AWS Lambda: Identifying cold starts

问题

Is there a clear way to identify "cold starts"? Either in runtime in the Lambda itself, or via the logs? I know that cold starts are characterized by longer runtimes, which I can actually see, but I'm looking for a clear cut way. I'm using Node.js if that matters.

Update: There are two good answers below, for two use cases: - Identifying the cold start as the lambda runs. - Identifying the cold start from the CloudWatch log.

回答1:

If you add some initialization code to the top of your NodeJS script, you will be able to tell in the code that it is a cold start, and you will then be able to log that if you want to see it in the logs. For example:

var coldStart = true;
console.log("This line of code exists outside the handler, and only executes on a cold start");


exports.myHandler = function(event, context, callback) {
  if (coldStart) {
    console.log("First time the handler was called since this function was deployed in this container");
  }
  coldStart = false;

   ...

  callback(...);
}

回答2:

If you're looking at CloudWatch logs, each LogGroup for your Lambda function represents a separate container and therefore the first invocation for that LogGroup is your cold start.

来源：https://stackoverflow.com/questions/47061146/aws-lambda-identifying-cold-starts