gcf-api-router

Simple Express-style HTTP request router to build API handlers with Google Cloud Functions.

Overview

const router = require('gcf-api-router')();

// Define routes and assign route/method handlers

router.route('/subscriptions')
      .get(listSubscriptions)
      .post(createSubscription);

router.route('/subscriptions/:id')
      .get(showSubscription)
      .put(updateSubscription)
      .delete(deleteSubscription);

// Export the router as Google Cloud HTTP Function

exports.myApiHandler = router.onRequest;

Each individual route/method handler must be designed to expect (req, res) as input arguments.

This module uses path-to-regex for matching the route paths. Therefore, route parameters can be specified following the route path conventions of Express. When a specific route includes parameters, the req.params property is updated with the actual set of parameter keys/values before invoking the route/method handler.

Example:

router.route('/models/:model/:year').get(showModel);

// GET /{basePath}/models/Model%20X/2017

function showModel(req, res) {
  console.log(req.params);
  // { model: 'Model X', year: '2017'}
}

In the above example, basePath is the path associated with your Google Cloud Function, i.e. the name of the function itself.

The API router automatically replies 404 Not Found - with no body and no event logging - to requests that do not match any of the specified routes. When needed, the behavior can be customized by assigning a dedicated handler to the not found case:

router.notFound(notFoundHandler);

Multiple handlers can be defined for each individual route/method and for the not found case. Example:

router.route('/sensors/:id/status')
      .get(showStatus)
      .put(enforceAuthorization, updateStatus);

router.notFound(doSomething, doSomethingElse);

When multiple handlers are used, each handler that is not the last of the list must be designed to expect (req, res, next) as input arguments, and to invoke next() to pass the control to the next following handler in the list. Example:

function doSomething(req, res, next) {
  if (someCondition) {
    // Respond without executing next handler
    res.status(400).send();
  } else {
    // Pass control to next handler
    next();
  }
}

function doSomethingElse(req, res) {
  res.send('Both handlers have been invoked in sequence');
}

This approach enables the direct reuse of some of the middleware designed for Express. As an example, the following snippet illustrates the use of the cookie-parser package.

const cookieParser = require('cookie-parser')();

router.route('/sensors/:id/status')
      .get(cookieParser, showStatus);

function showStatus(req, res) {
  // Find parsed cookies in req.cookies

  res.json(someData);
}

Installation

npm install gcf-api-router --save

Usage

The API router can be instantiated following either one of two possible options. The difference is merely a style preference.

// OPTION #1
const router = require('gcf-api-router')();

// OPTION #2
const apiRouter = require('gcf-api-router');
const router = apiRouter();

The following methods are supported:

router.onRequest(req, res)

This is the method that must be exported as entry point of the Google Cloud HTTP Function. For example, if Function to execute is set equal to myApiHandler in the Google Cloud Functions console, then:

exports.myApiHandler = router.onRequest;

Alternatively, in case every HTTP request must undergo some processing/verification/logging common to all routes, the router.onRequest method can be used in the following manner:

exports.myApiHandler = function(req, res) {

  // Some request processing/verification/logging here

  router.onRequest(req, res);
}

router.route(path)

Specifies a route path. The route path can include parameters encoded in accordance with the route path conventions of Express. Those conventions enable also compound names like the following:

router.route('/flights/:from-:to')

router.route('/plantae/:genus.:species')

A regular expression within parentheses can be used to have more control over the exact string that can be matched by a route parameter:

router.route('/user/:userId(\\d+)')

In the above example, note the escaping of \ due to the fact that the regular expression is part of a string.

router.get(reqHandler[, reqHandler2] ... [, reqHandlerN])

Specifies one or more request handlers to be invoked in sequence for GET requests. The router.get method must always be chained to a router.route method or to another router.{httpMethod} method. The chaining order of different router.{httpMethod} methods is irrelevant.

reqHandler must be a function that accepts (req, res) as arguments. When multiple handlers are specified, all handlers except the last of the sequence must also accept next as argument, i.e. (req, res, next).

If appropriate, the same requestHandler can be associated with multiple routes/methods.

router.post(reqHandler[, reqHandler2] ... [, reqHandlerN])

Same as router.get above, but for POST requests.

router.put(reqHandler[, reqHandler2] ... [, reqHandlerN])

Same as router.get above, but for PUT requests.

router.patch(reqHandler[, reqHandler2] ... [, reqHandlerN])

Same as router.get above, but for PATCH requests.

router.delete(reqHandler[, reqHandler2] ... [, reqHandlerN])

Same as router.get above, but for DELETE requests.

router.options(reqHandler[, reqHandler2] ... [, reqHandlerN])

Same as router.get above, but for OPTIONS requests.

router.notFound(reqHandler[, reqHandler2] ... [, reqHandlerN])

Specifies one or more request handlers to be invoked in sequence for requests that do not match any of the defined routes/methods.

reqHandler must be a function that accepts (req, res) as arguments. When multiple handlers are specified, all handlers except the last of the sequence must also accept next as argument, i.e. (req, res, next).

If the router.notFound method is not used, then the API router simply replies 404 Not Found - with no body and no event logging - to requests that do not match any of the defined routes/methods.