From afeced85a7f3523aed3655c3d498ecdc9314ef02 Mon Sep 17 00:00:00 2001
From: Brian Warner <warner@lothar.com>
Date: Wed, 16 Sep 2020 12:46:31 -0700
Subject: [PATCH] fix: clean up worker subprocess spawning

fixes #1777
---
 packages/SwingSet/src/controller.js           | 22 ++++++++++++++-----
 .../SwingSet/src/spawnSubprocessWorker.js     | 10 ++-------
 2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/packages/SwingSet/src/controller.js b/packages/SwingSet/src/controller.js
index e6ed646780e..ad6418803dd 100644
--- a/packages/SwingSet/src/controller.js
+++ b/packages/SwingSet/src/controller.js
@@ -2,6 +2,7 @@
 
 import fs from 'fs';
 import path from 'path';
+import process from 'process';
 import re2 from 're2';
 import { Worker } from 'worker_threads';
 import * as babelCore from '@babel/core';
@@ -353,6 +354,7 @@ export async function buildVatController(
     }`,
   );
 
+  // this launches a worker in a Node.js thread (aka "Worker")
   function makeNodeWorker() {
     // TODO: after we move away from `-r esm` and use real ES6 modules, point
     // this at nodeWorkerSupervisor.js instead of the CJS intermediate
@@ -362,17 +364,25 @@ export async function buildVatController(
     return new Worker(supercode);
   }
 
+  // launch a worker in a subprocess (which runs Node.js)
+  function startSubprocessWorkerNode() {
+    const supercode = require.resolve(
+      './kernel/vatManager/subprocessSupervisor.js',
+    );
+    return startSubprocessWorker(process.execPath, ['-r', 'esm', supercode]);
+  }
+
+  let startSubprocessWorkerXS;
+  const xsWorkerBin = locateWorkerBin({ resolve: path.resolve });
+  if (fs.existsSync(xsWorkerBin)) {
+    startSubprocessWorkerXS = () => startSubprocessWorker(xsWorkerBin);
+  }
+
   function writeSlogObject(_obj) {
     // TODO sqlite
     // console.log(`--slog ${JSON.stringify(obj)}`);
   }
 
-  const startSubprocessWorkerNode = () => startSubprocessWorker();
-  const xsWorkerBin = locateWorkerBin({ resolve: path.resolve });
-  const startSubprocessWorkerXS = fs.existsSync(xsWorkerBin)
-    ? () => startSubprocessWorker({ execPath: xsWorkerBin, args: [] })
-    : undefined;
-
   const kernelEndowments = {
     waitUntilQuiescent,
     hostStorage,
diff --git a/packages/SwingSet/src/spawnSubprocessWorker.js b/packages/SwingSet/src/spawnSubprocessWorker.js
index dbe5af44616..e02008d6225 100644
--- a/packages/SwingSet/src/spawnSubprocessWorker.js
+++ b/packages/SwingSet/src/spawnSubprocessWorker.js
@@ -1,5 +1,4 @@
 // this file is loaded by the controller, in the start compartment
-import process from 'process';
 import { spawn } from 'child_process';
 import Netstring from 'netstring-stream';
 
@@ -10,19 +9,14 @@ function parentLog(first, ...args) {
   // console.error(`--parent: ${first}`, ...args);
 }
 
-const supercode = require.resolve(
-  './kernel/vatManager/subprocessSupervisor.js',
-);
 // we send on fd3, and receive on fd4. We pass fd1/2 (stdout/err) through, so
 // console log/err from the child shows up normally. We don't use Node's
 // built-in serialization feature ('ipc') because the child process won't
 // always be Node.
 const stdio = harden(['inherit', 'inherit', 'inherit', 'pipe', 'pipe']);
 
-export function startSubprocessWorker(options) {
-  const execPath = options.execPath || process.execPath;
-  const args = options.args || ['-r', 'esm', supercode];
-  const proc = spawn(execPath, args, { stdio });
+export function startSubprocessWorker(execPath, procArgs = []) {
+  const proc = spawn(execPath, procArgs, { stdio });
 
   const toChild = Netstring.writeStream();
   toChild.pipe(proc.stdio[3]);