// private methods
private void ThreadStart()
{
_state = DnsMonitorState.Running;
try
{
Monitor();
}
catch (OperationCanceledException)
{
// ignore OperationCanceledException
}
catch (Exception exception)
{
_unhandledException = exception;
if (_sdamInformationEventHandler != null)
{
var message = $"Unhandled exception in DnsMonitor: {exception}.";
var sdamInformationEvent = new SdamInformationEvent(() => message);
_sdamInformationEventHandler(sdamInformationEvent);
}
_state = DnsMonitorState.Failed;
return;
}
_state = DnsMonitorState.Stopped;
}
private List <DnsEndPoint> GetValidEndPoints(List <SrvRecord> srvRecords)
{
var validEndPoints = new List <DnsEndPoint>();
foreach (var srvRecord in srvRecords)
{
var endPoint = srvRecord.EndPoint;
var host = endPoint.Host;
if (host.EndsWith(".", StringComparison.Ordinal))
{
host = host.Substring(0, host.Length - 1);
endPoint = new DnsEndPoint(host, endPoint.Port);
}
if (IsValidHost(endPoint))
{
validEndPoints.Add(endPoint);
}
else
{
if (_sdamInformationEventHandler != null)
{
var message = $"Invalid host returned by DNS SRV lookup: {host}.";
var sdamInformationEvent = new SdamInformationEvent(() => message);
_sdamInformationEventHandler(sdamInformationEvent);
}
}
}
return(validEndPoints);
}
private void Monitor()
{
while (true)
{
if (_processDnsResultHasEverBeenCalled && _cluster.ShouldDnsMonitorStop())
{
return;
}
List <SrvRecord> srvRecords = null;
try
{
srvRecords = _dnsResolver.ResolveSrvRecords(_service, _cancellationToken);
}
catch (Exception exception)
{
if (!_processDnsResultHasEverBeenCalled)
{
_cluster.ProcessDnsException(exception);
}
}
if (srvRecords != null)
{
var endPoints = GetValidEndPoints(srvRecords);
if (endPoints.Count > 0)
{
_cluster.ProcessDnsResults(endPoints);
_processDnsResultHasEverBeenCalled = true;
}
else
{
if (_sdamInformationEventHandler != null)
{
var message = $"A DNS SRV query on \"{_service}\" returned no valid hosts.";
var sdamInformationEvent = new SdamInformationEvent(() => message);
_sdamInformationEventHandler(sdamInformationEvent);
}
}
}
if (_cluster.ShouldDnsMonitorStop())
{
return;
}
_cancellationToken.ThrowIfCancellationRequested();
var delay = ComputeRescanDelay(srvRecords);
Thread.Sleep(delay);
}
}
private void Handle(SdamInformationEvent @event)
{
Info(TraceSourceEventHelper.ClusterIdBase + 9, "{0}", @event);
}
