Django如何自定义manage.py命令？达到启动后台进程的目的？

Posted 2020-08-14

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代码：

#-*- coding:utf-8 -*-
"""
The handle active user mail send
"""


from django.core.management.base import BaseCommand, CommandError
from django.db import models
#from placeholders import *
import os
import time
import logging

logger = logging.getLogger("file_protect.alarm_handler")
logger = logging.getLogger("file_protect.views")

class Command(BaseCommand):
    def handle(self, *args, **options):
        print ‘hello, django!‘
        while(True):
            logger.debug("hello, django")
            time.sleep(5)

启动

####################系统软件安装-使用apt-get安装####################
apt-get update -qq -y
apt-get install libmysqlclient-dev python-dev -qq -y
apt-get install libmysqlclient-dev python-dev daemon -qq -y


#################启动日志处理Daemon#############################
if daemon -n alarm_handler_daemon --running; then
    daemon -n alarm_handler_daemon --stop
fi

while daemon -n alarm_handler_daemon --running; do
    sleep 1
done

daemon -n alarm_handler_daemon -r /opt/ENV/ubuntu1227/bin/python $API_PROJECT_DIR/manage.py alarm_handler
echo "alarm_handler_daemon is running"

我们都用过Django的django-admin.py和manage.py。django-admin.py是一个命令行工具，可以执行一些管理任务，比如创建Django项目。而manage.py是在创建每个Django project时自动添加在项目目录下的，只是对manage.py的一个简单包装，其功能是将Django project放到sys.path目录中，同时设置DJANGO_SETTINGS_MODULE环境变量为当前project的setting.py文件。

django-admin.py调用django.core.management来执行命令:

#!/usr/bin/env python
from django.core import management
    
if __name__ == "__main__":
   management.execute_from_command_line()

excute_from_command_line()函数会根据命令行参数解析出命令的名称，根据命令名称调用相应的Command执行命令。Command位于各个管理模块的commands模块下面。

所谓管理模块，是指在app模块下的名字为management的模块。Django通过django.core.management.find_management_module函数发现"管理模块":

django.core.management.find_management_module()
def find_management_module(app_name):
    """
    Determines the path to the management module for the given app_name,
    without actually importing the application or the management module.

    Raises ImportError if the management module cannot be found for any reason.
    """
    parts = app_name.split(‘.‘)
    parts.append(‘management‘)
    parts.reverse()
    part = parts.pop()
    path = None

然后通过django.core.management.find_commands函数找到命令类。find_commands函数会在管理模块下查找.py文件，并将.py文件的名称匹配到命令名称:

def find_commands(management_dir):
    """
    Given a path to a management directory, returns a list of all the command
    names that are available.

    Returns an empty list if no commands are defined.
    """
    command_dir = os.path.join(management_dir, ‘commands‘)
    try:
        return [f[:-3] for f in os.listdir(command_dir)
           if not f.startswith(‘_‘) and f.endswith(‘.py‘)]
    except OSError:
    return []

最后，通过django.core.management.load_command_class函数加载该.py文件中的Command类:

def load_command_class(app_name, name):
    """
    Given a command name and an application name, returns the Command
    class instance. All errors raised by the import process
    (ImportError, AttributeError) are allowed to propagate.
    """
    module = import_module(‘%s.management.commands.%s‘ % (app_name, name))
    return module.Command()

在执行命令的时候，会执行相应Command类的handle方法。所有的Command类都应该是django.core.management.base.BaseCommand的直接或间接子类。

原理搞清楚了，扩展manage命令就很容易了。创建一个app并加入到settings的INSTALLED_APPS中，在该app下面创建management.commands模块，并创建hello.py文件:

from django.core.management.base import BaseCommand, CommandError
from django.db import models
#from placeholders import *
import os
    
class Command(BaseCommand):
     def handle(self, *args, **options):
         print ‘hello, django!‘

就可以使用hello命令了: