Canceling of job doesn't work

[Izayda]

Describe the bug
After starting reindexing i cancel job. But i can see job is still processed.
Video https://vendure-ecommerce.slack.com/archives/CKYMF0ZTJ/p1632919005096600
It was on redis job queue. But probably bug also exists in default job plugin.

To Reproduce
Steps to reproduce the behavior:

1. Run a job
2. Cancel it
3. See logs that job is still processed

Expected behavior
Job is successfully canceled.

Environment (please complete the following information):

• @vendure/core version: 1.2.2
• Database (mysql/postgres etc): postgresql

[michaelbromley]

For BullMQ, there is an open issue to allow cancellation of running jobs: taskforcesh/bullmq#632

I will check into the DefaultJobQueuePlugin.

[michaelbromley]

Ok, so on further investigation there is no easy way to cancel a running job, since the process function is Promise-based. As mentioned in the lined BullMQ issue above, there is the possibility of using the AbortController API but this is only stable in Node.js v16+, and I cannot see that it is natively integrated with Promises.

So one possible way to "cancel" a process function is to query the job state, and return from the function is the state is CANCELLED. Example:

process: async job => {
    let progress = 0;
    while (progress < 100) {

        if (job.state === JobState.CANCELLED) {
          // manually abort if job is cancelled
          return;
        }

        await new Promise(resolve => setTimeout(resolve, job.data.intervalMs));
        progress += 10;
        job.setProgress(progress);
    }
    Logger.info(`Completed job ${job.id}`);
    return 'Done!';
},

The problem is that to make all jobs cancellable, we would have to add such logic into all existing jobs, which in many cases would require quite a bit of refactoring.

[Izayda]

Hmmm, yeah, no easy way. Is there problem in default job plugin?

[michaelbromley]

In the default plugin, the job will appear as CANCELLED, but if the process function has started, it will continue until completion anyway. This is a fundamental issue with Promises unfortunately.