How to get the AWS Region in a Javascript/Nodejs Lambda Function:

Question

How do I identify the region from within a Nodejs/Javascript AWS Lambda function?

The AWS_DEFAULT_REGION environment variable gives a ReferenceError (See here, which is for Java, not Node/Javascript.)

I realize I can get the "invokedFunctionArn" from the context object and parse it for the region, but it seems like there should be a more direct way.

While it is not impossible to hack the way out to get the info; in my opinion, it is would be easier to feed in the REGION details as part of configuration details or environment info [i.e. explicitly add it to the code / config] — Naveen Vijay, Oct 06 '16 at 17:10

score 47 · Answer 1 · answered Feb 10 '17 at 22:46

47

Use the environment variable:

process.env.AWS_REGION

Source: http://docs.aws.amazon.com/lambda/latest/dg/current-supported-versions.html#lambda-environment-variables

answered Feb 10 '17 at 22:46

Andrew Clark

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2

The link changed; it's now: https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html – Sebastian J. Feb 20 '20 at 04:14

score 1 · Answer 2 · answered Oct 06 '16 at 23:03

1

You can take a look at the context that is passed in. There maybe more goodies to discover there.

exports.handler = function(event, context) {
    console.log('Function name:', context.functionName);
    context.succeed();
};

I don't know anything that simply tells you the region. An ugly hack would be exec-ing something in the containing OS (linux) and hoping for the info to show up. uname -a perhaps.

I'm just curious. What do you need it for? Some kind of debugging info?

answered Oct 06 '16 at 23:03

Bela Vizy

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The lambda will be deployed in different regions and consequently will have region-specific configuration values (SNS topics, for one). – ktippetts Oct 07 '16 at 17:18
Additionally (and most importantly), the config file (json) contains the config for all regions, with the key as the region. – ktippetts Oct 07 '16 at 20:06

score 0 · Answer 3 · answered Oct 13 '16 at 20:46

There just doesn't seem to be a more direct way to identify the region in a running lambda function, other than using context.invokedFunctionArn property.

Here's what I ended up doing:

exports.handler = (event,context, callback) => {
    var arnList = (context.invokedFunctionArn).split(":");
    var lambdaRegion = arnList[3] //region is the fourth element in a lambda function arn


    //more code
}

How to get the AWS Region in a Javascript/Nodejs Lambda Function:

3 Answers3