public Task StartAsync()

in src/WebJobs.Script/Workers/WorkerConcurrencyManager.cs [61:107]
41 lines of code
11 McCabe index (conditional complexity)

        public Task StartAsync(CancellationToken cancellationToken)
        {
            string workerRuntime = _environment.GetEnvironmentVariable(EnvironmentSettingNames.FunctionWorkerRuntime);
            if (!string.IsNullOrEmpty(workerRuntime))
            {
                // the feature applies only to "node","powershell","python"
                workerRuntime = workerRuntime.ToLower();
                if (workerRuntime == RpcWorkerConstants.NodeLanguageWorkerName
                || workerRuntime == RpcWorkerConstants.PowerShellLanguageWorkerName
                || workerRuntime == RpcWorkerConstants.PythonLanguageWorkerName)
                {
                    _functionInvocationDispatcher = _functionInvocationDispatcherFactory.GetFunctionDispatcher();

                    if (_functionInvocationDispatcher is HttpFunctionInvocationDispatcher)
                    {
                        _logger.LogDebug($"Http dynamic worker concurrency is not supported.");
                        return Task.CompletedTask;
                    }
                    if (!string.IsNullOrEmpty(_environment.GetEnvironmentVariable(RpcWorkerConstants.FunctionsWorkerProcessCountSettingName)))
                    {
                        return Task.CompletedTask;
                    }
                    if (_environment.IsWorkerDynamicConcurrencyEnabled())
                    {
                        _logger.LogDebug($"Dynamic worker concurrency monitoring is starting by app setting.");
                        Activate();
                    }
                    else if (_functionsHostingConfigOptionsMonitor.CurrentValue != null && _functionsHostingConfigOptionsMonitor.CurrentValue.FunctionsWorkerDynamicConcurrencyEnabled)
                    {
                        _logger.LogDebug($"Dynamic worker concurrency monitoring is starting by hosting config.");
                        Activate();

                        _hostingConfigOnChange = _functionsHostingConfigOptionsMonitor.OnChange(async (newOptions) =>
                        {
                            if (!newOptions.FunctionsWorkerDynamicConcurrencyEnabled)
                            {
                                // There is a known issue when OnChange fires twice: https://github.com/dotnet/aspnetcore/issues/2542
                                // Lets make sure we stopped the app once
                                await _stopApplication();
                            }
                        });
                    }
                }
            }

            return Task.CompletedTask;
        }