Python 第三方库之 Celery 分布式任务队列
一、Celery介紹和使用：
Celery 是一個 基于python開發的分布式異步消息任務隊列，通過它可以輕松的實現任務的異步處理， 如果你的業務場景中需要用到異步任務，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果返回，而是給你返回 一個任務ID,你過一段時間只需要拿著這個任務id就可以拿到任務執行結果， 在任務執行ing進行時，你可以繼續做其它的事情
- 你想做一個定時任務，比如每天檢測一下你們所有客戶的資料，如果發現今天是客戶的生日，就給他發個短信祝福
Celery 在執行任務時需要通過一個消息中間件來接收和發送任務消息，以及存儲任務結果， 一般使用rabbitMQ or Redis
1.1Celery有以下優點：
- 簡單：一旦熟悉了celery的工作流程后，配置和使用還是比較簡單的
- 高可用：當任務執行失敗或執行過程中發生連接中斷，celery 會自動嘗試重新執行任務
- 快速：一個單進程的celery每分鐘可處理上百萬個任務
- 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:
- Producer：任務委托方
- Broker：任務中心（中介），如RabbitMQ、Redis等1
- Beat：任務調度器
- Worker：任務執行者，可以有多個（分布式）
- Result：任務中心的數據庫，儲存任務執行結果2
- Backend：因為任務經由中介，而非直接委派到Worker手上，所以Producer并不知道任務被委派給了誰，以及任務的完成結果，所以這時候需要一個Backend（理解成手機，通過手機查看任務完成情況）
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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，安裝看這里
http://docs.celeryproject.org/en/latest/getting-started/brokers/rabbitmq.html#id3
使用Redis做broker也可以，安裝redis組件
$ pip install?-U?"celery[redis]"配置redis
# 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的執行結果，還需要配置一下把任務結果存在哪
# 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 使用Celery
安裝celery模塊
$ pip install celery創建一個celery application 用來定義你的任務列表
創建一個任務文件tasks.py
from?celery?import?Celeryapp?=?Celery('tasks', # 隨便broker='redis://localhost', # 中間件backend='redis://localhost') # 存儲# 弱如果redis 有密碼，改成下面的方式，password前面有冒號 # redis://:password@127.0.0.1:6379/2@app.task def?add(x,y):print("running...",x,y)return?x+y啟動Celery Worker來開始監聽并執行任務
$ celery -A tasks worker --loglevel=info調用任務，再打開一個終端， 進行命令行模式，調用任務
[root@localhost celerys]# python3 Python 3.5.2 (default, Jul 7 2017, 23:36:01) [GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux Type "help", "copyright", "credits" or "license" for more information. >>> from tasks import add # import add >>> add.delay(4,6) # 執行函數 <AsyncResult: 4b5a8ab6-693c-4ce5-b779-305cfcdf70cd> # 返回taskid>>> result.ready() # 是否運行完成 False>>> result = add.delay(4,6) # 執行函數 >>> result.get() # 同步獲取結果,一直等待 10>>> result.get(timeout=1) # 設置超時時間，過期錯誤異常 Traceback (most recent call last):--strip-- celery.exceptions.TimeoutError: The operation timed out.>>> result = add.delay(4,'a') # 執行錯誤命令 >>> result.get() # get后獲取到錯誤信息，觸發異常 Traceback (most recent call last):--strip-- celery.backends.base.TypeError: unsupported operand type(s) for +: 'int' and 'str'>>> result = add.delay(4,'a') >>> result.get(propagate=False) # propagate=False 不觸發異常，獲取錯誤信息 TypeError("unsupported operand type(s) for +: 'int' and 'str'",) >>> result.traceback # 獲取具體錯誤信息 log打印用 'Traceback (most recent call last):\n File "/usr/local/python3.5/lib/python3.5/site-packages/celery/app/trace.py", line 367, in trace_task\n R = retval = fun(*args, **kwargs)\n File "/usr/local/python3.5/lib/python3.5/site-packages/celery/app/trace.py", line 622, in __protected_call__\n return self.run(*args, **kwargs)\n File "/data/celerys/tasks.py", line 12, in add\n return x+y\nTypeError: unsupported operand type(s) for +: \'int\' and \'str\'\n'二、在項目中如何使用celery
可以把celery配置成一個應用，目錄格式如下
proj/__init__.py/celery.py/tasks.pyproj/celery.py內容
from?__future__?import?absolute_import, unicode_literals from?celery?import?Celeryapp?=?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，像不像一個c
-------------- 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 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: OKYou 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 -> 64052or stop it:
$ celery multi stop w1 -A proj -l infoThe?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
celery支持定時任務，設定好任務的執行時間，celery就會定時自動幫你執行， 這個定時任務模塊叫celery beat
寫一個腳本periodic_task.py
from?celery?import?Celery from?celery.schedules?import?crontabapp?=?Celery()@app.on_after_configure.connect def?setup_periodic_tasks(sender,?**kwargs):# Calls test('hello') every 10 seconds.# add_periodic_task 會添加一條定時任務sender.add_periodic_task(10.0, test.s('hello'), name='add every 10')# Calls test('world') every 30 secondssender.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)上面是通過調用函數添加定時任務，也可以像寫配置文件 一樣的形式添加， 下面是每30s執行的任務
app.conf.beat_schedule?=?{'add-every-30-seconds': {'task':?'tasks.add','schedule':?30.0,'args': (16,?16)}, } app.conf.timezone?=?'UTC'任務添加好了，需要讓celery單獨啟動一個進程來定時發起這些任務， 注意， 這里是發起任務，不是執行，這個進程只會不斷的去檢查你的任務計劃， 每發現有任務需要執行了，就發起一個任務調用消息，交給celery worker去執行
啟動任務調度器 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,負責執行celery beat發起的任務
啟動celery worker來執行任務
$ 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此時觀察worker的輸出，是不是每隔一小會，就會執行一次定時任務呢！
# 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: # beat需要將任務的最后運行時間存儲在本地數據庫文件中（默認情況下名為celerybeat schedule），自定義? $ celery -A periodic_task beat -s?/home/celery/var/run/celerybeat-schedule更復雜的定時配置
上面的定時任務比較簡單，只是每多少s執行一個任務，但如果你想要每周一三五的早上8點給你發郵件怎么辦呢？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執行時間
linux crontab?http://www.cnblogs.com/peida/archive/2013/01/08/2850483.html?
from?celery.schedules?import?crontabapp.conf.beat_schedule?=?{# Executes every Monday morning at 7:30 a.m.'add-every-monday-morning': { # 給任務起個名字'task':?'tasks.add', # 任務調用的函數'schedule': crontab(hour=7, minute=30, day_of_week=1), # 定時任務'args': (16,?16), # 任務調用的參數}, }上面的這條意思是每周1的早上7.30執行tasks.add任務。還有更多定時配置方式如下：
| 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. |
上面能滿足你絕大多數定時任務需求了，甚至還能根據潮起潮落來配置定時任務， 具體看 http://docs.celeryproject.org/en/latest/userguide/periodic-tasks.html#solar-schedules
四、最佳實踐之與django結合
django 可以輕松跟celery結合實現異步任務，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.pythen 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 # 絕對導入# 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 # 絕對導入Then we set the default?DJANGO_SETTINGS_MODULE?environment variable for the?celery?command-line program:
os.environ.setdefault('DJANGO_SETTINGS_MODULE',?'proj.settings') # 設置環境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:
celery 會自動發現目錄下的所有task
-?app1/-?tasks.py-?models.py -?app2/-?tasks.py-?models.pyFinally, 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
# 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里調用celery task
from?django.shortcuts?import?render,HttpResponse# Create your views here.from??bernard?import?tasksdef?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:
Use?pip?to install the package:
$ pip install django-celery-beatAdd 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.Apply Django database migrations so that the necessary tables are created:
$ python manage.py migrateStart the?celery beat?service using the?django?scheduler:
$ celery -A proj beat -l info -S djangoVisit 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
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此時啟動你的celery beat 和worker，會發現每隔2分鐘，beat會發起一個任務消息讓worker執行scp_task任務
注意，經測試，每添加或修改一個任務，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
文章鏈接https://www.cnblogs.com/alex3714/p/6351797.html
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