✨ Added workerMessageHandler option to ctr options

refs https://github.com/TryGhost/Ghost/issues/12496

- `workerMessageHandler` option allows for custom worker message handling and allows to eliminate a need for loggers of any type inside of jobs.
- removing loggers from jobs solves file hanle leak which used to cause Ghost process to crash (see referenced issue)

ghost/job-manager/lib/job-manager.js

@@ -30,8 +30,9 @@ class JobManager {
      * @param {Object} options
      * @param {Object} [options.logging] - custom logging handler, defaults to console
      * @param {Function} [options.errorHandler] - custom job error handler
+     * @param {Function} [options.workerMessageHandler] - custom message handler coming from workers
      */
-    constructor({logging, errorHandler}) {
+    constructor({logging, errorHandler, workerMessageHandler}) {
         this.queue = fastq(this, worker, 1);
 
         this.bree = new Bree({
@@ -39,7 +40,8 @@ class JobManager {
             hasSeconds: true, // precision is needed to avoid task overlaps after immediate execution
             outputWorkerMetadata: true,
             logger: logging,
-            errorHandler: errorHandler
+            errorHandler: errorHandler,
+            workerMessageHandler: workerMessageHandler
         });
 
         this.logging = logging;

ghost/job-manager/test/job-manager.test.js

@@ -225,6 +225,26 @@ describe('Job Manager', function () {
                 should(spyHandler.args[0][0].message).equal('job error');
                 should(spyHandler.args[0][1].name).equal('will-fail');
             });
+
+            it('uses worker message handler when job sends a message', async function (){
+                const workerMessageHandlerSpy = sinon.spy();
+                const jobManager = new JobManager({logging, workerMessageHandler: workerMessageHandlerSpy});
+
+                jobManager.addJob({
+                    job: path.resolve(__dirname, './jobs/message.js'),
+                    name: 'will-send-msg'
+                });
+                jobManager.bree.run('will-send-msg');
+
+                jobManager.bree.workers['will-send-msg'].postMessage('hello from Ghost!');
+
+                // Give time for worker (worker thread) <-> parent process (job manager) communication
+                await delay(1000);
+
+                should(workerMessageHandlerSpy.called).be.true();
+                should(workerMessageHandlerSpy.args[0][0].name).equal('will-send-msg');
+                should(workerMessageHandlerSpy.args[0][0].message).equal('hello from Ghost!');
+            });
         });
     });
 

ghost/job-manager/test/jobs/message.js

@@ -0,0 +1,19 @@
+const {parentPort} = require('bthreads');
+
+setInterval(() => { }, 10);
+
+if (parentPort) {
+    parentPort.on('message', (message) => {
+        if (message === 'error') {
+            throw new Error('oops');
+        }
+
+        if (message === 'cancel') {
+            parentPort.postMessage('cancelled');
+            return;
+        }
+
+        parentPort.postMessage(message);
+        process.exit(0);
+    });
+}