I really don't understand why no one seems to have asked this question before, but is there a TIMEOUT environment variable which references the set timeout in the Lambda function in AWS?
It doesn't seem to be on the list of environment variables available, and that doesn't seem to make sense either: https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html
I'm not sure of your programming environment but ever Lambda environment I've seen includes a Context object. That has the ability to check how much time is left in a Lambda run. In Java, for example:
public class ShowTimeout implements RequestStreamHandler {
public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context) throws IOException {
LambdaLogger logger = context.getLogger();
logger.log("there are " + context.getRemainingTimeInMillis() + "ms left to run");
}
}
logs how much time is left. By default this is 3 seconds but, of course, can change depending on how you configure the Lambda.
EDIT
This is not the total time set. But as the very first thing the Lambda does it's pretty close. For a 15 second timeout Lambda I got:
there are 14998ms left to run
and
there are 14999ms left to run
If you've started your Lambda and it looks like the number is too small then you can do something about it. If it's the first thing you do like my simple code then you'll be very close. I'd argue that a simple rounding would be accurate enough.
If you are using SAM for your lambda, then you may set the TIMEOUT as a parameter and refer to that parameter in your environment variables as well as timeout.
Transform: AWS::Serverless-2016-10-31
Description: >
This is a lambda function
Globals:
Function:
Timeout: !Ref TIMEOUT
Environment:
Variables:
TIMEOUT: !Ref TIMEOUT
Parameters:
TIMEOUT:
Type: Number
Resources:
myFunction:
Type: AWS::Serverless::Function
Properties:
FunctionName: functionName
Handler: app.handler
Runtime: nodejs18.x
Architectures:
- x86_64
Here, whatever value we will set as TIMEOUT will be the timeout of the lambda function and the same can be referenced in the code using process.env.TIMEOUT.
PS: For me, !Ref TIMEOUT didn't work when I added it within Resources -> Properties, but it worked when set as a global. This difference behaviour is not clearly documented though.
