tornado--SESSION框架，一致性hash，分布式存储

预备知识

1. tornado框架session要自己写

2. cookie存储在客户端浏览器上，session数据放在服务器上

3. session依赖cookie

4. 扩展tornado，返回请求前自定义session

5. 面向对象的知识，obj['xxx']==>_getitems__,obj['xxx']=xxx ==> __setitems__, del obj['xxx'] ==> __delitems__

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class Foo( object ):          def __getitem__( self , key):          print  '__getitem__' ,key          def __setitem__( self , key, value):          print '__setitem__' ,key,value          def __delitem__( self , key):          print '__delitem__' ,key             obj = Foo() result = obj[ 'k1' ] #obj['k2'] = 'wupeiqi' #del obj['k1']

session实现机制

1. tornado框架中，通过application的url映射到MainHandler类处理请求，根据请求的方式，通过反射执行对应的get或post等方法

2. tornado源码中有很多扩展点（钩子）供开发者使用，如在执行get或post方法之前先执行initialiaze方法，即使没有调用也执行

3. 扩展initialiaze，用户请求进来，读一下用户的cookie，如果有的话，能够拿到，没有可以创建一个

4. 为避免重复在每个映射的类里都写一遍initialiaze，可以在他们的共同的基类BaseHandler（自定义的类）里写initialiaze方法

5. 其实这些类应该继承tornado.web.RequestHandler类，让BaseHandler继承这个类，其他类也就继承了

6. initialiaze中定义了self.my_session字段，它是一个session类的对象，init中获取或创建session
   

7. 用户登录，通过__setitem__设置session中的内容，session保存在服务器中

8. session_container是用来保存session的字典

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import tornado.ioloop import tornado.web from hashlib import sha1 import os, time     session_container = {}     create_session_id = lambda : sha1( '%s%s' % (os.urandom( 16 ), time.time())).hexdigest()         class Session( object ):          session_id = "__sessionId__"          def __init__( self , request):          session_value = request.get_cookie(Session.session_id)          if not session_value:              self ._id = create_session_id()          else :              self ._id = session_value          request.set_cookie(Session.session_id, self ._id)          def __getitem__( self , key):          return session_container[ self ._id][key]          def __setitem__( self , key, value):          if session_container.has_key( self ._id):              session_container[ self ._id][key] = value          else :              session_container[ self ._id] = {key: value}          def __delitem__( self , key):          del session_container[ self ._id][key]         class BaseHandler(tornado.web.RequestHandler):          def initialize( self ):          # my_session['k1']访问 __getitem__ 方法          self .my_session = Session( self )         class MainHandler(BaseHandler):          def get( self ):          print self .my_session[ 'c_user' ]          print self .my_session[ 'c_card' ]          self .write( 'index' )     class LoginHandler(BaseHandler):          def get( self ):          self .render( 'login.html' , * * { 'status' : ''})          def post( self , * args, * * kwargs):              username = self .get_argument( 'name' )          password = self .get_argument( 'pwd' )          if username = = 'wupeiqi' and password = = '123' :                  self .my_session[ 'c_user' ] = 'wupeiqi'              self .my_session[ 'c_card' ] = '12312312309823012'                  self .redirect( '/index' )          else :              self .render( 'login.html' , * * { 'status' : '用户名或密码错误' })     settings = {      'template_path' : 'template' ,      'static_path' : 'static' ,      'static_url_prefix' : '/static/' ,      'cookie_secret' : 'aiuasdhflashjdfoiuashdfiuh' ,      'login_url' : '/login' }     application = tornado.web.Application([      (r "/index" , MainHandler),      (r "/login" , LoginHandler), ], * * settings)         if __name__ = = "__main__" :      application.listen( 8888 )      tornado.ioloop.IOLoop.instance().start()

session分布式

1. session可以存在其它地方，如redis，数据库，mongo等等

2. 当session规模达到很大数量级，就采用多台分布式存储，经过一致性hash算法，分配到对应的机器上
   

3. 根据cookie字符串转换成一串数字，每台机器分管的数字段区域不同，权重大的管的大

一致性哈希​

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#!/usr/bin/env python #coding:utf-8   import sys import math from bisect import bisect     if sys.version_info > = ( 2 , 5 ):      import hashlib      md5_constructor = hashlib.md5 else :      import md5      md5_constructor = md5.new     class HashRing( object ):      """一致性哈希"""            def __init__( self ,nodes):          '''初始化          nodes : 初始化的节点，其中包含节点已经节点对应的权重                  默认每一个节点有32个虚拟节点                  对于权重，通过多创建虚拟节点来实现                  如：nodes = [                          {'host':'127.0.0.1:8000','weight':1},                          {'host':'127.0.0.1:8001','weight':2},                          {'host':'127.0.0.1:8002','weight':1},                      ]          '''                    self .ring = dict ()          self ._sorted_keys = []            self .total_weight = 0                    self .__generate_circle(nodes)                                            def __generate_circle( self ,nodes):          for node_info in nodes:              self .total_weight + = node_info.get( 'weight' , 1 )                        for node_info in nodes:              weight = node_info.get( 'weight' , 1 )              node = node_info.get( 'host' , None )                                virtual_node_count = math.floor(( 32 * len (nodes) * weight) / self .total_weight)              for i in xrange ( 0 , int (virtual_node_count)):                  key = self .gen_key_thirty_two( '%s-%s' % (node, i) )                  if self ._sorted_keys.__contains__(key):                      raise Exception( '该节点已经存在.' )                  self .ring[key] = node                  self ._sorted_keys.append(key)                    def add_node( self ,node):          ''' 新建节点          node : 要添加的节点，格式为：{'host':'127.0.0.1:8002','weight':1}，其中第一个元素表示节点，第二个元素表示该节点的权重。          '''          node = node.get( 'host' , None )          if not node:                  raise Exception( '节点的地址不能为空.' )                            weight = node.get( 'weight' , 1 )                    self .total_weight + = weight          nodes_count = len ( self ._sorted_keys) + 1                    virtual_node_count = math.floor(( 32 * nodes_count * weight) / self .total_weight)          for i in xrange ( 0 , int (virtual_node_count)):              key = self .gen_key_thirty_two( '%s-%s' % (node, i) )              if self ._sorted_keys.__contains__(key):                  raise Exception( '该节点已经存在.' )              self .ring[key] = node              self ._sorted_keys.append(key)                def remove_node( self ,node):          ''' 移除节点          node : 要移除的节点 '127.0.0.1:8000'          '''          for key,value in self .ring.items():              if value = = node:                  del self .ring[key]                  self ._sorted_keys.remove(key)            def get_node( self ,string_key):          '''获取 string_key 所在的节点'''          pos = self .get_node_pos(string_key)          if pos is None :              return None          return self .ring[ self ._sorted_keys[pos]].split( ':' )            def get_node_pos( self ,string_key):          '''获取 string_key 所在的节点的索引'''          if not self .ring:              return None                        key = self .gen_key_thirty_two(string_key)          nodes = self ._sorted_keys          pos = bisect(nodes, key)          return pos            def gen_key_thirty_two( self , key):                    m = md5_constructor()          m.update(key)          return long (m.hexdigest(), 16 )                def gen_key_sixteen( self ,key):                    b_key = self .__hash_digest(key)          return self .__hash_val(b_key, lambda x: x)        def __hash_val( self , b_key, entry_fn):          return (( b_key[entry_fn( 3 )] << 24 )|(b_key[entry_fn( 2 )] << 16 )|(b_key[entry_fn( 1 )] << 8 )| b_key[entry_fn( 0 )] )        def __hash_digest( self , key):          m = md5_constructor()          m.update(key)          return map ( ord , m.digest())     """ nodes = [      {'host':'127.0.0.1:8000','weight':1},      {'host':'127.0.0.1:8001','weight':2},      {'host':'127.0.0.1:8002','weight':1}, ]   ring = HashRing(nodes) result = ring.get_node('98708798709870987098709879087') print result   """   一致性哈希

session

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from hashlib import sha1 import os, time     create_session_id = lambda : sha1( '%s%s' % (os.urandom( 16 ), time.time())).hexdigest()     class Session( object ):        session_id = "__sessionId__"        def __init__( self , request):          session_value = request.get_cookie(Session.session_id)          if not session_value:              self ._id = create_session_id()          else :              self ._id = session_value          request.set_cookie(Session.session_id, self ._id)        def __getitem__( self , key):          # 根据 self._id ，在一致性哈西中找到其对应的服务器IP          # 找到相对应的redis服务器，如： r = redis.StrictRedis(host='localhost', port=6379, db=0)          # 使用python redis api 链接          # 获取数据，即：          # return self._redis.hget(self._id, name)        def __setitem__( self , key, value):          # 根据 self._id ，在一致性哈西中找到其对应的服务器IP          # 使用python redis api 链接          # 设置session          # self._redis.hset(self._id, name, value)          def __delitem__( self , key):          # 根据 self._id 找到相对应的redis服务器          # 使用python redis api 链接          # 删除，即：          return self ._redis.hdel( self ._id, name)

来自为知笔记(Wiz)

转载于:https://www.cnblogs.com/daliangtou/p/5481577.html