Lambda Asynchronous Invocation

• Aysnchronous invokation happens when other services execute lambda.

  • In this case, they will be added into Lambda Resource Based Policies

• Services that will execute Async lambda

  • S3
  • SNS
  • CloudWatch Events/ EventBridge
  • CodeCommit
  • CodePipeline
  • Cli
  • ... and some other services

• Events will go to an Lambda Event Queue

• On error, attempts retries 2 times in total

  • 1st time: wait 1 minute
  • 2nd time: wait 2 minute

• Make sure the lambda function is idempotent

  • which mean incase of retries, the result is the same
  • For retrying it will use the same RequestID

• If retries happen, you might see duplicate logs in CloudWatch Logs

• We can define a Dead Letter Queue (SNS or SQS) for failed process (after retries)

  • Note: for SNS Dead Letter Queue, if there are no SNS receiver, the message will be lost.

Invoke Asynchronously on CLI

We set --invocation-type to Event (default RequestResponse which invokes synchronously)