Refactors configuration management (#4271)

* Adds flow types / Configuration interfaces

* Lets call it options

* Use a single interface to generate the configurations

* Translates options to definitions only if comments are set

* improves logic

* Moves objects around

* Fixes issue affecting logging of circular objects

* fixes undefined env

* Moves all defaults to defaults

* Adds back CLI defaults

* Restored defaults in commander.js

* Merge provided defaults and platform defaults

* Addresses visual nits

* Improves Config.js code

* Adds ability to pass the default value in trailing comments

* Load platform defaults from the definitions file

* proper default values on various options

* Adds ParseServer.start and server.start(options) as quick startup methods

* Moves creating liveQueryServer http into ParseServer.js

* removes dead code

* Adds tests to guarantee we can start a LQ Server from main module

* Fixes incorrect code regading liveQuery init port

* Start a http server for LQ if port is specified

* ensure we dont fail if config.port is not set

* Specify port

* ignore other path skipped in tests

* Adds test for custom middleware setting

* Refactors new Config into Config.get

- Hides AppCache from ParseServer.js, use Config.put which validates

* Extracts controller creation into Controllers/index.js

- This makes the ParseServer init way simpler

* Move serverURL inference into ParseServer

* review nits

src/cli/parse-server.js

@@ -1,11 +1,9 @@
 /* eslint-disable no-console */
-import express from 'express';
 import ParseServer from '../index';
 import definitions from './definitions/parse-server';
 import cluster from 'cluster';
 import os from 'os';
 import runner from './utils/runner';
-const path = require("path");
 
 const help = function(){
   console.log('  Get Started guide:');
@@ -29,79 +27,12 @@ const help = function(){
   console.log('');
 };
 
-function startServer(options, callback) {
-  const app = express();
-  if (options.middleware) {
-    let middleware;
-    if (typeof options.middleware == 'function') {
-      middleware = options.middleware;
-    } if (typeof options.middleware == 'string') {
-      middleware = require(path.resolve(process.cwd(), options.middleware));
-    } else {
-      throw "middleware should be a string or a function";
-    }
-    app.use(middleware);
-  }
-
-  const parseServer = new ParseServer(options);
-  const sockets = {};
-  app.use(options.mountPath, parseServer.app);
-
-  const server = app.listen(options.port, options.host, callback);
-  server.on('connection', initializeConnections);
-
-  if (options.startLiveQueryServer || options.liveQueryServerOptions) {
-    let liveQueryServer = server;
-    if (options.liveQueryPort) {
-      liveQueryServer = express().listen(options.liveQueryPort, () => {
-        console.log('ParseLiveQuery listening on ' + options.liveQueryPort);
-      });
-    }
-    ParseServer.createLiveQueryServer(liveQueryServer, options.liveQueryServerOptions);
-  }
-
-  function initializeConnections(socket) {
-    /* Currently, express doesn't shut down immediately after receiving SIGINT/SIGTERM if it has client connections that haven't timed out. (This is a known issue with node - https://github.com/nodejs/node/issues/2642)
-
-      This function, along with `destroyAliveConnections()`, intend to fix this behavior such that parse server will close all open connections and initiate the shutdown process as soon as it receives a SIGINT/SIGTERM signal. */
-
-    const socketId = socket.remoteAddress + ':' + socket.remotePort;
-    sockets[socketId] = socket;
-
-    socket.on('close', () => {
-      delete sockets[socketId];
-    });
-  }
-
-  function destroyAliveConnections() {
-    for (const socketId in sockets) {
-      try {
-        sockets[socketId].destroy();
-      } catch (e) { /* */ }
-    }
-  }
-
-  const handleShutdown = function() {
-    console.log('Termination signal received. Shutting down.');
-    destroyAliveConnections();
-    server.close();
-    parseServer.handleShutdown();
-  };
-  process.on('SIGTERM', handleShutdown);
-  process.on('SIGINT', handleShutdown);
-}
-
-
 runner({
   definitions,
   help,
   usage: '[options] <path/to/configuration.json>',
   start: function(program, options, logOptions) {
-    if (!options.serverURL) {
-      options.serverURL = `http://localhost:${options.port}${options.mountPath}`;
-    }
-
-    if (!options.appId || !options.masterKey || !options.serverURL) {
+    if (!options.appId || !options.masterKey) {
       program.outputHelp();
       console.error("");
       console.error('\u001b[31mERROR: appId and masterKey are required\u001b[0m');
@@ -132,12 +63,12 @@ runner({
           cluster.fork();
         });
       } else {
-        startServer(options, () => {
+        ParseServer.start(options, () => {
           console.log('[' + process.pid + '] parse-server running on ' + options.serverURL);
         });
       }
     } else {
-      startServer(options, () => {
+      ParseServer.start(options, () => {
         logOptions();
         console.log('');
         console.log('[' + process.pid + '] parse-server running on ' + options.serverURL);