Periodic tasks with Celery Beat in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Celery app instance in your Django project.

Django

from [1] import app as celery_app

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

Adjango_celery_beat

Bcelery

Cmyproject.celery

Dtasks

Attempts:

3 left

💡 Hint

Common Mistakes

Importing directly from 'celery' instead of your project celery file.

Using 'django_celery_beat' which is for scheduling, not the app instance.

You import the Celery app instance from your project's celery.py file, usually at myproject.celery.

2fill in blank

medium

Complete the code to define a periodic task using Celery Beat's @periodic_task decorator.

Django

@periodic_task(run_every=crontab(minute='*/[1]'))
def my_task():
    print('Task runs every 5 minutes')

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

A5

B0

C10

D15

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 which means only at the start of the hour.

Confusing the minute value with seconds.

The crontab(minute='*/5') means the task runs every 5 minutes.

3fill in blank

hard

Fix the error in the Celery Beat schedule dictionary to run a task every hour.

Django

CELERY_BEAT_SCHEDULE = {
    'hourly-task': {
        'task': 'app.tasks.my_task',
        'schedule': [1](hour='*', minute=0),
    },
}

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

Acrontab

Btimedelta

Cschedule

Dinterval

Attempts:

3 left

💡 Hint

Common Mistakes

Using timedelta which is not imported or used here.

Using interval which requires seconds, not crontab syntax.

The crontab function is used to schedule periodic tasks with specific time patterns like every hour.

4fill in blank

hard

Fill both blanks to create a periodic task that runs every day at midnight.

Django

CELERY_BEAT_SCHEDULE = {
    'daily-task': {
        'task': '[1]',
        'schedule': crontab(hour=[2], minute=0),
    },
}

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

Aapp.tasks.daily_cleanup

Bapp.tasks.hourly_cleanup

C0

D12

Attempts:

3 left

💡 Hint

Common Mistakes

Using hour 12 which is noon, not midnight.

Using the wrong task name.

The task name is app.tasks.daily_cleanup and crontab(hour=0, minute=0) runs it at midnight daily.

5fill in blank

hard

Fill all three blanks to define a periodic task that runs every Monday at 7:30 AM.

Django

CELERY_BEAT_SCHEDULE = {
    'weekly-task': {
        'task': '[1]',
        'schedule': crontab(hour=[2], minute=[3], day_of_week='1'),
    },
}

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

Aapp.tasks.weekly_report

B7

C30

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using hour 0 which is midnight.

Confusing day_of_week numbers.

The task app.tasks.weekly_report runs at 7:30 AM (hour=7, minute=30) every Monday (day_of_week='1').

Practice

1. What is the main purpose of Celery Beat in a Django project?

easy

A. To schedule and run periodic tasks automatically

B. To handle HTTP requests asynchronously

C. To manage database migrations

D. To serve static files efficiently

Solution

1. Step 1: Understand Celery Beat's role

   Celery Beat is designed to schedule tasks to run at specific times or intervals automatically.

2. Step 2: Differentiate from other components

   Handling HTTP requests, managing migrations, or serving static files are not functions of Celery Beat.

3. Final Answer:

   To schedule and run periodic tasks automatically -> Option A

4. Quick Check:

   Celery Beat = periodic task scheduler [OK]

Hint: Celery Beat schedules tasks, not handles requests [OK]

Common Mistakes:

• Confusing Celery Beat with Django's request handling
• Thinking Celery Beat manages database or static files
• Assuming Celery Beat runs tasks immediately without schedule

2. Which of the following is the correct way to define a periodic task schedule using Celery Beat with a crontab in Django settings?

easy

A. "beat_schedule = { 'task-name': { 'task': 'app.tasks.my_task', 'schedule': crontab(minute='0', hour='*/3') } }"

B. "beat_schedule = { 'task-name': { 'task': 'app.tasks.my_task', 'schedule': crontab('0', '*/3') } }"

C. "beat_schedule = { 'task-name': { 'task': 'app.tasks.my_task', 'schedule': crontab(minute=0, hour='every 3 hours') } }"

D. "beat_schedule = { 'task-name': { 'task': 'app.tasks.my_task', 'schedule': crontab(minute='0', hour='3/0') } }"

Solution

1. Step 1: Check crontab syntax

   The crontab function requires named arguments like minute and hour with string values representing schedule patterns.

2. Step 2: Validate correct usage

   "beat_schedule = { 'task-name': { 'task': 'app.tasks.my_task', 'schedule': crontab(minute='0', hour='*/3') } }" correctly uses crontab(minute='0', hour='*/3') to run every 3 hours at minute 0.

3. Final Answer:

   beat_schedule with crontab(minute='0', hour='*/3') -> Option A

4. Quick Check:

   Correct crontab syntax = "beat_schedule = { 'task-name': { 'task': 'app.tasks.my_task', 'schedule': crontab(minute='0', hour='*/3') } }" [OK]

Hint: Use named args with strings in crontab() [OK]

Common Mistakes:

• Passing positional arguments instead of named
• Using invalid hour format like '3/0'
• Mixing string and integer types incorrectly

3. Given this Celery Beat schedule snippet in Django settings:

beat_schedule = {
  'print-time': {
    'task': 'app.tasks.print_time',
    'schedule': crontab(minute='*/15')
  }
}

What will happen when Celery Beat and worker run?

medium

A. The task will not run due to syntax error

B. The task runs only once at minute 15

C. The task runs every hour at minute 0

D. The task 'print_time' runs every 15 minutes

Solution

1. Step 1: Interpret crontab(minute='*/15')

   This means the task runs every 15 minutes, at minute 0, 15, 30, 45 of each hour.

2. Step 2: Understand Celery Beat behavior

   When both Beat and worker run, Beat triggers the task on schedule, so it runs repeatedly every 15 minutes.

3. Final Answer:

   The task 'print_time' runs every 15 minutes -> Option D

4. Quick Check:

   crontab '*/15' means every 15 minutes [OK]

Hint: */15 in crontab means every 15 minutes [OK]

Common Mistakes:

• Thinking it runs only once
• Confusing minute '*/15' with fixed minute 15
• Assuming syntax error without checking carefully

4. You defined this schedule in your Django settings:

beat_schedule = {
  'cleanup-task': {
    'task': 'app.tasks.cleanup',
    'schedule': crontab(minute=0, hour='*')
  }
}

But the task never runs. What is the most likely cause?

medium

A. The task name 'cleanup-task' is invalid

B. You forgot to start the Celery Beat service

C. The crontab syntax is incorrect because minute should be a string

D. The worker must be restarted every hour

Solution

1. Step 1: Check if Celery Beat is running

   Celery Beat must be running to send scheduled tasks to the worker.

2. Step 2: Validate other options

   Task names can be any string, crontab accepts integer or string for minute, and workers do not need hourly restart.

3. Final Answer:

   You forgot to start the Celery Beat service -> Option B

4. Quick Check:

   Beat service must run for schedules to trigger [OK]

Hint: Always run Celery Beat alongside worker [OK]

Common Mistakes:

• Assuming task name format causes failure
• Thinking crontab minute must be string only
• Restarting worker unnecessarily

5. You want to run a Django Celery task every day at 2:30 AM and also every 10 minutes. How should you configure beat_schedule to achieve this?

hard

A. { 'daily-task': { 'task': 'app.tasks.daily', 'schedule': crontab(hour='2:30') }, 'frequent-task': { 'task': 'app.tasks.frequent', 'schedule': crontab(minute=10) } }

B. { 'daily-task': { 'task': 'app.tasks.daily', 'schedule': crontab(hour=2, minute=30) }, 'frequent-task': { 'task': 'app.tasks.frequent', 'schedule': crontab(minute=10) } }

C. { 'daily-task': { 'task': 'app.tasks.daily', 'schedule': crontab(hour=2, minute=30) }, 'frequent-task': { 'task': 'app.tasks.frequent', 'schedule': crontab(minute='*/10') } }

D. { 'daily-task': { 'task': 'app.tasks.daily', 'schedule': crontab(hour='2', minute='30') }, 'frequent-task': { 'task': 'app.tasks.frequent', 'schedule': crontab(minute='10') } }

Solution

1. Step 1: Define daily task schedule correctly

   Use crontab(hour=2, minute=30) or with strings '2' and '30' to run at 2:30 AM daily.

2. Step 2: Define frequent task schedule correctly

   Use crontab(minute='*/10') to run every 10 minutes; minute=10 runs only at minute 10 each hour.

3. Step 3: Check all options

   { 'daily-task': { 'task': 'app.tasks.daily', 'schedule': crontab(hour=2, minute=30) }, 'frequent-task': { 'task': 'app.tasks.frequent', 'schedule': crontab(minute='*/10') } } uses correct crontab syntax for both tasks; others have invalid formats or misunderstandings.

4. Final Answer:

   Use crontab(hour=2, minute=30) and crontab(minute='*/10') -> Option C

5. Quick Check:

   Daily at 2:30 and every 10 min = { 'daily-task': { 'task': 'app.tasks.daily', 'schedule': crontab(hour=2, minute=30) }, 'frequent-task': { 'task': 'app.tasks.frequent', 'schedule': crontab(minute='*/10') } } [OK]

Hint: Use '*/10' for every 10 minutes, not minute=10 [OK]

Common Mistakes:

• Using '2:30' as hour value
• Setting minute=10 instead of '*/10' for intervals
• Mixing string and integer types incorrectly