fix(sandbox): wait for result of sending start command

lib/process/master.js

@@ -10,13 +10,7 @@ let processor;
 let currentJobPromise;
 
 const { promisify } = require('util');
-
-// same as process.send but waits until the send is complete
-
-// the async version is used below because otherwise
-// the termination handler may exit before the parent
-// process has recived the messages it requires
-const processSendAsync = promisify(process.send.bind(process));
+const { asyncSend } = require('./utils');
 
 // https://stackoverflow.com/questions/18391212/is-it-not-possible-to-stringify-an-error-using-json-stringify
 if (!('toJSON' in Error.prototype)) {
@@ -95,7 +89,7 @@ process.on('message', msg => {
       currentJobPromise = (async () => {
         try {
           const result = (await processor(wrapJob(msg.job))) || {};
-          await processSendAsync({
+          await asyncSend(process, {
             cmd: 'completed',
             value: result
           });
@@ -104,7 +98,7 @@ process.on('message', msg => {
             // eslint-disable-next-line no-ex-assign
             err = new Error(err);
           }
-          await processSendAsync({
+          await asyncSend(process, {
             cmd: 'failed',
             value: err
           });
@@ -156,7 +150,7 @@ function wrapJob(job) {
       // so that we can return it from this process synchronously.
       progressValue = progress;
       // Send message to update job progress.
-      return processSendAsync({
+      return asyncSend(process, {
         cmd: 'progress',
         value: progress
       });
@@ -178,7 +172,7 @@ function wrapJob(job) {
    * Emulate the real job `log` function.
    */
   job.log = function(row) {
-    return processSendAsync({
+    return asyncSend(process, {
       cmd: 'log',
       value: row
     });

lib/process/sandbox.js

@@ -1,12 +1,14 @@
 'use strict';
 
+const { asyncSend } = require('./utils');
+
 module.exports = function(processFile, childPool) {
   return function process(job) {
-    return childPool.retain(processFile).then(child => {
+    return childPool.retain(processFile).then(async child => {
       let msgHandler;
       let exitHandler;
 
-      child.send({
+      await asyncSend(child, {
         cmd: 'start',
         job: job
       });

lib/process/utils.js

@@ -44,6 +44,27 @@ function killAsync(child, signal, timeoutMs) {
   return onExit;
 }
 
-module.exports = {
-  killAsync
+/*
+ asyncSend
+ Same as process.send but waits until the send is complete
+ the async version is used below because otherwise
+ the termination handler may exit before the parent
+ process has recived the messages it requires
+ */
+
+const asyncSend = (proc, msg) => {
+  return new Promise((resolve, reject) => {
+    proc.send(msg, err => {
+      if (err) {
+        reject(err);
+      } else {
+        resolve();
+      }
+    });
+  });
+};
+
+module.exports = {
+  killAsync,
+  asyncSend
 };