Job options (delay, attempts, priority) in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a delay of 5000 milliseconds to the job.

NestJS

this.queue.add('sendEmail', data, { delay: [1] });

Drag options to blanks, or click blank then click option'

A5

B5000

C500

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using 5 instead of 5000, which means 5 milliseconds, too short.

Using 500 which is 0.5 seconds, not 5 seconds.

The delay option expects the delay time in milliseconds. 5000 means 5 seconds delay before the job runs.

2fill in blank

medium

Complete the code to set the job to retry 3 times on failure.

NestJS

this.queue.add('processData', data, { attempts: [1] });

Drag options to blanks, or click blank then click option'

A3

B5

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Setting attempts to 0 which disables retries.

Setting attempts to 1 which means only one try, no retries.

The attempts option sets how many times the job will retry if it fails. Setting it to 3 means it will try up to 3 times.

3fill in blank

hard

Fix the error in setting the job priority to high (1 is highest).

NestJS

this.queue.add('generateReport', data, { priority: [1] });

Drag options to blanks, or click blank then click option'

A1

B5

C10

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 which is invalid priority.

Using 10 which is low priority.

In NestJS job queues, lower numbers mean higher priority. 1 is the highest priority, so use 1.

4fill in blank

hard

Fill both blanks to add a job with 2 attempts and 3 seconds delay.

NestJS

this.queue.add('cleanup', data, { attempts: [1], delay: [2] });

Drag options to blanks, or click blank then click option'

A2

B3

C3000

D2000

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing delay units and using 3 instead of 3000.

Setting attempts to 3 instead of 2.

Set attempts to 2 for two retries, and delay to 3000 for 3 seconds delay (3000 milliseconds).

5fill in blank

hard

Fill all three blanks to add a job with high priority (1), 4 attempts, and 1 second delay.

NestJS

this.queue.add('syncData', data, { priority: [1], attempts: [2], delay: [3] });

Drag options to blanks, or click blank then click option'

A1

B4

C1000

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 5 for priority which is low priority.

Using 1 for attempts which means only one try.

Using 1 for delay which is 1 millisecond, not 1 second.

Priority 1 is highest, attempts 4 means 4 retries, and delay 1000 means 1 second delay.

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