abacus-webapp/src/index.js

'use strict';

// Setup of Express in a Node cluster, a convenient starting point for Webapps.
// Also sets up some call perf metrics collection across the cluster.

const _ = require('underscore');
const wrap = _.wrap;

const express = require('abacus-express');
const cluster = require('abacus-cluster');
const vcapenv = require('abacus-vcapenv');
const perf = require('abacus-perf');
const hystrix = require('abacus-hystrix');
const eureka = require('abacus-eureka');
const oauth = require('abacus-oauth');
const cp = require('child_process');
const commander = require('commander');
const rc = require('abacus-rc');

// Setup debug log
const debug = require('abacus-debug')('abacus-webapp');
const edebug = require('abacus-debug')('e-abacus-webapp');

const defaultSecurity = () => process.env.SECURED === 'true';
const secured = () => process.env.HEALTHCHECK_SECURED === 'false' ? false : defaultSecurity();

const healthCheckScopes = 'abacus.system.read';

const defaultHealthCheck = (req, res) => {
  debug(`Entering ${secured ? 'secured' : ''} healthcheck`);
  const h = perf.healthy();
  debug('Returning app health %s', h);
  res.status(h ? 200 : 500).send({
    healthy: h
  });
};

// Configure a clustered Express-based Web app
//
// Use like this:
// const app = webapp();
// app.listen();
const webapp = () => {
  // Determine the app name
  const appname = vcapenv.appname();
  debug('Creating app %s', appname);

  // Create the app
  const app = cluster(express());

  // Configure the app to report its app instance id and instance index
  app.use(vcapenv.headers());

  let healthCheckMiddlware = defaultHealthCheck;

  /**
   * Specifies the healthcheck middleware to use for the
   * healthcheck endpoint.
   * If no middleware is specified or this method is not called, a
   * default one will be used.
   */
  app.useHealthCheck = (middlware) => {
    if (middlware) healthCheckMiddlware = middlware;
    else healthCheckMiddlware = defaultHealthCheck;
  };

  // Monkey patch the app listen function to register some of our middleware
  // after the app's middleware
  app.listen = wrap(app.listen, (listen, opt, cb) => {
    if (secured())
      app.use(
        '/hystrix.stream',
        oauth.basicStrategy(process.env.API, hystrix.scopes, process.env.JWTKEY, process.env.JWTALGO)
      );
    app.use('/hystrix.stream', hystrix.stream());

    if (secured())
      app.use(
        '/healthcheck',
        oauth.basicStrategy(process.env.API, healthCheckScopes, process.env.JWTKEY, process.env.JWTALGO)
      );
    app.get('/healthcheck', healthCheckMiddlware);

    // Call the original app listen function
    debug('Listening');
    const server = listen.call(app, opt, cb);

    // Optionally register the app instance in a Eureka registry
    if (cluster.isMaster() && eureka())
      eureka.register(eureka(), appname, vcapenv.iport() || server.address().port, vcapenv.iaddress(), (err, val) => {
        if (err) debug('Couldn\'t register app %s in Eureka registry, %o', appname, err);
        else debug('Registered app %s in Eureka registry', appname);
      });

    return server;
  });

  return app;
};

// Return a clustered basic Express app
const basic = () => {
  return cluster(express.basic());
};

// Let the Express module send messages to the cluster master
express.on('message', cluster.onMessage);

// Broadcast perf stat messages across the cluster. Only need to do that
// if we have more than one worker in the cluster.
if (cluster.size() > 1) {
  debug('Broadcasting perf stat messages across the cluster');
  cluster.on('message', perf.onMessage);
  perf.on('message', cluster.onMessage);
}

// Set default port and host name, command line has higher priority then
// the existing env, then rc files
const conf = () => {
  process.env.PORT = commander.port || process.env.PORT || 9080;
  if (commander.host) process.env.HOST = commander.host;
};

// Command line interface
const runCLI = () => {
  // Parse command line options
  commander
    .option('-p, --port <port>', 'port number [9080]')
    .option('-h, --host <hostname>', 'host name [*]')
    .option('start', 'start the server')
    .option('stop', 'stop the server')
    .parse(process.argv);

  // Load env from rc file
  rc();

  // Start a Webapp
  if (commander.start) {
    conf();

    // Run the app CLI
    const app = require(process.cwd());
    if (app && app.runCLI) app.runCLI();
  } else if (commander.stop)
    // Stop the Webapp
    cp.exec('pkill -f "node ' + vcapenv.appname() + '.* master"', (err, stdout, stderr) => {
      if (err) edebug('Stop error %o', err);
    });
};

// Export our public functions
module.exports = webapp;
module.exports.basic = basic;
module.exports.runCLI = runCLI;