Anti-patterns & Best Practices in AWS Lambda

node_aws_blackbelt_online_seminar_aws_lambda_part3.md

Note: AWS blackbelt online seminar - part3

Anti-patterns & Best Practices in AWS Lambda

Speaker: 西谷 圭介, AWS Japan

• The only tunable parameter is MEMORY, but, in fact, it affects all computing resources ex. CPU usage
• Reduce package size
  • using client library
    • ex) Uglify.js
• Do NOT use VPCs
  • 10-30 additional latencies for attachng ENIs
• 1 lambda function : 1 responsibility
• Separate handler code and busines logics
  • keep your business logic testabile
• Initialize in global scope
  • resources allocated in global scope is REUSED by another execution (if it's warm-start context)
• Do not write orchestration code in your function
  • easy to cause timeout
  • use AWS Step Functions instead
• In error handling...
  • Set timeouts for external services
    • ex) HTTP, Redis, DynamoDB
    • if lambda function timeouts before external service calls timeouts, no logs output
    • Retry invokations
      • use exponential backoff with jitter
• Do not use pre-installed SDKs
  • AWS periodically updates them
    • it may affect your code
• Use asyncronous invokation instead of syncronous invokation
• Keep idempotency for yourself
  • lambda may executes multiple times
• Do not hard-code
  • sepalate logics and configulations
    • easy to switch environments
    • reduce security risks
  • store configuration in managed services
    • System Manager - Paramteter Store (Free of charge)
    • Secret Manager (charges)
• Do not use RDB
  • hundreds & thousands of concurrent executions of Lambda Functions may exceeds max connection limits of RDB
  • VPC coldstart is unavoidable
• Use scalable database ex. Dynamo DB instead
  • connections scaleout
  • no VPC coldstart
  • throughputs also scaleout
• If you have to use RDB ...
  • control max concurrecy limit
• Do not use fixed IP addresses
  • VPC coldstart
  • ENI becomes single point of failure
• Allow minimum necessary permitions as possible
• If you test lambda function code ...
  • run unittext on your local machine
  • run integration test on actural managed services
    • maintaining mocks and stabs costs high
  • run test on pipeline