AWS Developer Tools Blog

Determining an Application’s Current Region

AWS regions allow you to run your applications in multiple geographically distributed locations all over the world. This allows you to position your applications and data near your customers for the best possible experience. There are ten AWS regions available today:

  • 4 regions in North America
  • 4 regions in Asia Pacific
  • 1 region in South America
  • 1 region in Europe

When you host an application in one region, you typically want to use the AWS services available in that region, since they’ll give you lower latency and higher throughput. If your application is running on Amazon EC2 instances, the latest version of the AWS SDK for Java enables you to easily detect what AWS region those instances are in. Before being able to detect this, if you wanted to run your application in multiple regions, you needed to give your application a region-specific configuration so it knew what regional endpoints to use. The new Regions.getCurrentRegion() method makes this a lot easier. For example, if you start an Amazon EC2 instance in us-west-1 and run your application on that instance, it would know it’s running in us-west-1 and you could use that information to easily configure your application to talk to other services in us-west-1.

// When running on an Amazon EC2 instance, this method
// will tell you what region your application is in
Region region = Regions.getCurrentRegion();

// If you aren’t running in Amazon EC2, then region will be null
// and you can set whatever default you want to use for development
if (region == null) region = Region.getRegion(Regions.US_WEST_1);

// Then just use that same region to construct clients 
// for all the services you want to work with
AmazonDynamoDBClient dynamo = new AmazonDynamoDBClient();
AmazonSQSClient sqs = new AmazonSQSClient();

How are you using AWS regions? Are you running any applications in multiple regions?