aws-sns

# AWS SNS Amazon Simple Notification Service (SNS) is a fully managed pub/sub messaging service for application-to-application (A2A) and application-to-person (A2P) communication. ## Table of Contents - [Core Concepts](#core-concepts) - [Common Patterns](#common-patterns) - [CLI Reference](#cli-reference) - [Best Practices](#best-practices) - [Troubleshooting](#troubleshooting) - [References](#references) ## Core Concepts ### Topics Named channels for publishing messages. Publishers send to topics, subscribers receive from topics. ### Topic Types | Type | Description | Use Case | |------|-------------|----------| | **Standard** | Best-effort ordering, at-least-once | Most use cases | | **FIFO** | Strict ordering, exactly-once | Order-sensitive | ### Subscription Protocols | Protocol | Description | |----------|-------------| | **Lambda** | Invoke Lambda function | | **SQS** | Send to SQS queue | | **HTTP/HTTPS** | POST to endpoint | | **Email** | Send email | | **SMS** | Send text message | | **Application** | Mobile push notification | ### Message Filtering Route messages to specific subscribers based on message attributes. ## Common Patterns ### Create Topic and Subscribe **AWS CLI:** ```bash # Create standard topic aws sns create-topic --name my-topic # Create FIFO topic aws sns create-topic \ --name my-topic.fifo \ --attributes FifoTopic=true # Subscribe Lambda aws sns subscribe \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --protocol lambda \ --notification-endpoint arn:aws:lambda:us-east-1:123456789012:function:my-function # Subscribe SQS aws sns subscribe \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --protocol sqs \ --notification-endpoint arn:aws:sqs:us-east-1:123456789012:my-queue # Subscribe email aws sns subscribe \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --protocol email \ --notification-endpoint user@example.com ``` **boto3:** ```python import boto3 sns = boto3.client('sns') # Create topic response = sns.create_topic(Name='my-topic') topic_arn = response['TopicArn'] # Subscribe Lambda sns.subscribe( TopicArn=topic_arn, Protocol='lambda', Endpoint='arn:aws:lambda:us-east-1:123456789012:function:my-function' ) # Subscribe SQS with filter sns.subscribe( TopicArn=topic_arn, Protocol='sqs', Endpoint='arn:aws:sqs:us-east-1:123456789012:order-queue', Attributes={ 'FilterPolicy': '{"event_type": ["order_created", "order_updated"]}' } ) ``` ### Publish Messages ```python import boto3 import json sns = boto3.client('sns') topic_arn = 'arn:aws:sns:us-east-1:123456789012:my-topic' # Simple publish sns.publish( TopicArn=topic_arn, Message='Hello, World!', Subject='Notification' ) # Publish with attributes (for filtering) sns.publish( TopicArn=topic_arn, Message=json.dumps({'order_id': '12345', 'status': 'created'}), MessageAttributes={ 'event_type': { 'DataType': 'String', 'StringValue': 'order_created' }, 'priority': { 'DataType': 'Number', 'StringValue': '1' } } ) ``` ### Message Filtering ```bash # Add filter policy to subscription aws sns set-subscription-attributes \ --subscription-arn arn:aws:sns:us-east-1:123456789012:my-topic:abc123 \ --attribute-name FilterPolicy \ --attribute-value '{ "event_type": ["order_created"], "priority": [{"numeric": [">=", 1]}] }' ``` Filter policy examples: ```json // Exact match {"event_type": ["order_created", "order_updated"]} // Prefix match {"customer_id": [{"prefix": "PREMIUM-"}]} // Numeric comparison {"price": [{"numeric": [">=", 100, "<=", 500]}]} // Exists check {"customer_id": [{"exists": true}]} // Anything but {"event_type": [{"anything-but": ["deleted"]}]} ``` ### Fan-Out Pattern (SNS to Multiple SQS) ```python import boto3 import json sns = boto3.client('sns') sqs = boto3.client('sqs') # Create topic topic = sns.create_topic(Name='orders-topic') topic_arn = topic['TopicArn'] # Create queues for different processors queues = { 'analytics': sqs.create_queue(QueueName='order-analytics')['QueueUrl'], 'fulfillment': sqs.create_queue(QueueName='order-fulfillment')['QueueUrl'], 'notification': sqs.create_queue(QueueName='order-notification')['QueueUrl'] } # Subscribe each queue for name, queue_url in queues.items(): queue_arn = sqs.get_queue_attributes( QueueUrl=queue_url, AttributeNames=['QueueArn'] )['Attributes']['QueueArn'] sns.subscribe( TopicArn=topic_arn, Protocol='sqs', Endpoint=queue_arn ) # One publish reaches all queues sns.publish( TopicArn=topic_arn, Message=json.dumps({'order_id': '12345', 'total': 99.99}) ) ``` ### Lambda Permission for SNS ```bash aws lambda add-permission \ --function-name my-function \ --statement-id sns-trigger \ --action lambda:InvokeFunction \ --principal sns.amazonaws.com \ --source-arn arn:aws:sns:us-east-1:123456789012:my-topic ``` ## CLI Reference ### Topic Management | Command | Description | |---------|-------------| | `aws sns create-topic` | Create topic | | `aws sns delete-topic` | Delete topic | | `aws sns list-topics` | List topics | | `aws sns get-topic-attributes` | Get topic settings | | `aws sns set-topic-attributes` | Update topic settings | ### Subscriptions | Command | Description | |---------|-------------| | `aws sns subscribe` | Create subscription | | `aws sns unsubscribe` | Remove subscription | | `aws sns list-subscriptions` | List all subscriptions | | `aws sns list-subscriptions-by-topic` | List topic subscriptions | | `aws sns confirm-subscription` | Confirm pending subscription | ### Publishing | Command | Description | |---------|-------------| | `aws sns publish` | Publish message | ## Best Practices ### Reliability - **Use SQS for durability** — SNS is push-based, SQS queues messages - **Configure DLQ** for failed deliveries - **Use FIFO topics** for ordering requirements ### Security - **Use topic policies** to control access - **Enable encryption** with SSE ```bash # Enable SSE aws sns set-topic-attributes \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --attribute-name KmsMasterKeyId \ --attribute-value alias/my-key ``` ### Cost Optimization - **Use message filtering** to reduce unnecessary deliveries - **Monitor and clean up** unused topics/subscriptions ## Troubleshooting ### Subscription Not Receiving Messages **Check:** 1. Subscription is confirmed (not pending) 2. Filter policy matches message attributes 3. Target permissions (Lambda, SQS) ```bash # Check subscription status aws sns list-subscriptions-by-topic \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic ``` ### Messages Not Matching Filter **Verify:** - Message attributes are set (not in body) - Attribute types match (String vs Number) - Filter policy syntax is correct ```python # Correct: attributes must be message attributes sns.publish( TopicArn=topic_arn, Message='body content', MessageAttributes={ 'event_type': { 'DataType': 'String', 'StringValue': 'order_created' # This is filtered } } ) # Wrong: body content is NOT filtered sns.publish( TopicArn=topic_arn, Message=json.dumps({'event_type': 'order_created'}) ) ``` ### SQS Not Receiving from SNS **Check SQS queue policy:** ```json { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Principal": {"Service": "sns.amazonaws.com"}, "Action": "sqs:SendMessage", "Resource": "arn:aws:sqs:us-east-1:123456789012:my-queue", "Condition": { "ArnEquals": { "aws:SourceArn": "arn:aws:sns:us-east-1:123456789012:my-topic" } } } ] } ``` ## References - [SNS Developer Guide](https://docs.aws.amazon.com/sns/latest/dg/) - [SNS API Reference](https://docs.aws.amazon.com/sns/latest/api/) - [SNS CLI Reference](https://docs.aws.amazon.com/cli/latest/reference/sns/) - [boto3 SNS](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/sns.html)