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Regions

AWS regions must be configured in JustSaying to specify where your SNS topics and SQS queues are located. Region configuration is required and is set using the .Messaging(...) fluent API.

Why Region Configuration is Required​

SNS topics and SQS queues are regional resources in AWS. You must specify which AWS region to use so that JustSaying knows where to create or access your messaging infrastructure.

Configuration Methods​

WithRegion(string region)​

Specify the AWS region using a region code string.

services.AddJustSaying(config =>
{
    config.Messaging(x =>
    {
        x.WithRegion("us-east-1");
    });
});

Common Region Codes:

  • us-east-1 - US East (Virginia)
  • us-west-2 - US West (Oregon)
  • eu-west-1 - Europe (Ireland)
  • eu-central-1 - Europe (Frankfurt)
  • ap-southeast-1 - Asia Pacific (Singapore)
  • ap-northeast-1 - Asia Pacific (Tokyo)

See the AWS Regions documentation for a complete list.

WithRegion(RegionEndpoint region)​

Specify the AWS region using the AWS SDK's RegionEndpoint enum. This provides compile-time safety and IntelliSense support.

using Amazon;

services.AddJustSaying(config =>
{
    config.Messaging(x =>
    {
        x.WithRegion(RegionEndpoint.USEast1);
    });
});

Configuration Patterns​

From Configuration​

Store the region in your application configuration (appsettings.json, environment variables, etc.):

appsettings.json:

{
  "AWS": {
    "Region": "us-east-1"
  }
}

Startup configuration:

services.AddJustSaying(config =>
{
    config.Messaging(x =>
    {
        x.WithRegion(configuration.GetValue<string>("AWS:Region"));
    });
});

Environment-Specific Regions​

Use different regions for different environments:

services.AddJustSaying(config =>
{
    config.Messaging(x =>
    {
        var region = hostEnvironment.IsProduction()
            ? "us-east-1"  // Production in US East
            : "us-west-2"; // Development in US West

        x.WithRegion(region);
    });
});

LocalStack Configuration​

LocalStack typically uses us-east-1 as the default region:

services.AddJustSaying(config =>
{
    config.Client(x =>
    {
        if (hostEnvironment.IsDevelopment())
        {
            x.WithServiceUri(new Uri("http://localhost:4566"))
             .WithAnonymousCredentials();
        }
    });

    config.Messaging(x =>
    {
        // LocalStack default region
        x.WithRegion("us-east-1");
    });
});

Multi-Region Considerations​

JustSaying currently supports a single region per MessagingBus instance. If you need to publish to or subscribe from multiple regions, you must create separate bus instances for each region:

// US East bus
services.AddJustSaying(config =>
{
    config.Messaging(x => x.WithRegion("us-east-1"));
    config.Publications(x => x.WithTopic<USOrderEvent>());
});

// EU West bus (requires additional configuration to avoid conflicts)
// Note: Multiple bus instances require careful service registration

For most applications, a single region is sufficient. Cross-region messaging can be implemented at the application level if needed.

Region and Credentials​

The region configuration is independent of credentials configuration:

services.AddJustSaying(config =>
{
    // Credentials (optional - uses IAM role by default)
    config.Client(x =>
    {
        x.WithBasicCredentials(accessKey, secretKey);
    });

    // Region (required)
    config.Messaging(x =>
    {
        x.WithRegion("eu-west-1");
    });
});

Common Errors​

"No region endpoint specified"​

This error occurs when the region is not configured. Ensure you call .WithRegion(...) in your messaging configuration:

config.Messaging(x =>
{
    x.WithRegion("us-east-1"); // Required
});

"The security token included in the request is invalid"​

This error may occur when credentials are valid for one region but you're trying to access resources in a different region. Verify that:

  1. The region specified in .WithRegion(...) matches where your resources are located
  2. Your IAM credentials have permissions for the specified region

See Also​