/// <summary>
/// Gets a connection from the next host according to the load balancing policy
/// </summary>
/// <exception cref="NoHostAvailableException"/>
/// <exception cref="InvalidQueryException">When keyspace does not exist</exception>
/// <exception cref="UnsupportedProtocolVersionException"/>
internal Connection GetNextConnection(IStatement statement, bool isLastChance = false)
{
var hostEnumerable = _session.Policies.LoadBalancingPolicy.NewQueryPlan(statement);
Host lastChanceHost = null;
//hostEnumerable GetEnumerator will return a NEW enumerator, making this call thread safe
foreach (var host in hostEnumerable)
{
if (!host.IsConsiderablyUp)
{
if (!isLastChance && host.Resurrect)
{
lastChanceHost = host;
}
continue;
}
_currentHost = host;
_triedHosts[host.Address] = null;
Connection connection = null;
try
{
var distance = _session.Policies.LoadBalancingPolicy.Distance(host);
var hostPool = _session.GetConnectionPool(host, distance);
connection = hostPool.BorrowConnection();
if (connection == null)
{
continue;
}
connection.Keyspace = _session.Keyspace;
return(connection);
}
catch (SocketException ex)
{
_session.SetHostDown(host, connection);
_triedHosts[host.Address] = ex;
host.Resurrect = CanBeResurrected(ex, connection);
if (!isLastChance && host.Resurrect)
{
lastChanceHost = host;
}
}
catch (InvalidQueryException)
{
//The keyspace does not exist
throw;
}
catch (UnsupportedProtocolVersionException)
{
//The version of the protocol is not supported
throw;
}
catch (Exception ex)
{
_logger.Error(ex);
_triedHosts[host.Address] = ex;
}
}
_currentHost = null;
if (lastChanceHost != null)
{
//There are no host available and some of them are due to network events.
//Probably there was a network event that reset all connections and it does not mean the connection
_logger.Warning("Suspected network reset. Getting one host up and retrying for a last chance");
lastChanceHost.BringUpIfDown();
return(GetNextConnection(statement, true));
}
throw new NoHostAvailableException(_triedHosts);
}