public async ValueTask <(Subchannel Subchannel, BalancerAddress Address, Action <CompletionContext> OnComplete)> PickAsync(PickContext context, bool waitForReady, CancellationToken cancellationToken)
{
SubchannelPicker?previousPicker = null;
// Wait for a valid picker. When the client state changes a new picker will be returned.
// Cancellation will break out of the loop. Typically cancellation will come from a
// deadline specified for a call being exceeded.
while (true)
{
var currentPicker = await GetPickerAsync(previousPicker, cancellationToken).ConfigureAwait(false);
ConnectionManagerLog.PickStarted(Logger);
var result = currentPicker.Pick(context);
switch (result.Type)
{
case PickResultType.Complete:
var subchannel = result.Subchannel !;
var address = subchannel.CurrentAddress;
if (address != null)
{
ConnectionManagerLog.PickResultSuccessful(Logger, subchannel.Id, address);
return(subchannel, address, result.Complete);
}
else
{
ConnectionManagerLog.PickResultSubchannelNoCurrentAddress(Logger, subchannel.Id);
previousPicker = currentPicker;
}
break;
case PickResultType.Queue:
ConnectionManagerLog.PickResultQueued(Logger);
previousPicker = currentPicker;
break;
case PickResultType.Fail:
if (waitForReady)
{
ConnectionManagerLog.PickResultFailureWithWaitForReady(Logger, result.Status);
previousPicker = currentPicker;
}
else
{
ConnectionManagerLog.PickResultFailure(Logger, result.Status);
throw new RpcException(result.Status);
}
break;
case PickResultType.Drop:
// Use metadata on the exception to signal the request was dropped.
// Metadata is checked by retry. If request was dropped then it isn't retried.
var metadata = new Metadata {
new Metadata.Entry(GrpcProtocolConstants.DropRequestTrailer, bool.TrueString)
};
throw new RpcException(result.Status, metadata);
default:
throw new InvalidOperationException($"Unexpected pick result type: {result.Type}");
}
}
}
