1、檔案內容

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.org
        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 100.1.7.19 100.1.7.19 weight 40 maxconn 4000

backend buy.oldboy.org
        server 100.1.7.90 100.1.7.90 weight 20 maxconn 3000

2、程式碼實現

filename = 'text_file\haproxy'
def fetch(backend):
    '''獲取檔案資料'''
    with open(filename, 'r') as f:
        result = []
        flag = False
        for line in f:
            if line.strip().startswith('backend') and line.strip() == 'backend ' + backend:
                flag = True
                continue
            elif flag and line.startswith('backend'):
                break
            elif flag and line.strip():
                result.append(line.strip())
    return result

#測試
ret = fetch("www.oldboy.org")
print(ret)


def add(backend,record):
    '''增加檔案資料'''
    record_list = fetch(backend)
    #先檢查backend是否存在
    if not record_list:
        #backend不存在
        with open(filename,'r') as old,open(r'text_file\new','w') as new:
            for line in old:
                new.write(line)
            new.write("\n\nbackend " + backend)
            new.write("\n" + " "*8 + record)
    else:
        #backend存在,判斷記錄是否存在
        if record in record_list:
            #record存在
            print("記錄已存在")
        else:
            #backend存在，record不存在
            record_list.append(record)
            with open(filename,'r') as old,open(r'text_file\new2','w') as new2:
                flag = False
                for line in old:
                    if line.strip().startswith('backend') and line.strip() == 'backend ' + backend:
                        #找到backend www.oldboy.org
                        flag = True
                        new2.write(line)#把backend行加入新檔案
                        for new_record in record_list:
                            #把record列表中的元素新增到新檔案
                            new2.write(" " * 8 + new_record + "\n")
                        continue
                    if flag and line.startswith('backend'):
                        flag = False
                        new2.write("\n" + line)
                        continue
                    if flag == False:
                        new2.write(line)

#測試
bk = "www.oldboy.org"
rd = "server 34.1.7.25 100.1.7.44 weight 99 maxconn 67"
add(bk,rd)
bk = "test.oldboy.org"
rd = "server 50.1.7.55 100.1.7.45 weight 99 maxconn 89"
add(bk,rd)


def delete(backend,record):
    '''刪除檔案資料'''
    #先判斷backend是否存在
    record_list = fetch(backend)
    if not record_list:
        print("記錄不存在")
    else:
        with open(filename,'r') as f,open(r'text_file\new3','w') as new3:
            if record in record_list:
                for line in f:
                    if line.strip() == record:
                        continue
                    else:
                        new3.write(line)

#測試
bk = "www.oldboy.org"
rd = "server 100.1.7.9 100.1.7.9 weight 20 maxconn 3000"
delete(bk,rd)