child_process: retain reference to data with advanced serialization

Do the same thing we do for other streams, and retain a reference to the Buffer that was sent over IPC while the write request is active, so that it doesn’t get garbage collected while the data is still in flight. (This is a good example of why it’s a bad idea that we’re not re-using the general streams implementation for IPC and instead maintain separate usage of the low-level I/O primitives.) Fixes: #34797 PR-URL: #38728 Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Minwoo Jung <[email protected]>

Author: addaleax

lib/internal/child_process/serialization.js

@@ -12,6 +12,7 @@ const{StringDecoder } = require('string_decoder');
 constv8=require('v8');
 const{ isArrayBufferView }=require('internal/util/types');
 constassert=require('internal/assert');
+const{ streamBaseState, kLastWriteWasAsync }=internalBinding('stream_wrap');
 
 constkMessageBuffer=Symbol('kMessageBuffer');
 constkJSONBuffer=Symbol('kJSONBuffer');
@@ -82,10 +83,16 @@ const advanced ={
 constserializedMessage=ser.releaseBuffer();
 constsizeBuffer=Buffer.allocUnsafe(4);
 sizeBuffer.writeUInt32BE(serializedMessage.length);
-returnchannel.writeBuffer(req,Buffer.concat([
+
+constbuffer=Buffer.concat([
 sizeBuffer,
 serializedMessage,
-]),handle);
+]);
+constresult=channel.writeBuffer(req,buffer,handle);
+// Mirror what stream_base_commons.js does for Buffer retention.
+if(streamBaseState[kLastWriteWasAsync])
+req.buffer=buffer;
+returnresult;
 },
 };
 

test/parallel/test-child-process-advanced-serialization-largebuffer.js

@@ -0,0 +1,27 @@
+'use strict';
+constcommon=require('../common');
+constassert=require('assert');
+constchild_process=require('child_process');
+
+// Regression test for https://github.com/nodejs/node/issues/34797
+consteightMB=8*1024*1024;
+
+if(process.argv[2]==='child'){
+for(leti=0;i<4;i++){
+process.send(newUint8Array(eightMB).fill(i));
+}
+}else{
+constchild=child_process.spawn(process.execPath,[__filename,'child'],{
+stdio: ['inherit','inherit','inherit','ipc'],
+serialization: 'advanced'
+});
+constreceived=[];
+child.on('message',common.mustCall((chunk)=>{
+assert.deepStrictEqual(chunk,newUint8Array(eightMB).fill(chunk[0]));
+
+received.push(chunk[0]);
+if(received.length===4){
+assert.deepStrictEqual(received,[0,1,2,3]);
+}
+},4));
+}