一、Celery介紹和基本使用

Celery 是一個 基于python開發(fā)的分布式異步消息任務(wù)隊列，通過它可以輕松的實現(xiàn)任務(wù)的異步處理， 如果你的業(yè)務(wù)場景中需要用到異步任務(wù)，就可以考慮使用celery， 舉幾個實例場景中可用的例子:

你想對100臺機器執(zhí)行一條批量命令，可能會花很長時間 ，但你不想讓你的程序等著結(jié)果返回，而是給你返回 一個任務(wù)ID,你過一段時間只需要拿著這個任務(wù)id就可以拿到任務(wù)執(zhí)行結(jié)果， 在任務(wù)執(zhí)行ing進行時，你可以繼續(xù)做其它的事情。
你想做一個定時任務(wù)，比如每天檢測一下你們所有客戶的資料，如果發(fā)現(xiàn)今天 是客戶的生日，就給他發(fā)個短信祝福

Celery 在執(zhí)行任務(wù)時需要通過一個消息中間件來接收和發(fā)送任務(wù)消息，以及存儲任務(wù)結(jié)果， 一般使用rabbitMQ or Redis,后面會講

1.1 Celery有以下優(yōu)點：

• 簡單：一單熟悉了celery的工作流程后，配置和使用還是比較簡單的
• 高可用：當任務(wù)執(zhí)行失敗或執(zhí)行過程中發(fā)生連接中斷，celery 會自動嘗試重新執(zhí)行任務(wù)
• 快速：一個單進程的celery每分鐘可處理上百萬個任務(wù)
• 靈活： 幾乎celery的各個組件都可以被擴展及自定制

Celery基本工作流程圖

1.2 Celery安裝使用

Celery的默認broker是RabbitMQ, 僅需配置一行就可以

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

rabbitMQ 沒裝的話請裝一下

使用Redis做broker也可以

安裝redis組件

pip install -U "celery[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.

如果想獲取每個任務(wù)的執(zhí)行結(jié)果，還需要配置一下把任務(wù)結(jié)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 開始使用Celery啦　　

安裝celery模塊

pip install celery

創(chuàng)建一個celery application 用來定義你的任務(wù)列表

創(chuàng)建一個任務(wù)文件就叫tasks.py吧

from celery import Celery
 
app = Celery('tasks',
 broker='redis://localhost',
 backend='redis://localhost')
 
@app.task
def add(x,y):
 print("running...",x,y)
 return x+y

啟動Celery Worker來開始監(jiān)聽并執(zhí)行任務(wù)

celery -A tasks worker --loglevel=info

調(diào)用任務(wù)

再打開一個終端， 進行命令行模式，調(diào)用任務(wù)

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

看你的worker終端會顯示收到 一個任務(wù)，此時你想看任務(wù)結(jié)果的話，需要在調(diào)用 任務(wù)時　賦值個變量

result = add.delay(4, 4)

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

>>> result.ready()
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)
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)

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

>>> result.traceback
…

二、在項目中如何使用celery　

可以把celery配置成一個應(yīng)用

目錄格式如下

1 proj/__init__.py
2 /celery.py
3 /tasks.py

proj/celery.py內(nèi)容

from __future__ import absolute_import, unicode_literals
from celery import Celery
 
app = Celery('proj',
 broker='amqp://',
 backend='amqp://',
 include=['proj.tasks'])
 
# Optional configuration, see the application user guide.
app.conf.update(
 result_expires=3600,
)
 
if __name__ == '__main__':
 app.start()

proj/tasks.py中的內(nèi)容

from __future__ import absolute_import, unicode_literals
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)

啟動worker

celery -A proj worker -l info #          

輸出

-------------- celery@Alexs-MacBook-Pro.local 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

后臺啟動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:

$ celery multi start w1 -A proj -l info
celery multi v4.0.0 (latentcall)
> Starting nodes...
> w1.halcyon.local: OK

You can restart it too:

$ 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:

$ celery multi stop w1 -A proj -l info                

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:

$ celery multi stopwait w1 -A proj -l info                 

三、Celery 定時任務(wù)

celery支持定時任務(wù)，設(shè)定好任務(wù)的執(zhí)行時間，celery就會定時自動幫你執(zhí)行， 這個定時任務(wù)模塊叫celery beat

寫一個腳本 叫periodic_task.py

from celery import Celery
from celery.schedules import crontab
 
app = Celery()
 
@app.on_after_configure.connect
def setup_periodic_tasks(sender, **kwargs):
 # Calls test('hello') every 10 seconds.
 sender.add_periodic_task(10.0, test.s('hello'), name='add every 10')
 
 # Calls test('world') every 30 seconds
 sender.add_periodic_task(30.0, test.s('world'), expires=10)
 
 # 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(arg)

add_periodic_task 會添加一條定時任務(wù)

上面是通過調(diào)用函數(shù)添加定時任務(wù)，也可以像寫配置文件 一樣的形式添加， 下面是每30s執(zhí)行的任務(wù)

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

任務(wù)添加好了，需要讓celery單獨啟動一個進程來定時發(fā)起這些任務(wù)， 注意， 這里是發(fā)起任務(wù)，不是執(zhí)行，這個進程只會不斷的去檢查你的任務(wù)計劃， 每發(fā)現(xiàn)有任務(wù)需要執(zhí)行了，就發(fā)起一個任務(wù)調(diào)用消息，交給celery worker去執(zhí)行

啟動任務(wù)調(diào)度器 celery beat

celery -A periodic_task beat

輸出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

此時還差一步，就是還需要啟動一個worker,負責執(zhí)行celery beat發(fā)起的任務(wù)

啟動celery worker來執(zhí)行任務(wù)

$ celery -A periodic_task worker
 
 -------------- celery@Alexs-MacBook-Pro.local 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，此時觀察worker的輸出，是不是每隔一小會，就會執(zhí)行一次定時任務(wù)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

更復(fù)雜的定時配置　　

上面的定時任務(wù)比較簡單，只是每多少s執(zhí)行一個任務(wù)，但如果你想要每周一三五的早上8點給你發(fā)郵件怎么辦呢？哈，其實也簡單，用crontab功能，跟linux自帶的crontab功能是一樣的，可以個性化定制任務(wù)執(zhí)行時間

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

上面的這條意思是每周1的早上7.30執(zhí)行tasks.add任務(wù)

還有更多定時配置方式如下：

上面能滿足你絕大多數(shù)定時任務(wù)需求了，甚至還能根據(jù)潮起潮落來配置定時任務(wù)

四、最佳實踐之與django結(jié)合

django 可以輕松跟celery結(jié)合實現(xiàn)異步任務(wù)，只需簡單配置即可

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　　

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', 'proj.settings')
 
app = Celery('proj')
 
# 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')
 
# Load task modules from all registered Django app configs.
app.autodiscover_tasks()
 
 
@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:

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']

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', 'proj.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('proj')                

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')                  

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()                   

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

- app1/

 - tasks.py
 - 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.

然后在具體的app里的tasks.py里寫你的任務(wù)

# Create your tasks here
from __future__ import absolute_import, unicode_literals
from celery import shared_task
 
 
@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)

在你的django views里調(diào)用celery task

from django.shortcuts import render,HttpResponse
 
# Create your views here.
 
from bernard import tasks
 
def task_test(request):
 
 res = tasks.add.delay(228,24)
 print("start running task")
 print("async task res",res.get() )
 
 return HttpResponse('res %s'%res.get())

五、在django中使用計劃任務(wù)功能　　

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

To install and use this extension:

1.Use pip to install the package:

$ pip install django-celery-beat               

2.Add the django_celery_beat module to INSTALLED_APPS in your Django project' settings.py:

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:

$ python manage.py migrate             


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

$ celery -A proj beat -l info -S django             

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

在admin頁面里，有3張表

配置完長這樣

此時啟動你的celery beat 和worker，會發(fā)現(xiàn)每隔2分鐘，beat會發(fā)起一個任務(wù)消息讓worker執(zhí)行scp_task任務(wù)

注意，經(jīng)測試，每添加或修改一個任務(wù)，celery beat都需要重啟一次，要不然新的配置不會被celery beat進程讀到

以上就是本文的全部內(nèi)容，希望對大家的學習有所幫助，也希望大家多多支持腳本之家。

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