Microsoft Docs

Queue Storage Concepts

Azure Queue Storage is a service that stores large numbers of small messages. This means that you can store reservations in the queue to be processed later. Each message in a queue is approximately 64 KB in size, and a queue can contain any number of messages. The total capacity of a storage account is typically 500 TB.

Key Concepts

• Queue: A named collection of messages. All queues must belong to a storage account. A queue name must be valid DNS names, consisting of lowercase letters, numbers, and hyphens.
• Message: A unit of data stored in a queue. A message can be any type of data, such as a JSON, XML, or plain text string. The maximum message size is 64 KB.
• Queue Service: The REST API for Queue Storage, which allows clients to interact with queues and messages.
• Storage Account: A top-level container for all Azure Storage data objects, including queues, tables, blobs, and files.

Message Lifecycle

Messages in a queue follow a specific lifecycle:

1. Added: A client adds a message to the queue.
2. Dequeued: A client retrieves a message from the queue. When a message is dequeued, it is made invisible to other clients for a specified period (visibility timeout).
3. Processed: The client that dequeued the message performs the necessary operations on it.
4. Deleted: After the message is successfully processed, the client explicitly deletes it from the queue. If the message is not deleted within the visibility timeout, it becomes visible again and can be dequeued by another client.

Operations

The Queue Storage service supports several operations:

• Enqueue Message: Adds a message to the queue.
• Dequeue Message: Retrieves and makes invisible the next message in the queue.
• Peek Message: Retrieves the next message in the queue without making it invisible.
• Clear Messages: Removes all messages from the queue.
• Delete Message: Deletes a specific message from the queue.
• Get Queue Metadata: Retrieves metadata about a queue, such as its approximate message count.
• Set Queue Metadata: Sets custom metadata for a queue.
• Delete Queue: Deletes a queue and all of its messages.

Use Cases

Queue Storage is ideal for decoupling application components and asynchronous task processing. Common use cases include:

• Distributing workloads across multiple workers.

  
  // Example of enqueuing a message
  string message = "{\"id\": \"12345\", \"task\": \"process_image\"}";
  queueClient.SendMessage(message);
                      

• Asynchronous operations, such as image processing or long-running business logic.
• Building resilient and scalable applications.

For more detailed information, refer to the official Azure Queue Storage Documentation.