Enabling DynamoDB stream settings on an existing table

enable-stream.sh

region=$1

# Quit on error
set -e

# 1. Update stream settings.
aws dynamodb update-table --table-name "JohnWickQuotes" --stream-specification StreamEnabled=true,StreamViewType=NEW_AND_OLD_IMAGES --region $region

subscribe-to-stream.sh

region=$1

functionName="quote-john-wick"

# Getting the stream name
streamArn="$(aws dynamodb describe-table --table-name "JohnWickQuotes" --region $region --output text --query 'Table.LatestStreamArn')"

# Check if a mapping already exists
mapping="$(aws lambda list-event-source-mappings --region us-east-1 --function-name $functionName --event-source-arn "$streamArn" --query 'EventSourceMappings[0]')"

if [[ $mapping = "null" ]]
then
  # Subscribing the handler to a stream
  aws lambda create-event-source-mapping \
  --region $region \
  --function-name $functionName \
  --event-source $streamArn \
  --batch-size 10 \
  --starting-position TRIM_HORIZON
else
  echo "Mapping already exists."
fi