protected override async Task ResolveAsync(CancellationToken cancellationToken)
{
try
{
var elapsedTimeSinceLastRefresh = SystemClock.UtcNow - _lastResolveStart;
if (elapsedTimeSinceLastRefresh < MinimumDnsResolutionRate)
{
var delay = MinimumDnsResolutionRate - elapsedTimeSinceLastRefresh;
DnsResolverLog.StartingRateLimitDelay(_logger, delay, MinimumDnsResolutionRate);
await Task.Delay(delay, cancellationToken).ConfigureAwait(false);
}
var lastResolveStart = SystemClock.UtcNow;
if (string.IsNullOrEmpty(_dnsAddress))
{
throw new InvalidOperationException($"Resolver address '{_originalAddress}' is not valid. Please use dns:/// for DNS provider.");
}
DnsResolverLog.StartingDnsQuery(_logger, _dnsAddress);
var addresses =
#if NET6_0_OR_GREATER
await Dns.GetHostAddressesAsync(_dnsAddress, cancellationToken).ConfigureAwait(false);
#else
await Dns.GetHostAddressesAsync(_dnsAddress).ConfigureAwait(false);
#endif
DnsResolverLog.ReceivedDnsResults(_logger, addresses.Length, _dnsAddress, addresses);
var endpoints = addresses.Select(a => new BalancerAddress(a.ToString(), _port)).ToArray();
var resolverResult = ResolverResult.ForResult(endpoints);
Listener(resolverResult);
// Only update last resolve start if successful. Backoff will handle limiting resolves on failure.
_lastResolveStart = lastResolveStart;
}
catch (Exception ex)
{
var message = $"Error getting DNS hosts for address '{_dnsAddress}'.";
DnsResolverLog.ErrorQueryingDns(_logger, _dnsAddress, ex);
Listener(ResolverResult.ForFailure(GrpcProtocolHelpers.CreateStatusFromException(message, ex, StatusCode.Unavailable)));
}
}