SNS topics and subscriptions in AWS - Mini Project: Build & Apply

SNS topics and subscriptions

📖 Scenario: You are setting up a simple notification system using AWS Simple Notification Service (SNS). You want to create a topic and subscribe an email endpoint to it so that notifications can be sent to that email.

🎯 Goal: Create an SNS topic named MyTopic and subscribe an email address [e-mail] to this topic.

📋 What You'll Learn

Create an SNS topic named MyTopic

Create a subscription for the topic with protocol email

Use the endpoint [e-mail] for the subscription

💡 Why This Matters

🌍 Real World

SNS topics and subscriptions are used to send notifications to users or systems automatically when events happen, such as alerts, updates, or messages.

💼 Career

Understanding how to configure SNS topics and subscriptions is essential for cloud engineers and developers to build event-driven and notification systems in AWS.

1

Create the SNS topic

Create an SNS topic resource named MyTopic using AWS CloudFormation syntax.

AWS

# Your code here to create an SNS topic named MyTopic

Hint

Use AWS::SNS::Topic as the resource type and set TopicName to MyTopic.

2

Add the subscription configuration

Add a subscription property to the MyTopic resource with protocol email and endpoint [e-mail].

AWS

Resources:
  MyTopic:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: MyTopic
      # Add subscription property here

Hint

The Subscription property is a list of subscription objects. Add one with Protocol and Endpoint.

3

Add a topic policy to allow publishing

Add a TopicPolicy resource that allows anyone to publish messages to the MyTopic SNS topic.

AWS

Resources:
  MyTopic:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: MyTopic
      Subscription:
        - Protocol: email
          Endpoint: [e-mail]
# Add TopicPolicy resource below

Hint

Use AWS::SNS::TopicPolicy resource type and attach the policy to MyTopic.

4

Add Outputs for the topic ARN

Add an Outputs section with an output named TopicArn that exports the ARN of the MyTopic SNS topic.

AWS

Resources:
  MyTopic:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: MyTopic
      Subscription:
        - Protocol: email
          Endpoint: [e-mail]
  MyTopicPolicy:
    Type: AWS::SNS::TopicPolicy
    Properties:
      Topics:
        - !Ref MyTopic
      PolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal: '*'
            Action: 'SNS:Publish'
            Resource: !Ref MyTopic

# Add Outputs section below

Hint

Outputs section should export the topic ARN using !Ref MyTopic.

Practice

1. What is the main purpose of an SNS topic in AWS?

easy

A. To store files and documents securely

B. To act as a message hub where messages are sent and distributed

C. To run virtual servers in the cloud

D. To manage user permissions and access

Solution

1. Step 1: Understand SNS topic role

   An SNS topic is like a message board where messages are posted for others to receive.

2. Step 2: Compare options to SNS function

   Only To act as a message hub where messages are sent and distributed describes a message hub, which matches SNS topic's purpose.

3. Final Answer:

   To act as a message hub where messages are sent and distributed -> Option B

4. Quick Check:

   SNS topic = message hub [OK]

Hint: SNS topics distribute messages to subscribers [OK]

Common Mistakes:

• Confusing SNS topics with storage services
• Thinking SNS manages servers
• Mixing SNS with user access control

2. Which of the following is the correct way to subscribe an email endpoint to an SNS topic using AWS CLI?

easy

A. aws sns subscribe --subscription-arn arn:aws:sns:us-east-1:123456789012:MyTopic --protocol email --notification-endpoint [e-mail]

B. aws sns subscribe --topic-arn arn:aws:sns:us-east-1:123456789012:MyTopic --notification-endpoint [e-mail]

C. aws sns subscribe --topic-arn arn:aws:sns:us-east-1:123456789012:MyTopic --protocol email --notification-endpoint [e-mail]

D. aws sns subscribe --topic-arn arn:aws:sns:us-east-1:123456789012:MyTopic --protocol email --endpoint [e-mail]

Solution

1. Step 1: Review AWS CLI subscribe syntax

   The correct command uses 'aws sns subscribe' with '--topic-arn', '--protocol', and '--endpoint' parameters.

2. Step 2: Check option correctness

   The correct command is 'aws sns subscribe --topic-arn arn:aws:sns:us-east-1:123456789012:MyTopic --protocol email --endpoint [e-mail]'. Distractors use incorrect parameters like --notification-endpoint, miss --protocol, or use --subscription-arn.

3. Final Answer:

   aws sns subscribe --topic-arn arn:aws:sns:us-east-1:123456789012:MyTopic --protocol email --endpoint [e-mail] -> Option D

4. Quick Check:

   Correct CLI syntax = aws sns subscribe --topic-arn arn:aws:sns:us-east-1:123456789012:MyTopic --protocol email --endpoint [e-mail] [OK]

Hint: Use --protocol and --endpoint with aws sns subscribe [OK]

Common Mistakes:

• Using wrong parameter names like --notification-endpoint instead of --endpoint
• Missing the --protocol flag
• Confusing topic ARN with subscription ARN

3. Given this Python code using boto3, what will be the output if the subscription is successful?

import boto3
sns = boto3.client('sns')
response = sns.subscribe(
    TopicArn='arn:aws:sns:us-east-1:123456789012:MyTopic',
    Protocol='email',
    Endpoint='[e-mail]'
)
print(response['SubscriptionArn'])

medium

A. 'pending confirmation' string indicating subscription needs confirmation

B. An error message about missing permissions

C. The ARN of the SNS topic

D. The ARN of the new subscription if confirmed

Solution

1. Step 1: Understand SNS email subscription behavior

   Email subscriptions require the user to confirm by clicking a link. Until then, the SubscriptionArn is 'pending confirmation'.

2. Step 2: Analyze the printed output

   The code prints response['SubscriptionArn'], which will be 'pending confirmation' until user confirms.

3. Final Answer:

   'pending confirmation' string indicating subscription needs confirmation -> Option A

4. Quick Check:

   Email subscription = pending confirmation [OK]

Hint: Email subscriptions show 'pending confirmation' until user confirms [OK]

Common Mistakes:

• Expecting immediate subscription ARN without confirmation
• Confusing topic ARN with subscription ARN
• Assuming no confirmation needed for email protocol

4. You wrote this AWS CLI command to subscribe an HTTP endpoint but get an error:

aws sns subscribe --topic-arn arn:aws:sns:us-east-1:123456789012:MyTopic --protocol http --notification-endpoint http://example.com/notify

What is the most likely cause of the error?

medium

A. The HTTP endpoint URL must use HTTPS, not HTTP

B. The topic ARN is invalid

C. The protocol should be 'https' instead of 'http'

D. The notification endpoint URL is missing a trailing slash

Solution

1. Step 1: Check protocol requirements for HTTP endpoints

   AWS SNS requires HTTP endpoints to use HTTPS for security; HTTP URLs cause errors.

2. Step 2: Validate the given URL and protocol

   The URL uses 'http://' which is not allowed; it must be 'https://'.

3. Final Answer:

   The HTTP endpoint URL must use HTTPS, not HTTP -> Option A

4. Quick Check:

   HTTP endpoints require HTTPS URL [OK]

Hint: Use HTTPS URLs for HTTP/HTTPS SNS subscriptions [OK]

Common Mistakes:

• Assuming HTTP URLs are accepted
• Thinking trailing slash matters
• Confusing protocol parameter values

5. You want to send a notification to multiple endpoints: an email, an SMS number, and a Lambda function. How should you configure SNS to achieve this?

hard

A. Send messages directly to each endpoint without using SNS topics

B. Create separate SNS topics for each endpoint type and publish messages to all

C. Create one SNS topic and subscribe all three endpoints to it

D. Use only email and SMS subscriptions; Lambda cannot subscribe to SNS

Solution

1. Step 1: Understand SNS subscription flexibility

   An SNS topic can have multiple subscriptions of different protocols (email, SMS, Lambda).

2. Step 2: Choose the simplest and best practice approach

   Using one topic with multiple subscriptions is efficient and standard practice.

3. Final Answer:

   Create one SNS topic and subscribe all three endpoints to it -> Option C

4. Quick Check:

   One topic, multiple subscriptions = Create one SNS topic and subscribe all three endpoints to it [OK]

Hint: One SNS topic can have many different subscriptions [OK]

Common Mistakes:

• Thinking Lambda cannot subscribe to SNS
• Creating multiple topics unnecessarily
• Sending messages directly without SNS