Simple Notification Service (SNS)

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SNS Icon

Basics

• When more that one receiver are interested in a message and needs to be processed, rather than using direct integration, one must prefer using SNS.

• It is a managed service.

• A typical architecuture looks like below,

• This pattern is called Pub/Sub pattern, useful when many different consumers are interested in same message.

Publishers

• Actors/Services responsible to send message to SNS Topic.

Subscribers

• Actors/Services interested in receiving message from SNS Topic.

SNS Topic

• Topic is a logical access point and communication channel.

• event producer (Publisher/s) only sends message to one SNS topic.

• Many services like CloudWatch Alarms, ASG, CFT changes, AWS Budgets, Lambda, DynamoDB, RDS Events, DMS etc can send data directly to SNS Topic for notifications.

• event receivers (subscriber/s) will listen to SNS topic notifications and receive all messages from this topic. Subscriber/s may receive specific messages from this topic, by filtering them.

• 12,50,00,000 subscribers can subscribe to one topic. Subscribers can be SQS, Email Service, Mobile Notification, HTTP endpoints, Kinesis Data Firehose (not Kinesis Data Stream) etc

• About 100,000 topics can be created and limit can be increased.

• SNS can be integrated with other AWS services like SQS, Lambda, Kinesis Data Firehose etc.

• There are two ways to publish,

  • Topic Publish (for AWS SDK)

  • Direct Publish (for mobile SDKs)

Steps to Topic publish (using SDK)

1. Create a Topic

2. Create a subscription

3. Publish to topic

Steps to Direct publish (using Mobile apps SDK)

1. Create a platform application

2. Create a platform endpoint

3. Publish to the platform endpoint

   • It works with Google GCM, Apple APNS, Amazon ADM to receive notifications.

Message Filtering

• This is a JSON policy used to filter messages sent to SNS topic's subscription.

• If a subscription does not have message filtering then it will receive every message.

Types of SNS Topics

• There are basically two types.

Standard Topic

• Does not ensure ordering of message delivery.

• Subscribers can be HTTP/HTTPS endpoint, SQS queues, Lambda, mobile applications endpoint, Email, SMS, Kinesis Data firehose etc.

FIFO Topic

• Ensures ordering of message delivery.

• Subscribers can be both SQS Standard and FIFO queue.

• Offers deduplication same as SQS FIFO.

• Offers messaage group based ordering same as SQS FIFO.

• Throughput is also similar to SQS FIFO queue.

• Subscribers can only be SQS queues.

• Name of fifo topic has be to suffixed with .fifo.

SNS Security

• Offers in-flight encryption using HTTPS API.

• Can also have at rest encryption using KMS keys.

• Client-side encryption can also be done if the client wants to perform encryption/decryption itself.

Access Control

• AWS IAM policies

  • Can be used to control access to SNS API.

• SNS Access policy

  • Can also be used to control the access, which is useful when needed to make a cross account access or control access to write to SNS Topic by other AWS services.