/// <summary>
/// Receives notification of any IO exceptions on the connection.
///
/// <p/>Upon receipt of a connection closed exception or any IOException, the fail-over process is attempted. If the fail-over fails, then
/// all method listeners and the application connection object are notified of the connection failure exception.
///
/// <p/>All other exception types are propagated to all method listeners.
/// </summary>
public void OnException(Exception cause)
{
_log.Warn("public void OnException(Exception cause = " + cause + "): called");
// Ensure that the method listener set cannot be changed whilst this exception is propagated to all listeners. This also
// ensures that this exception is fully propagated to all listeners, before another one can be processed.
lock (_lock)
{
if (cause is AMQConnectionClosedException || cause is System.IO.IOException)
{
// Try a fail-over because the connection has failed.
FailoverState failoverState = AttemptFailover();
// Check if the fail-over has failed, in which case notify all method listeners of the exception.
// The application connection object is also notified of the failure of the connection with the exception.
if (failoverState == FailoverState.FAILED)
{
_log.Debug("Fail-over has failed. Notifying all method listeners of the exception.");
AMQException amqe = new AMQException("Protocol handler error: " + cause, cause);
PropagateExceptionToWaiters(amqe);
_connection.ExceptionReceived(cause);
}
}
// Notify all method listeners of the exception.
else
{
PropagateExceptionToWaiters(cause);
_connection.ExceptionReceived(cause);
}
}
}
public void Run()
{
if (Thread.CurrentThread.IsBackground)
{
throw new InvalidOperationException("FailoverHandler must Run on a non-background thread.");
}
AMQProtocolListener pl = _connection.ProtocolListener;
pl.FailoverLatch = new ManualResetEvent(false);
// We wake up listeners. If they can handle failover, they will extend the
// FailoverSupport class and will in turn block on the latch until failover
// has completed before retrying the operation
_connection.ProtocolListener.PropagateExceptionToWaiters(new FailoverException("Failing over about to start"));
// Since failover impacts several structures we protect them all with a single mutex. These structures
// are also in child objects of the connection. This allows us to manipulate them without affecting
// client code which runs in a separate thread.
lock (_connection.FailoverMutex)
{
_log.Info("Starting failover process");
// We switch in a new state manager temporarily so that the interaction to get to the "connection open"
// state works, without us having to terminate any existing "state waiters". We could theoretically
// have a state waiter waiting until the connection is closed for some reason. Or in future we may have
// a slightly more complex state model therefore I felt it was worthwhile doing this.
AMQStateManager existingStateManager = _connection.ProtocolListener.StateManager;
_connection.ProtocolListener.StateManager = new AMQStateManager();
if (!_connection.FirePreFailover(_host != null))
{
_connection.ProtocolListener.StateManager = existingStateManager;
if (_host != null)
{
_connection.ExceptionReceived(new AMQDisconnectedException("Redirect was vetoed by client"));
}
else
{
_connection.ExceptionReceived(new AMQDisconnectedException("Failover was vetoed by client"));
}
pl.FailoverLatch.Set();
pl.FailoverLatch = null;
return;
}
bool failoverSucceeded;
// when host is non null we have a specified failover host otherwise we all the client to cycle through
// all specified hosts
// if _host has value then we are performing a redirect.
if (_host != null)
{
// todo: fix SSL support!
failoverSucceeded = _connection.AttemptReconnection(_host, _port, null);
}
else
{
failoverSucceeded = _connection.AttemptReconnection();
}
// XXX: at this point it appears that we are going to set StateManager to existingStateManager in
// XXX: both paths of control.
if (!failoverSucceeded)
{
_connection.ProtocolListener.StateManager = existingStateManager;
_connection.ExceptionReceived(
new AMQDisconnectedException("Server closed connection and no failover " +
"was successful"));
}
else
{
_connection.ProtocolListener.StateManager = existingStateManager;
try
{
if (_connection.FirePreResubscribe())
{
_log.Info("Resubscribing on new connection");
_connection.ResubscribeChannels();
}
else
{
_log.Info("Client vetoed automatic resubscription");
}
_connection.FireFailoverComplete();
_connection.ProtocolListener.FailoverState = FailoverState.NOT_STARTED;
_log.Info("Connection failover completed successfully");
}
catch (Exception e)
{
_log.Info("Failover process failed - exception being propagated by protocol handler");
_connection.ProtocolListener.FailoverState = FailoverState.FAILED;
try
{
_connection.ProtocolListener.OnException(e);
}
catch (Exception ex)
{
_log.Error("Error notifying protocol session of error: " + ex, ex);
}
}
}
}
pl.FailoverLatch.Set();
}
