Refactor checks to see if socket is in use

Summary:
These are utility methods that are not specific to startServer.

They will be reused by other components needing to check if something is listening to a port.

Make socket path is also extracted.

Reviewed By: passy

Differential Revision: D36473641

fbshipit-source-id: 73ed67912052896696b59670cb757d22761eeaa1

desktop/flipper-server/src/startServer.tsx

@@ -8,7 +8,7 @@
  */
 
 import os from 'os';
-import net from 'net';
+
 import express, {Express} from 'express';
 import http, {ServerResponse} from 'http';
 import path from 'path';
@@ -16,7 +16,8 @@ import fs from 'fs-extra';
 import {VerifyClientCallbackSync, WebSocketServer} from 'ws';
 import {WEBSOCKET_MAX_MESSAGE_SIZE} from 'flipper-server-core';
 import {parse} from 'url';
-import xdgBasedir from 'xdg-basedir';
+import {makeSocketPath, checkSocketInUse} from './utilities';
+
 import proxy from 'http-proxy';
 import exitHook from 'exit-hook';
 
@@ -78,66 +79,6 @@ async function startHTTPServer(
   return startProxyServer(config, app);
 }
 
-/**
- * Checks if a socket is in used for given path.
- * If the path doesn't exist then is not in use. If it does,
- * create a socket client and attempt to connect to it.
- * If the connection is established, then there's a process
- * already listening. Otherwise, it kind of indicates the
- * contrary.
- * @param path Path used instead of port number.
- * @returns True or false dependning on whether the socket is in
- * use or not.
- */
-async function checkSocketInUse(path: string): Promise<boolean> {
-  if (!(await fs.pathExists(path))) {
-    return false;
-  }
-  return new Promise((resolve, _reject) => {
-    const client = net
-      .createConnection(path, () => {
-        resolve(true);
-        client.destroy();
-      })
-      .on('error', (e) => {
-        if (e.message.includes('ECONNREFUSED')) {
-          resolve(false);
-        } else {
-          console.warn(
-            `[conn] Socket ${path} is in use, but we don't know why.`,
-            e,
-          );
-          resolve(false);
-        }
-        client.destroy();
-      });
-  });
-}
-
-/**
- * Creates a socket path. Used to open the socket at location.
- * Format: flipper-server-${userInfo}.sock
- * @returns The created socket path.
- */
-async function makeSocketPath(): Promise<string> {
-  const runtimeDir = xdgBasedir.runtime || '/tmp';
-  await fs.mkdirp(runtimeDir);
-  const filename = `flipper-server-${os.userInfo().uid}.sock`;
-  const path = `${runtimeDir}/${filename}`;
-
-  // Depending on the OS this is between 104 and 108:
-  // https://unix.stackexchange.com/a/367012/10198
-  if (path.length >= 104) {
-    console.warn(
-      'Ignoring XDG_RUNTIME_DIR as it would exceed the total limit for domain socket paths. See man 7 unix.',
-    );
-    // Even with the INT32_MAX userid, we should have plenty of room.
-    return `/tmp/${filename}`;
-  }
-
-  return path;
-}
-
 /**
  * Creates and starts the HTTP and proxy servers.
  * @param config Server configuration.

desktop/flipper-server/src/utilities.tsx

@@ -0,0 +1,73 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import os from 'os';
+import xdgBasedir from 'xdg-basedir';
+import net from 'net';
+import fs from 'fs-extra';
+
+/**
+ * Checks if a socket is in used for given path.
+ * If the path doesn't exist then is not in use. If it does,
+ * create a socket client and attempt to connect to it.
+ * If the connection is established, then there's a process
+ * already listening. Otherwise, it kind of indicates the
+ * contrary.
+ * @param path Path used instead of port number.
+ * @returns True or false dependning on whether the socket is in
+ * use or not.
+ */
+export async function checkSocketInUse(path: string): Promise<boolean> {
+  if (!(await fs.pathExists(path))) {
+    return false;
+  }
+  return new Promise((resolve, _reject) => {
+    const client = net
+      .createConnection(path, () => {
+        resolve(true);
+        client.destroy();
+      })
+      .on('error', (e) => {
+        if (e.message.includes('ECONNREFUSED')) {
+          resolve(false);
+        } else {
+          console.warn(
+            `[conn] Socket ${path} is in use, but we don't know why.`,
+            e,
+          );
+          resolve(false);
+        }
+        client.destroy();
+      });
+  });
+}
+
+/**
+ * Creates a socket path. Used to open the socket at location.
+ * Format: flipper-server-${userInfo}.sock
+ * @returns The created socket path.
+ */
+export async function makeSocketPath(): Promise<string> {
+  const runtimeDir = xdgBasedir.runtime || '/tmp';
+  await fs.mkdirp(runtimeDir);
+  const filename = `flipper-server-${os.userInfo().uid}.sock`;
+  const path = `${runtimeDir}/${filename}`;
+
+  // Depending on the OS this is between 104 and 108:
+  // https://unix.stackexchange.com/a/367012/10198
+  if (path.length >= 104) {
+    console.warn(
+      'Ignoring XDG_RUNTIME_DIR as it would exceed the total limit for domain socket paths. See man 7 unix.',
+    );
+    // Even with the INT32_MAX userid, we should have plenty of room.
+    return `/tmp/${filename}`;
+  }
+
+  return path;
+}