What is Azure Service Bus?

What is Azure Service Bus?

• Microsoft Azure Service Buss is a fully managed enterprise integration message broker.
• Commonly used to decople applications and services from each other and is reliable  and secure platform for asynchronous data and state transfer.
• Data is transferred between different applications and services using messages. A message is in binary format, which can contain JSON, XML, or just text.

Some common messaging scenarios are:

Messaging: transfer business data, such as sales or purchase orders, journals, or inventory movements.

Decouple applications: improve reliability and scalability of applications and services (client and service do not have to be online at the same time).

Topics and subscriptions: enable 1:n relationships between publishers and subscribers.

Message sessions: implement workflows that require message ordering or message deferral.

Namespaces: 

• It is a scoping container for all messaging components. 
• Multiple queues and topics can reside within a single namespace, and namespaces often serve as application containers.

Queues:

• Messages are sent to and received from queues. 
• Queues enable you to store messages until the receiving application is available to receive and process them.
• Messages in queues are ordered and timestamped on arrival. 
• Once accepted, the message is held safely in redundant storage. 
• Messages are delivered in pull mode, which delivers messages on request.

Topics:

• While a queue is often used for point-to-point communication, topics are useful in publish/subscribe scenarios.
• Topics can have multiple, independent subscriptions. 
• A subscriber to a topic can receive a copy of each message sent to that topic. 
• Subscriptions are named entities, which are durably created but can optionally expire or auto-delete.
• In some scenarios, you may not want individual subscriptions to receive all messages sent to a topic. If so, you can use rules and filters to define conditions that trigger optional actions, filter specified messages, and set or modify message properties.

Service Bus in Action:

This tutorial covers the following steps:

1. Create a Service Bus namespace, using the Azure portal.

2. Create a Service Bus queue, using the Azure portal.

3. Write a .NET Core console application to send a set of messages to the queue.

4. Write a .NET Core console application to receive those messages from the queue.

Pre-requisites:

1. Visual Studio 2017 Update 3 (version 15.3, 26730.01) or later.

2. NET Core SDK, version 2.0 or later.

3. An Azure subscription.

1. Create a namespace using the Azure portal:

To begin using Service Bus messaging entities in Azure, you must first create a namespace with a name that is unique across Azure. A namespace provides a scoping container for addressing Service Bus resources within your application.

To create a namespace:

1. Sign in to the Azure portal.

2. In the left navigation pane of the portal, click + Create a resource, then click Integration, and then click Service Bus.

3. In the Create namespace dialog, enter a namespace name. The system immediately checks to see if the name is available.

4. After making sure the namespace name is available, choose the pricing tier (Basic, Standard, or Premium). If you want to use topics and subscriptions, make sure to choose either Standard or Premium. Topics/subscriptions are not supported in the Basic pricing tier.

5. In the Subscription field, choose an Azure subscription in which to create the namespace.

6. In the Resource group field, choose an existing resource group in which the namespace will live, or create a new one.

7. In Location, choose the country or region in which your namespace should be hosted.

8. Click Create. The system now creates your namespace and enables it. You might have to wait several minutes as the system provisions resources for your account.

2. Obtain the management credentials

Creating a new namespace automatically generates an initial Shared Access Signature (SAS) rule with an associated pair of primary and secondary keys that each grant full control over all aspects of the namespace. See Service Bus authentication and authorization for information about how to create further rules with more constrained rights for regular senders and receivers. To copy the initial rule, follow these steps:

1. Click All resources, then click the newly created namespace name.

2. In the namespace window, click Shared access policies.

3. In the Shared access policies screen, click RootManageSharedAccessKey.

4. In the Policy: RootManageSharedAccessKey window, click the copy button next to Primary Connection String, to copy the connection string to your clipboard for later use. Paste this value into Notepad or some other temporary location.

Repeat the previous step, copying and pasting the value of Primary key to a temporary location for later use.

3. Create a queue using the Azure portal

1. Sign in to the Azure portal.

2. In the left navigation pane of the portal, click Service Bus (if you don't see Service Bus, click All services).

3. Click the namespace in which you would like to create the queue. In this case, it is myNarayanSBNS.

4. In the namespace window, click Queues, then in the Queues window, click + Queue.

5. Enter the queue Name and leave the other values with their defaults.

6. At the bottom of the window, click Create.

4. Send messages to the queue

To send messages to the queue, write a C# console application using Visual Studio.

Github Source Code:
https://github.com/shyamnarayan2001/DotNet_Projects/tree/master/AzureServiceBus/CoreAzureServiceBusSender

a) Create a console application

Launch Visual Studio and create a new Console App (.NET Core) project.

b) Add the Service Bus NuGet package

1.  Right-click the newly created project and select Manage NuGet Packages.

2. Click the Browse tab, search for Microsoft.Azure.ServiceBus, and then select the Microsoft.Azure.ServiceBus item. Click Install to complete the installation, then close this dialog box.

c) Write code to send messages to the queue

1. In Program.cs, add the following using statements at the top of the namespace definition, before the class declaration:

using System.Text;

using System.Threading;

using System.Threading.Tasks;

using Microsoft.Azure.ServiceBus;

2. Within the Program class, declare the following variables. Set the ServiceBusConnectionString variable to the connection string that you obtained when creating the namespace, and set QueueName to the name that you used when creating the queue: 

const string ServiceBusConnectionString = "<your_connection_string>";

const string QueueName = "<your_queue_name>";

static IQueueClient queueClient;

3. Replace the default contents of Main() with the following line of code:

MainAsync().GetAwaiter().GetResult();

4. Directly after Main(), add the following asynchronous MainAsync() method that calls the send messages method:

static async Task MainAsync()

{

const int numberOfMessages = 10;

queueClient = new QueueClient(ServiceBusConnectionString, QueueName);

Console.WriteLine("======================================================");

Console.WriteLine("Press ENTER key to exit after sending all the messages.");

Console.WriteLine("======================================================");

// Send messages.

await SendMessagesAsync(numberOfMessages);

Console.ReadKey();

await queueClient.CloseAsync();

}

5. Directly after the MainAsync() method, add the following SendMessagesAsync() method that performs the work of sending the number of messages specified by numberOfMessagesToSend (currently set to 10):

static async Task SendMessagesAsync(int numberOfMessagesToSend) { try { for (var i = 0; i < numberOfMessagesToSend; i++) { // Create a new message to send to the queue. string messageBody = $"Message {i}"; var message = new Message(Encoding.UTF8.GetBytes(messageBody)); // Write the body of the message to the console. Console.WriteLine($"Sending message: {messageBody}"); // Send the message to the queue. await queueClient.SendAsync(message); } } catch (Exception exception) { Console.WriteLine($"{DateTime.Now} :: Exception: {exception.Message}"); } }

6. Here is what your Program.cs file should look like.

namespace CoreSenderApp { using System; using System.Text; using System.Threading; using System.Threading.Tasks; using Microsoft.Azure.ServiceBus; class Program { // Connection String for the namespace can be obtained from the Azure portal under the // 'Shared Access policies' section. const string ServiceBusConnectionString = "<your_connection_string>"; const string QueueName = "<your_queue_name>"; static IQueueClient queueClient; static void Main(string[] args) { MainAsync().GetAwaiter().GetResult(); } static async Task MainAsync() { const int numberOfMessages = 10; queueClient = new QueueClient(ServiceBusConnectionString, QueueName); Console.WriteLine("======================================================"); Console.WriteLine("Press ENTER key to exit after sending all the messages."); Console.WriteLine("======================================================"); // Send Messages await SendMessagesAsync(numberOfMessages); Console.ReadKey(); await queueClient.CloseAsync(); } static async Task SendMessagesAsync(int numberOfMessagesToSend) { try { for (var i = 0; i < numberOfMessagesToSend; i++) { // Create a new message to send to the queue string messageBody = $"Message {i}"; var message = new Message(Encoding.UTF8.GetBytes(messageBody)); // Write the body of the message to the console Console.WriteLine($"Sending message: {messageBody}"); // Send the message to the queue await queueClient.SendAsync(message); } } catch (Exception exception) { Console.WriteLine($"{DateTime.Now} :: Exception: {exception.Message}"); } } } }

7. Run the program, and check the Azure portal: click the name of your queue in the namespace Overview window. The queue Essentials screen is displayed. Notice that the Active Message Count value for the queue is now 10. Each time you run the sender application without retrieving the messages (as described in the next section), this value increases by 10. Also note that the current size of the queue increments the Current value in the Essentials window each time the app adds messages to the queue.

5. Receive messages from the queue

Github Source Code:
https://github.com/shyamnarayan2001/DotNet_Projects/tree/master/AzureServiceBus/CoreAzureServiceBusReceiver

To receive the messages you just sent, create another .NET Core console application and install the Microsoft.Azure.ServiceBus NuGet package, similar to the previous sender application.

a) Write code to receive messages from the queue

1. In Program.cs, add the following using statements at the top of the namespace definition, before the class declaration:

using System.Text;

using System.Threading;

using System.Threading.Tasks;

using Microsoft.Azure.ServiceBus;

2. Within the Program class, declare the following variables. Set the ServiceBusConnectionString variable to the connection string that you obtained when creating the namespace, and set QueueName to the name that you used when creating the queue:

const string ServiceBusConnectionString = "<your_connection_string>";

const string QueueName = "<your_queue_name>";

static IQueueClient queueClient;

3. Replace the default contents of Main() with the following line of code:

MainAsync().GetAwaiter().GetResult();

4. Directly after Main(), add the following asynchronous MainAsync() method that calls the RegisterOnMessageHandlerAndReceiveMessages() method:

static async Task MainAsync()

{

queueClient = new QueueClient(ServiceBusConnectionString, QueueName);

Console.WriteLine("======================================================");

Console.WriteLine("Press ENTER key to exit after receiving all the messages.");

Console.WriteLine("======================================================");

// Register the queue message handler and receive messages in a loop

RegisterOnMessageHandlerAndReceiveMessages();

Console.ReadKey();

await queueClient.CloseAsync();

}

5. Directly after the MainAsync() method, add the following method that registers the message handler and receives the messages sent by the sender application:

static void RegisterOnMessageHandlerAndReceiveMessages() {

// Configure the message handler options in terms of exception handling,

// number of concurrent messages to deliver, etc.

var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler)

{

// Maximum number of concurrent calls to the callback ProcessMessagesAsync(),

//set to 1 for simplicity.

// Set it according to how many messages the application wants to process in parallel.

MaxConcurrentCalls = 1,

// Indicates whether the message pump should automatically complete the messages

// after returning from user callback.

// False below indicates the complete operation is handled by the user

// callback as in ProcessMessagesAsync().

AutoComplete = false

};

// Register the function that processes messages.

queueClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions);

}

6. Directly after the previous method, add the following ProcessMessagesAsync() method to process the received messages:

static async Task ProcessMessagesAsync(Message message, CancellationToken token) { // Process the message. Console.WriteLine($"Received message: SequenceNumber:{message.SystemProperties.SequenceNumber} Body:{Encoding.UTF8.GetString(message.Body)}"); // Complete the message so that it is not received again. // This can be done only if the queue Client is created in ReceiveMode.PeekLock mode (which is the default). await queueClient.CompleteAsync(message.SystemProperties.LockToken); // Note: Use the cancellationToken passed as necessary to determine if the queueClient has already been closed. // If queueClient has already been closed, you can choose to not call CompleteAsync() or AbandonAsync() etc. // to avoid unnecessary exceptions. }

7. Finally, add the following method to handle any exceptions that might occur:

// Use this handler to examine the exceptions received on the message pump. static Task ExceptionReceivedHandler(ExceptionReceivedEventArgs exceptionReceivedEventArgs) { Console.WriteLine($"Message handler encountered an exception {exceptionReceivedEventArgs.Exception}."); var context = exceptionReceivedEventArgs.ExceptionReceivedContext; Console.WriteLine("Exception context for troubleshooting:"); Console.WriteLine($"- Endpoint: {context.Endpoint}"); Console.WriteLine($"- Entity Path: {context.EntityPath}"); Console.WriteLine($"- Executing Action: {context.Action}"); return Task.CompletedTask; }

8. Here is what your Program.cs file should look like:

namespace CoreReceiverApp { using System; using System.Text; using System.Threading; using System.Threading.Tasks; using Microsoft.Azure.ServiceBus; class Program { // Connection String for the namespace can be obtained from the Azure portal under the // 'Shared Access policies' section. const string ServiceBusConnectionString = "<your_connection_string>"; const string QueueName = "<your_queue_name>"; static IQueueClient queueClient; static void Main(string[] args) { MainAsync().GetAwaiter().GetResult(); } static async Task MainAsync() { queueClient = new QueueClient(ServiceBusConnectionString, QueueName); Console.WriteLine("======================================================"); Console.WriteLine("Press ENTER key to exit after receiving all the messages."); Console.WriteLine("======================================================"); // Register QueueClient's MessageHandler and receive messages in a loop RegisterOnMessageHandlerAndReceiveMessages(); Console.ReadKey(); await queueClient.CloseAsync(); } static void RegisterOnMessageHandlerAndReceiveMessages() { // Configure the MessageHandler Options in terms of exception handling, number of concurrent messages to deliver etc. var messageHandlerOptions = new MessageHandlerOptions(ExceptionReceivedHandler) { // Maximum number of Concurrent calls to the callback `ProcessMessagesAsync`, set to 1 for simplicity. // Set it according to how many messages the application wants to process in parallel. MaxConcurrentCalls = 1, // Indicates whether MessagePump should automatically complete the messages after returning from User Callback. // False below indicates the Complete will be handled by the User Callback as in `ProcessMessagesAsync` below. AutoComplete = false }; // Register the function that will process messages queueClient.RegisterMessageHandler(ProcessMessagesAsync, messageHandlerOptions); } static async Task ProcessMessagesAsync(Message message, CancellationToken token) { // Process the message Console.WriteLine($"Received message: SequenceNumber:{message.SystemProperties.SequenceNumber} Body:{Encoding.UTF8.GetString(message.Body)}"); // Complete the message so that it is not received again. // This can be done only if the queueClient is created in ReceiveMode.PeekLock mode (which is default). await queueClient.CompleteAsync(message.SystemProperties.LockToken); // Note: Use the cancellationToken passed as necessary to determine if the queueClient has already been closed. // If queueClient has already been Closed, you may chose to not call CompleteAsync() or AbandonAsync() etc. calls // to avoid unnecessary exceptions. } static Task ExceptionReceivedHandler(ExceptionReceivedEventArgs exceptionReceivedEventArgs) { Console.WriteLine($"Message handler encountered an exception {exceptionReceivedEventArgs.Exception}."); var context = exceptionReceivedEventArgs.ExceptionReceivedContext; Console.WriteLine("Exception context for troubleshooting:"); Console.WriteLine($"- Endpoint: {context.Endpoint}"); Console.WriteLine($"- Entity Path: {context.EntityPath}"); Console.WriteLine($"- Executing Action: {context.Action}"); return Task.CompletedTask; } } }

9. Run the program, and check the portal again. Notice that the Active Message Count and Current values are now 0.

Congratulations! You have now created a queue, sent a set of messages to that queue, and received those messages from the same queue.