AWS Lambda

• Overview

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  • Function-as-a-service (FaaS) - short running & focused (Serverless!)
  • a deployment package - a piece of code with specific runtime (Python 3.8) in a runtime env.
  • scaled automatically
  • env. has a direct memory + indirect CPU allocation, CPU scales with memory
  • billed for the duration that a function runs
  • as default, each time you run lambda function it is in a new env.
  • 15 mins function timeout
  • common uses
    • serverless applications (S3, API gateway, Lambda)
    • file processing (S3, S3 event, lambda)
    • database triggers (dynamoDB, Streams, lamda)
    • serverless CRON (event brdge/ CWEvents + lambda)
    • real time stream data processing (kinesis+lambda)

• Two Network mode

  1. public lambda Untitled 1.png

  2. Private Lambda Untitled 2.png

     • network is created along with lambda functions
     • If same subnet and security group are used, 1 ENI is only needed. ⇒ scalable

• Security

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  • execution role needs to be provided with trust policy, assumed by lambda
  • temporary credential is created for Lambda function to interact with other resources
  • Lambda also have resource policy controlling what services and accounts can invoke it

• Logging

  • via Cloudwatch, cloudwatch logs & X-ray
  • logs from lambda executions - cloudwatchlogs recording metrics (success/ failure, retries, latency…)
  • integrated with X-ray fro distributed tracing
  • Cloudwatch logs requires permission via execution role

• Invocation

  1. Synchronous Invocation
  • client wait data to be return

  Untitled 4.png

  1. Asynchronous Invocation
  • not waiting, but order sent out and done
  • lambda function responsible for retries (configurable)
  • need to be Idempotent (no matter how many time the function has run, result is the same like run once)
    • not additive/ subtractive, to achieve a state

  Untitled 5.png

  1. Event source mapping

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  • Kinesis data sent out data in batch to event source mapping
  • Execution role is needed even Lamda doesn’t recieve data directly from Kinesis

• Version

  • a version is the code + configuration of lambda function
  • immutable & has its own ARN
  • $Latest points at latest version
  • can use Aliases point at a version, which can be changed

• Starting time

  • 1st time ⇒ cool start is needed
  • invoke again ⇒ warm start
  • Provisioned concurrency ⇒ create and keep X context warm and ready to use
  • temp space is to pre-download things, eg database connection. But have to maintain clean

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# to add required package into lambda


# linux
mkdir -p python
pip install requests -t python/
zip -r requests_layer.zip python

# window
mkdir python
pip install -r requirements.txt -t python
Compress-Archive -Path lambda_function\* -DestinationPath lambda_function.zip -force
powershell Compress-Archive -Path python -DestinationPath requests_layer.zip

# make a folder named python
# -t flag = install package inside the folder instead of default site-packages
# make a zip up folder that recursively include all files and subdirectories