使用Pyro4部署客户端-服务器应用

在本节中，我们会用 Pyro4 学习如何写一个简单的客户端-服务器应用。这里提供的示例并不完整，但是可以成功运行。

一个客户端-服务器程序就是，在一个网络内，客户端连接上服务器来请求特定的服务，可以与其他的客户端共享软件/硬件资源，并使用相同的协议。在本节的系统中，server 管理一个在线购物网站，客户端负责已注册的用户连接到 server 来购物。

如何做

为了让例子尽量简单一些，本例只有三个脚本。第一个代表 client 对象，用来管理用户。第二个脚本是 shop 对象，第二个脚本是 server .

Server 端的代码如下（ server.py ): :

"""The Shops server"""

from __future__ import print_function
import Pyro4
import shop

ns = Pyro4.naming.locateNS()
daemon = Pyro4.core.Daemon()
uri = daemon.register(shop.Shop())
ns.register("example.shop.Shop", uri)
print(list(ns.list(prefix="example.shop.").keys()))
daemon.requestLoop()

Client 端的代码如下 ( client.py ): :

from __future__ import print_function
import sys
import Pyro4

# A Shop client.
class client(object):
    def __init__(self, name, cash):
        self.name = name
        self.cash = cash

    def doShopping_deposit_cash(self, Shop):
        print("\n*** %s is doing shopping with %s:" % (self.name, Shop.name()))
        print("Log on")
        Shop.logOn(self.name)
        print("Deposit money %s" % self.cash)
        Shop.deposit(self.name, self.cash)
        print("balance=%.2f" % Shop.balance(self.name))
        print("Deposit money %s" % self.cash)
        Shop.deposit(self.name, 50)
        print("balance=%.2f" % Shop.balance(self.name))
        print("Log out")
        Shop.logOut(self.name)

    def doShopping_buying_a_book(self, Shop):
        print("\n*** %s is doing shopping with %s:" % (self.name, Shop.name()))
        print("Log on")
        Shop.logOn(self.name)
        print("Deposit money %s" % self.cash)
        Shop.deposit(self.name, self.cash)
        print("balance=%.2f" % Shop.balance(self.name))
        print("%s is buying a book for %s$" % (self.name, 37))
        Shop.buy(self.name, 37)
        print("Log out")
        Shop.logOut(self.name)


if __name__ == "__main__":
    ns = Pyro4.naming.locateNS()
    uri = ns.lookup("example.shop.Shop")
    print(uri)
    Shop = Pyro4.core.Proxy(uri)
    meeta = client("Meeta", 50)
    rashmi = client("Rashmi", 100)
    rashmi.doShopping_buying_a_book(Shop)
    meeta.doShopping_deposit_cash(Shop)
    print("")
    print("")
    print("")
    print("")
    print("The accounts in the %s:" % Shop.name())
    accounts = Shop.allAccounts()
    for name in accounts.keys():
        print("  %s : %.2f" % (name, accounts[name]))

Shop 对象的代码如下 ( shop.py ): :

class Account(object):
    def __init__(self):
        self._balance = 0.0

    def pay(self, price):
        self._balance -= price

    def deposit(self, cash):
        self._balance += cash

    def balance(self):
        return self._balance


class Shop(object):
    def __init__(self):
        self.accounts = {}
        self.clients = ["Meeta", "Rashmi", "John", "Ken"]

    def name(self):
        return "BuyAnythingOnline"

    def logOn(self, name):
        if name in self.clients:
            self.accounts[name] = Account()
        else:
            self.clients.append(name)
            self.accounts[name] = Account()

    def logOut(self, name):
        print("logout %s" % name)

    def deposit(self, name, amount):
        try:
            return self.accounts[name].deposit(amount)
        except KeyError:
            raise KeyError("unknown account")

    def balance(self, name):
        try:
            return self.accounts[name].balance()
        except KeyError:
            raise KeyError("unknown account")

    def allAccounts(self):
        accs = {}
        for name in self.accounts.keys():
            accs[name] = self.accounts[name].balance()
        return accs

    def buy(self, name, price):
        balance = self.accounts[name].balance()
        self.accounts[name].pay(price)

下面开始执行这段代码，首先启动 Pyro4 的 name server: :

C:>python -m Pyro4.naming
Not starting broadcast server for localhost.
NS running on localhost:9090 (127.0.0.1)
Warning: HMAC key not set. Anyone can connect to this server!
URI = PYRO:Pyro.NameServer@localhost:9090

然后，使用 python server.py 命令启动 Server. 命令行的显示如下图所示。

最后，用下面的命令启动客户端，模拟用户的动作。 :

python client.py

命令行的输出将如下所示： :

C:\Users\Utente\Desktop\Python CookBook\Python Parallel Programming
INDEX\Chapter 5 - Distributed Python\
 chapter 5 - codes\banks>python client.py
PYRO:obj_8c4a5b4ae7554c2c9feee5b0113902e0@localhost:59225
*** Rashmi is doing shopping with BuyAnythingOnline:
Log on
Deposit money 100
balance=100.00
Rashmi is buying a book for 37$
Log out
*** Meeta is doing shopping with BuyAnythingOnline:
Log on
Deposit money 50
balance=50.00
Deposit money 50
balance=100.00
Log out
The accounts in the BuyAnythingOnline:
  Meeta : 100.00
  Rashmi : 63.00

输出表示两个用户的会话， Meeta 和 Rashmi .

讨论

客户端应用必须找到 Shop() 对象，通过如下的调用： :

ns = Pyro4.naming.locateNS()

然后打开一个通讯的 channel: :

daemon = Pyro4.core.Daemon()
uri = daemon.register(shop.Shop())
ns.register("example.shop.Shop", uri)
daemon.requestLoop()

shop.py 有处理账户和购物的脚本。 shop 类将会管理每一个账户，它提供了登陆登出，管理用户的余额，以及处理购买动作： :

class Shop(object):
    def logOn(self, name):
        if name in self.clients:
            self.accounts[name] = Account()
        else:
            self.clients.append(name)
            self.accounts[name] = Account()

    def logOut(self, name):
        print("logout %s" % name)

    def deposit(self, name, amount):
        try:
            return self.accounts[name].deposit(amount)
        except KeyError:
            raise KeyError("unknown account")

    def balance(self, name):
        try:
            return self.accounts[name].balance()
        except KeyError:
            raise KeyError("unknown account")

    def buy(self, name, price):
        balance = self.accounts[name].balance()
        self.accounts[name].pay(price)

每一个顾客都有自己的 Account 对象，提供存款管理。 :

class Account(object):
    def __init__(self):
        self._balance = 0.0
    def pay(self, price):
        self._balance -= price
    def deposit(self, cash):
        self._balance += cash
    def balance(self):
        return self._balance

最后， client.py 有一个启动模拟客户行为的类。在 main 函数中，我们模拟了两个用户， Rashmi 和 Meeta : :

meeta = client('Meeta',50)
rashmi = client('Rashmi',100)
rashmi.doShopping_buying_a_book(Shop)
meeta.doShopping_deposit_cash(Shop)

他们在网站上存上一些现金，然后开始购物：

Rashmi 买了一本书： :

def doShopping_buying_a_book(self, Shop):
     Shop.logOn(self.name)
     Shop.deposit(self.name, self.cash)
     Shop.buy(self.name,37)
     Shop.logOut(self.name) 

Meeta 分两次充了 \$100 到账户中： :

def doShopping_deposit_cash(self, Shop):
    Shop.logOn(self.name)
    Shop.deposit(self.name, self.cash)
    Shop.deposit(self.name, 50)
    Shop.logOut(self.name)

最后程序打印出两个用户的存款： :

print("The accounts in the %s:" % Shop.name())
accounts = Shop.allAccounts()
for name in accounts.keys():
    print("  %s : %.2f" % (name, accounts[name]))