API Binary Proxy

Proxy to serve binaries such as images from an API that returns base64 encoded files inside a JSON structure.

Introduction

Currently a proof of concept with the plan to address performance issues and export a route that can be mounted in a parent application.

API

apiBinaryProxy(config)

Returns a route handler that can be used by Express.

Where config is of the shape {apiUrl, propertyNames, assumeMimeType}:

• apiUrl: The API url uses sprintf format (see below)
• propertyNames: An object of the shape {payload, extension, mime, filename}, containing property names that are expected in the upstream API. Each property will default to the property name if not supplied (i.e. payload defaults to "payload"):
  • payload: the base64 encoded file
  • extension: the file extension, this could be with or without an initial .
  • mime: the mime type of the file if available
  • filename: the full filename if available
• assumeMimeType: the mime type to use if it can't be identified from the upstream API. If not set, will return 404 for unknown mime types.
• forwardHeaders: Whether to forward incoming headers to the upstream API. Defaults to false.
• forwardQueryString: Whether to forward query string to the upstream API. Defaults to true.

Usage

With Express

const express = require('express')
const apiBinaryProxy = require('api-binary-proxy');

const app = express();

app.use('/files', apiBinaryProxy({
    apiUrl: 'http://localhost:3001/api/%1$s',
    propertyNames: {payload: 'image'},
    assumeMimeType: 'image/jpeg',
    forwardHeaders: true,
    forwardQueryString: true
}));

In the example above, %1$s will be replaced by any path after '/files' (req.path).

Sprintf

The API url uses sprintf format, for more information see the sprintf-js readme. This is to enable further configuration options to be added in future and to support alternative uses such as:

• http://localhost:3001/api/%1$s/binary
• http://localhost:3001/api/binaries/%1$s?format=jpeg

TODO:

• More configuration options on API url.
• Allow extensions such as '.jpg' to be appended to incoming api url.
• Improve error handling, possibly allowing a callback to be passed in for logging.
• Unit tests

Developing

npm i
npm run dev

Then browse to:

• http://localhost:3000/files/1
• http://localhost:3000/files/2
• http://localhost:3000/files/3
• http://localhost:3000/files/4