Logical Enigma
AWS Notes

Applications

SQS

  • Distributed Queueing system - pull based (polling)
  • Decouple the components of an application to run independently
  • 256 KB of text in any format (above that goes to S3)
  • 1 minute to 14 days (4 days retention default)
  • Visibility timeout is the amount of time that the message is invisible in the SQS queue after a reader picks up that message - max time is 12 hours. If duplicate processing start occurring, increase visibility timeout so gives time for processors to consume.
  • Long polling - doesn’t return a response until a message arrives in the q or the poll times out. Short polling returns immediately (even for no messages) - ReceiveMessageWaitTimeSeconds
  • Message-oriented API
  • Standard Queues
    • nearly unlimited transactions per second
    • Guaranteed to be deliver at least once
    • More than one copy of message might be delivered out order - but maintains best-effort ordering
  • FIFO
    • FIFO delivery
    • Exactly Once processing
    • No duplicates
    • Support message groups that allow multiple ordered message queue
    • Limited to 300 TPS

SWF - Simple Workflow Service

  • Coordinate work across distributed application components
  • Media processing, web app backends, business process workflows, analytics pipelines
  • Tasks represent invocations of various processing steps in an application which can be performed by executable code, web service calls, human actions, and scripts. (Think about a warehouse w/ human element)
  • Workflow executions can last up to 1 year
  • Task-oriented API (SDKs, but all accessible via HTTP)
  • Task is assigned only once, never duplicated
  • Tracks all tasks and events in an application
  • SWF Actors:
    • Workflow Starters - App that can initiate a workflow
    • Deciders - control the flow of activity tasks in a workflow execution - if something has finished/failed, a Decider decides what to do next
    • Activity Workers - carry out activity tasks
  • Domains provide a way of scoping SWF resources in your account

SNS - Simple Notification Service

  • Pay as you go, no up-front
  • Publish messages to subscribers or other apps - Push Based
  • Push notification
  • Delivery SMS, email to SQS, any http endpoint
  • Multiple recipients via topics - an access point for allowing recipients to dynamically subscribe
  • All messages stored redundantly across multiple AZ

Elastic Transcoder

  • Media transcoder in cloud - convert media across formats
  • Transcoding presets

Api Gateway

  • Fully managed service that makes it easy for devs to publish, maintain, and monitor API at any scale
  • Front door
  • Capabilities:
    • Expose HTTPS endpoints to define a restful API
    • Serverlessly connect to Lambda and DynamoDB
    • Send each API endpoint to a different target
    • Run efficiently w/ low cost
    • Scale effortless and automatic
    • Track and control usage by API
    • Throttle requests to prevent attacks
    • Log to Cloudwatch for monitoring
    • Maintain multiple versions
    • Set request/response transformations
  • Deploy API to a stage : API GW Domain by default, custom domain, AWS Certificates manager
  • Caching - TTL
  • Same Origin Policy - scripts from 2 pages can only talk if on same origin - enforced by web browsers (ignored by Postman and curl)
  • Cross Origin Resource Sharing (CORS) - restricted resources can be requested from another domain. OPTIONS call checks - “Origin policy cannot be read at the remote resource”

Kinesis

  • Streaming data is generated continuously by thousands of data sources, typically sending data records simultaneously and in small size
  • Makes it easy to load and process data
  • Kinesis Streams - data stored in shards
    • Data contained in shards, producers/consumers. Data persistence
    • Shards - total capacity of stream is the sum of the cap of shards
      • 5 tx per second for reads, up to max total data read rate of 2MB/sec and up to 1000 records/sec writes, up to total data write rate of 1 MB/sec (including partition keys)
      • Data capacity is a function of number of shards. Total capacity of the stream is the sum of the capacities of its shards
    • Store data 24 hrs to 7 days (persistence)
  • Kinesis Firehose
    • Components: Delivery streams, records of data and destinations
    • no persistence, must do something with it asap
    • Can have lambda function in firehose (output to S3, elastic search etc)
  • Kinesis Analytics
    • Analyze streams or firehose and store somewhere else
    • Output to S3, Redshift, Elasticsearch Cluster

Web Identity Federation and Cognito

  • Web Identity Federation lets you give users access to AWS resources after successful authenticated w/ provider like AMZN, FB, GOOG.
  • Receives authentication code from the Web ID provider, can be traded for temporary AWS security credentials
  • Sign up and in
  • Access for guest users
  • Acts as Identity Broker w/ Web Identity Provider
  • Syncs user data for multiple devices
  • Recommended for all mobile applications
  • No need to store AWS Credentials in app
  • User Pools - user directories used to manage sign up and sign in. Users can sign-in directly to the pool or use Federated. Successful authentication generates a JSON Web token (JWT)
  • Identity Pools enable provide temporary AWS credentials (IAM Role) to access AWS services like S3 or DDB
  • Cognito tracks the association between user identity and the various devices they sign in from. Uses Push Synchronization to push updates and sync user data across devices using SNS

Event Processing Patterns

  • Event Driven Architecture - Pub/Sub
    • Decoupled systems running in response to events
    • SNS Topic - async event notifications
    • Publisher sends message to SNS Topic; all subscribers receive the message
  • Dead-Letter Queue (DLQ) - Undeliverable message
    • SNS : as a SQS queue that fail to deliver
    • SQS: maxReceiveCount is exceeded send to DLQ (another SQS)
    • Lambda - async failures (2 retries by lambda) -> either SQS or SNS
  • Fanout Pattern - need to send to multiple systems
    • Publisher send message to SNS Topic first then subscribers get it (multiple SQS queues)
    • Solves this Problem - if send to 2 SQS queue (distributed), what happens if second one fails (no distributed tx)
    • Can be used to send same data to production and test system
  • S3 Event Notification - receive notifications when events happen in bucket
    • Delivers to SQS, SNS, Lambda
    • Filter the notifications (*.png)
    • Enable versioning to make sure get notification (otherwise not perfect)
    • Events:
      • Object Created
      • Object Removed
      • Object Restored
      • RRS object Lost
      • Replication (fails, > 15 mins, object no longer tracked by replication metrics)

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