fix(child-writer): Handle exits due to a signal (#1843)

This adds handling for cases where the writer child process
exits due to reception of a signal, while also adjusting some peripherals,
like the IPC socket directory and inherited process environment.

Another addition is that the child process is explicitly killed
should an error arise on the IPC.

Change-Type: patch

lib/child-writer/constants.js

@@ -17,6 +17,7 @@
 'use strict'
 
 const path = require('path')
+const os = require('os')
 
 /**
  * @summary Child writer constants
@@ -25,6 +26,13 @@ const path = require('path')
  */
 module.exports = {
 
+  /**
+   * @property {String} TMP_DIRECTORY
+   * @memberof CONSTANTS
+   * @constant
+   */
+  TMP_DIRECTORY: process.env.XDG_RUNTIME_DIR || os.tmpdir(),
+
   /**
    * @property {String} PROJECT_ROOT
    * @memberof CONSTANTS

lib/child-writer/index.js

@@ -26,6 +26,16 @@ const CONSTANTS = require('./constants')
 const EXIT_CODES = require('../shared/exit-codes')
 const robot = require('../shared/robot')
 
+// There might be multiple Etcher instances running at
+// the same time, therefore we must ensure each IPC
+// server/client has a different name.
+process.env.IPC_SERVER_ID = `etcher-server-${process.pid}`
+process.env.IPC_CLIENT_ID = `etcher-client-${process.pid}`
+
+ipc.config.id = process.env.IPC_SERVER_ID
+ipc.config.socketRoot = CONSTANTS.TMP_DIRECTORY
+ipc.config.silent = true
+
 /**
  * @summary Perform a write
  * @function
@@ -67,14 +77,6 @@ exports.write = (image, drive, options) => {
     unmountOnSuccess: options.unmountOnSuccess
   })
 
-  // There might be multiple Etcher instances running at
-  // the same time, therefore we must ensure each IPC
-  // server/client has a different name.
-  process.env.IPC_SERVER_ID = `etcher-server-${process.pid}`
-  process.env.IPC_CLIENT_ID = `etcher-client-${process.pid}`
-
-  ipc.config.id = process.env.IPC_SERVER_ID
-  ipc.config.silent = true
   ipc.serve()
 
   /**
@@ -192,7 +194,7 @@ exports.write = (image, drive, options) => {
 
     child.on('error', emitError)
 
-    child.on('close', (code) => {
+    child.on('exit', (code, signal) => {
       terminateServer()
 
       if (code === EXIT_CODES.CANCELLED) {
@@ -207,7 +209,11 @@ exports.write = (image, drive, options) => {
         return null
       }
 
-      return emitError(new Error(`Child process exited with error code: ${code}`))
+      const error = new Error(`Child process exited with code ${code}, signal ${signal}`)
+      error.code = code
+      error.signal = signal
+
+      return emitError(error)
     })
   })
 

lib/child-writer/writer-proxy.js

@@ -27,6 +27,9 @@ const EXIT_CODES = require('../shared/exit-codes')
 const robot = require('../shared/robot')
 const permissions = require('../shared/permissions')
 const packageJSON = require('../../package.json')
+const CONSTANTS = require('./constants')
+
+/* eslint-disable no-eq-null */
 
 // This script is in charge of spawning the writer process and
 // ensuring it has the necessary privileges. It might look a bit
@@ -64,6 +67,18 @@ const OPTIONS_INDEX_START = 2
  */
 const etcherArguments = process.argv.slice(OPTIONS_INDEX_START)
 
+ipc.config.id = process.env.IPC_CLIENT_ID
+ipc.config.socketRoot = CONSTANTS.TMP_DIRECTORY
+ipc.config.silent = true
+
+// > If set to 0, the client will NOT try to reconnect.
+// See https://github.com/RIAEvangelist/node-ipc/
+//
+// The purpose behind this change is for this process
+// to emit a "disconnect" event as soon as the GUI
+// process is closed, so we can kill the CLI as well.
+ipc.config.stopRetrying = 0
+
 permissions.isElevated().then((elevated) => {
   if (!elevated) {
     console.log('Attempting to elevate')
@@ -109,40 +124,7 @@ permissions.isElevated().then((elevated) => {
   console.log('Re-spawning with elevation')
 
   return new Bluebird((resolve, reject) => {
-    ipc.config.id = process.env.IPC_CLIENT_ID
-    ipc.config.silent = true
-
-    // > If set to 0, the client will NOT try to reconnect.
-    // See https://github.com/RIAEvangelist/node-ipc/
-    //
-    // The purpose behind this change is for this process
-    // to emit a "disconnect" event as soon as the GUI
-    // process is closed, so we can kill the CLI as well.
-    ipc.config.stopRetrying = 0
-
-    ipc.connectTo(process.env.IPC_SERVER_ID, () => {
-      ipc.of[process.env.IPC_SERVER_ID].on('error', reject)
-      ipc.of[process.env.IPC_SERVER_ID].on('connect', () => {
-        const child = childProcess.spawn(executable, etcherArguments, {
-          env: {
-
-            // The CLI might call operating system utilities (like `diskutil`),
-            // so we must ensure the `PATH` is inherited.
-            PATH: process.env.PATH,
-
-            ELECTRON_RUN_AS_NODE: 1,
-            ETCHER_CLI_ROBOT: 1,
-
-            // Enable extra logging from mountutils
-            // See https://github.com/resin-io-modules/mountutils
-            MOUNTUTILS_DEBUG: 1
-
-          }
-        })
-
-        ipc.of[process.env.IPC_SERVER_ID].on('disconnect', _.bind(child.kill, child))
-        child.on('error', reject)
-        child.on('close', resolve)
+    let child = null
 
     /**
      * @summary Emit an object message to the IPC server
@@ -166,6 +148,61 @@ permissions.isElevated().then((elevated) => {
       })
     }
 
+    /**
+     * @summary Emit an error message over the IPC and shut down the child
+     * @function
+     * @private
+     * @param {Error} error - error
+     * @example
+     * onError(error)
+     */
+    const onError = (error) => {
+      ipc.of[process.env.IPC_SERVER_ID].emit('message', {
+        error: error.message,
+        data: error.stack
+      })
+      child && child.kill()
+      reject(error)
+    }
+
+    ipc.connectTo(process.env.IPC_SERVER_ID, () => {
+      ipc.of[process.env.IPC_SERVER_ID].on('error', onError)
+      ipc.of[process.env.IPC_SERVER_ID].on('disconnect', () => {
+        onError(new Error('Writer process disconnected'))
+      })
+
+      ipc.of[process.env.IPC_SERVER_ID].on('connect', () => {
+        // Inherit the parent evnironment
+        const childEnv = _.assign({}, process.env, {
+
+          // The CLI might call operating system utilities (like `diskutil`),
+          // so we must ensure the `PATH` is inherited.
+          PATH: process.env.PATH,
+
+          ELECTRON_RUN_AS_NODE: 1,
+          ETCHER_CLI_ROBOT: 1,
+
+          // Enable extra logging from mountutils
+          // See https://github.com/resin-io-modules/mountutils
+          MOUNTUTILS_DEBUG: 1
+        })
+
+        child = childProcess.spawn(executable, etcherArguments, {
+          env: childEnv
+        })
+
+        child.on('error', onError)
+        child.on('exit', (code, signal) => {
+          if (code != null && signal == null) {
+            resolve(code)
+          } else {
+            const error = new Error(`Exited with code ${code}, signal ${signal}`)
+            error.code = code
+            error.signal = signal
+            reject(error)
+          }
+        })
+
         child.stdout.on('data', emitMessage)
         child.stderr.on('data', emitMessage)
       })