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Dequeueable.AzureQueueStorage

This project is inspired by the Azure Function Host. This project is an opinionated optimization on the Azure Function:

  • Build as a Console App
  • Being able to use optimized alpine/dotnet images
  • Have the freedom to use Keda or any other scalers to retrieve queue messages

This framework can run as a listener or job:

  • Listener: Highly scalable queue listener that will be invoked automatically when new messages are detected on the Azure Queue.
  • Job: Framework that depends on external queue triggers, eg; KEDA. When the host is started, new messages on the Azure Queue are being retrieved and executed. After execution the host will shutdown automatically.

Getting started

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

  1. Add a class that implements the IAzureQueueFunction.
  2. Add .AddAzureQueueStorageServices<TestFunction> in the DI container.
  3. Add the job or listener services:
    • Add RunAsJob in the DI container of your app to run the host as a job.
    • Add RunAsListener in the DI container of your app to run the app as a back ground listener.
await Host.CreateDefaultBuilder(args)
    .ConfigureServices((context, services) =>
    {
        services.AddAzureQueueStorageServices<TestFunction>()
        .RunAsJob(options =>
        {
            // ...
        });
     })
    .RunConsoleAsync();

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.AddAzureQueueStorageServices<TestFunction>()
        .RunAsJob(options =>
        {
            options.AuthenticationScheme = new DefaultAzureCredential();
            options.VisibilityTimeout = TimeSpan.FromMinutes(10);
            options.QueueName = "testqueue";
        });
    })
    .RunConsoleAsync();

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 both the job as the listener project:

Setting Description Default Required
QueueName The queue used to retrieve the messages. Yes
ConnectionString The connection string used to authenticate to the queue. Yes, when not using Azure Identity
PoisonQueueSuffix Suffix that will be used after the QueueName, eg queuename-suffix. poison No
AccountName The storage account name, used for identity flow. Only when using Identity
QueueUriFormat The uri format to the queue storage. Used for identity flow. Use {accountName} and {queueName} for variable substitution. https://{accountName}.queue.core.windows.net/{queueName} No
AuthenticationScheme Token credential used to authenticate via AD, Any token credential provider can be used that inherits the abstract class Azure.Core.TokenCredential. Yes, if you want to use Identity
BatchSize The maximum number of messages processed in parallel. 16 No
MaxDequeueCount Max dequeue count before moving to the poison queue. 5 No
VisibilityTimeoutInSeconds The timeout after the queue message is visible again for other services. 300 No
QueueClientOptions Provides the client configuration options for connecting to Azure Queue Storage. new QueueClientOptions { MessageEncoding = QueueMessageEncoding.Base64 } No

Listener options

Setting Description Default Required
NewBatchThreshold The threshold at which a new batch of messages will be fetched. This setting is ignored when using the singleton function. BatchSize / 2 No
MinimumPollingIntervalInMilliseconds The minimum polling interval to check the queue for new messages. 5 No
MaximumPollingIntervalInMilliseconds The maximum polling interval to check the queue for new messages. 10000 No
DeltaBackOff The delta used to randomize the polling interval. MinimumPollingInterval No

Authentication

SAS

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

"WebHost": {
    "ConnectionString": "UseDevelopmentStorage=true",
    ...
  }
    services.AddAzureQueueStorageServices<TestFunction>()
    // .RunAsListener(options =>
    // .RunAsJob(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 singleton function.

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

    services.AddAzureQueueStorageServices<TestFunction>()
    // .RunAsListener(options =>
    // .RunAsJob(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 singleton function, 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 });
        }
    }

Singleton

A singleton can be applied 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 always leased for 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

To run the host as singleton, call the .AsSingleton() in the DI container:

services.AddAzureQueueStorageServices<TestFunction>()
    .RunAsJob()
    .AsSingleton(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!

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 function. Only a single message containing 500 will be executed at an given time.

Singleton Options

You can specify the following singleton options via the singleton function .AsSingleton(opt => {}) or via the appsettings.json using the Dequeueable:Singleton section:

{
  "Dequeueable": {
    "Singleton": {
      "Scope": "id"
    }
  }
}
Setting Description Default Required
LeaseDurationInSeconds The duration of the Blob lease, in seconds. 60 No
MinimumIntervalInSeconds The minimum polling interval to check if a new lease can be acquired. 10 No
MaximumIntervalInSeconds The maximum polling interval to check if a new lease can be acquired. 120 No
MaxRetries The max retries to acquire a lease. 3 No
ContainerName The container name for the lock files. webjobshost No
BlobUriFormat The uri format to the blob storage. Used for identity flow. Use {accountName}, {containerName} and {blobName} for variable substitution. "https://{accountName}.blob.core.windows.net/{containerName}/{blobName}" No

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 Get(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