Monocle API Router for Connect

Monocle is a an API router that focuses on consistency, flexibility and performance.

Consistency

Monocle implements various features to encourage consistency across all endpoints.

Schemas

Monocle requires that each resource path includes a schema defined in JSON Schema format. The schema is shared among all HTTP verbs for the resource, e.g. GET, POST, PUT, etc. Monocle also validates all input and output with the schema, ensuring that the schema remains the source of truth for how data is structured.

Server-Side Symlinks

Monocle supports "Server-Side Symlinks" to easily embed a resource in another resource. The Monocle Framework will automatically resolve these symlinks on the server, resulting in a complete response for clients. By utilizing Server-Side Symlinks, consistency comes for free when the Symlinked resources are updated.

Flexibility

Monocle makes no assumptions about how clients consume the data -- the only assumption it makes is that client needs will change regularly.

Property Filtering

Monocle allows clients to specify how much data to return for any given resource. Property filtering supports top-level properties, nested properties, and plucking properties from arrays. See Monocle API Props for details on how property filtering works.

Performance

Monocle allows for performance optimization via caching and property routing.

Caching

Monocle provides cache-control headers for basic REST, but also supports nested resource caching when using the Monocle Client. Collection caching is also supported via the use of weak e-tags.

Property Routing

For large resources, Monocle allows you to provide it with various callbacks that map to each of the properties in the resource. When used with Property Filtering, Monocle will automatically call only the required callbacks to fulfill the request.

Quick Start

To get started, make sure you're using Node 8.8.1 or greater, and create a new node project in an empty directory:

$ mkdir my-monocle-server
$ cd my-monocle-server
$ npm init

After filling in the details, install the required dependencies:

$ npm install monocle-api connect body-parser

Create a file named server.js and add the following code:

const connect = require('connect');
const app = connect();

// Allow parsing of JSON-encoded request body
const bodyParser = require('body-parser');
app.use(bodyParser.json());

// Create an API Router instance
const MonocleApi = require('monocle-api');
const api = new MonocleApi();
const Resource = MonocleApi.Resource;

// For this simple demo we'll set up a simple in-memory data store for the user resources.
const users = {
  1: {
    userId: 1,
    displayName: 'Alice',
    age: 27,
    gender: 'female',
  },
  2: {
    userId: 2,
    displayName: 'Fred',
    age: 22,
    gender: 'male',
  },
};

// Configure your first API route
api.route(
  // Define the URL pattern for this resource
  '/users/:userId',

  // Define the schema for this resource. The schema will be shared across the supported HTTP methods for this resource.
  {
    name: 'User',
    description: 'A user resource',
    type: 'object',
    properties: {
      userId: { type: 'integer', minimum: 1, readOnly: true, sample: 123 },
      displayName: { type: 'string', minLength: 1, maxLength: 255 },
      age: { type: 'integer', minimum: 18, maximum: 99 },
      gender: { type: 'string', enum: ['male', 'female'] },
    },
  },

  // Define the HTTP methods that are supported by this url.
  {
    // Handle GET requests for this resource
    get: (request) => {
      let userId = request.getParam('userId'); // extracts userId param from url, automatically casts it to int due to schema definition

      let user = users[userId];
      if (!user) {
        return request.error(404, { message: 'User not found' });
      }

      // Resolve promise with the user object and it will be converted to JSON automatically
      // Monocle will also validate the return value and return a 500-level error code if the value does not validate.
      return new Resource(`/users/${userId}`, user, 60000);
    },

    // Handle PUT requests for this resource
    put: (request) => {
      let userId = request.getParam('userId'); // extracts userId param from url, automatically casts it to int due to schema definition

      // Replace entire user object with provided resource, which is automatically JSON-decoded
      // Monocle will have rejected this request if the provided resource did not validate with the schema.
      user = request.getResource();

      // Resolve promise with the updated user object
      return new Resource(`/users/${userId}`, user, 60000);
    },
  }
);

// Add the API middleware to your connect app
app.use(api.middleware());

// Create web server and listen on port 5150
const http = require('http');
http.createServer(app).listen(5150, function() {
  console.log("Monocle API is now listening on port 5150");
});

You can now start your monocle server by running node server.js.

REST

Monocle API supports RESTful API calls:

$ curl -i http://127.0.0.1:5150/users/1
HTTP/1.1 200 OK
Content-Type: application/json
cache-control: private, max-age=60000
Date: Thu, 08 Feb 2018 23:27:30 GMT
Connection: keep-alive
Content-Length: 144

{
  "$type": "resource",
  "$id": "/users/1",
  "$expires": 60000,
  "userId": 1,
  "displayName": "Alice",
  "age": 27,
  "gender": "female"
}


$ curl -X PUT -H 'Content-Type: application/json' -d '{"displayName": "Joe", "age": 42, "gender": "male"}' -i http://127.0.0.1:5150/users/1
HTTP/1.1 200 OK
Content-Type: application/json
cache-control: private, max-age=60000
Date: Thu, 08 Feb 2018 23:29:48 GMT
Connection: keep-alive
Content-Length: 125

{
  "$type": "resource",
  "$id": "/users/1",
  "$expires": 60000,
  "displayName": "Joe",
  "age": 42,
  "gender": "male"
}


$ curl -i http://127.0.0.1:5150/users/3
HTTP/1.1 404 Not Found
Content-Type: application/json
Date: Thu, 08 Feb 2018 23:37:36 GMT
Connection: keep-alive
Content-Length: 145

{
  "code": 2000,
  "error": "UNKNOWN",
  "message": "User not found",
  "properties": [],
  "$httpStatus": 404,
  "$httpMessage": "NOT FOUND"
}

Property filtering can be used to restrict how much data is returned.

$ curl -i http://127.0.0.1:5150/users/1?props=displayName,age
HTTP/1.1 200 OK
Content-Type: application/json
cache-control: private, max-age=60000
Date: Thu, 08 Feb 2018 23:39:04 GMT
Connection: keep-alive
Content-Length: 107

{
  "$type": "resource",
  "$id": "/users/1",
  "$expires": 60000,
  "displayName": "Alice",
  "age": 27
}

See demo/index.js for advanced usage.

Files and Directory Structure

The following describes the various files in this repo and the directory structure.

Note: Files and directories prefixed by * are auto-generated and excluded from the repository via .gitignore.

.
├── Gruntfile.js            # grunt task configuration
├── README.md               # this file
├── *docs                   # autogenerated documentation
│   └── *index.html         # each JS file in `./lib` has a corresponding HTML file for documentation
├── lib                     # all code for this library will be placed here
│   └── index.js            # main entry point for the API router
├── *node_modules           # all dependencies will be installed here by npm
├── package.json            # description of this package for npm, including dependency lists
└── test                    # unit test configuration, reports, and specs
    ├── *coverage.html      # code coverage report
    ├── lib                 # specs go here with a 1:1 mapping to code in `./lib`
    │   └── index_test.js   # spec for `./lib/index.js`
    ├── mocha.opts          # runtime options for mocha
    └── test_runner.js      # configures mocha environment (e.g. chai, sinon, etc.)