Job options (delay, attempts, priority) in NestJS

Introduction

Job options help control how and when background tasks run. They let you delay jobs, retry failed jobs, and set job importance.

You want to run a task after some waiting time, like sending a reminder email later.

You want to retry a task if it fails, like trying to save data again after a network error.

You want important jobs to run before less important ones, like processing urgent orders first.

Syntax

NestJS

queue.add('jobName', data, { delay: number, attempts: number, priority: number })

delay is in milliseconds and delays job start.

attempts sets the maximum number of attempts for the job (including the first one).

priority is a number where lower means higher priority.

Examples

This delays the email job by 60 seconds before running.

NestJS

queue.add('sendEmail', { to: '[e-mail]' }, { delay: 60000 })

This retries the order processing up to 3 times if it fails.

NestJS

queue.add('processOrder', { orderId: 123 }, { attempts: 3 })

This sets the report job to high priority (1 is high).

NestJS

queue.add('generateReport', {}, { priority: 1 })

Sample Program

This example shows a job that sends a welcome email. It waits 5 seconds before starting, tries up to 2 times, and has medium priority (5).

If the job ultimately fails after all attempts, the @OnQueueFailed handler logs the failure.

NestJS

import { Processor, Process, OnQueueFailed } from '@nestjs/bull';
import { Job } from 'bull';

@Processor('email')
export class EmailProcessor {
  @Process('sendWelcome')
  async handleSendWelcome(job: Job) {
    console.log(`Sending welcome email to ${job.data.email}`);
    if (Math.random() < 0.5) {
      throw new Error('Random failure');
    }
    return 'Email sent';
  }

  @OnQueueFailed()
  onFailed(job: Job, error: Error) {
    console.log(`Job ${job.id} failed: ${error.message}`);
  }
}

// Adding a job with options
queue.add('sendWelcome', { email: '[e-mail]' }, { delay: 5000, attempts: 2, priority: 5 });

Important Notes

Delay uses milliseconds, so 1000 means 1 second.

Attempts help handle temporary errors by retrying jobs automatically.

Priority lets you control job order: lower numbers run first.

Summary

Job options control timing, retries, and order of background tasks.

Use delay to wait before running a job.

Use attempts to retry failed jobs automatically.

Use priority to run important jobs first.

Practice

1. In NestJS job queues, what does the delay option do when adding a job?

easy

A. It sets the maximum number of retries for the job.

B. It postpones the job execution by a specified time.

C. It assigns the job a priority level.

D. It cancels the job immediately.

Solution

1. Step 1: Understand the purpose of delay in job options

   The delay option is used to postpone when a job starts running after being added to the queue.

2. Step 2: Compare with other options

   attempts controls retries, priority controls order, so they do not delay execution.

3. Final Answer:

   It postpones the job execution by a specified time. -> Option B

4. Quick Check:

   delay = postpone job start [OK]

Hint: Delay means wait before running the job [OK]

Common Mistakes:

• Confusing delay with attempts (retry count)
• Thinking delay sets job priority
• Assuming delay cancels the job

2. Which of the following is the correct way to add a job with 3 retry attempts and a 5-second delay in NestJS?

easy

A. queue.add('jobName', data, { retries: 3, wait: 5000 })

B. queue.add('jobName', data, { delay: 3, attempts: 5000 })

C. queue.add('jobName', data, { attempts: '3', delay: '5000' })

D. queue.add('jobName', data, { attempts: 3, delay: 5000 })

Solution

1. Step 1: Identify correct option keys and values

   The correct keys are attempts for retries and delay for postponing in milliseconds.

2. Step 2: Check value types and order

   Values must be numbers, not strings. queue.add('jobName', data, { attempts: 3, delay: 5000 }) uses correct keys and numeric values.

3. Final Answer:

   queue.add('jobName', data, { attempts: 3, delay: 5000 }) -> Option D

4. Quick Check:

   Correct keys and numeric values = queue.add('jobName', data, { attempts: 3, delay: 5000 }) [OK]

Hint: Use numeric attempts and delay keys exactly [OK]

Common Mistakes:

• Using wrong keys like retries or wait
• Passing numbers as strings
• Swapping delay and attempts values

3. Given this code snippet, what will be the order of job execution?

queue.add('job1', data1, { priority: 2 });
queue.add('job2', data2, { priority: 1 });
queue.add('job3', data3, { priority: 3 });

medium

A. job2, job1, job3

B. job3, job1, job2

C. job1, job2, job3

D. job1, job3, job2

Solution

1. Step 1: Understand priority values

   Lower priority number means higher priority and runs first.

2. Step 2: Order jobs by priority

   job2 has priority 1 (highest), job1 priority 2, job3 priority 3 (lowest).

3. Final Answer:

   job2, job1, job3 -> Option A

4. Quick Check:

   Lower priority number runs first = job2, job1, job3 [OK]

Hint: Lower priority number runs first [OK]

Common Mistakes:

• Assuming higher number means higher priority
• Ignoring priority and using add order
• Mixing up job names and priorities

4. Identify the error in this job addition code:

queue.add('emailJob', data, { delay: '1000', attempts: 5 });

medium

A. The attempts option is invalid and should be removed.

B. The job name must be an object, not a string.

C. The delay value should be a number, not a string.

D. The data parameter is missing.

Solution

1. Step 1: Check types of job options

   delay expects a number in milliseconds, but here it is a string '1000'.

2. Step 2: Validate other parameters

   attempts is valid, job name as string is correct, data is present.

3. Final Answer:

   The delay value should be a number, not a string. -> Option C

4. Quick Check:

   delay must be number, not string [OK]

Hint: Delay must be number type, not string [OK]

Common Mistakes:

• Passing delay as string instead of number
• Removing valid attempts option
• Thinking job name must be object

5. You want to add a job that should run after 10 seconds, retry up to 4 times if it fails, and run before other jobs with default priority. Which job options object is correct?

hard

A. { delay: 10000, attempts: 4 }

B. { delay: 10000, attempts: 4, priority: 1 }

C. { attempts: 4, priority: 0 }

D. { delay: 10000, priority: 0 }

Solution

1. Step 1: Understand default priority

   If priority is not set, jobs have default priority (usually 0 or normal). To run before others, priority must be lower number.

2. Step 2: Check options for delay and attempts

   Delay 10000 ms (10 seconds) and attempts 4 are required. Priority is optional if default is acceptable.

3. Step 3: Analyze options

   { delay: 10000, attempts: 4, priority: 1 } sets priority to 1 (lower priority than default 0), so it runs after default priority jobs. { delay: 10000, attempts: 4 } omits priority, so default priority applies, running before jobs with priority 1.

4. Final Answer:

   { delay: 10000, attempts: 4 } -> Option A

5. Quick Check:

   Delay + attempts with default priority = { delay: 10000, attempts: 4 } [OK]

Hint: Omit priority for default; delay and attempts must be set [OK]

Common Mistakes:

• Setting priority higher than default to run first
• Forgetting delay or attempts
• Assuming priority 0 is higher than 1