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By Rohan Patel in aws —

DVA-C01 studying - Lambda, API Gateway, Step Functions, X-Ray

Serverless Computing

What it is

  • https://aws.amazon.com/serverless/

  • allows you to run application code on the cloud without needing to manage a server

  • AWS handles managing the infrastructure

    • capacity provisioning
    • patching
    • auto scaling
    • high availability

  • Advantages

    • speed to market - no server management overhead

    • automatic scaling

    • lower costs

      • never need to pay for over-provisioning
      • event driven so you only get charged when the code is triggered to run

  • AWS services include: Lambda, API Gateway, DynamoDB, S3, SNS, SQS

Lambda

What it is
deploying code to lambda
  • CloudFomartion Aws::Lambda::Function resource can create a Lambda function
  • zip your code and upload it to Lambda - must upload via S3 then Lambda if the package is more than 50MB
  • write code directly in Lambda's web IDE
Pricing - request volume, run duration, and memory used

  • first 1 million requests - free

    • $0.20 per month per 1 million requests after

  • charged in 1ms increments

    • price depends on how much memory you allocated to the Lambda function

  • $0.00001667 per GB-second

    • first 400,000 GB-seconds per month free
Versioning

  • when you create a function, it is by default $LATEST

  • new versions of the function (new code) becomes $LATEST

  • you can still reference other versions of the function through aliases that reference that version - easy rollback

  • if you use an alias instead of $LATEST in your application, it will not change the version of function it's calling when you change the function

    • need to explicitly update your alias
Concurrent Execution Limit

  • default 1,000 per region, afterwards you'll see rejections

    • TooManyRequestsException
    • status code 429
    • the throughput limit was exceeded

  • increases on this limit can be requested through AWS support

  • Reserved Concurrency

    • guarantees a set number of concurrent executions always be available to the specific function

      • limits the function's concurrent executions to this number instead of the default
accessing VPC resources

  • need to allow the function to connect to the private subnet

  • VPC information Lambda needs:

    • private subnet ID
    • security group ID (with required access) - allows your function to access VPC resources
    • (configuration doable in the AWS Console)

  • VPC information is used to set up ENIs using an IP from the private subnet CIDR range

misc
  • timeout issues - review logs of the API call and adjust the timeout settings

API Gateway

What it is

  • https://aws.amazon.com/api-gateway/

  • API - application programming interface; API Gateway supports:

    • REST - uses JSON
    • Websocket APIs
    • SOAP - uses XML (god have mercy if you're still using SOAP)

  • provides a single endpoint for all client traffic interacting with the backend of your application

    • connects to applications running on Lambda, EC2, Elastic Beanstalk, and AWS services i.e. DynamoDB, Kinesis, etc
    • supports multiple endpoints
    • supports multiple versions

  • supports easy rollback to restore a previous stage

  • integrates with CloudWatch

    • can log API calls, latencies, errors, etc

  • supports throttling

    • Per-client throttling limits can be used to limit a client's API key to specified limits and quotas

  • supports importing your own APIs

Caching

  • when enabled, default TTL is 300s

  • caches your endpoint's response

    • looks up response in the cache instead of making a new request to your application
    • reduces number of request made to your application from API Gateway
    • improves (reduces) latency
Throttling

  • default limit for steady-state requests - 10,000 requests/second per Region

  • maximum 5,000 concurrent requests across all APIs per region

    • increases on this limit can be requested through AWS support

  • Exceeding these limit returns a 429 Too Many Requests error

Step Functions

What it is

  • https://aws.amazon.com/step-functions/

  • provides visual interface for serverless applications

  • allows you to automate/orchestrate your serverless applications

    • run serverless applications as a series of steps - executing in order (automatically triggering)
    • logs the state of each step - helpful for isolating and debugging errors
Workflows

  • Standard Workflows

    • long running (up to a year)

      • durable
      • great for auditable workflows

    • full execution history is available for 90 days

    • at-most-once - tasks are never executed more than once

      • can explicitly specify to retry requests

    • non-idempotent

      • causes a change a change in state
      • identical requests will always cause a change in state

  • Express Workflows

    • short lived (up to 5mins)

      • great for high-volume, event-processing workloads

    • at-least-once - tasks run at least one time or need to be run concurrently

    • idempotent

      • identical requests result in no change in state

    • can be synchronous or asynchronous

    • not all Express workflows return the result after finishing

  • Synchronous Express Workflows

    • return the result after the workflow finishes

    • workflow begins -> waits till it is finished -> returns the result -> next step is triggered

    • the workflow must complete before the next step is executed

      • next task depends on prior task

  • Asynchronous Express Workflows

    • workflow begins -> workflow is confirmed to be running

    • results of the workflow are available in CloudWatch logs

    • tasks can be executed without needing the prior step to wait for the workflow to finish

      • next task does not depend on prior task

X-Ray

What it is

  • https://docs.aws.amazon.com/xray/latest/devguide/xray-api.html

  • provides an end-to-end view of your overall application

  • service that collects data about requests being served by your application

  • helps developer analyze and/or debug distributed applications

  • provides a visualization of your applications components - Service Map

  • services that provide integration with X-Ray: Elastic Load Balancing, Lambda, API Gateway, EC2, Elastic Container Service, Elastic Beanstalk, SNS, SQS, DyamoDB

    • automatically captures API calls

  • X-Ray can integrate with S3

    • traces upstream requests to update your buckets
    • if a service is using the X-Ray SDK to trace requests, S3 can send the tracing headers to downstream event subscribers

  • integrates with: java, python, go, nodejs, ruby, and .net

  • X-Ray agent/daemon needs to be installed on your instance or container

    • use the X-Ray SDK to instrument (configure) the data it's gathering - HTTP requests, errors, etc
    • X-Ray SDK gathers information and sends it off to X-Ray daemon that buffers it in a queue and sends them to X-Ray (the actual service) in batches
    • both the X-Ray SDK and X-Ray daemon need to be on the system you want to connect

  • on-premise servers or EC2 instances

    • install X-Ray daemon on your instance or server

  • Elastic Beanstalk

    • install X-Ray daemon on the EC2 instance inside the environment

  • Elastic Container Service

    • install X-Ray daemon in it's own container on your ECS cluster (not on the same container as the application)
Annotations
  • annotations can be used to record additional information about requests - done during instrumenting (configuring)
  • key-value pairs that are indexed - allows for filtering and searching

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