/// <summary>
/// Pop the current server and put onto the end of the list.
/// Select head of list as long as number of reconnect attempts under MaxReconnect.
/// </summary>
/// <returns>The next server endpoint, or null</returns>
internal ServerConnectionStatus SelectNextServer()
{
lock (this._locker)
{
ServerConnectionStatus s = this._currentServer;
if (s == null)
{
return(null);
}
//remove the current server.
this._servers.Remove(s);
if (this._options.MaxReconnect > 0 &&
s.ReconnectionCount < this._options.MaxReconnect
)
{
//if we haven't surpassed max reconnects, add it to try again.
this._servers.AddLast(s);
}
this._currentServer = this._servers.FirstOrDefault();
return(this._currentServer);
}
}
/// <summary>
/// Creates an instance of <see cref="TcpConnection"/> using the
/// specified <see cref="ServerConnectionStatus"/> as parameters.
/// </summary>
/// <param name="options"></param>
/// <param name="s"></param>
/// <param name="token"></param>
/// <returns></returns>
internal static TcpConnection Create(
ClientOptions options,
ServerConnectionStatus s,
CancellationToken token
)
{
var instance = new TcpConnection();
instance._options = options;
var client = new TcpClient();
try
{
//it seems there's no way to better make a connection attempt
//within a certain timeout.
//the solution is connecting in the async-fashion, then
//controlling the task timeout and cancellation in the sync-fashion
bool success = client
.ConnectAsync(s.EndPoint.Address, s.EndPoint.Port)
.Wait((int)options.Timeout.TotalMilliseconds, token);
if (success)
{
//set-up the socket
client.NoDelay = false;
client.ReceiveBufferSize = Defaults.defaultBufSize * 2;
client.SendBufferSize = Defaults.defaultBufSize;
client.SendTimeout = InitialSocketSendTimeout;
client.ReceiveTimeout = InitialSocketReceiveTimeout;
instance._client = client;
instance._netStream = client.GetStream();
// save off the hostname
instance._hostName = s.EndPoint.Address.ToString();
instance.CreateReaderWriter();
}
else
{
throw new NATSConnectionException("timeout");
}
}
catch (Exception ex)
{
client.Dispose();
throw ex;
}
//Console.WriteLine("socket connected");
return(instance);
}
/// <summary>
/// Main entry-point to connect to a server
/// </summary>
/// <param name="initialPresentation">Indicates whether it's the very first attempt to connect,
/// or rather some retry due to a connection drop.</param>
/// <param name="token">Propagates notification that operations should be canceled.</param>
/// <returns>The <see cref="TcpConnection"/> useful to exchange data with the server.</returns>
internal TcpConnection ConnectToAServer(
bool initialPresentation,
CancellationToken token
)
{
//select an iterator against the proper server list
IEnumerator <ServerConnectionStatus> iter;
lock (this._locker)
{
if (initialPresentation)
{
iter = this._servers.GetEnumerator();
}
else
{
iter = new ServerStatusEnumerator(this);
}
}
//task cancelation will raise an exception
token.ThrowIfCancellationRequested();
Exception lastex = null;
while (iter.MoveNext())
{
ServerConnectionStatus s = iter.Current;
try
{
//connection attempt
var tcp = TcpConnection.Create(this._options, s, token);
s.DidConnect = true;
s.ReconnectionCount = 0;
this._currentServer = s;
return(tcp);
}
catch (OperationCanceledException ex)
{
throw ex;
}
catch (Exception ex)
{
lastex = ex;
}
if (initialPresentation == false)
{
//manage stats
s.ReconnectionCount++;
this.IncrementStatsCounter?.Invoke();
//waits before retrying again
Helpers.CancelableDelay(this._options.ReconnectWait, token);
}
}
if (lastex != null)
{
throw lastex;
}
this._currentServer = null;
return(null);
}
