Azure supports two types of queue mechanisms: Service Bus queues and Storage queues.

Consider using Service Bus queues when:

• Receive messages without having to poll the queue ( long-polling receive operation using the TCP-based protocols)
• Guaranteed first-in-first-out (FIFO) ordered delivery (Message Session )
• Automatic duplicate detection
• Parallel long-running streams -
• Messages that can exceed 64 KB but won't likely approach the 256-KB limit.

Consider using Storage queues when:

• store over 80 gigabytes of messages in a queue.
• track progress for processing a message in the queue
• server side logs of all of the transactions

Advanced features

Service Bus

Service Bus tiers

Key Concepts

Queues

First In, First Out (FIFO) message delivery to one or more competing consumers.

A related benefit is load-leveling, which enables producers and consumers to send and receive messages at different rates.

Receive modes

• Receive and delete (marks the message as being consumed and returns it to the consumer application)
• Peek lock (two-stage)
  • Finds the next message to be consumed, locks it to prevent other consumers from receiving it, and then, return the message to the application.
  • After the application finishes processing the message, it requests the Service Bus service to complete the second stage of the receive process. Then, the service marks the message as being consumed. otherwise (abandon / unlock)

Topics and subscriptions

topics and subscriptions provide a one-to-many form of communication in a publish and subscribe pattern

consumers don't receive messages directly from the topic. Instead,consumers receive messages from subscriptions of the topic

Rules and actions

While Service Bus subscriptions see all messages sent to the topic, you can only copy a subset of those messages to the virtual subscription queue

Topic filters and actions

All rules without actions are combined using an OR condition and result in a single message on the subscription even if you have multiple matching rules.

Each rule with an action produces a copy of the message. This message will have a property called RuleName where the value is the name of the matching rule.

Filters: Service Bus supports three filter conditions:

• SQL Filters: SQL-like conditional expression that is evaluated in the broker against the arriving messages' user-defined properties and system properties. All system properties must be prefixed with sys.

• Boolean filters - The TrueFilter and FalseFilter either cause all arriving messages (true) or none of the arriving messages (false) to be selected for the subscription. These two filters derive from the SQL filter.

• Correlation Filters: holds a set of conditions that are matched against one or more of an arriving message's user and system properties.

Actions: With SQL filter conditions, you can define an action that can annotate the message by adding, removing, or replacing properties and their values.

Service Bus message payloads and serialization

payload and metadata. The metadata is in the form of key-value pair properties, and describes the payload

The broker properties are predefined by the system. user properties are a collection of key-value pairs

Message routing and correlation

patterns:

• Simple request/reply: A publisher sends a message into a queue and expects a reply from the message consumer. To receive the reply, the publisher owns a queue into which it expects replies to be delivered. The address of that queue is expressed in the ReplyTo property of the outbound message. When the consumer responds, it copies the MessageId of the handled message into the CorrelationId property of the reply message and delivers the message to the destination indicated by the ReplyTo property. One message can yield multiple replies, depending on the application context.

• Multicast request/reply: a publisher sends the message into a topic and multiple subscribers become eligible to consume the message. This pattern is used in discovery or roll-call scenarios. If ReplyTo points to a topic can be distributed to an audience.

• Multiplexing This session feature enables multiplexing of streams of related messages through a single queue or subscription such that each session (or group) of related messages, identified by matching SessionId values, is routed to a specific receiver while the receiver holds the session under lock.

• Multiplexed request/reply: This session feature enables multiplexed replies, allowing several publishers to share a reply queue. By setting ReplyToSessionId, the publisher can instruct the consumer(s) to copy that value into the SessionId property of the reply message. The publishing queue or topic does not need to be session-aware. As the message is sent, the publisher can then specifically wait for a session with the given SessionId to materialize on the queue by conditionally accepting a session receiver.

Payload serialization

ContentType property

In Action

Create a Service Bus messaging namespace

az servicebus namespace create \
    --resource-group az204-svcbus-rg \
    --name $myNameSpaceName \
    --location $myLocation

Create a service bus queue

az servicebus queue create --resource-group az204-svcbus-rg \
    --namespace-name $myNameSpaceName \
    --name az204-queue

Send a message (C#)

client = new ServiceBusClient(connectionString);
sender = client.CreateSender(queueName);

// create a batch  using ServiceBusMessageBatch messageBatch = await sender.CreateMessageBatchAsync();

// try adding a message to the batch
messageBatch.TryAddMessage(new ServiceBusMessage($"Message {i}")));

await sender.SendMessagesAsync(messageBatch);

Receive a message

// Create the client object that will be used to create sender and receiver objects client = new ServiceBusClient(connectionString);

// create a processor that we can use to process the messages
processor = client.CreateProcessor(queueName, new ServiceBusProcessorOptions());

// add handler to process messages
processor.ProcessMessageAsync += MessageHandler;

// add handler to process any errors
processor.ProcessErrorAsync += ErrorHandler;

// start processing
await processor.StartProcessingAsync();

Azure Queue Storage

storing large numbers of messages

components:

• URL format
• Storage account
• Queue
• Message (up to 64 KB / TTL a positive number or -1 )

Create a queue

// Instantiate a QueueClient which will be used to create and manipulate the queue
QueueClient queueClient = new QueueClient(connectionString, queueName);

// Create the queue
queueClient.CreateIfNotExists();

// Send a message to the queue
queueClient.SendMessage(message);

// Peek at the next message
PeekedMessage[] peekedMessage = queueClient.PeekMessages();

// Update the message contents
    queueClient.UpdateMessage(message[0].MessageId,
            message[0].PopReceipt,
            "Updated contents",
            TimeSpan.FromSeconds(60.0)  // Make it invisible for another 60 seconds
        );

De-queue the next message

// Instantiate a QueueClient which will be used to manipulate the queue
QueueClient queueClient = new QueueClient(connectionString, queueName);

if (queueClient.Exists())
{
    // Get the next message
    QueueMessage[] retrievedMessage = queueClient.ReceiveMessages();

    // Process (i.e. print) the message in less than 30 seconds
    Console.WriteLine($"Dequeued message: '{retrievedMessage[0].Body}'");

    // Delete the message
    queueClient.DeleteMessage(retrievedMessage[0].MessageId, retrievedMessage[0].PopReceipt);
}