By combining pub\/sub and queueing components we are able to build resilient, scalable and fault-tolerant architecture with AWS<\/a>. This is an overview of AWS Simple Notification Service, Simple Queue Service and how they can be used in isolation or together to send persistent and immediate messages.<\/p>\n\n\n\n
What is SNS?<\/a>
When to use SNS<\/a>
What is SQS?<\/a>
When to use SQS<\/a>
When to use them together<\/a><\/p><\/blockquote>\n\n\n\n
\n\n\n\nWhat is SNS?<\/h2>\n\n\n\n
- SNS is a fully managed pub\/sub messaging service from AWS.<\/li>
- It is used in application integration and allows apps and services to communicate with messages when these are decoupled.<\/li>
- Messages are in JSON format and are pushed<\/strong> to subscribers.<\/li>
- ‘Topics’ are logical access points and allow recipients to subscribe to identical copies of the same message.<\/li>
- Notifications are then formatted for the protocol receiving the message and can be delivered as text messages, emails, and to SQS or HTTP endpoints.<\/li><\/ul>\n\n\n\n
\n\n\n\n<\/figure><\/div>\n\n\n\n
\n\n\n\nWhen to use SNS<\/h2>\n\n\n\n
- SNS can be used to send large numbers of time-sensitive messages<\/strong> to end-users in the form of a push notification, SMS and email. Clients can subscribe to topics and specify the endpoint.<\/li>
- In this example<\/a>, we see how SNS can be used in conjunction with Lambda to perform calculations. By using SNS we ensure that the message gets through.<\/li><\/ul>\n\n\n\n
\n\n\n\nWhat is SQS?<\/h2>\n\n\n\n
- SNS is a fully managed message queue service from AWS.<\/li>
- It is used in application integration and allows apps and services to communicate with messages when these are decoupled.<\/li>
- SQS can store messages up to 256KB in any format for up to 12 hours while waiting for a system to pull<\/strong> them to process them.<\/li>
- If the job isn\u2019t processed before the time out expires the message will be placed back in the queue, which could cause the message to be processed twice.<\/li>
- Auto-scaling groups can monitor the SQS group and scale up and down depending on the number of messages in the queue.<\/li>
- The Standard<\/strong> queue uses ‘best-effort’ ordering, FIFO<\/strong> queues guarantee messages are pulled in the order that they arrive.<\/li>
- By default short polling returns messages immediately. Long polling waits until there is a message in the queue or until the timeout expires.<\/li><\/ul>\n\n\n\n
\n\n\n\n<\/figure><\/div>\n\n\n\n
\n\n\n\nWhen to use SQS<\/h2>\n\n\n\n
- SQS can be used to throttle workload and process work in batches with non-time sensitive<\/strong> messages being stored for up to 14 days.<\/li>
- In this example<\/a> we see how using Dead Letter Queues allows error handling logic from the application logic<\/li><\/ul>\n\n\n\n
\n\n\n\nWhen to use them together<\/h2>\n\n\n\n
- By combining SNS topics and SQS queues together, you can send immediate and persisted messages.<\/li>
- In this example<\/a>, we see how to use the two services and Lambda together.<\/li>
- The architecture involves S3<\/a> event notifications, an SNS topic, an SQS queue, and a Lambda function sending a message to the Slack channel.<\/li>
- This shows how it is possible to implement an event processing pipeline with potentially multiple consumers and producers.<\/li><\/ul>\n\n\n\n
\n\n\n\nUseful Links<\/h2>\n\n\n\n