public static async Task ServiceBusQueueProcessorAsync()

in ProcessManager/BackendQueueProcessor/BackendQueueProcessor.cs [28:81]
45 lines of code
4 McCabe index (conditional complexity)

        public static async Task ServiceBusQueueProcessorAsync(
            [ServiceBusTrigger("%SERVICE_BUS_QUEUE%")] Message message, MessageReceiver messageReceiver, ILogger logger)
        {
            var timestamp = DateTime.UtcNow;
            var queueName = Environment.GetEnvironmentVariable("SERVICE_BUS_QUEUE", EnvironmentVariableTarget.Process);
            logger.LogTrace($@"[{message.UserProperties[@"TaskId"]}]: Message received at {timestamp}: {JObject.FromObject(message)}");

            AppInsightsLogger appInsightsLogger = new AppInsightsLogger(logger, LOGGING_SERVICE_NAME + ": " + queueName, LOGGING_SERVICE_VERSION);

            var enqueuedTime = message.ScheduledEnqueueTimeUtc;
            var elapsedTimeMs = (timestamp - enqueuedTime).TotalMilliseconds;

            var taskId = message.UserProperties["TaskId"].ToString();
            var backendUri = message.UserProperties["Uri"].ToString();
            var messageBody = Encoding.UTF8.GetString(message.Body);

            try
            {
                appInsightsLogger.LogInformation($"Sending request to {backendUri} for taskId {taskId} from queue {queueName}. Queued for {elapsedTimeMs/60} seconds.", backendUri, taskId);

                var client = new HttpClient();
                client.DefaultRequestHeaders.Add("taskId", taskId);
                
                var httpContent = new StringContent(messageBody, Encoding.UTF8, "application/json");
                var res = await client.PostAsync(backendUri, httpContent);

                if (res.StatusCode == (System.Net.HttpStatusCode)429) // Special return value indicating that the service is busy.
                {
                    var retryDelay = int.Parse(Environment.GetEnvironmentVariable(QUEUE_RETRY_DELAY_MS_VARIABLE_NAME, EnvironmentVariableTarget.Process));
                    appInsightsLogger.LogInformation($"Service is busy. Will try again in {retryDelay/1000} seconds.", backendUri, taskId);
                    await UpdateTaskStatus(taskId, backendUri, messageBody, $"Awaiting service availability. Queued for {elapsedTimeMs/60} seconds.", "created", appInsightsLogger);

                    // Artifical delay is needed since the ServiceBusTrigger will retry immediately.
                    await Task.Delay(retryDelay);
                    await messageReceiver.AbandonAsync(message.SystemProperties.LockToken);
                    throw new ApplicationException($"Service is busy. Will try again in {retryDelay/1000} seconds.");
                }
                else if (!res.IsSuccessStatusCode)
                {
                    await messageReceiver.CompleteAsync(message.SystemProperties.LockToken);    //Need to complete even though we have failure. This removes it from the queue to avoid an infinite state.
                    appInsightsLogger.LogWarning($"Unable to send request to backend. Status: {res.StatusCode.ToString()}, Reason: {res.ReasonPhrase}", backendUri, taskId);
                    await UpdateTaskStatus(taskId, backendUri, messageBody, $"Unable to send request to backend.", "failed", appInsightsLogger);
                }
                else
                {
                    await messageReceiver.CompleteAsync(message.SystemProperties.LockToken);
                    appInsightsLogger.LogInformation($"taskId {taskId} has successfully been pushed to the backend from queue {queueName}. Queue time: {elapsedTimeMs/60} seconds.", backendUri, taskId);
                }
            }
            catch (Exception ex)
            {
                appInsightsLogger.LogError(ex, backendUri, taskId);
            }
        }