Tutorial: AWS Certified Developer - Associate (DVA-C02)

Messaging services (for example, Amazon Simple Queue Service [Amazon SQS], Amazon Simple Notification Service [Amazon SNS])

Concepts

Messaging services are an integral part of distributed systems and cloud architecture, allowing components of a system to communicate reliably and effectively. Amazon Web Services (AWS) offers various messaging services tailored for different use cases, including Amazon Simple Queue Service (Amazon SQS) and Amazon Simple Notification Service (Amazon SNS). Understanding these services is crucial for candidates preparing for the AWS Certified Developer – Associate exam.

Amazon Simple Queue Service (Amazon SQS)

Amazon SQS is a fully managed message queuing service that enables you to decouple and scale microservices, distributed systems, and serverless applications. With SQS, you can send, store, and receive messages between software components without losing messages or requiring other services to be available.

SQS offers two types of message queues:

Standard Queues: These offer maximum throughput, best-effort ordering, and at-least-once delivery.
FIFO Queues: These queues ensure messages are processed exactly once, in the exact order that they are sent.

Key features of Amazon SQS include:

Unlimited Throughput: SQS allows an unlimited number of messages in a queue, with no limit to how many transactions per second you can do.
Durability: Messages are stored redundantly across multiple servers and data centers.
Scalability: Automatically scales to handle the load without user intervention.

Visibility Timeout: Controls the period a message is invisible to other queue consumers after a retrieve request.

Amazon Simple Notification Service (Amazon SNS)

Amazon SNS is a fully managed pub/sub messaging service that provides message delivery from publishers to subscribers (also known as producers and consumers). SNS enables you to set up, operate, and send notifications that are delivered to a large number of subscribers.

There are different types of SNS topics you can create:

Standard Topics: These are capable of delivering messages to many subscribers, including Amazon SQS queues, AWS Lambda functions, and HTTP/S webhooks.
FIFO Topics: These ensure messages are sent and received in a strict sequence and are delivered exactly once.

Key features of Amazon SNS include:

Durability: SNS features durable storage of messages traveling through the service.
Scalability: Can handle a large number of recipients for each message.
Fan-out Pattern: Sends messages to all interested subscribers efficiently.

Message Filtering: Subscribers can filter messages based on message attributes.

Comparison Between Amazon SQS and SNS

Feature	Amazon SQS	Amazon SNS
Type	Message Queue Service	Publish/Subscribe Messaging Service
Message Delivery	At least once	At least once; exactly once with FIFO
Ordering	Standard (best-effort); FIFO (strict ordering)	No strict ordering; FIFO (strict ordering for FIFO topics)
Subscriber Types	Consuming services/polls for messages	Push-based to multiple subscribers
Use Case	Decoupling components, work-off queues	Fan-out messaging to multiple endpoints

Overview and Examples

Using Amazon SQS:

A typical use case for SQS includes task queues, where each message corresponds to a task that a worker node might process.

import boto3

# Create SQS client
sqs = boto3.client(‘sqs’)

# Create a new SQS queue
queue = sqs.create_queue(QueueName=’MyQueue’)

# Send a message to the SQS queue
response = sqs.send_message(
QueueUrl=queue[‘QueueUrl’],
MessageBody=’Hello from SQS!’
)

print(response[‘MessageId’])

Using Amazon SNS:

Amazon SNS can be utilized for scenarios such as triggering an email or SMS notification when a certain event occurs in your application.

import boto3

# Create SNS client
sns = boto3.client(‘sns’)

# Create a topic
response = sns.create_topic(Name=’MyTopic’)

# Publish a message to the topic
response = sns.publish(
TopicArn=response[‘TopicArn’],
Message=’Hello from SNS!’,
Subject=’My SNS message’
)

print(response[‘MessageId’])

Overall, both Amazon SQS and SNS are valuable for developing resilient, scalable applications, and understanding how to implement them is critical for the AWS Certified Developer – Associate exam. By ensuring message durability, scalability, and proper decoupling, these services enable applications to react to changes, workloads, and system failures gracefully. When preparing for the exam, be sure to focus on the differences between the services and the optimal scenarios for using each.

Answer the Questions in Comment Section

1) True or False: Amazon SQS allows for message ordering, ensuring that messages are delivered and processed in the order they are sent.

1) True

2) False

Answer: False

Explanation: Standard queues in Amazon SQS do not guarantee message ordering; however, FIFO (First-In-First-Out) queues do ensure messages are delivered and processed in the exact order they are sent.

2) Which Amazon service is best suited for fan-out messaging patterns?

1) Amazon SWF
2) Amazon SNS
3) Amazon SQS

4) Amazon SES

Answer: Amazon SNS

Explanation: Amazon Simple Notification Service (SNS) is ideal for fan-out messaging patterns because it can distribute messages to multiple subscribers, including Amazon SQS queues, AWS Lambda functions, and HTTP/S endpoints.

3) What type of message filtering is available with Amazon SNS?

1) SQL-based filtering
2) Attribute-based filtering
3) No filtering; all messages are delivered to all subscribers

4) Content-based filtering

Answer: Attribute-based filtering

Explanation: Amazon SNS allows for attribute-based message filtering, which enables subscribers to receive only the messages of interest, based on the attributes attached to the messages.

4) True or False: In Amazon SQS, a message is deleted from the queue as soon as it is read by a consumer.

1) True
2) False

Answer: False

Explanation: In Amazon SQS, a message is not automatically deleted upon retrieval; it is the responsibility of the consuming service to delete the message from the queue after processing, typically by using the message’s receipt handle.

5) Which service would you use to trigger an AWS Lambda function in response to new messages added in a queue?

1) Amazon SES
2) Amazon S3

3) Amazon SNS
4) Amazon SQS

Answer: Amazon SQS

Explanation: Amazon SQS is often used to trigger AWS Lambda functions when new messages are available for processing in a queue.

6) True or False: Amazon SNS supports message delivery status tracking for all its supported protocols.

1) True
2) False

Answer: False

Explanation: Amazon SNS supports message delivery status tracking for SMS, email, and HTTP/S endpoints, but not for every supported protocol, such as SQS and application endpoints.

7) Which of the following is not a feature of Amazon SQS?

1) At-least-once delivery

2) Exactly-once processing
3) Unlimited throughput
4) Short and long polling

Answer: Exactly-once processing

Explanation: Amazon SQS supports at-least-once delivery, but does not inherently guarantee exactly-once processing; additional application-level logic is required to achieve exactly-once processing.

8) Amazon SNS and SQS both support which of the following types of communication?

1) Point-to-point

2) Publish/subscribe
3) Request/response
4) All of the above

Answer: Publish/subscribe

Explanation: Both Amazon SNS and SQS support the publish/subscribe messaging paradigm, where publishers send messages to a topic or queue without knowing about the subscribers.

9) True or False: Amazon SQS messages can contain up to 2 GB of text data.

1) True

2) False

Answer: False

Explanation: Amazon SQS messages can contain up to 256 KB of text data in any format (not 2 GB). If you need to store more data, you can use Amazon S3 in conjunction with SQS.

10) Which feature of Amazon SNS allows you to group multiple recipients who subscribe to a topic?

1) SQS queues
2) SNS topics
3) SNS platform applications

4) SNS email subscriptions

Answer: SNS topics

Explanation: SNS topics allow you to group multiple recipients together, to which any publisher can publish messages, and all subscribers to the topic will receive the messages.

11) True or False: Amazon SQS automatically scales to handle a high number of messages per second.

1) True
2) False

Answer: True

Explanation: Amazon SQS is a fully managed service that automatically scales to handle a high number of messages per second, which allows you to scale your applications as needed without managing the underlying infrastructure.

12) In Amazon SNS, what is the role of a publisher?

1) To receive notifications from a topic
2) To process messages from a queue

3) To send messages to a topic
4) To store messages for delayed processing

Answer: To send messages to a topic

Explanation: In Amazon SNS, a publisher sends messages to a topic. Subscribers who are subscribed to the topic then receive those messages through the protocol they have configured (e.g., email, HTTP, Lambda, SQS).