electron: fork backend in node process

Simplify Electron's src-gen to always spawn the Theia backend in a Node.js process, and make sure to patch the `process.versions.electron` variable, for packages to correctly understand their environment (Electron vs Node). Add a debug configuration for both electron-main process and backend process. Signed-off-by: Paul Maréchal <paul.marechal@ericsson.com>
eclipse-theia · Mar 20, 2020 · 4445668 · 4445668
1 parent ae5591e
commit 4445668
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Showing 4 changed files with 95 additions and 56 deletions.
diff --git a/.vscode/launch.json b/.vscode/launch.json
@@ -19,30 +19,65 @@
     {
       "type": "node",
       "request": "launch",
-      "name": "Launch Electron Backend",
-      "runtimeExecutable": "${workspaceRoot}/node_modules/.bin/electron",
-      "windows": {
-        "runtimeExecutable": "${workspaceRoot}/node_modules/.bin/electron.cmd"
-      },
+      "name": "Launch Electron Main Process",
+      "runtimeExecutable": "yarn",
+      "runtimeArgs": [
+        "electron",
+        "--inspect-brk=9228", // This config connects to port 9228.
+        "--remote-debugging-port=9222", // Allow attaching to browser-windows.
+      ],
       "cwd": "${workspaceRoot}/examples/electron",
       "protocol": "inspector",
+      "port": 9228,
       "args": [
         ".",
         "--log-level=debug",
         "--hostname=localhost",
         "--no-cluster",
         "--app-project-path=${workspaceRoot}/examples/electron",
-        "--remote-debugging-port=9222",
         "--no-app-auto-install"
       ],
       "env": {
         "NODE_ENV": "development",
+        "THEIA_BACKEND_EXEC_ARGV": "[\"--inspect=9229\"]", // Pass debug flags to backend process.
         "THEIA_WEBVIEW_EXTERNAL_ENDPOINT": "${env:THEIA_WEBVIEW_EXTERNAL_ENDPOINT}"
       },
       "sourceMaps": true,
       "outFiles": [
         "${workspaceRoot}/examples/electron/src-gen/frontend/electron-main.js",
-        "${workspaceRoot}/examples/electron/src-gen/backend/main.js",
+        "${workspaceRoot}/examples/electron/src-gen/backend/main.js"
+      ],
+      "smartStep": true,
+      "internalConsoleOptions": "openOnSessionStart",
+      "outputCapture": "std"
+    },
+    {
+      "type": "node",
+      "request": "launch",
+      "name": "Launch Electron Node Backend",
+      "runtimeExecutable": "yarn",
+      "runtimeArgs": [
+        "electron",
+        "--remote-debugging-port=9222", // Allow attaching to browser-windows.
+      ],
+      "cwd": "${workspaceRoot}/examples/electron",
+      "protocol": "inspector",
+      "port": 9229,
+      "args": [
+        ".",
+        "--log-level=debug",
+        "--hostname=localhost",
+        "--no-cluster",
+        "--app-project-path=${workspaceRoot}/examples/electron",
+        "--no-app-auto-install"
+      ],
+      "env": {
+        "NODE_ENV": "development",
+        "THEIA_BACKEND_EXEC_ARGV": "[\"--inspect-brk=9229\"]", // Pass debug flags to backend process.
+        "THEIA_WEBVIEW_EXTERNAL_ENDPOINT": "${env:THEIA_WEBVIEW_EXTERNAL_ENDPOINT}"
+      },
+      "sourceMaps": true,
+      "outFiles": [
         "${workspaceRoot}/examples/electron/lib/**/*.js",
         "${workspaceRoot}/packages/*/lib/**/*.js",
         "${workspaceRoot}/dev-packages/*/lib/**/*.js"
@@ -51,6 +86,18 @@
       "internalConsoleOptions": "openOnSessionStart",
       "outputCapture": "std"
     },
+    {
+      "type": "node",
+      "request": "attach",
+      "name": "Attach to Electron Node Backend",
+      "port": 9229
+    },
+    {
+      "type": "chrome",
+      "request": "attach",
+      "name": "Attach to Electron Frontend",
+      "port": 9222
+    },
     {
       "type": "node",
       "request": "launch",
@@ -149,12 +196,6 @@
       "url": "http://localhost:3000/",
       "webRoot": "${workspaceRoot}"
     },
-    {
-      "type": "chrome",
-      "request": "attach",
-      "name": "Attach to Electron Frontend",
-      "port": 9222
-    },
     {
       "name": "Launch VS Code Tests",
       "type": "node",
@@ -184,7 +225,7 @@
     {
       "name": "Launch Electron Backend & Frontend",
       "configurations": [
-        "Launch Electron Backend",
+        "Launch Electron Node Backend",
         "Attach to Electron Frontend"
       ]
     }

diff --git a/dev-packages/application-manager/src/generator/backend-generator.ts b/dev-packages/application-manager/src/generator/backend-generator.ts
@@ -27,6 +27,12 @@ export class BackendGenerator extends AbstractGenerator {
     protected compileServer(backendModules: Map<string, string>): string {
         return `// @ts-check
 require('reflect-metadata');
+
+// Patch electron version if missing, see https://github.com/eclipse-theia/theia/pull/7361#pullrequestreview-377065146
+if (typeof process.versions.electron === 'undefined' && typeof process.env.THEIA_ELECTRON_VERSION === 'string') {
+    process.versions.electron = process.env.THEIA_ELECTRON_VERSION;
+}
+
 const path = require('path');
 const express = require('express');
 const { Container } = require('inversify');

diff --git a/dev-packages/application-manager/src/generator/frontend-generator.ts b/dev-packages/application-manager/src/generator/frontend-generator.ts
@@ -325,43 +325,42 @@ app.on('ready', () => {
     // https://github.com/eclipse-theia/theia/issues/3297#issuecomment-439172274
     process.env.THEIA_APP_PROJECT_PATH = resolve(__dirname, '..', '..');
 
-    // Set the electron version for both the dev and the production mode. (https://github.com/eclipse-theia/theia/issues/3254)
-    // Otherwise, the forked backend processes will not know that they're serving the electron frontend.
-    const { versions } = process;
-    // @ts-ignore
-    if (versions && typeof versions.electron !== 'undefined') {
-        // @ts-ignore
-        process.env.THEIA_ELECTRON_VERSION = versions.electron;
+    // Used for debugging:
+    // The backend runs in a separate process, we may want to pass options to it.
+    const theiaNodeBackendExecArgv = [...process.execArgv];
+    if (typeof process.env.THEIA_BACKEND_EXEC_ARGV === 'string') {
+        const parsedExecArgv = JSON.parse(process.env.THEIA_BACKEND_EXEC_ARGV);
+        if (!Array.isArray(parsedExecArgv)) {
+            throw new TypeError('process.env.THEIA_BACKEND_EXEC_ARGV should be a serialized JSON array.');
+        }
+        theiaNodeBackendExecArgv.push(...parsedExecArgv);
+        delete process.env.THEIA_BACKEND_EXEC_ARGV;
     }
 
     const mainPath = join(__dirname, '..', 'backend', 'main');
-    // We need to distinguish between bundled application and development mode when starting the clusters.
-    // See: https://github.com/electron/electron/issues/6337#issuecomment-230183287
-    if (devMode) {
-        process.env[ElectronSecurityToken] = JSON.stringify(electronSecurityToken);
-        require(mainPath).then(address => {
-            loadMainWindow(address.port);
-        }).catch((error) => {
-            console.error(error);
-            app.exit(1);
-        });
-    } else {
-        const cp = fork(mainPath, [], { env: Object.assign({
+    const theiaNodeBackend = fork(mainPath, [], {
+        execArgv: theiaNodeBackendExecArgv,
+        env: Object.assign({
             [ElectronSecurityToken]: JSON.stringify(electronSecurityToken),
-        }, process.env) });
-        cp.on('message', (address) => {
-            loadMainWindow(address.port);
-        });
-        cp.on('error', (error) => {
-            console.error(error);
-            app.exit(1);
-        });
-        app.on('quit', () => {
-            // If we forked the process for the clusters, we need to manually terminate it.
-            // See: https://github.com/eclipse-theia/theia/issues/835
-            process.kill(cp.pid);
-        });
-    }
+            /**
+             * Set the electron version for both the dev and the production mode. (https://github.com/eclipse-theia/theia/issues/3254)
+             * Otherwise, the forked backend processes will not know that they're serving the electron frontend.
+             * The forked backend should patch its \`process.versions.electron\` with this value if it is missing.
+             */
+            THEIA_ELECTRON_VERSION: process.versions.electron,
+        }, process.env)
+    });
+    theiaNodeBackend.on('message', (address) => {
+        loadMainWindow(address.port);
+    });
+    theiaNodeBackend.on('error', (error) => {
+        console.error(error);
+        app.exit(1);
+    });
+    app.on('quit', () => {
+        // Avoid process leak, see: https://github.com/eclipse-theia/theia/issues/835
+        process.kill(theiaNodeBackend.pid);
+    });
 });
 `;
     }

diff --git a/dev-packages/application-package/src/environment.ts b/dev-packages/application-package/src/environment.ts
@@ -21,20 +21,13 @@ const isElectron: () => boolean = require('is-electron');
  */
 class ElectronEnv {
 
-    /**
-     * Environment variable that can be accessed on the `process` to check if running in electron or not.
-     */
-    readonly THEIA_ELECTRON_VERSION = 'THEIA_ELECTRON_VERSION';
-
     /**
      * `true` if running in electron. Otherwise, `false`.
      *
-     * Can be called from both the `main` and the render process. Also works for forked cluster workers.
+     * Can be called from both the `main` and the render process.
      */
     is(): boolean {
-        // When forking a new process from the cluster, we can rely neither on `process.versions` nor `process.argv`.
-        // Se we look into the `process.env` as well. `is-electron` does not do it for us.
-        return isElectron() || typeof process !== 'undefined' && typeof process.env === 'object' && !!process.env.THEIA_ELECTRON_VERSION;
+        return isElectron();
     }
 
     /**