Check if server is already listening

Summary:
Right now, this simply avoids trying to create a server instance if one appears to be already running.

In a future change, we may decide to kill the existing instance and replace it with a new one.

But, in this case, running this as is will be useful as it will provide the connection URL with the auth token.

Also remove flipper server dependency from finding installation. In this case, we don't need it and can use `os.getPlatform()` instead.

Reviewed By: antonk52

Differential Revision: D46144843

fbshipit-source-id: 2922843b916d37e0126e43ae65a622f87a6920ec

desktop/flipper-server/src/index.tsx

@@ -19,6 +19,7 @@ import yargs from 'yargs';
 import open from 'open';
 import {initCompanionEnv} from 'flipper-server-companion';
 import {
+  checkPortInUse,
   getEnvironmentInfo,
   startFlipperServer,
   startServer,
@@ -76,7 +77,7 @@ const argv = yargs
   .parse(process.argv.slice(1));
 
 console.log(
-  `Starting flipper server with ${
+  `[flipper-server] Starting flipper server with ${
     argv.bundler ? 'UI bundle from source' : 'pre-bundled UI'
   }`,
 );
@@ -105,16 +106,9 @@ async function start() {
       keytar = electronRequire(keytarPath);
     }
   } catch (e) {
-    console.error('Failed to load keytar:', e);
+    console.error('[flipper-server] Failed to load keytar:', e);
   }
 
-  const {app, server, socket, readyForIncomingConnections} = await startServer({
-    staticPath,
-    entry: `index.web${argv.bundler ? '.dev' : ''}.html`,
-    port: argv.port,
-    tcp: argv.tcp,
-  });
-
   const isProduction =
     process.env.NODE_ENV !== 'development' && process.env.NODE_ENV !== 'test';
 
@@ -124,6 +118,18 @@ async function start() {
     true,
   );
 
+  if (await checkPortInUse(argv.port)) {
+    console.warn(`[flipper-server] Port ${argv.port} is already in use`);
+    return;
+  }
+
+  const {app, server, socket, readyForIncomingConnections} = await startServer({
+    staticPath,
+    entry: `index.web${argv.bundler ? '.dev' : ''}.html`,
+    port: argv.port,
+    tcp: argv.tcp,
+  });
+
   const flipperServer = await startFlipperServer(
     rootPath,
     staticPath,
@@ -147,7 +153,7 @@ async function start() {
     flipperServer.on('server-state', ({state}) => {
       if (state === 'error') {
         console.error(
-          '[flipper-server-process-exit] state changed to error, process will exit.',
+          '[flipper-server] state changed to error, process will exit.',
         );
         process.exit(1);
       }
@@ -165,7 +171,7 @@ async function start() {
 
 process.on('uncaughtException', (error) => {
   console.error(
-    '[flipper-server-process-exit] uncaught exception, process will exit.',
+    '[flipper-server] uncaught exception, process will exit.',
     error,
   );
   process.exit(1);
@@ -183,17 +189,23 @@ process.on('unhandledRejection', (reason, promise) => {
 start()
   .then(async (flipperServer) => {
     if (!argv.tcp) {
-      console.log('Flipper server started');
       return;
     }
-    console.log(
-      'Flipper server started and is listening at port ' +
-        chalk.green(argv.port),
-    );
-    const token = await getAuthToken();
+
+    console.log('[flipper-server] listening at port ' + chalk.green(argv.port));
+
+    let token: string | undefined;
+    if (flipperServer) {
+      token = await getAuthToken();
+    } else {
+      const tokenPath = path.resolve(staticPath, 'auth.token');
+      token = await fs.readFile(tokenPath, 'utf-8');
+    }
+
     const searchParams = new URLSearchParams({token: token ?? ''});
     const url = new URL(`http://localhost:${argv.port}?${searchParams}`);
-    console.log('Go to: ' + chalk.green(chalk.bold(url)));
+
+    console.log('[flipper-server] Go to: ' + chalk.green(chalk.bold(url)));
     if (!argv.open) {
       return;
     }
@@ -201,7 +213,7 @@ start()
     if (argv.bundler) {
       open(url.toString());
     } else {
-      const path = await findInstallation(flipperServer);
+      const path = await findInstallation();
       open(path ?? url.toString());
     }
   })