Background Stream in Azure Web Role

Question

Can we start the stream from the WebRole.cs OnStart () method so that we can access it through the aspx page to do background work? I know that the right way to do this would be to use the worker role, but I want to keep the running costs as low as possible.

The idea would be to create a thread that always worked and was waiting for a job, for example, if I want to do a blocking operation, for example, sending email, I would use a thread that provides the SendEmail method, can I do it? If so, can you provide me with a few examples that could point me in the right direction?

Answer 1

I would suggest a solution different from the solution of Leon and David:

• David's solution is OK, but it is not sustainable. What is this instance / process disconnected during task processing?
• Leon's solution is mainly related to scheduled tasks, but sending email is not always planned (maybe you want to send an email when someone logs into your application).

Another option that you should pay attention to is to use the Windows Azure Storage Queues (which are very cheap) in this scenario:

• Your web application: sends messages to the queue (for example, "send an email to [e-mail] ")
• WebRole.cs: create a new thread when you start the instance and ask him to listen to messages from this queue. Whenever a message arrives, process it. If successful, delete the message from the queue.

This solution has many advantages. WebRole.cs works in a different process than your web application, so it does not affect the flow of requests. And besides, if for some reason the sending of the mail failed, the message will remain in the queue and will be processed the next time. This ensures that you won’t lose any tasks if the application or process crashes.

Here is an example to get you started. Please note that you need to improve this code if you want it to be ready for production (retry policy, exception handling, poll polling, ...):

using System; using System.Collections.Generic; using System.Linq; using Microsoft.WindowsAzure; using Microsoft.WindowsAzure.Diagnostics; using Microsoft.WindowsAzure.ServiceRuntime; using Microsoft.WindowsAzure.StorageClient; using System.Threading.Tasks; namespace MvcWebRole1 { public class WebRole : RoleEntryPoint { public override bool OnStart() { Task.Factory.StartNew(InitializeQueueListener); return base.OnStart(); } private void InitializeQueueListener() { Microsoft.WindowsAzure.CloudStorageAccount.SetConfigurationSettingPublisher((configName, configSetter) => { configSetter(Microsoft.WindowsAzure.ServiceRuntime.RoleEnvironment.GetConfigurationSettingValue(configName)); }); var storageAccount = CloudStorageAccount.FromConfigurationSetting("DataConnectionString"); var queueStorage = storageAccount.CreateCloudQueueClient(); var queue = queueStorage.GetQueueReference("myqueue"); queue.CreateIfNotExist(); while (true) { CloudQueueMessage msg = queue.GetMessage(); if (msg != null) { // DO SOMETHING HERE queue.DeleteMessage(msg); } else { System.Threading.Thread.Sleep(1000); } } } } } 

Answer 2

Absolutely, you can create a stream (or a lot of them). The web role is basically Windows 2008 Server. To create a background task, you do not need a separate worker role. Of course, you can have a separate work role that allows you to scale these instances regardless of instances of the web role. Here you will need to balance performance / scaling with cost.

Answer 3

I found this when I was looking for "scheduled Azzure tasks": http://www.ronaldwidha.net/2011/02/23/cron-job-on-azure-using-scheduled-task-on-a-web-role- to-replace-azure-worker-role-for-background-job /

It seems exactly what you are looking for.