From bace2de2bd35a36dc57b7985062c34704644668c Mon Sep 17 00:00:00 2001
From: Zachary Golba <zachary.golba@postlight.com>
Date: Wed, 17 Aug 2016 12:04:23 -0400
Subject: [PATCH] fix: errors occuring during application boot fail silently
 (#316)

* fix: errors occuring during application boot fail silently

* fix: Cluster#reload does not work Cluster#workers is empty

* fix: prevent Cluster#fork from never resolving

* style: move .from() to a second line

* refactor: simplify type decls in Cluster
---
 .../compiler/utils/create-boot-script.js      |  7 +-
 src/packages/pm/cluster/index.js              | 98 +++++++++++++------
 2 files changed, 73 insertions(+), 32 deletions(-)

diff --git a/src/packages/compiler/utils/create-boot-script.js b/src/packages/compiler/utils/create-boot-script.js
index 59fa2bec..690e44b2 100644
--- a/src/packages/compiler/utils/create-boot-script.js
+++ b/src/packages/compiler/utils/create-boot-script.js
@@ -23,7 +23,12 @@ export default async function createBootScript(dir: string, {
         path: CWD,
         port: PORT
       })
-    );
+    ).catch(err => {
+      process.send({
+        error: err ? err.stack : void 0,
+        message: 'error'
+      });
+    });
   `;
 
   if (useStrict) {
diff --git a/src/packages/pm/cluster/index.js b/src/packages/pm/cluster/index.js
index 2e66b378..bbc4026d 100644
--- a/src/packages/pm/cluster/index.js
+++ b/src/packages/pm/cluster/index.js
@@ -7,6 +7,9 @@ import { red, green } from 'chalk';
 
 import { NODE_ENV } from '../../../constants';
 
+import { line } from '../../logger';
+
+import omit from '../../../utils/omit';
 import range from '../../../utils/range';
 
 import type { Worker } from 'cluster';
@@ -83,7 +86,7 @@ class Cluster extends EventEmitter {
     this.forkAll().then(() => this.emit('ready'));
   }
 
-  fork(retry: boolean = true): Promise<Worker> {
+  fork(retry: boolean = true) {
     return new Promise(resolve => {
       if (this.workers.size < this.maxWorkers) {
         const worker = cluster.fork({
@@ -94,9 +97,6 @@ class Cluster extends EventEmitter {
         const timeout = setTimeout(() => {
           handleError();
 
-          worker.removeListener('exit', handleExit);
-          worker.kill();
-
           if (retry) {
             this.fork(false);
           }
@@ -108,36 +108,67 @@ class Cluster extends EventEmitter {
           worker.removeListener('message', handleMessage);
 
           if (typeof code === 'number') {
-            this.logger.info(
-              `Worker process: ${red(`${pid}`)} exited with code ${code}`
-            );
+            this.logger.info(line`
+              Worker process: ${red(`${pid}`)} exited with code ${code}
+            `);
           }
 
           this.logger.info(`Removing worker process: ${red(`${pid}`)}`);
 
-          this.workers.delete(worker);
+          cleanUp(true);
+
           this.fork();
         };
 
-        const handleError = () => {
-          this.logger.info(
-            `Removing worker process: ${red(`${worker.process.pid}`)}`
-          );
+        const handleError = (err?: string) => {
+          if (err) {
+            this.logger.error(err);
+          }
 
-          this.workers.delete(worker);
-          clearTimeout(timeout);
+          this.logger.info(line`
+            Removing worker process: ${red(`${worker.process.pid}`)}
+          `);
+
+          cleanUp(true);
+          resolve(worker);
         };
 
-        const handleMessage = (message: string) => {
-          if (message === 'ready') {
-            this.logger.info(
-              `Adding worker process: ${green(`${worker.process.pid}`)}`
-            );
+        const handleMessage = (message: string | Object) => {
+          let data = {};
+
+          if (typeof message === 'object') {
+            data = omit(message, 'message');
+            message = message.message;
+          }
+
+          switch (message) {
+            case 'ready':
+              this.logger.info(line`
+                Adding worker process: ${green(`${worker.process.pid}`)}
+              `);
 
-            this.workers.add(worker);
+              this.workers.add(worker);
 
-            clearTimeout(timeout);
-            resolve(worker);
+              cleanUp(false);
+              resolve(worker);
+              break;
+
+            case 'error':
+              handleError(data.error);
+              break;
+          }
+        };
+
+        const cleanUp = (remove: boolean) => {
+          clearTimeout(timeout);
+
+          if (remove) {
+            worker.kill();
+            worker.removeAllListeners();
+
+            this.workers.delete(worker);
+          } else {
+            worker.removeListener('error', handleError);
           }
         };
 
@@ -148,7 +179,7 @@ class Cluster extends EventEmitter {
     });
   }
 
-  shutdown(worker: Worker): Promise<Worker> {
+  shutdown<T: Worker>(worker: T): Promise<T> {
     return new Promise(resolve => {
       this.workers.delete(worker);
 
@@ -164,18 +195,23 @@ class Cluster extends EventEmitter {
     });
   }
 
-  async reload(): Promise<void> {
-    const workers: Array<[Worker, Worker]> = Array.from(this.workers)
-      .reduce((arr, item, idx, src) => {
-        return (idx + 1) % 2 ? [...arr, src.slice(idx, idx + 2)] : arr;
-      }, []);
+  async reload() {
+    if (this.workers.size) {
+      const workers = Array
+        .from(this.workers)
+        .reduce((arr, item, idx, src) => {
+          return (idx + 1) % 2 ? [...arr, src.slice(idx, idx + 2)] : arr;
+        }, []);
 
-    for (const group of workers) {
-      await Promise.all(group.map(worker => this.shutdown(worker)));
+      for (const group of workers) {
+        await Promise.all(group.map(worker => this.shutdown(worker)));
+      }
+    } else {
+      await this.fork();
     }
   }
 
-  forkAll(): Promise<Worker> {
+  forkAll() {
     return Promise.race(Array.from(range(1, this.maxWorkers)).map(() => {
       return this.fork();
     }));