private void Acquire(TimeSpan timeout)
{
var isLockAcquired = false;
try
{
var now = DateTime.Now;
var lockTimeoutTime = now.Add(timeout);
while (!isLockAcquired && (lockTimeoutTime >= now))
{
isLockAcquired = Acquire();
if (!isLockAcquired)
{
_signal.Wait($@"{nameof(MongoDistributedLock)}.{_resource}", timeout);
now = DateTime.Now;
}
}
}
catch (OperationCanceledException)
{
// The signal wait timed out
}
catch (Exception ex)
{
throw new MongoDistributedLockException($"Could not place a lock on the resource \'{_resource}\': Check inner exception for details.", ex);
}
if (!isLockAcquired)
{
throw new DistributedLockTimeoutException(
$"Could not place a lock on the resource \'{_resource}\': The lock request timed out.");
}
}
public IFetchedJob Dequeue(string[] queues, CancellationToken cancellationToken)
{
if (queues == null)
{
throw new ArgumentNullException(nameof(queues));
}
if (queues.Length == 0)
{
throw new ArgumentException("Queue array must be non-empty.", nameof(queues));
}
var filter = Builders <JobQueueDto> .Filter;
var fetchConditions = new[]
{
filter.Eq(_ => _.FetchedAt, null),
filter.Lt(_ => _.FetchedAt, DateTime.UtcNow.AddSeconds(_storageOptions.InvisibilityTimeout.Negate().TotalSeconds))
};
var fetchConditionsIndex = 0;
var options = new FindOneAndUpdateOptions <JobQueueDto>
{
IsUpsert = false,
ReturnDocument = ReturnDocument.After
};
JobQueueDto fetchedJob = null;
while (fetchedJob == null)
{
cancellationToken.ThrowIfCancellationRequested();
var fetchCondition = fetchConditions[fetchConditionsIndex];
foreach (var queue in queues)
{
fetchedJob = _database.JobQueue.FindOneAndUpdate(
fetchCondition & filter.Eq(_ => _.Queue, queue),
Builders <JobQueueDto> .Update.Set(_ => _.FetchedAt, DateTime.UtcNow),
options,
cancellationToken);
if (fetchedJob != null)
{
break;
}
}
if (fetchedJob == null)
{
// No more jobs found in any of the requested queues...
if (fetchConditionsIndex == fetchConditions.Length - 1)
{
// ...and we are out of fetch conditions as well.
// Wait for a while before polling again.
var waitNames = queues.Select(q => $@"JobQueue.{q}");
_signal.Wait(waitNames.ToArray(), cancellationToken);
}
}
// Move on to next fetch condition
fetchConditionsIndex = (fetchConditionsIndex + 1) % fetchConditions.Length;
}
return(new MongoFetchedJob(_database, fetchedJob.Id, fetchedJob.JobId, fetchedJob.Queue));
}