Getting started with Amazon MQ
This article will give a brief explanation of Amazon MQ.
Amazon offers Amazon MQ, which is an implementation of ActiveMQ, integrated into its AWS cloud services. AmazonMQ is also called Amazon ActiveMQ.
Let’s get started.
What is a message queue?
A queue is a collection of entities that are maintained in a sequence and can be modified by the addition of entities at one end of the sequence and the removal of entities from the other end of the sequence. A message queue is a queue of messages sent between applications.
A message is the data transported between the sender and the receiver application.
In a message queue, there are client applications called producers that create messages and deliver them to the message queue. And there are applications called consumers, which gets messages from the queue to be processed. Messages placed into the queue are stored until the consumer retrieves them.
What are the benefits of message queuing systems?
- They provide communication between clients.
- Message queues remove dependencies between components and significantly simplify the coding of decoupled applications.
- Can be used to order transactions.
- Helps to ensure that each transaction occurs only once.
- They provide high scalability and elasticity.
- Can be very handy for application monitoring.
What is ActiveMQ?
ActiveMQ (Active Message Queuing) is a message queue service. It is an open-source, multi-protocol Java-based messaging server (JMS). It supports many languages like C, C++, Python, .Net. ActiveMQ offers the power and flexibility to support any messaging use-case.
Some common use cases are:
- Multi-platform applications can be integrated into ActiveMQ with AMQP (Advanced Message Queuing Protocol).
- Establish communication between your web applications using STOMP (Streaming Text Oriented Messaging Protocol) over web sockets.
- Manage your IoT devices using MQTT (Message Queuing Telemetry Transport).
ActiveMQ transmits messages from sender to receiver. It can connect multiple clients and servers and allows messages to be held in a queue, instead of requiring both the client and server to be available simultaneously in order to communicate. Messaging can still happen even if one application is temporarily unavailable.
ActiveMQ sends messages between producers, which create messages and submit them for delivery, and consumers, which receive and process messages. The ActiveMQ Broker routes each message through one of two types of destinations:
- A queue, where it awaits delivery to a single consumer (point-to-point).
- A topic, to be delivered to multiple consumers that are subscribed to that topic (publish/subscribe, or “pub/sub”).
ActiveMQ gives you the flexibility to send messages through both queues and topics using a single Broker. In point-to-point messaging, the Broker acts as a load balancer by routing each message from the queue to one of the available consumers in a round-robin pattern. When you use pub/sub messaging, the Broker delivers each message to every consumer that is subscribed to the topic.
Before we create our first Broker let’s go through some basic terms of queuing.
a. Failover String
If a JMS Broker goes down, ActiveMQ can automatically reconnect to an available JMS Broker using the
failover: protocol. Not only does this automatically recovers connection, but it will also keep all temporary destinations, sessions, producers, and most importantly consumers' information.
e.g. connecting to the URL
b. Enqueue and Dequeue
Enqueue operation is to add/send an item to the queue. Dequeue operation is to delete/pop an item from the queue.
The acknowledge method determines how messages received by the application will be acknowledged.
There are three acknowledgment modes in JMS. These are AUTO_ACKNOWLEDGE, CLIENT_ACKNOWLEDGE, and DUPS_OK_ACKNOWLEDGE.
- AUTO_ACKNOWLEDGE: The session automatically acknowledges each message received by the application.
- CLIENT_ACKNOWLEDGE: The application acknowledges the messages it receives by calling the Acknowledge method of the Message class.
- DUPS_OK_ACKNOWLEDGE: The session acknowledges the messages at times determined by the application.
ActiveMQ also has Transactional and IndividualAcknowledge modes.
Create a Broker on Amazon
The broker is a message broker environment running on Amazon MQ. AMQP, MQTT, MQTT over WebSocket, OpenWire, STOMP, STOMP over WebSocket protocols are officially supported on Broker.
Follow these steps to create a Broker:
- Sign-in to Aws.
- Select ‘Amazon MQ’ under the ‘Services’ section.
- Click the ‘Create Broker’ button at the top right of the page.
- After you create a Broker, you will see the Amazon MQ page.
- Go to details.
- Note down your failover string, username and password. We will use them for our .Net Core application.
More information about the Broker
Before we create an application that uses ActiveMQ, let’s learn about our Broker.
- Go to your Broker details.
- Look at the ‘Connections’ section.
- Find the link below ‘ActiveMQ Web Console’ that redirects you to a web page. (Other links will redirect you to a Not Found page. These are our failover link in case our Broker goes down)
- You will see a webpage like below.
- Click ‘Manage ActiveMQ Broker’.
- Enter your credentials in the pop-up.
- You will see a page like below.
- You can check your Queues/Topic here.
- Click ‘Queues’.
- This page shows all active queues and details.
- Create a queue.
- Give your queue a name by clicking ‘Queue Name’.
- You have a queue now!
- ‘Number Of Pending Messages’ column shows messages waiting in the queue.
- ‘Number Of Consumers’ column shows how many consumers do use that queue.
- ‘Messages Enqueued’ column shows total enqueue count.
- ‘Messages Dequeued’ column shows total dequeue count.
- ‘Send To’ operation is used to send an item to the queue.
- ‘Purge’ operation sets all column values to zero but does not delete your queue.
- ‘Delete’ deletes your queue.
- Click ‘Send To’.
- You will see a page like below.
- Enter a message to ‘Message body’ and click send.
- ‘Number Of Pending Messages’ count and ‘Messages Enqueued’ are set to one now.
- You can also try out Purge and Delete operations.
- Topic operations are similar to Queue operations.
How to use ActiveMQ with .Net Core?
- Create a .Net Core Console Application.
- Firstly, Install Apache.NMS.ActiveMQ.NetCore package from NuGet.
- Let’s do an enqueue operation.
- BrokerUri is your failover string. Username and Passwords are your Broker credentials.
- To make an enqueue operation, create a connection, set your credentials, start your connection, create a session, create a destination with a queueDestination (Queue Name), create a producer that you can enqueue items with, and sent an item to your queue.
- After the enqueue operation you can check your Broker.
- Let’s dequeue from our queue.
- Dequeue operation is similar to the enqueue operation. To make a dequeue operation, create a connection, set your credentials, start your connection, create a session, create a destination with a queueDestination (Queue Name), create a consumer that can dequeue items from the queue and receive the message.
- After the dequeue operation, you can check your Broker.
- Now let’s get the pending message count. Firstly enqueue three items to the queue. Then run the GetPendingMessageCount method.
- With this method, you can connect to your queue and get the count of queued items without doing any enqueue operation.
- So, how to get your pending messages without doing enqueue from the queue?
- This method is similar to the GetPendingMessageCount method.
- How to delete your destination (queue)?
- To perform the delete destination operation you have to declare IQueue object.
- When you can check your Broker, you will see that your queue is gone.
- If you need your queue back just do any queue operation (given the same queueDestination as before) and your Broker will recreate a queue automatically in the background.
- Now check out topic operations. How to enqueue a topic?
- This method is similar to the EnqueueToQueue method. But this time your destination is specified as a topic.
- How to dequeue from a topic?
- This method is similar to the DequeueToQueue method. But this time your destination is specified as a topic.
- If you check out my example project and run it, you will see the following output.
About most popular top three Message Queuing Systems
- Amazon SQS
- Amazon SNS
- IBM MQ
- Azure Service Bus
- Apache NiFi
We learned about Message Queuing Systems and gain basic knowledge of how a queue is processing. We learned about the benefits of using a Message Queue, the most popular ones, and alternatives. We checked out Amazon MQ (Apache ActiveMQ). Also, we did a quick tutorial on how to use ActiveMQ in .Net Core and how to create/use a Broker.