Job options (delay, attempts, priority) in NestJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

Understanding delay option in NestJS Bull jobs

What will be the behavior of a job scheduled with a delay of 5000 milliseconds in NestJS Bull queue?

NestJS

queue.add('sendEmail', { userId: 123 }, { delay: 5000 });

A The job will wait 5 seconds before it becomes eligible for processing.

B The job will be retried 5 times with 1 second delay between retries.

C The job will be assigned the highest priority and processed first.

D The job will start processing immediately after being added to the queue.

💡 Hint

Think about what the delay option controls in job scheduling.

The delay option specifies how long the job should wait before it is processed. A delay of 5000 means the job will be delayed for 5 seconds.

❓ state_output

intermediate

Effect of attempts option on job retries

If a job is configured with { attempts: 3 } and it fails twice before succeeding, how many times will the job processor run?

NestJS

queue.add('processData', { data: 'info' }, { attempts: 3 });

A The processor will run 1 time only.

B The processor will run 2 times total.

C The processor will run 4 times total.

D The processor will run 3 times total.

💡 Hint

Remember that attempts count includes the first try plus retries.

The attempts option sets the maximum number of tries including the first attempt. So 3 attempts means the job can run up to 3 times if it keeps failing.

📝 Syntax

advanced

Correct syntax for setting job priority in NestJS Bull

Which option correctly sets a job priority of 10 when adding a job to a Bull queue in NestJS?

NestJS

queue.add('generateReport', { reportId: 42 }, ???);

A { priority: 10 }

B { priority: '10' }

C { priority: true }

D { priority: -10 }

💡 Hint

Priority should be a positive integer number.

The priority option expects a positive integer. Strings or booleans are invalid and negative numbers lower priority.

🔧 Debug

advanced

Identifying error with invalid delay value

What error will occur if you set delay to a negative number like -1000 in a Bull job options?

NestJS

queue.add('cleanup', {}, { delay: -1000 });

A RangeError: Delay must be a positive integer

B TypeError: Delay option must be a string

C No error, job will be processed immediately

D SyntaxError: Unexpected token '-'

💡 Hint

Think about what negative delay means for scheduling.

Bull does not throw an error for negative delay values. The job timestamp will be in the past, causing it to be processed immediately.

🧠 Conceptual

expert

How priority affects job processing order in Bull queues

Given three jobs added with priorities 5, 10, and 1 respectively, in what order will Bull process them assuming no delay or attempts?

NestJS

queue.add('job1', {}, { priority: 5 });
queue.add('job2', {}, { priority: 10 });
queue.add('job3', {}, { priority: 1 });

A job3, job1, job2

B job2, job1, job3

C job1, job2, job3

D job1, job3, job2

💡 Hint

Higher priority numbers mean higher priority in Bull.

Bull processes jobs with higher priority numbers first. So priority 10 runs before 5, which runs before 1.