private async Task ConnectTransportAsync()
{
// There shouldn't be a previous connect in progress, but cancel the CTS to ensure they're no longer running.
_connectCts?.Cancel();
_connectCts = new CancellationTokenSource();
var backoffPolicy = _manager.BackoffPolicyFactory.Create();
try
{
SubchannelLog.ConnectingTransport(_logger, Id);
for (var attempt = 0; ; attempt++)
{
lock (Lock)
{
if (_state == ConnectivityState.Shutdown)
{
return;
}
}
if (await Transport.TryConnectAsync(_connectCts.Token).ConfigureAwait(false))
{
return;
}
_connectCts.Token.ThrowIfCancellationRequested();
_delayInterruptTcs = new TaskCompletionSource <object?>(TaskCreationOptions.RunContinuationsAsynchronously);
var delayCts = new CancellationTokenSource();
var backoffTicks = backoffPolicy.NextBackoff().Ticks;
// Task.Delay supports up to Int32.MaxValue milliseconds.
// Note that even if the maximum backoff is configured to this maximum, the jitter could push it over the limit.
// Force an upper bound here to ensure an unsupported backoff is never used.
backoffTicks = Math.Min(backoffTicks, TimeSpan.TicksPerMillisecond * int.MaxValue);
var backkoff = TimeSpan.FromTicks(backoffTicks);
SubchannelLog.StartingConnectBackoff(_logger, Id, backkoff);
var completedTask = await Task.WhenAny(Task.Delay(backkoff, delayCts.Token), _delayInterruptTcs.Task).ConfigureAwait(false);
if (completedTask != _delayInterruptTcs.Task)
{
// Task.Delay won. Check CTS to see if it won because of cancellation.
delayCts.Token.ThrowIfCancellationRequested();
}
else
{
SubchannelLog.ConnectBackoffInterrupted(_logger, Id);
// Delay interrupt was triggered. Reset back-off.
backoffPolicy = _manager.BackoffPolicyFactory.Create();
// Cancel the Task.Delay that's no longer needed.
// https://github.com/davidfowl/AspNetCoreDiagnosticScenarios/blob/519ef7d231c01116f02bc04354816a735f2a36b6/AsyncGuidance.md#using-a-timeout
delayCts.Cancel();
}
}
}
catch (OperationCanceledException)
{
SubchannelLog.ConnectCanceled(_logger, Id);
}
catch (Exception ex)
{
SubchannelLog.ConnectError(_logger, Id, ex);
UpdateConnectivityState(ConnectivityState.TransientFailure, "Error connecting to subchannel.");
}
}
private async Task ConnectTransportAsync()
{
// There shouldn't be a previous connect in progress, but cancel the CTS to ensure they're no longer running.
_connectCts?.Cancel();
_connectCts = new CancellationTokenSource();
const int InitialBackOffMs = 1000;
try
{
SubchannelLog.ConnectingTransport(_logger, Id);
var backoffMs = InitialBackOffMs;
for (var attempt = 0; ; attempt++)
{
lock (Lock)
{
if (_state == ConnectivityState.Shutdown)
{
return;
}
}
if (await Transport.TryConnectAsync(_connectCts.Token).ConfigureAwait(false))
{
return;
}
_connectCts.Token.ThrowIfCancellationRequested();
_delayInterruptTcs = new TaskCompletionSource <object?>(TaskCreationOptions.RunContinuationsAsynchronously);
var delayCts = new CancellationTokenSource();
var delay = TimeSpan.FromMilliseconds(backoffMs);
SubchannelLog.StartingConnectBackoff(_logger, Id, delay);
var completedTask = await Task.WhenAny(Task.Delay(delay, delayCts.Token), _delayInterruptTcs.Task).ConfigureAwait(false);
if (completedTask != _delayInterruptTcs.Task)
{
// Task.Delay won. Check CTS to see if it won because of cancellation.
delayCts.Token.ThrowIfCancellationRequested();
}
else
{
SubchannelLog.ConnectBackoffInterrupted(_logger, Id);
// Delay interrupt was triggered. Reset back-off.
backoffMs = InitialBackOffMs;
// Cancel the Task.Delay that's no longer needed.
// https://github.com/davidfowl/AspNetCoreDiagnosticScenarios/blob/519ef7d231c01116f02bc04354816a735f2a36b6/AsyncGuidance.md#using-a-timeout
delayCts.Cancel();
}
// Exponential backoff with max.
backoffMs = (int)Math.Min(backoffMs * 1.6, 1000 * 120);
}
}
catch (OperationCanceledException)
{
SubchannelLog.ConnectCanceled(_logger, Id);
}
catch (Exception ex)
{
SubchannelLog.ConnectError(_logger, Id, ex);
UpdateConnectivityState(ConnectivityState.TransientFailure, "Error connecting to subchannel.");
}
}