CMDB02/ 单例模式、资产采集参考命令、日志处理

CMDB02/单例模式、资产采集参考命令、日志处理

CMDB02/单例模式、资产采集参考命令、日志处理

1. 单例模式

1.1 多例模式

代码示例

class Foo(object):
	def __init__(self,name,age):
		self.name = name
		self.age = age
	
	def func(self):
		msg = "%s-%s" %(self.name,self.age)
		
		
obj1 = Foo("张三",18)   # Foo的一个对象/Foo类的一个实例
obj1.func()

obj2 = Foo("李四",19)
obj2.func()

1.2 单例模式

代码示例/以前：

class Foo(object):
	instance = None
	def __init__(self,name,age):
		self.name = name
		self.age = age
	
	def __new__(cls,*arg,**kawrgs):
		if not cls.instance:
			cls.instance = object.__new__(cls)
		return cls.instance

class Singleton(object):
    instance = None

    def __init__(self):
        self.name = None

    def __new__(cls, *arg, **kawrgs):
        if not cls.instance:
            cls.instance = object.__new__(cls)
        return cls.instance

应用场景：

django配置文件，只要加载一次，以后使用都用同一份值。

class Singleton(object):
    instance = None

    def __init__(self):
        self.k0 = 0
        self.k1 = 1
        self.k2 = 2
        ...

    def __new__(cls, *arg, **kawrgs):
        if not cls.instance:
            cls.instance = object.__new__(cls)
        return cls.instance
    
obj1 = Singleton()
obj2 = Singleton()
obj3 = Singleton()

django的admin，在注册models中用，希望所有的model类注册到同一个列表中。

1.2.1 单例模式/错误

代码示例：

class Singleton(object):
    instance = None

    def __init__(self):
        self.name = None

    def __new__(cls, *arg, **kawrgs):
        if not cls.instance:
            cls.instance = object.__new__(cls)
        return cls.instance

1.2.2 单例模式 new/正确

代码示例：

import time
import threading

class Singleton(object):
    instance = None
    lock = threading.RLock()
    
    def __new__(cls, *arg, **kwargs):
        if cls.instance:
            return cls.instance
        with cls.lock:
            if not cls.instance:
                cls.instance = object.__new__(cls)
            return cls.instance
        
obj1 = Singleton()
obj2 = Singleton()

1.2.3 单例模式之文件导入/正确，在源码中的应用

代码示例1：

# xx.py

class Site(object):
    def __init__(self):
        self.names = []

    def xx(self):
        pass
site = Site()

import xx

print(xx.site)

代码示例2：

# xx.py 

class Singleton(object):

    def __init__(self):
        self._registry = []

    def register(self,model_class):
        self._registry.append(model_class)

site = Singleton()

import xx
xx.site

1.3 单例模式补充

基于__new__实现单例模式，在init中不设置值。

是单例，但数据会被覆盖

class Singleton(object):
    instance = None

    def __init__(self):
        self.registry = []

    def __new__(cls, *arg, **kawrgs):
        if not cls.instance:
            cls.instance = object.__new__(cls)
        return cls.instance

    def register(self, val):
        self.registry.append(val)

# {registry：[]}
obj1 = Singleton()
# {registry：[x1]}
obj1.register('x1')

# instance = {registry：[x1]}
# instance = {registry：[]}
obj2 = Singleton()
# instance = {registry：[x2]}
obj2.register('x2')

print(obj2.registry)
print(obj1.registry)

单例模式/数据不会覆盖

class Singleton(object):
    instance = None
    registry = []

    def __new__(cls, *arg, **kawrgs):
        if not cls.instance:
            cls.instance = object.__new__(cls)
        return cls.instance

    def register(self, val):
        self.registry.append(val)


obj1 = Singleton()
obj1.register('x1')

obj2 = Singleton()
obj2.register('x2')

print(obj2.registry)
print(obj1.registry)

2. 日志

代码示例：

import logging
import settings

class AutoLogger(object):
    def __init__(self,log_path,log_name):
        file_handler = logging.FileHandler(log_path, 'a', encoding='utf-8')
        fmt = logging.Formatter(fmt="%(asctime)s - %(name)s - %(levelname)s -%(module)s:  %(message)s")
        file_handler.setFormatter(fmt)

        self.logger = logging.Logger(log_name, level=logging.DEBUG)
        self.logger.addHandler(file_handler)

    def log(self,msg):
        self.logger.error(msg)


logger = AutoLogger(settings.LOG_FILE_PATH,'cmdb')

获取日志堆栈信息

import traceback

def run():
    try:
        int('lbzhk')
    except Exception as e:
        print(traceback.format_exc())
        
if __name__ == '__main__':
    run()

3. 获取资产信息的命令

内存信息

sudo dmidecode  -q -t 17 2>/dev/null

# 注意：linux上要提前安装 yum install dmidecode

硬盘（安装MegaCli）
```
sudo MegaCli  -PDList -aALL
```
网卡
```
sudo ip link show
sudo ip addr show
```
主板
```
sudo dmidecode -t1
```
CPU
```
cat /proc/cpuinfo
```

4. 数据封装

代码示例：

class BaseResponse(object):
    def __init__(self):
        self.status = True
        self.data = None
        self.error = None
    @property
    def dict(self):
        return self.__dict__


def process():
    info = BaseResponse()
    try:
        info.status = True
        info.data = "lbzhk"
    except Exception:
        pass
    return info.dict

result = process()
print(result)

5.表关系

总结：

cmdb资产采集后，为什么不直接放到数据库？
- 单独编写api，为了给其他系统提供数据支持（接口）
- 维护的数据库连接比较多，修改不方便。
手写单例模式
- new+锁

其他单例模式

使用模块

class Singleton(object):
    def foo(self):
        pass
singleton = Singleton()

from a import singleton

使用装饰器

def Singleton(cls):
    _instance = {}

    def _singleton(*args, **kargs):
        if cls not in _instance:
            _instance[cls] = cls(*args, **kargs)
        return _instance[cls]

    return _singleton


@Singleton
class A(object):
    a = 1
    def __init__(self, m=0):
        self.m = m

a1 = A(1)
a2 = A(2)

使用类 -- 可以防止多线程的时候出问题

import time
import threading
class Singleton(object):
    _instance_lock = threading.Lock()

    def __init__(self):
        time.sleep(1)

    @classmethod
    def instance(cls, *args, **kwargs):
        with Singleton._instance_lock:
            if not hasattr(Singleton, "_instance"):
                Singleton._instance = Singleton(*args, **kwargs)
        return Singleton._instance


def task(arg):
    obj = Singleton.instance()
    print(obj)
for i in range(10):
    t = threading.Thread(target=task,args=[i,])
    t.start()
time.sleep(20)
obj = Singleton.instance()
print(obj)

基于__new__实现，代码如上

__new__方法返回的是什么
- 新创建的对象，内部没有数据，需要经过init来进行初始化。
单利模式应用场景：
- django的配置文件
- django的admin
- 数据库链接池（单例模式）
- 写日志