Storing AWS Lambda Function code directly in S3 Bucket

Question

AWS Lambda Functions have an option to enter the code uploaded as a file from S3. I have a successfully running lambda function with the code taken as a zip file from an S3 Bucket, however, any time you would like to update this code you would need to either manually edit the code inline within the lambda function or upload a new zip file to S3 and go into the lambda function and manually re-upload the file from S3. Is there any way to get the lambda function to link to a file in S3 so that it will automatically update its function code when you update the code file (or zip file) contained in S3?

Answer 1

Lambda doesn't actually reference the S3 code when it runs--just when it sets up the function. It is like it takes a copy of the code in your bucket and then runs the copy. So while there isn't a direct way to get the lambda function to automatically run the latest code in your bucket, you can make a small script to update the function code using SDK methods. I don't know which language you might want to use, but for example, you could write a script to call the AWS CLI to update the function code. See https://docs.aws.amazon.com/cli/latest/reference/lambda/update-function-code.html

Updates a Lambda function's code.

The function's code is locked when you publish a version. You can't modify the code of a published version, only the unpublished version.

See also: AWS API Documentation

See 'aws help' for descriptions of global parameters.

Synopsis

update-function-code --function-name [--zip-file ] [--s3-bucket ] [--s3-key ] [--s3-object-version ] [--publish | --no-publish] [--dry-run | --no-dry-run] [--revision-id ] [--cli-input-json ] [--generate-cli-skeleton ]

You could do similar things using Python or PowerShell as well, such as using https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/lambda.html#Lambda.Client.update_function_code

Answer 2

You can set up an AWS Code deploy pipeline to get your code build and deployed on code commit in your code repository(github,bitbucket,etc)

CodeDeploy is a deployment service that automates application deployments to Amazon EC2 instances, on-premises instances, serverless Lambda functions, or Amazon ECS services.

Answer 3

Also, wanted to add if you want to go on a more unattended route of deploying your Updated code to the Lambda use this flow in your code Pipeline
Source -> Code Build (npm installs and zipping etc.) -> S3 Upload (sourcecode.zip in S3 bucket) -> Code Build (another build just for aws lambda update-funtion-code)

Make sure the role for the last stage has both S3 getObject and Lambda UpdateFunctionCode policies attached to it.