需求
1、查
输入：www.oldboy.org
    获取当前backend下的所有记录

2、新建
    输入：
        arg = {
            'bakend': 'www.oldboy.org',
            'record':{
                'server': '100.1.7.9',
                'weight': 20,
                'maxconn': 30
            }
        }

3、删除
    输入：
        arg = {
            'bakend': 'www.oldboy.org',
            'record':{
                'server': '100.1.7.9',
                'weight': 20,
                'maxconn': 30
            }
        }


操作haproxy.cfg的haproxy.py文件

#!/usr/bin/evn python
#-*- coding=utf-8 -*-
import json
import os

# 根据backend名字查找backend信息
def fetch(backend_name):
    line_list = []
    flag = False
    with open('D:/python/day03/haproxy.cfg','r') as ha:
        for line in ha:
            if line.startswith("backend %s" % backend_name):
                flag = True
                continue
            if flag and line.strip().startswith('server'):
                line_list.append(line.strip())
            if line.startswith('backend'):
                # flag = False
                break

    return line_list

# 添加backend信息
def add(info_dict):
    current_title = info_dict['backend']
    current_list = 'server %s %s weight %d maxconn %d' % (info_dict['record']['server'],info_dict['record']['server'],info_dict['record']['weight'],info_dict['record']['maxconn'])
    fetch_list = fetch(current_title)
    # backend是否存在
    if fetch_list:
        if current_list in fetch_list:
            pass
        else:
            fetch_list.append(current_list)
        # 如果根据backend找到了这个backend说明有记录，继续添加server即可

        flag = False
        has_write = False
        with open('haproxy.cfg') as read_obj,open('haproxy.new','w') as write_obj:
            for read_line in read_obj:
                # 将haproxy.cfg分为上、中、下三部分
                # fetch_list为中间部分

                # 读取配置文件，写信配置文件
                # 读上-->写上
                # 将处理完的配置文件fetch_list写入新的配置文件中
                # 读下-->写下
                if read_line.strip() == 'backend %s' % current_title:
                    write_obj.write(read_line)
                    flag = True
                    continue
                if flag and read_line.startswith('backend'):
                    flag = False
                if flag:
                    for i in fetch_list:
                        if not has_write:
                            write_obj.write('%s%s\n' % (' '*8,i))
                    has_write = True
                else:
                    write_obj.write(read_line)
    else:
        # 没有这条记录需要添加backend和server
        with open('haproxy.cfg') as read_obj,open('haproxy.new','w') as write_obj:
            for read_line in read_obj:
                write_obj.write(read_line)
            write_obj.write('backend %s\n' % current_title)
            write_obj.write(' '*8 + current_list)
    # 先将haproxy.cfg备份为haproxy.cfg.bak，将新的文件替换为haproxy.cfg
    os.rename('haproxy.cfg','haproxy.cfg.bak')
    os.rename('haproxy.new','haproxy.cfg')

# 删除backend信息函数
def del_backend(info_dict):
    current_title = info_dict.get('backend')
    fetch_list = fetch(current_title)

    current_record = 'server %s %s weight %d maxconn %d' % (info_dict['record']['server'],info_dict['record']['server'],info_dict['record']['weight'],info_dict['record']['maxconn'])

    # 判断是否有这条记录
    if fetch_list:
        if current_record in fetch_list:
            # 将该记录删掉
            fetch_list.remove(current_record)
            print fetch_list
            with open('haproxy.cfg') as read_obj,open('haproxy.new','w') as write_obj:
                flag = False
                has_write = False
                for read_line in read_obj:

                    if read_line.strip() == 'backend %s' % current_title:
                        write_obj.write(read_line)
                        flag = True
                        continue
                    if flag and read_line.startswith('backend'):
                        flag = False
                    if flag:
                        if not has_write:
                            for line in fetch_list:
                                write_obj.write('%s%s\n' % (' '*8,line))
                        has_write = True
                    else:
                        write_obj.write(read_line)
        else:
            print('no this server record')

        if os.path.exists('D:/python/day03/haproxy.new'):
            os.rename('haproxy.cfg','haproxy.cfg.bak')
            os.rename('haproxy.new','haproxy.cfg')
    else:
        print('no this record')

# 需要添加的记录
data = '{"backend": "www.oldboy.org","record":{"server": "100.1.7.168","weight": 20,"maxconn": 30}}'
# 转换为json格式
info_dict = json.loads(data)

input_num = raw_input('please input your select : ')
if str.isdigit(input_num):
    input_num = int(input_num)
# 1.查找记录 2.增加记录 3.删除记录
if input_num == 1:
    pass
elif input_num == 2:
    add(info_dict)
elif input_num == 3:
    del_backend(info_dict)


haproxy.cfg配置文件

global
        log 127.0.0.1 local2
        daemon
        maxconn 256
        log 127.0.0.1 local2 info
defaults
        log global
        mode http
        timeout connect 5000ms
        timeout client 50000ms
        timeout server 50000ms
        option  dontlognull

listen stats :8888
        stats enable
        stats uri       /admin
        stats auth      admin:1234

frontend oldboy
        bind 0.0.0.0:80
        option httplog
        option httpclose
        option  forwardfor
        log global
        acl www hdr_reg(host) -i www.oldboy.org
        use_backend www.oldboy.org if www

backend www.oldboy.org
        server 100.1.7.9 100.1.7.9 weight 20 maxconn 3000
        server 100.1.7.10 100.1.7.10 weight 10 maxconn 2000
backend mysqlserver
        server mysql1 10.1.1.110:3306 weight 20 maxconn 300
        server mysql2 10.1.1.120:3306 weight 10 maxconn 200
frontend mysql
        bind *:3306
        mode tcp
        log global
        default_backend mysqlserver