process: move child process IPC setup condition into node.js

Instead of branching in main_thread_only.js, move the branch on process.env.NODE_CHANNEL_FD in node.js so it's easier to tell when this needs to happen. Also added comments about what side effect this causes, and lazy load `assert`. PR-URL: #25130 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Jeremiah Senkpiel <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Luigi Pinca <[email protected]>
nodejs · Dec 22, 2018 · 0c1a388 · 0c1a388
1 parent 55a1889
commit 0c1a388
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Showing 2 changed files with 14 additions and 13 deletions.
diff --git a/lib/internal/bootstrap/node.js b/lib/internal/bootstrap/node.js
@@ -155,7 +155,12 @@ function startup() {
     return;
   }
 
-  if (isMainThread) {
+  // If the process is spawned with env NODE_CHANNEL_FD, it's probably
+  // spawned by our child_process module, then initialize IPC.
+  // This attaches some internal event listeners and creates:
+  // process.send(), process.channel, process.connected,
+  // process.disconnect()
+  if (isMainThread && process.env.NODE_CHANNEL_FD) {
     mainThreadSetup.setupChildProcessIpcChannel();
   }
 

diff --git a/lib/internal/process/main_thread_only.js b/lib/internal/process/main_thread_only.js
@@ -21,8 +21,6 @@ const {
   getMainThreadStdio
 } = require('internal/process/stdio');
 
-const assert = require('assert').strict;
-
 function setupStdio() {
   setupProcessStdio(getMainThreadStdio());
 }
@@ -163,18 +161,16 @@ function setupSignalHandlers(internalBinding) {
 }
 
 function setupChildProcessIpcChannel() {
-  // If we were spawned with env NODE_CHANNEL_FD then load that up and
-  // start parsing data from that stream.
-  if (process.env.NODE_CHANNEL_FD) {
-    const fd = parseInt(process.env.NODE_CHANNEL_FD, 10);
-    assert(fd >= 0);
+  const assert = require('assert').strict;
 
-    // Make sure it's not accidentally inherited by child processes.
-    delete process.env.NODE_CHANNEL_FD;
+  const fd = parseInt(process.env.NODE_CHANNEL_FD, 10);
+  assert(fd >= 0);
 
-    require('child_process')._forkChild(fd);
-    assert(process.send);
-  }
+  // Make sure it's not accidentally inherited by child processes.
+  delete process.env.NODE_CHANNEL_FD;
+
+  require('child_process')._forkChild(fd);
+  assert(process.send);
 }
 
 module.exports = {