Celery是一个基于Python编写的分布式任务队列(Distributed Task Queue), 通过对Celery进行简单操作就可以实现任务(耗时任务, 定时任务)的异步处理
一. Celery的安装
Celery4.0版本开始,不支持windows平台
1.1 通过pip方式安装celery
pip install -U "Celery[redis]"
注意事项:
在windows上安装后,可能会出现如下报错:
ValueError: '__name__' in __slots__ conflicts with class variable
此时先卸载celery, 然后尝试通过如下命令重新进行安装
pip install -U https://github.com/celery/py-amqp/zipball/master pip install -U https://github.com/celery/billiard/zipball/master pip install -U https://github.com/celery/kombu/zipball/master pip install -U https://github.com/celery/celery/zipball/master pip install -U "Celery[redis]"
1.2 给celery创建一个软连接
ln -s ~/.venv/project_dj/bin/celery /usr/bin/celery
1.3 执行celery命令
[root@localhost ~]$ celery --help Options: -A, --app APPLICATION -b, --broker TEXT --result-backend TEXT --loader TEXT --config TEXT --workdir PATH -C, --no-color -q, --quiet --version --help Show this message and exit. Commands: amqp AMQP Administration Shell. beat Start the beat periodic task scheduler. call Call a task by name. control Workers remote control. events Event-stream utilities. graph The ``celery graph`` command. inspect Inspect the worker at runtime. list Get info from broker. logtool The ``celery logtool`` command. migrate Migrate tasks from one broker to another. multi Start multiple worker instances. purge Erase all messages from all known task queues. report Shows information useful to include in bug-reports. result Print the return value for a given task id. shell Start shell session with convenient access to celery symbols. status Show list of workers that are online. upgrade Perform upgrade between versions. worker Start worker instance.
二. Celery的基本使用
2.1 创建celery应用, 并定义任务
# -*- coding: utf-8 -*- # @Time : 2021/5/24 11:20 # @Author : chinablue # @File : task.py from celery import Celery # 创建一个app(Celery实例),作为所有celery操作的切入点 broker_url = f"redis://:123456@127.0.0.1:6379/5" backend_url = f"redis://:123456@127.0.0.1:6379/6" app = Celery("tasks", broker=broker_url, backend=backend_url) # 定义一个任务 @app.task def add(x, y): return x + y
事项说明：
1) 创建Celery实例时，需要指定一个消息代理(broker)来接收和发送任务消息. 本文使用的是Redis(docker redis搭建)
2) broker和backend参数的格式: redis://:password@hostname:port/db_number
2.2 启动celery worker服务端
celery -A tasks worker --loglevel=INFO
事项说明：
1) 在生产环境中, 会使用supervisor工具将celery服务作为守护进程在后台运行
2.3 调用任务
打开终端, 进入python命令行模式:
>>> result = add.delay(4, 4)
>>> result = add.apply_async((4, 4), countdown=5)
事项说明：
1) add.apply_async((4, 4)) 可以简写为 add.delay(4, 4)
2) add.apply_async((4, 4), countdown=5) 表示任务发出5秒后再执行
2.4 追踪任务信息
若想获取每个任务的执行信息,在创建Celery实例时, 需要指定一个后端(backend). 本文使用的是Redis(docker redis搭建)
result = add.delay(4, 4) result.ready() # 任务状态: 进行中, 已完成 result.failed() # 任务完成, 任务失败 result.successful() # 任务完成, 任务成功 result.state # 任务状态: PENDING, STARTED, SUCCESS result.get() # 获取任务的返回值 result.get(timeout=10) result.get(propagate=False) # 如果任务引发了异常, propagate=False表示异常不会被抛出来(默认情况会抛出来) result.id # 任务id
注意事项：
1) 在celery中，如果想配置backend参数，有如下三种方式
# -*- coding: utf-8 -*- # @Time : 2021/5/24 11:20 # @Author : chinablue # @File : task.py from celery import Celery # 创建一个app(Celery实例),作为所有celery操作的切入点 broker_url = f"redis://:123456@127.0.0.1:6379/5" backend_url = f"redis://:123456@127.0.0.1:6379/6" app = Celery("tasks", broker=broker_url, backend=backend_url) # 定义一个任务 @app.task def add(x, y): return x + y
# -*- coding: utf-8 -*- # @Time : 2021/5/24 11:20 # @Author : chinablue # @File : task.py from celery import Celery broker_url = f"redis://:123456@127.0.0.1:6379/5" backend_url = f"redis://:123456@127.0.0.1:6379/6" app = Celery("tasks") app.conf.update({ "broker_url": broker_url, "result_backend": backend_url, }) # 定义一个任务 @app.task def add(x, y): return x + y
# -*- coding: utf-8 -*- # @Time : 2021/5/24 11:20 # @Author : chinablue # @File : task.py from celery import Celery broker_url = f"redis://:123456@127.0.0.1:6379/5" backend_url = f"redis://:123456@127.0.0.1:6379/6" app = Celery("tasks") app.conf.broker_url = broker_url app.conf.result_backend = backend_url # 定义一个任务 @app.task def add(x, y): return x + y