Named jobs in NestJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a named job is added twice with the same name?

Consider a NestJS Bull queue where you add a named job twice with the same name but different data. What will be the behavior?

NestJS

await queue.add('email', { to: '[e-mail]' });
await queue.add('email', { to: '[e-mail]' });

A The second job replaces the first job in the queue.

B Both jobs are added separately and processed independently.

C Only the first job is added; the second is ignored silently.

D An error is thrown because job names must be unique.

💡 Hint

Think about how queues handle jobs with the same name but different data.

Named jobs in Bull are just labels. Adding two jobs with the same name but different data creates two separate jobs. They are processed independently in the order they were added.

📝 Syntax

intermediate

Which code correctly adds a named job with repeat options in NestJS Bull?

Choose the correct syntax to add a named job called 'cleanup' that repeats every hour.

A await queue.add('cleanup', {}, { repeat: { cron: '0 * * * *' } });

B await queue.add({ name: 'cleanup', data: {}, repeat: { cron: '0 * * * *' } });

C await queue.add('cleanup', {}, { repeat: '0 * * * *' });

D await queue.add('cleanup', { repeat: { cron: '0 * * * *' } });

💡 Hint

Remember the method signature: add(name, data, options).

The correct syntax uses the job name as the first argument, job data as the second, and options (including repeat) as the third argument.

🔧 Debug

advanced

Why does this named job never run in NestJS Bull?

Given the following code, why does the named job 'processData' never execute?

NestJS

queue.process('processData', async (job) => {
  console.log('Processing:', job.data);
});

await queue.add('processdata', { id: 1 });

A The process() method is missing a concurrency parameter, so it never runs.

B The job data is missing required fields, so the job is skipped.

C The job name in add() is lowercase 'processdata', but process() listens for 'processData' (case mismatch).

D The queue is not started, so no jobs run.

💡 Hint

Check the exact spelling and casing of job names.

Job names are case sensitive. The job was added with name 'processdata' but the processor listens for 'processData'. They do not match, so the job is never processed.

❓ state_output

advanced

What is the job count after adding and removing named jobs?

Consider this sequence:

await queue.add('task1', {});
await queue.add('task2', {});
const job = await queue.getJob('task1');
await job?.remove();
const count = await queue.count();

What is the value of count?

A 2

B Throws an error because getJob expects a job ID, not a name.

C 0

D 1

💡 Hint

Check the parameter type expected by getJob().

The getJob() method expects a job ID, not a job name. Passing a name returns null, so job?.remove() does nothing. The count remains 2.

🧠 Conceptual

expert

How does Bull handle concurrency for named jobs in NestJS?

In NestJS Bull, if you define multiple processors for the same named job with different concurrency values, what happens?

A Bull throws an error because multiple processors for the same job name are not allowed.

B Bull uses the highest concurrency value among processors for that job name.

C Only the first registered processor runs; others are ignored.

D Bull runs all processors in parallel, each with its own concurrency setting.

💡 Hint

Think about how Bull distributes jobs to processors.

Bull allows multiple processors for the same named job. Each processor runs independently with its own concurrency. Jobs are distributed among them.