/// <summary>
/// Enqueue the SmtpOutboundClient for use by another message.
/// </summary>
/// <param name="client">The client to queue.</param>
public void Enqueue(SmtpOutboundClient client)
{
SmtpClientMxRecords mxConnections = this._OutboundConnections.GetOrAdd(client.SmtpStream.LocalAddress.ToString(), new SmtpClientMxRecords());
SmtpClientQueue clientQueue = null;
lock (this._ClientPoolLock)
{
if (!mxConnections.TryGetValue(client.MXRecord.Host, out clientQueue))
{
clientQueue = new SmtpClientQueue();
if (!mxConnections.TryAdd(client.MXRecord.Host, clientQueue))
{
throw new Exception("Failed to add new SmtpClientQueue");
}
}
}
clientQueue.Enqueue(client);
try
{
clientQueue.InUseConnections.Remove(client);
}
catch (Exception)
{
// Already removed.
}
}
/// <summary>
/// Attempts to get a SmtpClient using the outbound IP address and the specified MX records collection.
///
/// WARNING: returned SmtpOutboundClient will have it's IsActive flag set to true make sure to set it to
/// false when done with it or it will never be removed by the idle timeout.
/// </summary>
/// <param name="ipAddress">The local outbound endpoint we wan't to use.</param>
/// <param name="mxs">The MX records for the domain we wan't a client to connect to.</param>
/// <returns>Tuple containing a DequeueAsyncResult and either an SmtpOutboundClient or Null if failed to dequeue.</returns>
public async Task <SmtpOutboundClientDequeueResponse> DequeueAsync(VirtualMTA ipAddress, MXRecord[] mxs)
{
// If there aren't any remote mx records then we can't send
if (mxs.Length < 1)
{
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.NoMxRecords));
}
SmtpClientMxRecords mxConnections = this._OutboundConnections.GetOrAdd(ipAddress.IPAddress.ToString(), new SmtpClientMxRecords());
SmtpOutboundClient smtpClient = null;
// Check that we aren't being throttled.
if (!ThrottleManager.Instance.TryGetSendAuth(ipAddress, mxs[0]))
{
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.Throttled));
}
// Loop through all the MX Records.
for (int i = 0; i < mxs.Length; i++)
{
try
{
// To prevent us bombarding a server that is blocking us we will check the service not available manager
// to see if we can send to this MX, Max 1 message/minute, if we can't we won't.
// At the moment we stop to all MXs for a domain if one of them responds with service unavailable.
// This could be improved to allow others to continue, we should however if blocked on all MX's with
// lowest preference not move on to the others.
if (ServiceNotAvailableManager.IsServiceUnavailable(ipAddress.IPAddress.ToString(), mxs[i].Host))
{
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.ServiceUnavalible));
}
SmtpClientQueue clientQueue = null;
lock (this._ClientPoolLock)
{
if (!mxConnections.TryGetValue(mxs[i].Host, out clientQueue))
{
clientQueue = new SmtpClientQueue();
if (!mxConnections.TryAdd(mxs[i].Host, clientQueue))
{
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.FailedToAddToSmtpClientQueue));
}
}
}
// Loop through the client queue and make sure we get one thats still connected.
// They may have idled out while waiting.
while (!clientQueue.IsEmpty)
{
if (clientQueue.TryDequeue(out smtpClient))
{
if (smtpClient.Connected)
{
clientQueue.InUseConnections.Add(smtpClient);
smtpClient.LastActive = DateTime.UtcNow;
smtpClient.IsActive = true;
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.Success, smtpClient));
}
}
}
// Nothing was in the queue or all queued items timed out.
CreateNewConnectionAsyncResult createNewConnectionResult = await clientQueue.CreateNewConnectionAsync(ipAddress, mxs[i]);
if (createNewConnectionResult.Exception == null)
{
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.Success, createNewConnectionResult.OutboundClient));
}
else if (createNewConnectionResult.Exception is MaxConnectionsException)
{
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.FailedMaxConnections));
}
else
{
throw createNewConnectionResult.Exception;
}
}
catch (SocketException ex)
{
// We have failed to connect to the remote host.
Logging.Warn("Failed to connect to " + mxs[i].Host, ex);
// If we fail to connect to an MX then don't try again for at least a minute.
ServiceNotAvailableManager.Add(ipAddress.IPAddress.ToString(), mxs[i].Host, DateTime.UtcNow);
// Failed to connect to MX
if (i == mxs.Length - 1)
{
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.FailedToConnect));
}
}
catch (Exception ex)
{
// Something unexpected and unhandled has happened, log it and return unknown.
Logging.Error("SmtpClientPool.DequeueAsync Unhandled Exception", ex);
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.Unknown));
}
}
// It we got here then we have failed to connect to the remote host.
return(new SmtpOutboundClientDequeueResponse(SmtpOutboundClientDequeueAsyncResult.FailedToConnect));
}
