1. What is APScheduler?

• APScheduler (advanced Python scheduler) is a timing task tool developed by Python. User Guide https://apscheduler.readthedocs.io/en/latest/userguide.html#starting-the-scheduler
• APScheduler has four components: Scheduler, executors, add timing tasks. add_job, trigger Tigger

2. The usage scenario of APScheduler?

• When redis persistent storage, APScheduler is used to synchronize data.
• Users must pay within 30 minutes after placing an order, otherwise cancel the order.

3. What's the difference between APScheduler and crontab as timed task tools?

How does APScheduler work?

1. Installation

pip install apscheduler

2 Ways of Use

from apscheduler.schedulers.background import BackgroundScheduler

# Create scheduler objects for timed tasks
scheduler = BackgroundScheduler()

# Define Timing Tasks
def my_job(param1, param2):
    pass

# Add Timing Tasks to Scheduler
scheduler.add_job(my_job, 'date', args=[100, 'python'])

# Start Timing Task Scheduler Work
scheduler.start()

3. Scheduler

• Using Blocking Scheduler for stand-alone runtime

from apscheduler.schedulers.blocking import BlockingScheduler

  scheduler = BlockingScheduler()
  scheduler.start()  # Here the program will block

• Use BackgroundScheduler in framework programs such as Django and Flask:

  from apscheduler.schedulers.background import BackgroundScheduler

  scheduler = BackgroundScheduler()
  scheduler.start()  # There will be no blocking in this program.

4. executors can use ThreadPool Executor and Process Pool Executor

• Thread process pool

from apscheduler.executors.pool import ThreadPoolExecutor
ThreadPoolExecutor(max_workers)  
ThreadPoolExecutor(20) # Up to 20 threads execute simultaneously

Usage method:

executors = {
      'default': ThreadPoolExecutor(20)
  }
  scheduler = BackgroundScheduler(executors=executors)

• Process pool

from apscheduler.executors.pool import ProcessPoolExecutor
ProcessPoolExecutor(max_workers)
ProcessPoolExecutor(5) # Up to five processes are executed simultaneously

Usage method:

 executors = {
      'default': ProcessPoolExecutor(3)
  }
  scheduler = BackgroundScheduler(executors=executors)

5. Trigger Tigger

• Scheduling of tasks:

interval: Execute at specified intervals

weeks (int) – number of weeks to wait
days (int) – number of days to wait
hours (int) – number of hours to wait
minutes (int) – number of minutes to wait
seconds (int) – number of seconds to wait
start_date (datetime|str) – starting point for the interval calculation
end_date (datetime|str) – latest possible date/time to trigger on
timezone (datetime.tzinfo|str) – time zone to use for the date/time calculations

cron: Execution on a specified period

year (int|str) – 4-digit year
month (int|str) – month (1-12)
day (int|str) – day of the (1-31)
week (int|str) – ISO week (1-53)
day_of_week (int|str) – number or name of weekday (0-6 or mon,tue,wed,thu,fri,sat,sun)
hour (int|str) – hour (0-23)
minute (int|str) – minute (0-59)
second (int|str) – second (0-59)
start_date (datetime|str) – earliest possible date/time to trigger on (inclusive)
end_date (datetime|str) – latest possible date/time to trigger on (inclusive)
t>imezone (datetime.tzinfo|str) – time zone to use for the date/time calculations (defaults to scheduler timezone)

• Example:

 # The code of the function is executed at 0 o'clock every day, and at 0 o'clock, hour can write it without writing it.
App. scheduler. add_job (function name,'cron', hour = 0, args= [parameters that the function needs to pass]) 

# Code execution at 3 a.m. every day
 App. scheduler. add_job (function name,'cron', hour = 3, args= [app])

# If there is no parameter after date, it is to execute the code immediately, which is usually used for testing.
App. scheduler. add_job (function name,'date', args= [app])

6. Program Running:

scheduler.start()

7. Stop APScheduler running

scheduler.shutdown()