Clean up socket on exit

Summary: Be more aggressive in cleaning up after ourselves. Using a tiny library by Sindre that handles standard exit events, SIGTERM and SIGINT.

Reviewed By: aigoncharov

Differential Revision: D35281772

fbshipit-source-id: a789f90f172b3aa3e187739cf2b7fefa75405891

desktop/flipper-server/package.json

@@ -10,6 +10,7 @@
   "bugs": "https://github.com/facebook/flipper/issues",
   "dependenciesComment": "mac-ca is required dynamically for darwin, node-fetch is treated special in electron-requires, not sure why",
   "dependencies": {
+    "exit-hook": "^2.1.1",
     "http-proxy": "^1.18.1",
     "mac-ca": "^1.0.6",
     "node-fetch": "^2.6.7",

desktop/flipper-server/src/startBaseServer.tsx

@@ -18,6 +18,7 @@ import {WEBSOCKET_MAX_MESSAGE_SIZE} from 'flipper-server-core';
 import {parse} from 'url';
 import xdgBasedir from 'xdg-basedir';
 import proxy from 'http-proxy';
+import exitHook from 'exit-hook';
 
 import {userInfo} from 'os';
 
@@ -145,6 +146,13 @@ async function startProxyServer(
   console.log('Starting socket server on ', socketPath);
   console.log(`Starting proxy server on http://localhost:${config.port}`);
 
+  exitHook(() => {
+    console.log('Cleaning up socket on exit:', socketPath);
+    // This *must* run synchronously and we're not blocking any UI loop by definition.
+    // eslint-disable-next-line node/no-sync
+    fs.rmSync(socketPath, {force: true});
+  });
+
   proxyServer.on('error', (err, _req, res) => {
     console.warn('Error in proxy server:', err);
     if (res instanceof ServerResponse) {