Python 异步任务队列Celery 使用

Posted 2023-04-27

参考技术A

在 Python 中定义 Celery 的时候，我们要引入 Broker，中文翻译过来就是“中间人”的意思。在工头(生产者)提出任务的时候，把所有的任务放到 Broker 里面，在 Broker 的另外一头，一群码农(消费者)等着取出一个个任务准备着手做。这种模式注定了整个系统会是个开环系统，工头对于码农们把任务做的怎样是不知情的。所以我们要引入 Backend 来保存每次任务的结果。这个 Backend 也是存储任务的信息用的，只不过这里存的是那些任务的返回结果。我们可以选择只让错误执行的任务返回结果到 Backend，这样我们取回结果，便可以知道有多少任务执行失败了。

其实现架构如下图所示：

可以看到，Celery 主要包含以下几个模块：

celery可以通过pip自动安装。

broker 可选择使用RabbitMQ/redis，backend可选择使用RabbitMQ/redis/MongoDB。RabbitMQ/redis/mongoDB的安装请参考对应的官方文档。

------------------------------rabbitmq相关----------------------------------------------------------

官网安装方法： http://www.rabbitmq.com/install-windows.html

启动管理插件：sbin/rabbitmq-plugins enable rabbitmq_management 启动rabbitmq：sbin/rabbitmq-server -detached

rabbitmq已经启动，可以打开页面来看看 地址： http://localhost:15672/#/

用户名密码都是guest 。进入可以看到具体页面。 关于rabbitmq的配置，网上很多 自己去搜以下就ok了。

------------------------------rabbitmq相关--------------------------------------------------------

项目结构如下：

使用前，需要三个方面：celery配置，celery实例，需执行的任务函数，如下：

Celery 的配置比较多，可以在 官方配置文档： http://docs.celeryproject.org/en/latest/userguide/configuration.html 查询每个配置项的含义。

当然，要保证上述异步任务and下述定时任务都能正常执行，就需要先启动celery worker，启动命令行如下:

需 启动beat ，执行定时任务时, Celery会通过celery beat进程来完成。Celery beat会保持运行, 一旦到了某一定时任务需要执行时, Celery beat便将其加入到queue中. 不像worker进程, Celery beat只需要一个即可。而且为了避免有重复的任务被发送出去，所以Celery beat仅能有一个。

命令行启动：

如果你想将celery worker/beat要放到后台运行，推荐可以扔给supervisor。

supervisor.conf如下：

Celery 分布式任务队列快速入门

Celery介绍和基本使用

在项目中如何使用celery

启用多个workers

Celery 定时任务

与django结合

通过django配置celery periodic task

 

 

一、Celery介绍和基本使用 

Celery 是一个 基于python开发的分布式异步消息任务队列，通过它可以轻松的实现任务的异步处理， 如果你的业务场景中需要用到异步任务，就可以考虑使用celery， 举几个实例场景中可用的例子:

1. 你想对100台机器执行一条批量命令，可能会花很长时间 ，但你不想让你的程序等着结果返回，而是给你返回 一个任务ID,你过一段时间只需要拿着这个任务id就可以拿到任务执行结果， 在任务执行ing进行时，你可以继续做其它的事情。 
2. 你想做一个定时任务，比如每天检测一下你们所有客户的资料，如果发现今天 是客户的生日，就给他发个短信祝福

 

Celery 在执行任务时需要通过一个消息中间件来接收和发送任务消息，以及存储任务结果， 一般使用rabbitMQ or Redis,后面会讲

1.1 Celery有以下优点：

1. 简单：一单熟悉了celery的工作流程后，配置和使用还是比较简单的
2. 高可用：当任务执行失败或执行过程中发生连接中断，celery 会自动尝试重新执行任务
3. 快速：一个单进程的celery每分钟可处理上百万个任务
4. 灵活： 几乎celery的各个组件都可以被扩展及自定制

Celery基本工作流程图

1.2 Celery安装使用

Celery的默认broker是RabbitMQ, 仅需配置一行就可以

broker_url = \'amqp://guest:guest@localhost:5672//\'

rabbitMQ 没装的话请装一下，安装看这里  http://docs.celeryproject.org/en/latest/getting-started/brokers/rabbitmq.html#id3

 

使用Redis做broker也可以

安装redis组件

$ pip install -U "celery[redis]"

python连接的redis组件

pip3 install redis

配置

Configuration is easy, just configure the location of your Redis database:

app.conf.broker_url = \'redis://localhost:6379/0\'

　　

Where the URL is in the format of:

redis://:password@hostname:port/db_number

all fields after the scheme are optional, and will default to localhost on port 6379, using database 0.

 

如果想获取每个任务的执行结果，还需要配置一下把任务结果存在哪

If you also want to store the state and return values of tasks in Redis, you should configure these settings:

app.conf.result_backend = \'redis://localhost:6379/0\'

　　

1. 3 开始使用Celery啦　　

安装celery模块

$ pip install celery

创建一个celery application 用来定义你的任务列表

创建一个任务文件就叫tasks.py吧　　　　　　\'redis://:123456@192.168.31.128:6379/0\'

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from celery import Celery

app = Celery(\'tasks\',
             broker=\'redis://:123456@192.168.31.128\',　　
             backend=\'redis://:123456@192.168.31.128\')　　#拿到结果把结果写到某个地方


@app.task
def add(x, y):  #这是worker可以执行的一个任务
    print("running...", x, y)
    return x + y

@app.task
def cmd(cmd_str):
    print("running cmd",cmd_str)

启动Celery Worker来开始监听并执行任务

$ celery -A tasks worker --loglevel=info

$ celery -A celery_test worker -l debug

　　所有任务

[tasks]
  . celery.accumulate
  . celery.backend_cleanup
  . celery.chain
  . celery.chord
  . celery.chord_unlock
  . celery.chunks
  . celery.group
  . celery.map
  . celery.starmap
  . celery_test.add　　***
  . celery_test.cmd　　***

调用任务

再打开一个终端， 进行命令行模式，调用任务　

>>> from tasks import add
>>> add.delay(4, 4)

看你的worker终端会显示收到 一个任务，此时你想看任务结果的话，需要在调用 任务时　赋值个变量

>>> result = add.delay(4, 4)

>>> add.delay(45,8)    #发送任务
<AsyncResult: 73f83dce-61e7-48c7-816a-802c9516b014>   
>>> t1=add.delay(45,3)    赋值给t1
>>> t1    #拿到的是一个实例
<AsyncResult: ff47acc1-99b5-4b41-8744-3368af3e27e0>
>>> t1.get()    #实例.get()拿到结果
48

The ready() method returns whether the task has finished processing or not:

>>> result.ready()　　#检测任务有没有完
False

You can wait for the result to complete, but this is rarely used since it turns the asynchronous call into a synchronous one:

>>> result.get(timeout=1)#超过时间就不等，但超时的时候会报错
8

In case the task raised an exception, get() will re-raise the exception, but you can override this by specifying the propagate argument:

>>> result.get(propagate=False)    #不让程序报错

If the task raised an exception you can also gain access to the original traceback:

>>> result.traceback    #拿到错误结果
…

　　

二、在项目中如何使用celery　

可以把celery配置成一个应用

目录格式如下

proj/__init__.py
    /celery.py
    /tasks.py

proj/celery.py内容

from __future__ import absolute_import, unicode_literals
#从python的绝对路径导入而不是当前的脚本     #在python2和python3做兼容支持的
from celery import Celery

app = Celery(\'proj\',#app的名字
             broker=\'redis://:123456@192.168.31.128\',#连rabbitmq或redis
             backend=\'redis://:123456@192.168.31.128\',
             include=[\'s3proj.tasks\',\'s3proj.tasks2\'])

# Optional configuration, see the application user guide.
app.conf.update(#给app设置参数
    result_expires=3600,#保存时间为1小时
)

if __name__ == \'__main__\':
    app.start()

proj/tasks.py中的内容

from __future__ import absolute_import, unicode_literals
#从python的绝对路径导入而不是当前的脚本     #在python2和python3做兼容支持的
from .celery import app

@app.task
def add(x, y):
    return x + y

@app.task
def mul(x, y):
    return x * y

@app.task
def xsum(numbers):
    return sum(numbers)

####################################

from __future__ import absolute_import, unicode_literals
#从python的绝对路径导入而不是当前的脚本     #在python2和python3做兼容支持的
from .celery import app


@app.task
def cmd(cmd):
    print("running cmd",cmd)


@app.task
def file_transfer(filename):
    print("sending file",filename)

　　

启动worker 

$ celery -A proj worker -l info

输出

-------------- [e-mail] v4.0.2 (latentcall)
---- **** -----
--- * ***  * -- Darwin-15.6.0-x86_64-i386-64bit 2017-01-26 21:50:24
-- * - **** ---
- ** ---------- [config]
- ** ---------- .> app:         proj:0x103a020f0
- ** ---------- .> transport:   redis://localhost:6379//
- ** ---------- .> results:     redis://localhost/
- *** --- * --- .> concurrency: 8 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** -----
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery

后台启动worker

In the background

In production you’ll want to run the worker in the background, this is described in detail in the daemonization tutorial.

The daemonization scripts uses the celery multi command to start one or more workers in the background:

后台开启celery，可以同时开启多个celery

[root@wenwen szw]# celery multi start w1 -A s3proj -l info
celery multi v4.0.2 (latentcall)
> Starting nodes...
	> [e-mail]: OK

You can restart it too:

重启celery

$ celery  multi restart w1 -A proj -l info
celery multi v4.0.0 (latentcall)
> Stopping nodes...
    > w1.halcyon.local: TERM -> 64024
> Waiting for 1 node.....
    > w1.halcyon.local: OK
> Restarting node w1.halcyon.local: OK
celery multi v4.0.0 (latentcall)
> Stopping nodes...
    > w1.halcyon.local: TERM -> 64052

or stop it:

停止celery

[root@wenwen szw]# celery multi stop w1    #杀掉celery进程
celery multi v4.0.2 (latentcall)
> Stopping nodes...
	> [e-mail]: TERM -> 39496

The stop command is asynchronous so it won’t wait for the worker to shutdown. You’ll probably want to use the stopwait command instead, this ensures all currently executing tasks is completed before exiting:

确保执行完了再停止

$ celery multi stopwait w1 -A proj -l info

　　

三、Celery 定时任务

 celery支持定时任务，设定好任务的执行时间，celery就会定时自动帮你执行， 这个定时任务模块叫celery beat

写一个脚本 叫periodic_task.py

from __future__ import absolute_import, unicode_literals
#从python的绝对路径导入而不是当前的脚本     #在python2和python3做兼容支持的
from celery.schedules import crontab
from .celery import app


@app.on_after_configure.connect
def setup_periodic_tasks(sender, **kwargs):#用sender添加任务
    # Calls test(\'hello\') every 10 seconds.
    sender.add_periodic_task(10.0, test.s(\'hello\'), name=\'add every 10\')
            #每隔10秒执行一次task函数    .s是传的参数                 #任务名

    # Calls test(\'world\') every 30 seconds
    sender.add_periodic_task(30.0, test.s(\'world\'), expires=10)
                                                    #任务结果保存10秒钟
    # Executes every Monday morning at 7:30 a.m.
    sender.add_periodic_task(
        crontab(hour=7, minute=30, day_of_week=1),
        test.s(\'Happy Mondays!\'),
    )


@app.task
def test(arg):
    print("run func:",arg)

add_periodic_task 会添加一条定时任务

 

上面是通过调用函数添加定时任务，也可以像写配置文件 一样的形式添加， 下面是每30s执行的任务

app.conf.beat_schedule = {
    \'add-every-30-seconds\': {
        \'task\': \'tasks.add\',
        \'schedule\': 30.0,
        \'args\': (16, 16)
    },
}
app.conf.timezone = \'UTC\'

任务添加好了，需要让celery单独启动一个进程来定时发起这些任务， 注意， 这里是发起任务，不是执行，这个进程只会不断的去检查你的任务计划， 每发现有任务需要执行了，就发起一个任务调用消息，交给celery worker去执行

启动任务调度器 celery beat

$ celery -A periodic_task beat

$ celery -A s3proj.periodic_tasks beat -l debug    #启动定时任务，必须指定哪个文件启动定时任务

输出like below

celery beat v4.0.2 (latentcall) is starting.
__    -    ... __   -        _
LocalTime -> 2017-02-08 18:39:31
Configuration ->
    . broker -> redis://localhost:6379//
    . loader -> celery.loaders.app.AppLoader
    . scheduler -> celery.beat.PersistentScheduler
    . db -> celerybeat-schedule
    . logfile -> [stderr]@%WARNING
    . maxinterval -> 5.00 minutes (300s)

此时还差一步，就是还需要启动一个worker,负责执行celery beat发起的任务

启动celery worker来执行任务

$ celery -A periodic_task worker
  
 -------------- [e-mail] v4.0.2 (latentcall)
---- **** -----
--- * ***  * -- Darwin-15.6.0-x86_64-i386-64bit 2017-02-08 18:42:08
-- * - **** ---
- ** ---------- [config]
- ** ---------- .> app:         tasks:0x104d420b8
- ** ---------- .> transport:   redis://localhost:6379//
- ** ---------- .> results:     redis://localhost/
- *** --- * --- .> concurrency: 8 (prefork)
-- ******* ---- .> task events: OFF (enable -E to monitor tasks in this worker)
--- ***** -----
 -------------- [queues]
                .> celery           exchange=celery(direct) key=celery

好啦，此时观察worker的输出，是不是每隔一小会，就会执行一次定时任务呢！

注意：Beat needs to store the last run times of the tasks in a local database file (named celerybeat-schedule by default), so it needs access to write in the current directory, or alternatively you can specify a custom location for this file:

$ celery -A periodic_task beat -s /home/celery/var/run/celerybeat-schedule

　　

更复杂的定时配置　　

上面的定时任务比较简单，只是每多少s执行一个任务，但如果你想要每周一三五的早上8点给你发邮件怎么办呢？哈，其实也简单，用crontab功能，跟linux自带的crontab功能是一样的，可以个性化定制任务执行时间

linux crontab http://www.cnblogs.com/peida/archive/2013/01/08/2850483.html 

from celery.schedules import crontab
 
app.conf.beat_schedule = {
    # Executes every Monday morning at 7:30 a.m.
    \'add-every-monday-morning\': {
        \'task\': \'s3proj.tasks.add\',
        \'schedule\': crontab(hour=7, minute=30, day_of_week=1),
        \'args\': (16, 16),
    },
}

上面的这条意思是每周1的早上7.30执行tasks.add任务

还有更多定时配置方式如下：

上面的这条意思是每周1的早上7.30执行tasks.add任务

还有更多定时配置方式如下：

Example	Meaning
crontab()	Execute every minute.
crontab(minute=0, hour=0)	Execute daily at midnight.
crontab(minute=0, hour=\'*/3\')	Execute every three hours: midnight, 3am, 6am, 9am, noon, 3pm, 6pm, 9pm.
crontab(minute=0, hour=\'0,3,6,9,12,15,18,21\')	Same as previous.
crontab(minute=\'*/15\')	Execute every 15 minutes.
crontab(day_of_week=\'sunday\')	Execute every minute (!) at Sundays.
crontab(minute=\'*\', hour=\'*\',day_of_week=\'sun\')	Same as previous.
crontab(minute=\'*/10\', hour=\'3,17,22\',day_of_week=\'thu,fri\')	Execute every ten minutes, but only between 3-4 am, 5-6 pm, and 10-11 pm on Thursdays or Fridays.
crontab(minute=0,hour=\'*/2,*/3\')	Execute every even hour, and every hour divisible by three. This means: at every hour except: 1am, 5am, 7am, 11am, 1pm, 5pm, 7pm, 11pm
crontab(minute=0, hour=\'*/5\')	Execute hour divisible by 5. This means that it is triggered at 3pm, not 5pm (since 3pm equals the 24-hour clock value of “15”, which is divisible by 5).
crontab(minute=0, hour=\'*/3,8-17\')	Execute every hour divisible by 3, and every hour during office hours (8am-5pm).
crontab(0, 0,day_of_month=\'2\')	Execute on the second day of every month.
crontab(0, 0, day_of_month=\'2-30/3\')	Execute on every even numbered day.
crontab(0, 0, day_of_month=\'1-7,15-21\')	Execute on the first and third weeks of the month.
crontab(0, 0,day_of_month=\'11\', month_of_year=\'5\')	Execute on the eleventh of May every year.
crontab(0, 0, month_of_year=\'*/3\')	Execute on the first month of every quarter.

 

上面能满足你绝大多数定时任务需求了，甚至还能根据潮起潮落来配置定时任务， 具体看 http://docs.celeryproject.org/en/latest/userguide/periodic-tasks.html#solar-schedules 　

 

 

四、最佳实践之与django结合 

django 可以轻松跟celery结合实现异步任务，只需简单配置即可

If you have a modern Django project layout like:

- proj/
  - proj/__init__.py
  - proj/settings.py
  - proj/urls.py
- manage.py

then the recommended way is to create a new proj/proj/celery.py module that defines the Celery instance:

file: proj/proj/celery.py　　写了一个这个就把selery的配置写好了

from __future__ import absolute_import, unicode_literals
import os
from celery import Celery

# set the default Django settings module for the \'celery\' program.
os.environ.setdefault(\'DJANGO_SETTINGS_MODULE\', \'PerfectCRM.settings\')#配置环境变量

app = Celery(\'celery_task\')

# Using a string here means the worker don\'t have to serialize
# the configuration object to child processes.
# - namespace=\'CELERY\' means all celery-related configuration keys
#   should have a `CELERY_` prefix.
app.config_from_object(\'django.conf:settings\', namespace=\'CELERY\')
#你可以把celery连接的RabbitMQ存到settings但你必须按他规定的格式，必须CELERY大写开头

# Load task modules from all registered Django app configs.
app.autodiscover_tasks()    #app下自动发现selery
#能够找到所有app下的selery任务

@app.task(bind=True)
def debug_task(self):
    print(\'Request: {0!r}\'.format(self.request))

Then you need to import this app in your proj/proj/__init__.py module. This ensures that the app is loaded when Django starts so that the @shared_task decorator (mentioned later) will use it:　　

proj/proj/__init__.py:　　#找这个项目下所有app

from __future__ import absolute_import, unicode_literals

# This will make sure the app is always imported when
# Django starts so that shared_task will use this app.
from .celery import app as celery_app

__all__ = [\'celery_app\']
#找这个所有项目下的所有APP

Note that this example project layout is suitable for larger projects, for simple projects you may use a single contained module that defines both the app and tasks, like in the First Steps with Celery tutorial.　　

Let’s break down what happens in the first module, first we import absolute imports from the future, so that our celery.py module won’t clash with the library:

from __future__ import absolute_import

Then we set the default DJANGO_SETTINGS_MODULE environment variable for the celery command-line program:

os.environ.setdefault(\'DJANGO_SETTINGS_MODULE\', \'PerfectCRM.settings\')
　　　　　　　　　　　　　　　　　　　　　　　　　　　　#项目名.settings

You don’t need this line, but it saves you from always passing in the settings module to the celery program. It must always come before creating the app instances, as is what we do next:

app = Celery(\'celery_task\')

This is our instance of the library.

 

We also add the Django settings module as a configuration source for Celery. This means that you don’t have to use multiple configuration files, and instead configure Celery directly from the Django settings; but you can also separate them if wanted.

The uppercase name-space means that all Celery configuration options must be specified in uppercase instead of lowercase, and start with CELERY_, so for example the task_always_eager` setting becomes CELERY_TASK_ALWAYS_EAGER, and the broker_url setting becomes CELERY_BROKER_URL.

You can pass the object directly here, but using a string is better since then the worker doesn’t have to serialize the object.

app.config_from_object(\'django.conf:settings\', namespace=\'CELERY\')

#你可以把celery连接的RabbitMQ存到settings但你必须按他规定的格式，必须CELERY大写开头

Next, a common practice for reusable apps is to define all tasks in a separate tasks.pymodule, and Celery does have a way to  auto-discover these modules:

app.autodiscover_tasks()
#不管你在那个app里创建clelry任务,他都能自动发现，就像djangoadmin一样能自动发现

With the line above Celery will automatically discover tasks from all of your installed apps, following the tasks.py convention:

- app1/
    - tasks.py    #必须叫这个名字
    - models.py
- app2/
    - tasks.py
    - models.py

Finally, the debug_task example is a task that dumps its own request information. This is using the new bind=True task option introduced in Celery 3.1 to easily refer to the current task instance.

#每个app下面都可以有一个tasks文件，必须叫这个名字

然后在具体的app里的tasks.py里写你的任务

from __future__ import absolute_import, unicode_literals
from celery import shared_task
#在这个app里的任务和其他app里的任务是可以互相共享d

@shared_task
def add(x, y):
    return x + y


@shared_task
def mul(x, y):
    return x * y


@shared_task
def xsum(numbers):
    return sum(numbers)

 进到项目里面启动　worker

celery -A PerfectCRM worker -l debug

 进到项目里面启动项目

python3 manage.py runserver 0.0.0.0:9000

 settings里配置

CELERY_BROKER_URL="redis://localhost"
CELERY_RESULT_BACKEND="redis://localhost"

在你的django views里调用celery task

from crm.tasks import add,mul   #导入worker
from celery.result import AsyncResult
# Create your views here.



def celery_test(request):
    """
    掉一个视图，把任务交给celery，并返回任务id
    :param request:
    :return:
    """
    task=add.delay(4,42)
    # res=task.get()
    # return HttpResponse(res)#返回的是任务结果
    return HttpResponse(task.id)#返回的是任务id
    
def celery_res(request):
    """
    通过任务id取出任务结果
    :param request:
    :return:
    """
    task_id="686c19f5-89d1-4c57-8e91-669f9e2716e5"
    res=AsyncResult(id=task_id)
    return HttpResponse(res.get())

　　

 

五、在django中使用计划任务功能　　

There’s  the django-celery-beat extension that stores the schedule in the Django database, and presents a convenient admin interface to manage periodic tasks at runtime.

To install and use this extension:

1. Use pip to install the package:　　安装定时任务要装的插件

   $ pip install django-celery-beat
   

2. Add the django_celery_beat module to INSTALLED_APPS in your Django project’ settings.py:　　#settings里需要配置

   INSTALLED_APPS = (
           ...,
           \'django_celery_beat\',
       )

   Note that there is no dash in the module name, only underscores. 

3. Apply Django database migrations so that the necessary tables are created:

   因为需要创建几张表

   $ python manage.py migrate
   

    

4. Start the celery beat service using the django scheduler:

   #从django里面读数据要加 -S django 不加的话不会报错也不会从django里面读数据
   $ celery -A proj beat -l info -S django
   

5. Visit the Django-Admin interface to set up some periodic tasks.

　　

在admin页面里，有3张表

 多长时间

每隔多长时间

 

配置完长这样

 

 此时启动你的celery beat 和worker，会发现每隔2分钟，beat会发起一个任务消息让worker执行scp_task任务

 

 注意，经测试，每添加或修改一个任务，celery beat都需要重启一次，要不然新的配置不会被celery beat进程读到