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SNS AWS Boto3: A Guide

SNS is short for Amazon Simple Notification Service. It is a fully managed messaging service that facilitates communication between distributed systems, microservices, and serverless applications.

With Boto3, we can easily interact with SNS using Python to create topics, manage subscriptions, and publish messages. Today we are going to take a quick look at the key operations, features, and examples of using SNS with Boto3.

An Overview:

• Key Features of SNS
• Getting Started with AWS SNS and Boto3
• 1. Create an SNS Topic
• 2. Subscribe to a Topic
• 3. Publish Messages to a Topic
• 4. Publish Messages with Attributes
• 5. Message Filtering with SNS
• 6. Delete an SNS Topic
• 7. List Topics and Subscriptions
• 8. Unsubscribe from a Topic
• 9. Integrate SNS with Other AWS Services
• Best Practices for Using AWS SNS
• Troubleshooting SNS Issues

Key Features of SNS

• Topics:

  Central channels that group subscribers, enabling simultaneous message delivery.
• Message Delivery:

  Supports delivery through various protocols, including email, HTTP/HTTPS, SMS, Lambda functions, and SQS.
• Message Filtering:

  Allows message filtering based on attributes, so subscribers receive only relevant messages.
• Fan-out Pattern:

  Distributes messages to multiple subscribers from a single topic (e.g., Lambda, SQS, SMS).

Getting Started with AWS SNS and Boto3

Before using Boto3 to interact with SNS, we have to check if we have the necessary configurations:

1. Install Boto3:

   pip install boto3
2. Configure AWS credentials:

   aws configure
3. Set up the SNS client:

   import boto3
sns_client = boto3.client('sns', region_name='us-east-1')


1. Create an SNS Topic

Topics are central to SNS and represent a channel to which subscribers can connect.

response = sns_client.create_topic(Name='MyTopic')
topic_arn = response['TopicArn']
print(f"Topic ARN: {topic_arn}")


Here, Name is a unique topic name within the AWS account. TopicArn is the ARN that uniquely identifies the topic.

2. Subscribe to a Topic

We can add different types of subscribers to an SNS topic, including email, SMS, HTTP, SQS, and Lambda.

response = sns_client.subscribe(
TopicArn=topic_arn,
Protocol='email',
Endpoint='example@example.com'
)
print(f"Subscription ARN: {response['SubscriptionArn']}")


Here, Protocol defines the type of subscriber, and Endpoint is the target for the messages.

3. Publish Messages to a Topic

Once we have subscribers, we can publish messages to the topic.

response = sns_client.publish(
TopicArn=topic_arn,
Message='This is a test message for SNS',
Subject='Test SNS Message'
)
print(f"Message ID: {response['MessageId']}")


Here, Message is the content of the message to be sent and Subject is useful for email notifications.

4. Publish Messages with Attributes

Messages can include attributes that help with filtering.

response = sns_client.publish(
TopicArn=topic_arn,
Message='This is a message with attributes',
MessageAttributes={
'Attribute1': {'DataType': 'String', 'StringValue': 'Value1'},
'Attribute2': {'DataType': 'Number', 'StringValue': '100'}
}
)
print(f"Message ID: {response['MessageId']}")


Here, MessageAttributes includes key-value pairs that provide metadata for filtering.

5. Message Filtering with SNS

SNS supports filtering messages based on attributes, allowing specific subscribers to receive only relevant messages.

response = sns_client.subscribe(
TopicArn=topic_arn,
Protocol='sqs',
Endpoint='arn:aws:sqs:us-east-1:123456789012:MyQueue',
Attributes={'FilterPolicy': '{"Attribute1": ["Value1"]}'}
)


Here, FilterPolicy specifies conditions for delivering messages to subscribers.

6. Delete an SNS Topic

Once we no longer need a topic, we can delete it.

response = sns_client.delete_topic(TopicArn=topic_arn)
print("Topic deleted")


7. List Topics and Subscriptions

List all topics or subscriptions to get an overview of the SNS setup.

We can list topics as seen here:

for topic in response[‘Topics’]:
print(topic[‘TopicArn’])

To list subscriptions:


response = sns_client.list_subscriptions()
for subscription in response['Subscriptions']:
print(subscription['SubscriptionArn'])


8. Unsubscribe from a Topic

If we want to remove a subscription, use the unsubscribe method.

response = sns_client.unsubscribe(
SubscriptionArn='arn:aws:sns:us-east-1:123456789012:MyTopic:abcd1234'
)
print("Unsubscribed successfully")


9. Integrate SNS with Other AWS Services

SNS can be integrated with other AWS services for advanced use cases:

• Lambda:

  Automatically trigger a Lambda function upon message reception.
• SQS:

  Implement a fan-out pattern by sending messages to multiple SQS queues.
• CloudWatch:

  Use SNS to send alerts for CloudWatch alarms.

Best Practices for Using AWS SNS

• Filtering:

  Leverage message attributes to ensure only relevant messages reach subscribers.
• Enable Encryption:

  Use AWS KMS to encrypt messages for sensitive topics.
• Implement Error Handling:

  Use dead-letter queues (DLQs) to handle failed message deliveries.
• Automate with Boto3: Create scripts for managing SNS topics, subscriptions, and message publishing to streamline workflows.

Troubleshooting SNS Issues

Effective troubleshooting of Amazon SNS plays a big role in smooth and reliable message delivery.

When messages are not delivered as expected, you can use the following steps to identify and resolve issues:

• Ensure that all subscribers have confirmed their subscription to the topic. Unconfirmed subscriptions do not receive messages.
• Use the SNS Console or the `list-subscriptions` command in the AWS CLI to see the status of all subscriptions. Look for the `PendingConfirmation` status, which indicates unconfirmed subscriptions.

Furthermore, if message filters are applied, make sure the messages contain the right attributes that match the filters defined for each subscription. We can use the MessageAttributes parameter while publishing messages to add specific attributes.

We can use Amazon CloudWatch to enable delivery status logging for SNS topics. This provides detailed information about message delivery, including success or failure codes.

If we are using endpoints like HTTP/HTTPS or Lambda, make sure they are accessible and not facing connectivity issues.

If the message volume is high, subscribers may experience throttling. AWS SNS has limits on message delivery, so ensure we haven’t reached these limits.

If a dead-letter queue (DLQ) is configured, messages that fail multiple delivery attempts will be routed there. So, check the DLQ to identify failed messages and investigate the root cause.

With these steps, we can easily troubleshoot any message delivery failures and confirm that all subscriptions are properly verified.

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Conclusion

Amazon SNS, combined with Boto3, provides a robust messaging solution for Python developers. Whether we are building a microservices architecture, handling notifications, or implementing a fan-out pattern, SNS offers versatile functionality to manage and distribute messages effectively.

In brief, our Support Experts introduced us to SNS AWS Boto3.