dynamodb-add-ttl-lambda

Lambda function to add a ttl attribute to an existing table based on an existing attribute

Purpose

This lambda function is designed to be used as a DynamoDB trigger in order to add a ttl attribute to an existing table for new rows. It will base the new ttl attribute on an existing timestamp attibute by reading the existing attribute and adding a number of days to it. The existing attribute, number of days and new ttl attribute name are all configurable

Installing

The easiest deployment of this solution is using AWS SAM

• export your AWS credentials (or use --profile option with sam commands)
• update the samconfig.toml file
  • stack_name - name for the CFN stack
  • region - if other than us-east-1
  • parameter overrides
    • ttlReferenceAttribute - existing attribute used to calculate TTL
    • timeToLive - duration of TTL (in days)
    • ttlAttributeName - what to name the TTL (e.g. ttl)
    • tableName - the DynamoDB table to watch
    • streamARN - the ARN of the DynamoDB stream for the table above
• deploy the lambda using SAM: ./utils/deploy.sh default

This should deploy the lambda and set up the associated dynamodb trigger for the appropriate table.

NOTE: As per the StartingPosition property on the DynamoDB event trigger - this lambda will only process NEW records. You may need a separate process to backfill existing records.

You can then monitor the stats for the function and the cloudwatch log to ensure TTLs are being added correctly for new rows.