{
int deferedCnt = this._TryFillCacheDefered(tempStore, dirName, cancellationToken);
if (deferedCnt == 0)
{
this._lastNoDefered = DateTime.Now.Ticks;
}
}
int fileCnt = this._TryFillCache(tempStore, dirName, cancellationToken);
if (fileCnt == 0)
{
this._lastNoMessage = DateTime.Now.Ticks;
}
foreach (string name in tempStore.OrderBy(name => TransportHelper.GetFileUtcDate(name)))
{
this._filesQueue.Enqueue(name);
}
this._TryDequeue(out fullPath);
}
}
}
finally
{
Interlocked.CompareExchange(ref _accessCounter, 0, 1);
}
}
return(fullPath);
}
private int _TryFillCacheDefered(List <string> tempStore, string dirName, CancellationToken cancellationToken)
{
DirectoryInfo info = new DirectoryInfo(dirName);
var nowUtc = DateTime.Now.ToUniversalTime();
var files = info.EnumerateFiles("d*.json").Where(p => TransportHelper.GetFileUtcDate(p.Name) <= nowUtc).OrderBy(p => p.Name).Take(DEFER_CACHE_SIZE).ToList();
int cnt = 0;
foreach (var file in files)
{
lock (this._filesCacheLock)
{
if (!this._filesCache.Contains(file.Name))
{
tempStore.Add(file.Name);
this._filesCache.Add(file.Name);
++cnt;
}
}
cancellationToken.ThrowIfCancellationRequested();
}
return(cnt);
}
