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Django Celery

一、知识要点概览表

模块	知识点	掌握程度要求
Celery基础	配置、任务定义、任务执行	深入理解
异步任务	任务状态、结果存储、错误处理	熟练应用
周期任务	定时任务、Crontab、任务调度	熟练应用
监控管理	Flower、任务监控、性能优化	理解应用

二、基础配置实现

1. 安装和配置

# requirements.txt
celery==5.3.1
django-celery-results==2.5.1
django-celery-beat==2.5.0
redis==4.6.0# settings.py
INSTALLED_APPS = [...'django_celery_results','django_celery_beat',
]# Celery配置
CELERY_BROKER_URL = 'redis://localhost:6379/0'
CELERY_RESULT_BACKEND = 'django-db'
CELERY_ACCEPT_CONTENT = ['json']
CELERY_TASK_SERIALIZER = 'json'
CELERY_RESULT_SERIALIZER = 'json'
CELERY_TIMEZONE = 'Asia/Shanghai'# celery.py
import os
from celery import Celeryos.environ.setdefault('DJANGO_SETTINGS_MODULE', 'myproject.settings')app = Celery('myproject')
app.config_from_object('django.conf:settings', namespace='CELERY')
app.autodiscover_tasks()@app.task(bind=True)
def debug_task(self):print(f'Request: {self.request!r}')

三、异步任务实现

1. 基本任务定义

# tasks.py
from celery import shared_task
from django.core.mail import send_mail
from .models import User@shared_task
def send_welcome_email(user_id):"""发送欢迎邮件"""try:user = User.objects.get(id=user_id)send_mail('欢迎加入我们的平台',f'你好 {user.username}，欢迎使用我们的服务！','noreply@example.com',[user.email],fail_silently=False,)return Trueexcept Exception as e:return str(e)@shared_task(bind=True, max_retries=3)
def process_payment(self, order_id):"""处理支付任务"""from .models import Ordertry:order = Order.objects.get(id=order_id)result = process_payment_gateway(order)if result.success:order.status = 'paid'order.save()return 'Payment processed successfully'else:raise ValueError('Payment failed')except Exception as exc:self.retry(exc=exc, countdown=60*5)  # 5分钟后重试

2. 任务链和组

from celery import chain, group, chord
from .tasks import process_payment, send_notification, update_inventorydef process_order(order):# 任务链：按顺序执行任务task_chain = chain(process_payment.s(order.id),update_inventory.s(order.id),send_notification.s(order.user.id))return task_chain()def process_bulk_orders(orders):# 任务组：并行执行多个任务task_group = group(process_payment.s(order.id)for order in orders)return task_group()def process_orders_with_summary(orders):# 和弦：并行执行任务后执行回调def on_complete(results):successful = sum(1 for r in results if r == 'success')failed = len(results) - successfulreturn f"处理完成：{successful}成功，{failed}失败"task_chord = chord((process_payment.s(order.id) for order in orders),on_complete.s())return task_chord()

3. 自定义任务类

from celery import Task
from django.core.cache import cacheclass BaseTaskWithRetry(Task):abstract = Truemax_retries = 3default_retry_delay = 60  # 60秒后重试def on_failure(self, exc, task_id, args, kwargs, einfo):"""任务失败时的处理"""print(f'Task {task_id} failed: {str(exc)}')super().on_failure(exc, task_id, args, kwargs, einfo)def on_retry(self, exc, task_id, args, kwargs, einfo):"""任务重试时的处理"""print(f'Task {task_id} retrying: {str(exc)}')super().on_retry(exc, task_id, args, kwargs, einfo)@shared_task(base=BaseTaskWithRetry)
def process_data(data_id):try:# 处理数据的逻辑result = process_complex_data(data_id)return resultexcept Exception as exc:raise self.retry(exc=exc)

四、周期任务实现

1. 基本周期任务

# tasks.py
from celery.schedules import crontab
from celery.task import periodic_task@periodic_task(run_every=timedelta(hours=24))
def daily_cleanup():"""每日清理任务"""cleanup_expired_tokens()cleanup_old_logs()return "Daily cleanup completed"@periodic_task(run_every=crontab(hour=0, minute=0),name="generate_daily_report"
)
def generate_daily_report():"""生成每日报告"""report = Report.objects.create(date=timezone.now(),type='daily')report.generate()return f"Report generated: {report.id}"

2. 动态周期任务

# models.py
from django_celery_beat.models import PeriodicTask, IntervalSchedule
from django.db import modelsclass ScheduledReport(models.Model):name = models.CharField(max_length=100)interval = models.IntegerField(help_text='间隔（分钟）')enabled = models.BooleanField(default=True)def save(self, *args, **kwargs):super().save(*args, **kwargs)self.update_periodic_task()def update_periodic_task(self):schedule, _ = IntervalSchedule.objects.get_or_create(every=self.interval,period=IntervalSchedule.MINUTES,)PeriodicTask.objects.update_or_create(name=f'generate_report_{self.id}',defaults={'task': 'myapp.tasks.generate_report','interval': schedule,'args': [self.id],'enabled': self.enabled})

3. 任务调度器

from django_celery_beat.models import CrontabSchedule, PeriodicTask
import jsondef schedule_report_task(name, hour, minute, day_of_week):"""创建定时报告任务"""schedule, _ = CrontabSchedule.objects.get_or_create(hour=hour,minute=minute,day_of_week=day_of_week,)task = PeriodicTask.objects.create(crontab=schedule,name=f'generate_report_{name}',task='myapp.tasks.generate_report',args=json.dumps([name]),)return task# 使用示例
schedule_report_task('weekly_summary', hour=0, minute=0, day_of_week='1')  # 每周一

五、监控和管理

1. Flower配置

# requirements.txt
flower==2.0.1# settings.py
CELERY_FLOWER_USER = 'admin'
CELERY_FLOWER_PASSWORD = 'password'# 启动Flower
# celery -A myproject flower --port=5555

2. 任务监控中间件

# middleware.py
from celery.signals import task_prerun, task_postrun
import time
import logginglogger = logging.getLogger('celery.tasks')@task_prerun.connect
def task_prerun_handler(task_id, task, args, kwargs, **kw):"""任务执行前的处理"""task.start_time = time.time()@task_postrun.connect
def task_postrun_handler(task_id, task, args, kwargs, retval, state, **kw):"""任务执行后的处理"""if hasattr(task, 'start_time'):duration = time.time() - task.start_timelogger.info(f'Task {task.name}[{task_id}] 'f'completed in {duration:.2f}s with state {state}')

六、Celery工作流程图

七、实际应用示例

1. 图片处理任务

# tasks.py
from PIL import Image
import os
from celery import shared_task@shared_task
def process_uploaded_image(image_path, sizes=[(800, 600), (400, 300)]):"""处理上传的图片"""try:img = Image.open(image_path)filename = os.path.basename(image_path)name, ext = os.path.splitext(filename)results = []for size in sizes:resized = img.copy()resized.thumbnail(size)new_filename = f"{name}_{size[0]}x{size[1]}{ext}"new_path = os.path.join(os.path.dirname(image_path), new_filename)resized.save(new_path)results.append(new_path)return resultsexcept Exception as e:return str(e)

2. 站点监控任务

# tasks.py
import requests
from celery import shared_task
from django.core.mail import mail_admins
from .models import SiteMonitor@shared_task(bind=True, max_retries=3)
def monitor_website(self, url):"""监控网站可用性"""try:response = requests.get(url, timeout=10)status = response.status_code == 200response_time = response.elapsed.total_seconds()SiteMonitor.objects.create(url=url,status=status,response_time=response_time)if not status:mail_admins(f'网站{url}不可用',f'状态码：{response.status_code}')return {'url': url,'status': status,'response_time': response_time}except Exception as exc:self.retry(exc=exc, countdown=60)

八、最佳实践建议

1. 任务设计原则：

   • 保持任务原子性
   • 实现幂等性
   • 合理设置超时时间
   • 添加适当的重试机制

2. 性能优化：

   • 使用合适的序列化方式
   • 控制任务粒度
   • 合理设置并发数
   • 监控任务执行情况

3. 错误处理：

   • 完善的异常捕获
   • 详细的日志记录
   • 合适的重试策略
   • 失败通知机制

这就是关于Django Celery的详细内容，包括异步任务队列和周期任务的实现。通过实践这些内容，你将能够在Django项目中熟练使用Celery处理异步任务。如果有任何问题，欢迎随时提出！

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