Revert "[kbn/optimizer] poll parent process to avoid zombie processes (…

…#67059)"

This reverts commit e824ac3.

packages/kbn-optimizer/src/common/index.ts

@@ -21,7 +21,6 @@ export * from './bundle';
 export * from './bundle_cache';
 export * from './worker_config';
 export * from './worker_messages';
-export * from './parent_messages';
 export * from './compiler_messages';
 export * from './ts_helpers';
 export * from './rxjs_helpers';

packages/kbn-optimizer/src/common/worker_messages.ts

@@ -24,17 +24,13 @@ import {
   CompilerErrorMsg,
 } from './compiler_messages';
 
-export type InternalWorkerMsg =
-  | WorkerPingMsg
+export type WorkerMsg =
   | CompilerRunningMsg
   | CompilerIssueMsg
   | CompilerSuccessMsg
   | CompilerErrorMsg
   | WorkerErrorMsg;
 
-// ping messages are internal, they don't apper in public message streams
-export type WorkerMsg = Exclude<InternalWorkerMsg, WorkerPingMsg>;
-
 /**
  * Message sent when the worker encounters an error that it can't
  * recover from, no more messages will be sent and the worker
@@ -46,10 +42,6 @@ export interface WorkerErrorMsg {
   errorStack?: string;
 }
 
-export interface WorkerPingMsg {
-  type: 'ping';
-}
-
 const WORKER_STATE_TYPES: ReadonlyArray<WorkerMsg['type']> = [
   'running',
   'compiler issue',
@@ -58,19 +50,10 @@ const WORKER_STATE_TYPES: ReadonlyArray<WorkerMsg['type']> = [
   'worker error',
 ];
 
-export const isWorkerPing = (value: any): value is WorkerPingMsg =>
-  typeof value === 'object' && value && value.type === 'ping';
-
 export const isWorkerMsg = (value: any): value is WorkerMsg =>
   typeof value === 'object' && value && WORKER_STATE_TYPES.includes(value.type);
 
 export class WorkerMsgs {
-  ping(): WorkerPingMsg {
-    return {
-      type: 'ping',
-    };
-  }
-
   error(error: Error): WorkerErrorMsg {
     return {
       type: 'worker error',

packages/kbn-optimizer/src/optimizer/observe_worker.ts

@@ -22,14 +22,12 @@ import { Readable } from 'stream';
 import { inspect } from 'util';
 
 import * as Rx from 'rxjs';
-import { map, filter, takeUntil } from 'rxjs/operators';
+import { map, takeUntil } from 'rxjs/operators';
 
-import { isWorkerMsg, isWorkerPing, WorkerConfig, WorkerMsg, Bundle, ParentMsgs } from '../common';
+import { isWorkerMsg, WorkerConfig, WorkerMsg, Bundle } from '../common';
 
 import { OptimizerConfig } from './optimizer_config';
 
-const parentMsgs = new ParentMsgs();
-
 export interface WorkerStdio {
   type: 'worker stdio';
   stream: 'stdout' | 'stderr';
@@ -148,16 +146,6 @@ export function observeWorker(
       observeStdio$(proc.stderr, 'stderr'),
       Rx.fromEvent<[unknown]>(proc, 'message')
         .pipe(
-          // filter out ping messages so they don't end up in the general message stream
-          filter(([msg]) => {
-            if (!isWorkerPing(msg)) {
-              return true;
-            }
-
-            proc.send(parentMsgs.pong());
-            return false;
-          }),
-
           // validate the messages from the process
           map(([msg]) => {
             if (!isWorkerMsg(msg)) {