@benswinburne/closest-aws-region

Find the Closest AWS Region

Why?

Whilst using lambda@edge your code runs in any one of the available data centres, which is not necessarily true for your data or other services perhaps.

For example, if I'm using Dynamodb global tables and my data exists in eu-west-1, us-east-2 and ap-southeast-1, when my lambda@edge function runs and sets up a DocumentClient using process.env.AWS_REGION, the value of this environment variable may be any of the available AWS regions, perhaps eu-central-1.

What this means is that the DocumentClient will fail to retrieve the data as it attempts to access it from Dynamodb at eu-central-1 as it hasn't been replicated to that region.

Rather than hard coding or chosing one of the three regions in which I've stored my data, using this package I can determine which of the regions which contains my data is closest to process.env.AWS_REGION (or at least has the lowest latency).

Installation

npm install @benswinburne/closest-aws-region

Import/Require

CommonJS:

var closestAWSRegion = require('@benswinburne/closest-aws-region')

ES Modules:

import closestAWSRegion from '@benswinburne/closest-aws-region'

Quick Start

// AWS_REGION = eu-central-1

const region = findClosestAWSRegion(process.env.AWS_REGION, {
  filters: ['eu-west-1', 'us-east-1', 'ap-southeast-1'],
}); // eu-west-1

API

closestAWSRegion(to, [options])

Find the closest region to that specified in to.

Note: If options.filters is not set, the closest region will always be to.

Options

default

The default region to select in the event that no region is found. This defaults to us-east-1 if not set.

filters

Specify the region(s) to limit your search to.

// AWS_REGION = eu-central-1

const region = findClosestAWSRegion(process.env.AWS_REGION, {
  filters: ['eu-west-1', 'us-east-1']
}); // eu-west-1

excludeTo (defaults to false)

If for example you are looking for the closest region to eu-west-1, with no filters applied obviously eu-west-1 is the closted region. By excluding to, the return value will be the closest region to eu-west-1 which is not eu-west-1.

data

This option allows for overwriting the static datasource. The format must follow the structure used by cloudping.co.

Note: it's not recommended that a remote datasource is used with lambda@edge because the latency savings by finding the closest region are lost during the roundtrip to an external source

// AWS_REGION = eu-central-1

const response = await fetch('https://api.cloudping.co/averages');
const data = await response.json();

const region = findClosestAWSRegion(process.env.AWS_REGION, {
  data: data
});