AWS Services Study Notes, Integration

SNS, SQS, etc.

Amazon Simple Notification Services, SNS

  • Simple Notification Service (SNS) is a key part of AWS application integration products.
  • AWS SNS works based on push technology
  • It provides a pub/sub-based notification system, which supports a wide range of subscriber endpoint types.
  • SNS coordinates and manages the sending and delivery of messages. Messages sent to a topic are delivered to subscribers.
  • SNS is integrated with many AWS services and can be used for certain event notifications, e.g., CloudFormation stack creation
  • using SNS, CloudWatch can notify admins of important alerts
  • SNS can be used for mobile push notifications

SNS Components

  • Topic: An isolated configuration for SNS, including permissions.
    • messages (<= 256KB) are sent to a topic
    • subscribers to that topic receive messages
  • Subscriber protocols: endpoints that receive messages for a topic
    • HTTP(S)
    • Email and Email-JSON
    • SQS (message can be added to one or more queues)
    • Mobile push notifications (ios, android, Amazon, MS)
    • lambda functions (function invoked)
    • SMS (cellular message)
  • Publisher: an entity that publishes/sends messages to a queue
    • Application
    • AWS services, including S3 (S3 events), CloudWatch, CloudFormation, etc

Common Amazon SNS scenarios

  1. Fanout
    • SNS message is sent to a topic and then replicated and pushed to multiple Amazon SQS queues, HTTP endpoints, or email addresses.
    • This allows for parallel asynchronous processing
  2. Application and system alerts
  3. Push email and text messaging
  4. Mobile push notifications
  5. Message durability

SNS + lambda

When a publisher publishes a message to an SNS topic and a Lambda function is subscribed to the same SNS topic, that Lambda function is invoked with the payload of a published message.

Amazon Simple Queue Service, SQS

  • SQS provides fully managed, highly available message queues for inter-process/server/service messaging.
  • SQS is used mainly to create decoupled architectures.
  • Messages are added to a queue and retrieved via polling

Polling Types

  • Short polling: Available messages are returned ASAP - a short poll might return 0 messages. Causes increased number of API calls
  • Long polling: Waits for messages for a given WaitTimeSeconds, it’s more efficient: less empty API calls/responses

two types of queues

  1. standard queues Standard queues are distributed and scalable to nearly unlimited message volume. the order is not guaranteed, best-effort only, and messages are guaranteed to be delivered at least once but sometimes more than once.
  2. FIFO queues first-in, first-out. Messages are delivered once only - duplicates do not occur. The throughput is limited to ~3,000 messages per second with batching or ~300 without by default.

Each SQS message can contain up to 256KB of data but can link data stored in S3 for any larger payloads.

When a message is polled, it’s hidden in the queue. It can be deleted when processing is completed - otherwise, after a VisibilityTimeOut period, it will return to the queue.

Queues can be configured with a maxReveiveCount, allowing messages that are failing to be moved to a dead-letter queue.

Lambda functions can be invoked based on messages on a queue offering better scaling and faster response than Auto Scaling groups for any messages that can be processed quickly.

Dead Letter Queue (DLQ)

Dead Letter Queue (DLQ) is used by other queues for storing failed messages that are not successfully consumed by consumer processes.

SNS + SQS fanout architecture

  • SNS allows applications to send time-critical messages to multiple subscribers through a “push” mechanism, eliminating the need to periodically check or “poll” for updates
  • SQS is used by distributed applications to exchange messages through a polling model, and can be used to decouple sending and receiving components—without requiring each component to be concurrently available
  • Using Amazon SNS and Amazon SQS together, messages can be delivered to applications that require immediate notification of an event, and also persisted in an Amazon SQS queue for other applications to process at a later time.

A publisher sends a message to an SNS topic and it distributes this topic to many SQS queues in parallel.

  • SNS pushes them to everywhere they need to go
  • SQS queues the messages

AWS Elastic Transcoder

Elastic Transcoder is an AWS service that allows you to convert media files from an input format to one or more output formats. it’s delivered as a service, and you’re billed a per-minute charge while using the service.

A pip line is a queue for jobs. It stores source and destination settings, notification, security, and other high settings. Jobs are processed in the order they are added as resources allow.

A job defines the input object and up to 30 output objects/formats. Jobs are added to a pipeline in the same region and use the buckets defined in the pipeline for input/output.

Presets contains transcoding settings and can be applied to jobs to ensure output compatible with various devices, such as iPhones, tablets, or other form factors.