@smithy/middleware-endpoint

What is @smithy/middleware-endpoint?

@smithy/middleware-endpoint is a middleware package for the AWS SDK for JavaScript (v3) that helps in resolving and customizing endpoints for service clients. It allows developers to modify endpoint resolution logic, making it easier to direct requests to different endpoints based on custom logic or configuration.

What are @smithy/middleware-endpoint's main functionalities?

Custom Endpoint Resolution

This feature allows you to customize the endpoint resolution logic. In this example, the middleware modifies the request's hostname to a custom endpoint before passing it to the next middleware in the stack.

const { EndpointMiddleware } = require('@smithy/middleware-endpoint');
const { HttpRequest } = require('@smithy/protocol-http');

const customEndpointMiddleware = (next, context) => async (args) => {
  const request = args.request;
  if (HttpRequest.isInstance(request)) {
    request.hostname = 'custom-endpoint.example.com';
  }
  return next({ ...args, request });
};

// Usage in a client configuration
const client = new SomeAWSClient({
  region: 'us-west-2',
  middlewareStack: [customEndpointMiddleware]
});

Conditional Endpoint Resolution

This feature allows you to conditionally resolve endpoints based on the operation being performed. In this example, the middleware changes the endpoint only for the 'GetItem' operation.

const { EndpointMiddleware } = require('@smithy/middleware-endpoint');
const { HttpRequest } = require('@smithy/protocol-http');

const conditionalEndpointMiddleware = (next, context) => async (args) => {
  const request = args.request;
  if (HttpRequest.isInstance(request) && context.operationName === 'GetItem') {
    request.hostname = 'get-item-endpoint.example.com';
  }
  return next({ ...args, request });
};

// Usage in a client configuration
const client = new SomeAWSClient({
  region: 'us-west-2',
  middlewareStack: [conditionalEndpointMiddleware]
});

Other packages similar to @smithy/middleware-endpoint

axios

Axios is a promise-based HTTP client for the browser and Node.js. It allows you to intercept requests and responses, making it possible to modify endpoints and other request parameters. Compared to @smithy/middleware-endpoint, Axios is more general-purpose and not specifically tailored for AWS SDK.

request

Request is a simplified HTTP client for Node.js with support for various features like custom endpoints, redirects, and more. While it provides similar functionalities for modifying request parameters, it is not specialized for AWS SDK like @smithy/middleware-endpoint.

got

Got is a human-friendly and powerful HTTP request library for Node.js. It supports hooks that can be used to modify request options, including endpoints. Like Axios and Request, Got is a general-purpose HTTP client and not specifically designed for AWS SDK.

README

@smithy/middleware-endpoint

An internal package

Usage

You probably shouldn't, at least directly.