Runtime Configuration for scheduled AWS Lambda function

I found a way. For the test version of the function, I am calling it TEST-CopyFtpFilesToS3 and for the production version of the function I am naming the function PRODUCTION-CopyFtpFilesToS3. This allows me pull out the environment name using a regular expression.

Then I am storing config/test.json and config/production.json in the zip file that I upload as code for the function. This zip file will be extracted into the directory process.env.LAMBDA_TASK_ROOT when the function runs. So I can load that file and get the config I need.

Some people don't like storing the config in the code zip file, which is fine - you can just load a file from S3 or use whatever strategy you like.

Code for reading the file from the zip:

const readConfiguration = () => {
  return new Promise((resolve, reject) => {
    let environment = /^(.*?)-.*/.exec(process.env.AWS_LAMBDA_FUNCTION_NAME)[1].toLowerCase();
    console.log(`environment is ${environment}`);

    fs.readFile(`${process.env.LAMBDA_TASK_ROOT}/config/${environment}.json`, 'utf8', function (err,data) {
      if (err) {
        reject(err);
      } else {
        var config = JSON.parse(data);
        console.log(`configuration is ${data}`);
        resolve(config);
      }
    });
  });
};