## 7) 负载均衡上报Host主机信息API(V0.4) ### 7.1 proto通信协议定义 ```protobuf syntax = "proto3"; package lars; /* Lars系统的消息ID */ enum MessageId { ID_UNKNOW = 0; //proto3 enum第一个属性必须是0，用来占位 ID_GetRouteRequest = 1; //向DNS请求Route对应的关系的消息ID ID_GetRouteResponse = 2; //DNS回复的Route信息的消息ID ID_ReportStatusRequest = 3; //上报host调用状态信息请求消息ID ID_GetHostRequest = 4; //API 发送请求host信息给 Lb Agent模块 消息ID ID_GetHostResponse = 5; //agent 回执给 API host信息的 消息ID ID_ReportRequest = 6; //API report get_host的调用结果给agent的 消息ID } //... //... // API 上报调用结果给 Agent(UDP) message ReportRequest { int32 modid = 1; int32 cmdid = 2; HostInfo host = 3; int32 retcode = 4; } ``` `ID_ReportRequest`和 `message ReportRequest `是针对API层与agent的请求互通协议。 ### 7.2 Lars-API:Reporter()方法客户端实现 > Lars/api/cpp/lars_api/lars_api.h ```c #pragma once #include "lars_reactor.h" #include <string> class lars_client { public: lars_client(); ~lars_client(); //lars 系统获取host信息 得到可用host的ip和port int get_host(int modid, int cmdid, std::string& ip, int &port); //lars 系统上报host调用信息 void report(int modid, int cmdid, const std::string &ip, int port, int retcode); private: int _sockfd[3]; //3个udp socket fd 对应agent 3个udp server uint32_t _seqid; //消息的序列号 }; ``` ​ 新增`report()`方法。 > Lars/api/cpp/lars_api/lars_api.cpp ```c //lars 系统上报host调用信息 void lars_client::report(int modid, int cmdid, const std::string &ip, int port, int retcode) { //1 封装上报消息 lars::ReportRequest req; req.set_modid(modid); req.set_cmdid(cmdid); req.set_retcode(retcode); //1.1 host信息 lars::HostInfo *hp = req.mutable_host(); //ip struct in_addr inaddr; inet_aton(ip.c_str(), &inaddr); int ip_num = inaddr.s_addr; hp->set_ip(ip_num); //port hp->set_port(port); //2. send char write_buf[4096]; //消息头 msg_head head; head.msglen = req.ByteSizeLong(); head.msgid = lars::ID_ReportRequest; memcpy(write_buf, &head, MESSAGE_HEAD_LEN); req.SerializeToArray(write_buf + MESSAGE_HEAD_LEN, head.msglen); int index = (modid+cmdid)%3; int ret = sendto(_sockfd[index], write_buf, head.msglen + MESSAGE_HEAD_LEN, 0, NULL, 0); if (ret == -1) { perror("sendto"); } } ``` > Lars/api/cpp/example/example.cpp ```c int ret = api.get_host(modid, cmdid, ip, port); if (ret == 0) { std::cout << "host is " << ip << ":" << port << std::endl; //上报调用结果 api.report(modid, cmdid, ip, port, 0); } ``` ​ 在example的业务应用中，加上调用上报api。在每次调用完`get_host`。 ### 7.3 report业务添加的配置参数信息 > Lars/lars_loadbalance_agent/conf/lars_lb_agent.conf ```ini [reporter] ip = 127.0.0.1 port = 7779 [dnsserver] ip = 127.0.0.1 port = 7778 [loadbalance] ;经过若干次获取请求host节点后，试探选择一次overload过载节点 probe_num=10 ;初始化host_info主机信息访问成功的个数，防止刚启动时少量失败就认为过载 init_succ_cnt=180 ;当idle节点失败率高于此值，节点变overload状态 err_rate=0.1 ;当overload节点成功率高于此值，节点变成idle状态 succ_rate=0.95 ;当idle节点连续失败次数超过此值，节点变成overload状态 contin_err_limit=15 ;当overload节点连续成功次数超过此值, 节点变成idle状态 contin_succ_limit=15 ``` 配置文件里在`[loadbalance]`中新增了一些字段。 那么我们需要在启动lb_agent的时候，加载这些配置文件参数. > lars_loadbalance_agent/include/main_server.h ```c #pragma once #include "lars_reactor.h" #include "lars.pb.h" #include "route_lb.h" struct load_balance_config { //经过若干次获取请求host节点后，试探选择一次overload过载节点 int probe_num; //初始化host_info主机信息访问成功的个数，防止刚启动时少量失败就认为过载 int init_succ_cnt; //************************************************** //当idle节点失败率高于此值，节点变overload状态 float err_rate; //当overload节点成功率高于此值，节点变成idle状态 float succ_rate; //当idle节点连续失败次数超过此值，节点变成overload状态 int contin_err_limit; //当overload节点连续成功次数超过此值, 节点变成idle状态 int contin_succ_limit; //当前agent本地ip地址(用于上报 填充caller字段) uint32_t local_ip; //************************************************** }; ``` > lars_loadbalance_agent/src/main_server.cpp ```c #include "main_server.h" #include "lars.pb.h" #include <netdb.h> // ... //--------- 全局资源 ---------- static void init_lb_agent() { //1. 加载配置文件 config_file::setPath("./conf/lars_lb_agent.conf"); lb_config.probe_num = config_file::instance()->GetNumber("loadbalance", "probe_num", 10); lb_config.init_succ_cnt = config_file::instance()->GetNumber("loadbalance", "init_succ_cnt", 180); lb_config.err_rate = config_file::instance()->GetFloat("loadbalance", "err_rate", 0.1); lb_config.succ_rate = config_file::instance()->GetFloat("loadbalance", "succ_rate", 0.92); lb_config.contin_succ_limit = config_file::instance()->GetNumber("loadbalance", "contin_succ_limit", 10); lb_config.contin_err_limit = config_file::instance()->GetNumber("loadbalance", "contin_err_limit", 10); //2. 初始化3个route_lb模块 create_route_lb(); //3. 加载本地ip char my_host_name[1024]; if (gethostname(my_host_name, 1024) == 0) { struct hostent *hd = gethostbyname(my_host_name); if (hd) { struct sockaddr_in myaddr; myaddr.sin_addr = *(struct in_addr*)hd->h_addr; lb_config.local_ip = ntohl(myaddr.sin_addr.s_addr); } } if (!lb_config.local_ip) { struct in_addr inaddr; inet_aton("127.0.0.1", &inaddr); lb_config.local_ip = ntohl(inaddr.s_addr); } } // ... ``` 这里的本地ip，是之后在上报的时候，发送消息需要一个caller参数，这个caller参数我们就暂时默认是当前agent的ip为caller。 ### 7.4 Agent UDP Server处理API-Report请求 ​ 接下来我们针对API发送的report的`ID_ReportRequest`进行处理. > lars_loadbalance_agent/src/agent_udp_server.cpp ```c #include "lars_reactor.h" #include "main_server.h" // ... static void report_cb(const char *data, uint32_t len, int msgid, net_connection *net_conn, void *user_data) { lars::ReportRequest req; req.ParseFromArray(data, len); route_lb *ptr_route_lb = (route_lb*)user_data; ptr_route_lb->report_host(req); } void * agent_server_main(void * args) { long index = (long)args; short port = index + 8888; event_loop loop; udp_server server(&loop, "0.0.0.0", port); //给server注册消息分发路由业务, 针对ID_GetHostRequest处理 每个udp拥有一个对应的route_lb server.add_msg_router(lars::ID_GetHostRequest, get_host_cb, r_lb[port-8888]); //====================================================== //给server注册消息分发路由业务，针对ID_ReportRequest处理 server.add_msg_router(lars::ID_ReportRequest, report_cb, r_lb[port-8888]); //====================================================== printf("agent UDP server :port %d is started...\n", port); loop.event_process(); return NULL; } void start_UDP_servers(void) { for (long i = 0; i < 3; i ++) { pthread_t tid; int ret = pthread_create(&tid, NULL, agent_server_main, (void*)i); if (ret == -1) { perror("pthread_create"); exit(1); } pthread_detach(tid); } } ``` 这里主要是通过一个udp server中的route_lb对象来调用的`report_host(req)`方法。我们来实现这个方法。 > lars_loadbalance_agent/src/route_lb.cpp ```c //agent 上报某主机的获取结果 void route_lb::report_host(lars::ReportRequest req) { int modid = req.modid(); int cmdid = req.cmdid(); int retcode = req.retcode(); int ip = req.host().ip(); int port = req.host().port(); uint64_t key = ((uint64_t)modid << 32) + cmdid; pthread_mutex_lock(&_mutex); if (_route_lb_map.find(key) != _route_lb_map.end()) { load_balance *lb = _route_lb_map[key]; lb->report(ip, port, retcode); //上报信息给远程reporter服务器 lb->commit(); } pthread_mutex_unlock(&_mutex); } ``` 当然，route_lb最终还是分管每个modid/cmdid对应的load_balance模块,那么选择一个可用的load_balance对象，调用`load_balance`的`report()`方法.而通过`commit()`方法，将report的上报结果提交到远程的`report service`中去。 接下来我们看一下`load_balance`的report方法实现. > lars_loadbalance_agent/src/load_balance.cpp ```c //上报当前host主机调用情况给远端repoter service void load_balance::report(int ip, int port, int retcode) { uint64_t key = ((uint64_t)ip << 32) + port; if (_host_map.find(key) == _host_map.end()) { return; } //1 计数统计 host_info *hi = _host_map[key]; if (retcode == lars::RET_SUCC) { // retcode == 0 //更新虚拟成功、真实成功次数 hi->vsucc ++; hi->rsucc ++; //连续成功增加 hi->contin_succ ++; //连续失败次数归零 hi->contin_err = 0; } else { //更新虚拟失败、真实失败次数 hi->verr ++; hi->rerr ++; //连续失败个数增加 hi->contin_err++; //连续成功次数归零 hi->contin_succ = 0; } //2.检查节点状态 //检查idle节点是否满足overload条件 //或者overload节点是否满足idle条件 //--> 如果是dile节点,则只有调用失败才有必要判断是否达到overload条件 if (hi->overload == false && retcode != lars::RET_SUCC) { bool overload = false; //idle节点，检查是否达到判定为overload的状态条件 //(1).计算失败率,如果大于预设值失败率，则为overload double err_rate = hi->verr * 1.0 / (hi->vsucc + hi->verr); if (err_rate > lb_config.err_rate) { overload = true; } //(2).连续失败次数达到阈值，判定为overload if( overload == false && hi->contin_err >= (uint32_t)lb_config.contin_err_limit) { overload = true; } //判定overload需要做的更改流程 if (overload) { struct in_addr saddr; saddr.s_addr = htonl(hi->ip); printf("[%d, %d] host %s:%d change overload, succ %u err %u\n", _modid, _cmdid, inet_ntoa(saddr), hi->port, hi->vsucc, hi->verr); //设置hi为overload状态 hi->set_overload(); //移出_idle_list,放入_overload_list _idle_list.remove(hi); _overload_list.push_back(hi); return; } } //--> 如果是overload节点，则只有调用成功才有必要判断是否达到idle条件 else if (hi->overload == true && retcode == lars::RET_SUCC) { bool idle = false; //overload节点，检查是否达到回到idle状态的条件 //(1).计算成功率，如果大于预设值的成功率，则为idle double succ_rate = hi->vsucc * 1.0 / (hi->vsucc + hi->verr); if (succ_rate > lb_config.succ_rate) { idle = true; } //(2).连续成功次数达到阈值，判定为idle if (idle == false && hi->contin_succ >= (uint32_t)lb_config.contin_succ_limit) { idle = true; } //判定为idle需要做的更改流程 if (idle) { struct in_addr saddr; saddr.s_addr = htonl(hi->ip); printf("[%d, %d] host %s:%d change idle, succ %u err %u\n", _modid, _cmdid, inet_ntoa(saddr), hi->port, hi->vsucc, hi->verr); //设置为idle状态 hi->set_idle(); //移出overload_list, 放入_idle_list _overload_list.remove(hi); _idle_list.push_back(hi); return; } } //TODO 窗口检查和超时机制 } ``` 其中`set_idle()`与`set_overload()`方法实现如下： > lars_loadbalance_agent/src/host_info.cpp ```c #include "host_info.h" #include "main_server.h" void host_info::set_idle() { vsucc = lb_config.init_succ_cnt; verr = 0; rsucc = 0; rerr = 0; contin_succ = 0; contin_err = 0; overload = false; } void host_info::set_overload() { vsucc = 0; verr = lb_config.init_err_cnt;//overload的初试虚拟err错误次数 rsucc = 0; rerr = 0; contin_err = 0; contin_succ = 0; overload = true; } ``` `load_balance`的`report()`方法实现主要是针对两个链表做节点的交替处理。和成功率失败率的判断。 > 节点失败率 = 节点`verr` / (`vsucc` + `verr`) > 节点成功率 = 节点`vsucc` / (`vsucc` + `verr`) 当idle节点的失败率>预设值（默认10%），将节点判定为overload； 当overload节点的成功率>预设值（默认95%），将节点判定为idle； 而不可以idle/overload节点都只关注成功率or都只关注失败率，这样可能造成节点在idle/overload状态间频繁切换 为idle节点、overload节点设置不同的阈值可以区别对待。 ​ 接下来我们来实现`load_balance`的`commit()`方法。 > lars_loadbalance_agent/src/load_balance.cpp ```c //提交host的调用结果给远程reporter service上报结果 void load_balance::commit() { if (this->empty() == true) { return; } //1. 封装请求消息 lars::ReportStatusRequest req; req.set_modid(_modid); req.set_cmdid(_cmdid); req.set_ts(time(NULL)); req.set_caller(lb_config.local_ip); //2. 从idle_list取值 for (host_list_it it = _idle_list.begin(); it != _idle_list.end(); it++) { host_info *hi = *it; lars::HostCallResult call_res; call_res.set_ip(hi->ip); call_res.set_port(hi->port); call_res.set_succ(hi->rsucc); call_res.set_err(hi->rerr); call_res.set_overload(false); req.add_results()->CopyFrom(call_res); } //3. 从over_list取值 for (host_list_it it = _overload_list.begin(); it != _overload_list.end(); it++) { host_info *hi = *it; lars::HostCallResult call_res; call_res.set_ip(hi->ip); call_res.set_port(hi->port); call_res.set_succ(hi->rsucc); call_res.set_err(hi->rerr); call_res.set_overload(true); req.add_results()->CopyFrom(call_res); } //4 发送给report_client 的消息队列 report_queue->send(req); } ``` --- ### 关于作者： 作者：`Aceld(刘丹冰)` mail: [danbing.at@gmail.com](mailto:danbing.at@gmail.com) github: [https://github.com/aceld](https://github.com/aceld) 原创书籍: [https://www.kancloud.cn/@aceld](https://www.kancloud.cn/@aceld)  >**原创声明:未经作者允许请勿转载, 如果转载请注明出处**