Django框架中使用定时任务APScheduler

Posted 2021-06-18 以梦为马&不负韶华

文章目录

• 前言
• 一、安装模块
• 二、配置
• • 1.修改**settings.py**文件
  • 2.执行迁移命令
• 二、创建任务
• • 1.前提必备
  • 2.装饰器创建任务---适合于写代码的人自己创建任务
  • 3.add_job函数创建任务---适合用户通过页面输入参数，并提交来手动创建定时任务
• 三、删除任务
• • 1.remove_job示例
  • 2.DjangoJobStore源码分析---remove_job、get_all_jobs、add_job、update_job等
• 总结

---

前言

Django框架中使用定时任务APScheduler：django-apschedule
本文需要已掌握Python定时任务框架APSchedule，如果不会，可以查看我另一篇博客Python定时任务框架APScheduler快速入门，快速学习。

---

一、安装模块

pip install django-apscheduler 

二、配置

1.修改settings.py文件

在INSTALLED_APPS中加入django-apscheduler应用：

INSTALLED_APPS = [
    ......
    'django_apscheduler',#定时执行任务
]

2.执行迁移命令

在django项目的manage同级终端下：

python manage.py migrate

会自动生成两张表:django_apschedule_djangojob（存储任务）和django_apschedule_djangojobexecution（任务执行情况）

django_apschedule_djangojob如下：

django_apschedule_djangojobexecution如下：

status: 执行状态
duration: 执行了多长时间
exception: 是否出现了什么异常

二、创建任务

两种创建任务的方法：装饰器和add_job函数。添加完成后，数据库中就可以显示

1.前提必备

必须在总路由中导入对应分路由 对应分路由可以为空
总路由：

from django.conf.urls import url, include
from django.contrib import admin

urlpatterns = [
    url(r'^admin/', admin.site.urls),
    # url(r'', include('cron.urls')),
]

对应分路由

urlpatterns = [
]

2.装饰器创建任务—适合于写代码的人自己创建任务

在任意view.py中实现代码

from apscheduler.schedulers.background import BackgroundScheduler
from django_apscheduler.jobstores import DjangoJobStore, register_events, register_job

#开启定时工作
try:
    # 实例化调度器
    scheduler = BackgroundScheduler()
    # 调度器使用DjangoJobStore()
    scheduler.add_jobstore(DjangoJobStore(), "default")
    # 设置定时任务，选择方式为interval，时间间隔为10s
    # 另一种方式为每天固定时间执行任务，对应代码为：
    # @register_job(scheduler, 'cron', day_of_week='mon-fri', hour='9', minute='30', second='10',id='task_time')
    @register_job(scheduler,"interval", seconds=10)
    def my_job():
        # 这里写你要执行的任务
        pass
    register_events(scheduler)
    scheduler.start()
except Exception as e:
    print(e)
    # 有错误就停止定时器
    scheduler.shutdown()

3.add_job函数创建任务—适合用户通过页面输入参数，并提交来手动创建定时任务

如果想让用户通过页面输入参数，并提交来手动创建定时任务，就需要使用add_job函数。
下面这个小例子，接收json数据给后端，触发insert_cron_job函数，来添加任务：

import json
from django.http import JsonResponse
from apscheduler.schedulers.background import BackgroundScheduler
from django_apscheduler.jobstores import DjangoJobStore, register_events, register_job


scheduler = BackgroundScheduler()
scheduler.add_jobstore(DjangoJobStore(), 'default')

# cron
def insert_cron_job(json):  # 传入 状态策略 开始任务 结束任务
    # 接收参数
    try:
        # 获取json中对应数据
        # add_job添加任务，传入：my_job为要执行的定时任务，trigger指定任务触发器（triggers）—不同定时模式，args传参，id定时任务命名–id，等其他配置，根据trigger不同，传入不同的 时间格式进行触发
        scheduler.add_job(my_job, trigger="", args=["s", ], id=start_job_id)
    except Exception as e:
        print("获取数据异常")
        return

# 具体要执行的代码
def my_job(s):
    pass
    
register_events(scheduler)
scheduler.start()

三、删除任务

删除完成后，可以查看数据库中对应的任务id已经删除完成

1.remove_job示例

DjangoJobStore.remove_job(DjangoJobStore(), job_id=需要删除的job_id)

import json
from django.http import JsonResponse
from apscheduler.schedulers.background import BackgroundScheduler
from django_apscheduler.jobstores import DjangoJobStore, register_events, register_job


scheduler = BackgroundScheduler()
scheduler.add_jobstore(DjangoJobStore(), 'default')

# cron
def insert_cron_job(json):  # 传入 状态策略 开始任务 结束任务
    # 接收参数
    try:
        # 获取json中对应数据
        # add_job添加任务，传入：my_job为要执行的定时任务，trigger指定任务触发器（triggers）—不同定时模式，args传参，id定时任务命名–id，等其他配置，根据trigger不同，传入不同的 时间格式进行触发
        scheduler.add_job(my_job, trigger="", args=["s", ], id=start_job_id)
    except Exception as e:
        print("获取数据异常")
        return
 
def delete_cron_job(json):
    # 接收参数
    # 获取需要删除的job_id
    try:
        DjangoJobStore.remove_job(DjangoJobStore(), job_id=需要删除的job_id)  
    except Exception as e:
        print("删除定时任务异常:", e)
# 具体要执行的代码
def my_job(s):
    pass
    
register_events(scheduler)
scheduler.start()

2.DjangoJobStore源码分析—remove_job、get_all_jobs、add_job、update_job等

使用django_apscheduler操作DjangoJobStore这个类来进行各项操作
点开DjangoJobStore源码如下：

找到删除操作的源码：
可以看到是操作数据库，使用的DjangoJob这个模型类，有了这个我们可以进一步分析，也可以直接操作这个类完成对应操作

对应操作即可
其他还有get_all_jobs、add_job、update_job等，需要什么操作，对应即可
DjangoJob模型类如下：

from datetime import timedelta, datetime

from django.db import models, transaction
from django.utils import timezone
from django.utils.translation import ugettext_lazy as _

import logging

from django_apscheduler import util
from django_apscheduler.util import get_django_internal_datetime

logger = logging.getLogger(__name__)


class DjangoJob(models.Model):
    id = models.CharField(
        max_length=255, primary_key=True, help_text=_("Unique id for this job.")
    )

    next_run_time = models.DateTimeField(
        db_index=True,
        blank=True,
        null=True,
        help_text=_(
            "Date and time at which this job is scheduled to be executed next."
        ),
    )

    job_state = models.BinaryField()

    def __str__(self):
        status = (
            f"next run at: {util.get_local_dt_format(self.next_run_time)}"
            if self.next_run_time
            else "paused"
        )
        return f"{self.id} ({status})"

    class Meta:
        ordering = ("next_run_time",)


class DjangoJobExecutionManager(models.Manager):
    def delete_old_job_executions(self, max_age: int):
        """
        Delete old job executions from the database.

        :param max_age: The maximum age (in seconds). Executions that are older
        than this will be deleted.
        """
        self.filter(run_time__lte=timezone.now() - timedelta(seconds=max_age)).delete()


class DjangoJobExecution(models.Model):
    SENT = "Started execution"
    SUCCESS = "Executed"
    MISSED = "Missed!"
    MAX_INSTANCES = "Max instances!"
    ERROR = "Error!"

    STATUS_CHOICES = [(x, x) for x in [SENT, ERROR, SUCCESS,]]

    id = models.BigAutoField(
        primary_key=True, help_text=_("Unique ID for this job execution.")
    )

    job = models.ForeignKey(
        DjangoJob,
        on_delete=models.CASCADE,
        help_text=_("The job that this execution relates to."),
    )

    status = models.CharField(
        max_length=50,
        # TODO: Replace this with enumeration types when we drop support for Django 2.2
        # See: https://docs.djangoproject.com/en/dev/ref/models/fields/#field-choices-enum-types
        choices=STATUS_CHOICES,
        help_text=_("The current status of this job execution."),
    )

    run_time = models.DateTimeField(
        db_index=True, help_text=_("Date and time at which this job was executed."),
    )

    # We store this value in the DB even though it can be calculated as `finished - run_time`. This allows quick
    # calculation of average durations directly in the database later on.
    duration = models.DecimalField(
        max_digits=15,
        decimal_places=2,
        default=None,
        null=True,
        help_text=_("Total run time of this job (in seconds)."),
    )

    finished = models.DecimalField(
        max_digits=15,
        decimal_places=2,
        default=None,
        null=True,
        help_text=_("Timestamp at which this job was finished."),
    )

    exception = models.CharField(
        max_length=1000,
        null=True,
        help_text=_(
            "Details of exception that occurred during job execution (if any)."
        ),
    )

    traceback = models.TextField(
        null=True,
        help_text=_(
            "Traceback of exception that occurred during job execution (if any)."
        ),
    )

    objects = DjangoJobExecutionManager()

    @classmethod
    def atomic_update_or_create(
        cls,
        lock,
        job_id: str,
        run_time: datetime,
        status: str,
        exception: str = None,
        traceback: str = None,
    ) -> "DjangoJobExecution":
        """
        Uses an APScheduler lock to ensures that only one database entry can be created / updated at a time.

        This keeps django_apscheduler in sync with APScheduler and maintains a 1:1 mapping between APScheduler events
        that are triggered and the corresponding DjangoJobExecution model instances that are persisted to the database.
        :param lock: The lock to use when updating the database - probably obtained by calling _scheduler._create_lock()
        :param job_id: The ID to the APScheduler job that this job execution is for.
        :param run_time: The scheduler runtime for this job execution.
        :param status: The new status for ths job execution.
        :param exception: Details of any exceptions that need to be logged.
        :param traceback: Traceback of any exceptions that occurred while executing the job.
        :return: The ID of the newly created or updated DjangoJobExecution.
        """

        # Ensure that only one update / create can be processed at a time, staying in sync with corresponding
        # scheduler.
        with lock:
            # Convert all datetimes to internal Django format before doing calculations and persisting in the database.
            run_time = get_django_internal_datetime(run_time)

            finished = get_django_internal_datetime(timezone.now())
            duration = (finished - run_time).total_seconds()
            finished = finished.timestamp()

            try:
                with transaction.atomic():
                    job_execution = DjangoJobExecution.objects.select_for_update().get(
                        job_id=job_id, run_time=run_time
                    )

                    if status == DjangoJobExecution.SENT:
                        # Ignore 'submission' events for existing job executions. APScheduler does not appear to
                        # guarantee the order in which events are received, and it is not unusual to receive an
                        # `executed` before the corresponding `submitted` event. We just discard `submitted` events
                        # that are received after the job has already been executed.
                        #
                        # If there are any more instances like this then we probably want to implement a full blown
                        # state machine using something like `pytransitions`
                        # See https://github.com/pytransitions/transitions
                        return job_execution

                    job_execution.finished = finished
                    job_execution.duration = duration
                    job_execution.status = status

                    if exception:
                        job_execution.exception = exception

                    if traceback:
                        job_execution.traceback = traceback

                    job_execution.save()

            except DjangoJobExecution.DoesNotExist:
                # Execution was not created by a 'submit' previously - do so now
                if status == DjangoJobExecution.SENT:
                    # Don't log durations until after job has been submitted for execution
                    finished = None
                    duration = None

                job_execution = DjangoJobExecution.objects.create(
                    job_id=job_id,
                    run_time=run_time,
                    status=status,
                    duration=duration,
                    finished=finished,
                    exception=exception,
                    traceback=traceback,
                )

        return job_execution

    def __str__(self):
        return f"{self.id}: job '{self.job_id}' ({self.status})"

    class Meta:
        ordering = ("-run_time",)

总结

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