Dequeueable 1.0.0

Dequeueable

This project is an opinionated, cloud-native ephemeral job runner for Azure Queue Storage.

It is designed to be triggered by external queue scalers (e.g., KEDA), process a single message, and immediately shut down upon completion. If no message is found, the host shuts down without executing.

• Built as a Console App
• Compatible with optimized alpine/dotnet images
• Works with KEDA or any other external queue scaler

Getting started

Scaffold a new project, you can either use a console or web app.

1. Add a class that implements the IQueueJob.
2. Add .AddDequeueable<YourJob> in the DI container.
3. Call .RunJobAsync on the host builder to run as a job.

await Host.CreateDefaultBuilder(args)
.ConfigureServices(services =>
{
    services.AddDequeueable<TestJob>(options =>
    {
       // ...
    });
}).RunJobAsync();

Configurations

You can configure the host via the appsettings.json or via the IOptions pattern during registration.

Appsettings

Use the Dequeueable section to configure the settings:

"Dequeueable": {
    "ConnectionString": "UseDevelopmentStorage=true",
    "QueueName": "queue-name"
  }

Options

await Host.CreateDefaultBuilder(args)
    .ConfigureServices((context, services) =>
    {
        services.AddDequeueable<TestJob>(options =>
        {
            options.AuthenticationScheme = new DefaultAzureCredential();
             options.VisibilityTimeoutInSeconds = 600;
            options.QueueName = "testqueue";
        });
    })
    .RunJobAsync();

Settings

The library uses the IOptions pattern to inject the configured app settings. These settings will be validated on startup.

Host options

These options can be set for the job project:

Authentication

SAS

You can authenticate to the storage account & queue by setting the ConnectionString:

"Dequeueable": {
    "ConnectionString": "UseDevelopmentStorage=true",
    ...
  }

    services.AddDequeueable<TestJob>(options =>
    {
        // ...
        options.ConnectionString = "UseDevelopmentStorage=true";
    });

Identity

Authenticating via Azure Identity is also possible and the recommended option. Make sure that the identity used have the following roles on the storage account

• 'Storage Queue Data Contributor'
• 'Storage Blob Data Contributor' - Only when making use of the distributed lock.

Set the AuthenticationScheme and the AccountName options to authenticate via azure AD:

    services.AddDequeueable<TestJob>(options =>
    {
        options.AuthenticationScheme = new DefaultAzureCredential();
        options.AccountName = "thestorageaccountName";
    });

Any token credential provider can be used that inherits the abstract class Azure.Core.TokenCredential

The QueueUriFormat options is used to format the correct URI to the queue. When making use of the distributed lock, the BlobUriFormat is used to format the correct URI to the blob lease.

Custom QueueProvider

There are plenty ways to construct the QueueClient, and not all are by default supported. You can override the default implementations to retrieve the queue client by implementing the IQueueClientProvider. You still should register your custom provider in your DI container, specific registration order is not needed:

internal class MyCustomQueueProvider : IQueueClientProvider
    {
        public QueueClient GetQueue()
        {
            return new QueueClient(new Uri("https://myaccount.chinacloudapi.cn/myqueue"), new QueueClientOptions { MessageEncoding = QueueMessageEncoding.Base64 });
        }

        public QueueClient GetPoisonQueue()
        {
            return new QueueClient(new Uri("https://myaccount.chinacloudapi.cn/mypoisonqueue"), new QueueClientOptions { MessageEncoding = QueueMessageEncoding.Base64 });
        }
    }

Distributed Lock

A distributed lock can be applied to the job to ensure that only a single instance of the job is executed at any given time. It uses the blob lease and therefore distributed lock is guaranteed. The blob is leased for the duration configured by LeaseDurationInSeconds (default: 60 seconds). The lease will be released if no longer required. It will be automatically renewed if executing the message(s) takes longer.

NOTE: The blob files will not be automatically deleted. If needed, consider specifying data lifecycle rules for the blob container: https://learn.microsoft.com/en-us/azure/storage/blobs/lifecycle-management-overview

If making use of the Identity Flow, the lease requires the Storage Blob Data Contributor role because the library writes and manages the lease blob for distributed locking.

To run the host with a distributed lock, call the .WithDistributedLock() in the DI container:

services.AddDequeueable<TestJob>()
.WithDistributedLock(opt =>
    {
        opt.Scope = "id";
    });

Only messages containing a JSON format is supported. The scope should always be a property in the message body that exists.

Given a queue message with the following body:

{
  "Id": "d89c209a-6b81-4266-a768-8cde6f613753"
  // ...
}

When the scope is set to "Id" on the job. Only a single message containing Id "d89c209a-6b81-4266-a768-8cde6f613753" will be executed at an given time. This is case sensitive, the scope string must match the JSON key exactly!

Nested properties are also supported. Given a queue message with the following body:

{
  "My": {
    "Nested": {
      "Property": 500
    }
  }
  // ...
}

When the scope is set to "My:Nested:Property" on the job. Only a single message containing 500 will be executed at an given time.

Lock Options

You can specify the following lock options via the .WithDistributedLock(opt => {}) or via the appsettings.json using the Dequeueable:DistributedLock section:

{
  "Dequeueable": {
    "DistributedLock": {
      "Scope": "id"
    }
  }
}

Custom BlobClientProvider

There are plenty ways to construct the BlobClient, and not all are by default supported. You can override the default implementations to retrieve the blob client for the lease by implementing the IBlobClientProvider. You still should register your custom provider in your DI container, specific registration order is not needed:

internal class MyCustomBlobClientProvider : IBlobClientProvider
    {
        public BlobClient GetClient(string blobName)
        {
            return new BlobClient(new Uri($"https://myaccount.chinacloudapi.cn/mycontainer/{blobName}"),
                new BlobClientOptions { GeoRedundantSecondaryUri = new Uri($"https://mysecaccount.chinacloudapi.cn/mycontainer/{blobName}") });
        }
    }

Timeouts

Visibility Timeout Queue Message

The visibility timeout of the queue messages is automatically updated. It will be updated when the half VisibilityTimeout option is reached. Choose this setting wisely to prevent talkative hosts. When renewing the timeout fails, the host cannot guarantee if the message is executed only once. Therefore the CancelationToken is set to Cancelled. It is up to you how to handle this scenario!

Lease timeout

The lease timeout of the blob lease is automatically updated. It will be updated when the half lease is reached. When renewing the timeout fails, the host cannot guarantee the lock. Therefore the CancelationToken is set to Cancelled. It is up to you how to handle this scenario!

Sample

• Job Console app