Move async work out of the Server constructor

Summary:
I feel like doing async stuff here isn't a good idea in general.
But more pressingly, it means you can't immediately call server.close() after new Server(), because the things to close haven't been created yet.

Reviewed By: danielbuechele

Differential Revision: D10488301

fbshipit-source-id: 76ebe91e0c09f353e0bdb9f2e4116757e757abb2

src/__tests__/server.electron.js

@@ -24,6 +24,7 @@ beforeAll(() => {
   }
 
   server = new Server(new LogManager(), mockStore);
+  return server.init();
 });
 
 test('servers starting at ports', done => {

src/dispatcher/server.js

@@ -13,6 +13,7 @@ import type Client from '../Client.js';
 
 export default (store: Store, logger: Logger) => {
   const server = new Server(logger, store);
+  server.init();
 
   server.addListener('new-client', (client: Client) => {
     store.dispatch({

src/server.js

@@ -44,6 +44,7 @@ export default class Server extends EventEmitter {
   connectionTracker: ConnectionTracker;
   logger: Logger;
   store: Store;
+  initialisePromise: Promise<void>;
 
   constructor(logger: Logger, store: Store) {
     super();
@@ -52,7 +53,6 @@ export default class Server extends EventEmitter {
     this.certificateProvider = new CertificateProvider(this, logger);
     this.connectionTracker = new ConnectionTracker(logger);
     this.store = store;
-    this.init();
   }
 
   on: ((event: 'new-client', callback: (client: Client) => void) => void) &
@@ -60,12 +60,16 @@ export default class Server extends EventEmitter {
     ((event: 'clients-change', callback: () => void) => void);
 
   init() {
-    this.certificateProvider
+    this.initialisePromise = this.certificateProvider
       .loadSecureServerConfig()
       .then(
         options => (this.secureServer = this.startServer(SECURE_PORT, options)),
-      );
-    this.insecureServer = this.startServer(INSECURE_PORT);
+      )
+      .then(() => {
+        this.insecureServer = this.startServer(INSECURE_PORT);
+        return;
+      });
+    return this.initialisePromise;
   }
 
   startServer(port: number, sslConfig?: SecureServerConfig) {
@@ -232,9 +236,14 @@ export default class Server extends EventEmitter {
     };
   };
 
-  close() {
-    this.secureServer.stop();
-    this.insecureServer.stop();
+  close(): Promise<void> {
+    if (this.initialisePromise) {
+      return this.initialisePromise.then(_ => {
+        this.secureServer.stop();
+        this.insecureServer.stop();
+      });
+    }
+    return Promise.resolve();
   }
 
   toJSON() {