Ejemplo n.º 1
0
        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.");
            }
        }
Ejemplo n.º 2
0
        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.");
            }
        }