How to Specify Additional Parameter to AWS Lambda Function Triggered by S3

Question

I am creating an AWS Lambda function that is triggered for each PUT on an S3 bucket. A separate Java application creates the S3 bucket, sets up the trigger to the Lambda on Put, and PUTs a set of files into the bucket. The Lambda function executes a compiled binary, it passes to the binary a script, which acts on the new S3 object.

All of this is working fine.

My problem is that I have a set of close to 100 different scripts, and am regularly developing new scripts. The ZIP for the Lambda contains all the scripts. Scripts correspond to different types of files, so when I run the Java application, I want to specify WHICH script in the Lambda function to use. I'm trying to avoid having to create a new Lambda for each script, since each one effectively does the exact same thing but for the name of the script.

When you INVOKE a Lambda, you can put parameters into the context. But my Lambda is triggered, so most of what I react to is in the event. I can't figure out how to communicate this simple parameter to the Lambda efficiently as I set up the S3 bucket and the event trigger.

How can I do this?

Answer 1

You can't have S3 post extra parameters to your Lambda function. What you can do is create a DynamoDB table that maps S3 buckets to scripts, or S3 prefixes to scripts, or something of the sort. Then your Lambda function can lookup that mapping before executing your script.