这篇文章主要介绍“C++基于reactor的服务器百万并发如何实现”，在日常操作中，相信很多人在C++基于reactor的服务器百万并发如何实现问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”C++基于reactor的服务器百万并发如何实现”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
并发量和承载的概念
并发量：一个服务器能同时承载客户端的数量
承载：客户端发送给服务器的请求(http或tcp等)在200ms内可以返回正确的结果
一、服务器的代码实现与讲解
结构体代码主要构建的结构如图所示
链表结构，每个eventblock结点，包括一个ntyevent数组，数组中存储fd
struct ntyevent {int fd;//要监听的文件描述符int events;//对应的监听事件，EPOLLIN和EPOLLOUT（不同的事件，走不同的回调函数）void *arg;//指向自己结构体指针int (*callback)(int fd, int events, void *arg);int status;//是否在监听：1->在红黑树上（监听），0->不在（不监听）char buffer[BUFFER_LENGTH];int length;long last_active;};struct eventblock {struct eventblock *next;struct ntyevent *events;//数组};struct ntyreactor {//句柄int epfd;//结点个数int blkcnt;struct eventblock *evblk; //fd --> 100w};初始化fd 上树、下树代码
//nty_event_set(event, sockfd, acceptor, reactor);//初始化sockfdvoid nty_event_set(struct ntyevent *ev, int fd, NCALLBACK callback, void *arg) {ev->fd = fd;ev->callback = callback;ev->events = 0;ev->arg = arg;ev->last_active = time(NULL);return ;}//nty_event_add(reactor->epfd, EPOLLIN, event);//对监听的epoll红黑树上的结点的修改int nty_event_add(int epfd, int events, struct ntyevent *ev) {struct epoll_event ep_ev = {0, {0}};ep_ev.data.ptr = ev;ep_ev.events = ev->events = events;int op;if (ev->status == 1) {op = EPOLL_CTL_MOD;} else {op = EPOLL_CTL_ADD;ev->status = 1;}if (epoll_ctl(epfd, op, ev->fd, &ep_ev) < 0) {printf("event add failed [fd=%d], events[%d]\n", ev->fd, events);return -1;}return 0;}int nty_event_del(int epfd, struct ntyevent *ev) {struct epoll_event ep_ev = {0, {0}};if (ev->status != 1) {return -1;}ep_ev.data.ptr = ev;ev->status = 0;epoll_ctl(epfd, EPOLL_CTL_DEL, ev->fd, &ep_ev);return 0;}回调函数代码的书写
注意看recv_cb的回调函数中，recv之后，立马下树，然后又重新初始化fd，上树。这样做的目的是因为代码逻辑是recv收到数据后，立即原样send,所以需要对fd的属性进行更改，需要重新初始化赋值，然后上树
int recv_cb(int fd, int events, void *arg) {struct ntyreactor *reactor = (struct ntyreactor*)arg;struct ntyevent *ev = ntyreactor_idx(reactor, fd);int len = recv(fd, ev->buffer, BUFFER_LENGTH , 0); // nty_event_del(reactor->epfd, ev);if (len > 0) {ev->length = len;ev->buffer[len] = '\0';printf("C[%d]:%s\n", fd, ev->buffer);nty_event_set(ev, fd, send_cb, reactor);nty_event_add(reactor->epfd, EPOLLOUT, ev);} else if (len == 0) {close(ev->fd);//printf("[fd=%d] pos[%ld], closed\n", fd, ev-reactor->events); } else {close(ev->fd);printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));}return len;}int send_cb(int fd, int events, void *arg) {struct ntyreactor *reactor = (struct ntyreactor*)arg;struct ntyevent *ev = ntyreactor_idx(reactor, fd);int len = send(fd, ev->buffer, ev->length, 0);if (len > 0) {printf("send[fd=%d], [%d]%s\n", fd, len, ev->buffer);nty_event_del(reactor->epfd, ev);nty_event_set(ev, fd, recv_cb, reactor);nty_event_add(reactor->epfd, EPOLLIN, ev);} else {close(ev->fd);nty_event_del(reactor->epfd, ev);printf("send[fd=%d] error %s\n", fd, strerror(errno));}return len;}int accept_cb(int fd, int events, void *arg) {struct ntyreactor *reactor = (struct ntyreactor*)arg;if (reactor == NULL) return -1;struct sockaddr_in client_addr;socklen_t len = sizeof(client_addr);int clientfd;if ((clientfd = accept(fd, (struct sockaddr*)&client_addr, &len)) == -1) {if (errno != EAGAIN && errno != EINTR) {}printf("accept: %s\n", strerror(errno));return -1;}int flag = 0;if ((flag = fcntl(clientfd, F_SETFL, O_NONBLOCK)) < 0) {printf("%s: fcntl nonblocking failed, %d\n", __func__, MAX_EPOLL_EVENTS);return -1;}struct ntyevent *event = ntyreactor_idx(reactor, clientfd);nty_event_set(event, clientfd, recv_cb, reactor);nty_event_add(reactor->epfd, EPOLLIN, event);printf("new connect [%s:%d], pos[%d]\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), clientfd);return 0;}链表的初始化与销毁
//初始化链表int ntyreactor_init(struct ntyreactor *reactor) {if (reactor == NULL) return -1;memset(reactor, 0, sizeof(struct ntyreactor));reactor->epfd = epoll_create(1);if (reactor->epfd <= 0) {printf("create epfd in %s err %s\n", __func__, strerror(errno));return -2;}struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));if (evs == NULL) {printf("ntyreactor_alloc ntyevents failed\n");return -2;}memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));struct eventblock *block = (struct eventblock *)malloc(sizeof(struct eventblock));if (block == NULL) {printf("ntyreactor_alloc eventblock failed\n");return -2;}memset(block, 0, sizeof(struct eventblock));block->events = evs;block->next = NULL;reactor->evblk = block;reactor->blkcnt = 1;return 0;}找到fd应在链表数组中存储的位置并返回
//新增块数(eventblock结点个数)//ntyreactor_alloc(reactor);int ntyreactor_alloc(struct ntyreactor *reactor) {if (reactor == NULL) return -1;if (reactor->evblk == NULL) return -1;struct eventblock *blk = reactor->evblk;while (blk->next != NULL) {blk = blk->next;}struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));if (evs == NULL) {printf("ntyreactor_alloc ntyevents failed\n");return -2;}memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));struct eventblock *block = (struct eventblock *)malloc(sizeof(struct eventblock));if (block == NULL) {printf("ntyreactor_alloc eventblock failed\n");return -2;}memset(block, 0, sizeof(struct eventblock));block->events = evs;block->next = NULL;blk->next = block;reactor->blkcnt ++; //return 0;}//struct ntyevent *event = ntyreactor_idx(reactor, sockfd);struct ntyevent *ntyreactor_idx(struct ntyreactor *reactor, int sockfd) {int blkidx = sockfd / MAX_EPOLL_EVENTS;//如果块数(eventblock结点个数)不能满足新的sockfd的存放while (blkidx >= reactor->blkcnt) {//新增块数(eventblock结点个数)ntyreactor_alloc(reactor);}//找到存放sockfd的块(eventblock对应的结点)int i = 0;struct eventblock *blk = reactor->evblk;while(i ++ < blkidx && blk != NULL) {blk = blk->next;}//返回对应块(eventblock对应的结点)的存放sockfd数组的那个具体位置return &blk->events[sockfd % MAX_EPOLL_EVENTS];}上树，并初始化链表数组上对应的fd
//ntyreactor_addlistener(reactor, sockfds[i], accept_cb);//上树，并初始化链表数组上对应的fdint ntyreactor_addlistener(struct ntyreactor *reactor, int sockfd, NCALLBACK *acceptor) {if (reactor == NULL) return -1;if (reactor->evblk == NULL) return -1;//reactor->evblk->events[sockfd];//找到sock所在的具体位置struct ntyevent *event = ntyreactor_idx(reactor, sockfd);初始化sockfdnty_event_set(event, sockfd, acceptor, reactor);//对监听的epoll红黑树上的结点的修改nty_event_add(reactor->epfd, EPOLLIN, event);return 0;}epollwait
//ntyreactor_run(reactor);int ntyreactor_run(struct ntyreactor *reactor) {if (reactor == NULL) return -1;if (reactor->epfd < 0) return -1;if (reactor->evblk == NULL) return -1;struct epoll_event events[MAX_EPOLL_EVENTS+1];int checkpos = 0, i;while (1) {int nready = epoll_wait(reactor->epfd, events, MAX_EPOLL_EVENTS, 1000);if (nready < 0) {printf("epoll_wait error, exit\n");continue;}for (i = 0;i < nready;i ++) {struct ntyevent *ev = (struct ntyevent*)events[i].data.ptr;//看fd连接是否发生变化if ((events[i].events & EPOLLIN) && (ev->events & EPOLLIN)) {ev->callback(ev->fd, events[i].events, ev->arg);}if ((events[i].events & EPOLLOUT) && (ev->events & EPOLLOUT)) {ev->callback(ev->fd, events[i].events, ev->arg);}}}}main函数；此服务器代码开设了100个监听的端口，目的是因为客户端测试程序也是运行在虚拟机的Ubuntu上，通过开三台来充当客户端来进行测试。有因为一台Ubuntu最多有6w个端口，3台有18w端口。如果服务器只开设一个监听端口，则最多有18w端口。因此要达到100w并发则应多开设端口
// 3, 6w, 1, 100 == // <remoteip, remoteport, localip, localport>int main(int argc, char *argv[]) {unsigned short port = SERVER_PORT; // listen 8888if (argc == 2) {port = atoi(argv[1]);//把参数 str 所指向的字符串转换为一个整数（类型为 int 型）}struct ntyreactor *reactor = (struct ntyreactor*)malloc(sizeof(struct ntyreactor));ntyreactor_init(reactor);int i = 0;int sockfds[PORT_COUNT] = {0};for (i = 0;i < PORT_COUNT;i ++) {//端口号的监听sockfds[i] = init_sock(port+i);//上树ntyreactor_addlistener(reactor, sockfds[i], accept_cb);}// epoll_waitntyreactor_run(reactor);//ntyreactor_destory(reactor);for (i = 0;i < PORT_COUNT;i ++) {close(sockfds[i]);}free(reactor);return 0;}完整服务器代码展示
#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/socket.h>#include <sys/epoll.h>#include <arpa/inet.h>#include <fcntl.h>#include <unistd.h>#include <errno.h>#include <time.h>#define BUFFER_LENGTH4096#define MAX_EPOLL_EVENTS1024#define SERVER_PORT8888#define PORT_COUNT100typedef int NCALLBACK(int ,int, void*);//struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));struct ntyevent {int fd;//要监听的文件描述符int events;//对应的监听事件，EPOLLIN和EPOLLOUT（不同的事件，走不同的回调函数）void *arg;//指向自己结构体指针int (*callback)(int fd, int events, void *arg);int status;//是否在监听：1->在红黑树上（监听），0->不在（不监听）char buffer[BUFFER_LENGTH];int length;long last_active;};struct eventblock {struct eventblock *next;struct ntyevent *events;//数组};struct ntyreactor {//句柄int epfd;//结点个数int blkcnt;struct eventblock *evblk; //fd --> 100w};int recv_cb(int fd, int events, void *arg);int send_cb(int fd, int events, void *arg);struct ntyevent *ntyreactor_idx(struct ntyreactor *reactor, int sockfd);//nty_event_set(event, sockfd, acceptor, reactor);//初始化sockfdvoid nty_event_set(struct ntyevent *ev, int fd, NCALLBACK callback, void *arg) {ev->fd = fd;ev->callback = callback;ev->events = 0;ev->arg = arg;ev->last_active = time(NULL);return ;}//nty_event_add(reactor->epfd, EPOLLIN, event);//对监听的epoll红黑树上的结点的修改int nty_event_add(int epfd, int events, struct ntyevent *ev) {struct epoll_event ep_ev = {0, {0}};ep_ev.data.ptr = ev;ep_ev.events = ev->events = events;int op;if (ev->status == 1) {op = EPOLL_CTL_MOD;} else {op = EPOLL_CTL_ADD;ev->status = 1;}if (epoll_ctl(epfd, op, ev->fd, &ep_ev) < 0) {printf("event add failed [fd=%d], events[%d]\n", ev->fd, events);return -1;}return 0;}int nty_event_del(int epfd, struct ntyevent *ev) {struct epoll_event ep_ev = {0, {0}};if (ev->status != 1) {return -1;}ep_ev.data.ptr = ev;ev->status = 0;epoll_ctl(epfd, EPOLL_CTL_DEL, ev->fd, &ep_ev);return 0;}int recv_cb(int fd, int events, void *arg) {struct ntyreactor *reactor = (struct ntyreactor*)arg;struct ntyevent *ev = ntyreactor_idx(reactor, fd);int len = recv(fd, ev->buffer, BUFFER_LENGTH , 0); // nty_event_del(reactor->epfd, ev);if (len > 0) {ev->length = len;ev->buffer[len] = '\0';printf("C[%d]:%s\n", fd, ev->buffer);nty_event_set(ev, fd, send_cb, reactor);nty_event_add(reactor->epfd, EPOLLOUT, ev);} else if (len == 0) {close(ev->fd);//printf("[fd=%d] pos[%ld], closed\n", fd, ev-reactor->events);} else {close(ev->fd);printf("recv[fd=%d] error[%d]:%s\n", fd, errno, strerror(errno));}return len;}int send_cb(int fd, int events, void *arg) {struct ntyreactor *reactor = (struct ntyreactor*)arg;struct ntyevent *ev = ntyreactor_idx(reactor, fd);int len = send(fd, ev->buffer, ev->length, 0);if (len > 0) {printf("send[fd=%d], [%d]%s\n", fd, len, ev->buffer);nty_event_del(reactor->epfd, ev);nty_event_set(ev, fd, recv_cb, reactor);nty_event_add(reactor->epfd, EPOLLIN, ev);} else {close(ev->fd);nty_event_del(reactor->epfd, ev);printf("send[fd=%d] error %s\n", fd, strerror(errno));}return len;}int accept_cb(int fd, int events, void *arg) {struct ntyreactor *reactor = (struct ntyreactor*)arg;if (reactor == NULL) return -1;struct sockaddr_in client_addr;socklen_t len = sizeof(client_addr);int clientfd;if ((clientfd = accept(fd, (struct sockaddr*)&client_addr, &len)) == -1) {if (errno != EAGAIN && errno != EINTR) {}printf("accept: %s\n", strerror(errno));return -1;}int flag = 0;if ((flag = fcntl(clientfd, F_SETFL, O_NONBLOCK)) < 0) {printf("%s: fcntl nonblocking failed, %d\n", __func__, MAX_EPOLL_EVENTS);return -1;}struct ntyevent *event = ntyreactor_idx(reactor, clientfd);nty_event_set(event, clientfd, recv_cb, reactor);nty_event_add(reactor->epfd, EPOLLIN, event);printf("new connect [%s:%d], pos[%d]\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), clientfd);return 0;}int init_sock(short port) {int fd = socket(AF_INET, SOCK_STREAM, 0);fcntl(fd, F_SETFL, O_NONBLOCK);struct sockaddr_in server_addr;memset(&server_addr, 0, sizeof(server_addr));server_addr.sin_family = AF_INET;server_addr.sin_addr.s_addr = htonl(INADDR_ANY);server_addr.sin_port = htons(port);bind(fd, (struct sockaddr*)&server_addr, sizeof(server_addr));if (listen(fd, 20) < 0) {printf("listen failed : %s\n", strerror(errno));}return fd;}//新增块数(eventblock结点个数)//ntyreactor_alloc(reactor);int ntyreactor_alloc(struct ntyreactor *reactor) {if (reactor == NULL) return -1;if (reactor->evblk == NULL) return -1;struct eventblock *blk = reactor->evblk;while (blk->next != NULL) {blk = blk->next;}struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));if (evs == NULL) {printf("ntyreactor_alloc ntyevents failed\n");return -2;}memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));struct eventblock *block = (struct eventblock *)malloc(sizeof(struct eventblock));if (block == NULL) {printf("ntyreactor_alloc eventblock failed\n");return -2;}memset(block, 0, sizeof(struct eventblock));block->events = evs;block->next = NULL;blk->next = block;reactor->blkcnt ++; //return 0;}//struct ntyevent *event = ntyreactor_idx(reactor, sockfd);struct ntyevent *ntyreactor_idx(struct ntyreactor *reactor, int sockfd) {int blkidx = sockfd / MAX_EPOLL_EVENTS;//如果块数(eventblock结点个数)不能满足新的sockfd的存放while (blkidx >= reactor->blkcnt) {//新增块数(eventblock结点个数)ntyreactor_alloc(reactor);}//找到存放sockfd的块(eventblock对应的结点)int i = 0;struct eventblock *blk = reactor->evblk;while(i ++ < blkidx && blk != NULL) {blk = blk->next;}//返回对应块(eventblock对应的结点)的存放sockfd数组的那个具体位置return &blk->events[sockfd % MAX_EPOLL_EVENTS];}//初始化链表int ntyreactor_init(struct ntyreactor *reactor) {if (reactor == NULL) return -1;memset(reactor, 0, sizeof(struct ntyreactor));reactor->epfd = epoll_create(1);if (reactor->epfd <= 0) {printf("create epfd in %s err %s\n", __func__, strerror(errno));return -2;}struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));if (evs == NULL) {printf("ntyreactor_alloc ntyevents failed\n");return -2;}memset(evs, 0, (MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));struct eventblock *block = (struct eventblock *)malloc(sizeof(struct eventblock));if (block == NULL) {printf("ntyreactor_alloc eventblock failed\n");return -2;}memset(block, 0, sizeof(struct eventblock));block->events = evs;block->next = NULL;reactor->evblk = block;reactor->blkcnt = 1;return 0;}int ntyreactor_destory(struct ntyreactor *reactor) {close(reactor->epfd);//free(reactor->events);struct eventblock *blk = reactor->evblk;struct eventblock *blk_next = NULL;while (blk != NULL) {blk_next = blk->next;free(blk->events);free(blk);blk = blk_next;}return 0;}//ntyreactor_addlistener(reactor, sockfds[i], accept_cb);//上树，并初始化链表数组上对应的fdint ntyreactor_addlistener(struct ntyreactor *reactor, int sockfd, NCALLBACK *acceptor) {if (reactor == NULL) return -1;if (reactor->evblk == NULL) return -1;//reactor->evblk->events[sockfd];//找到sock所在的具体位置struct ntyevent *event = ntyreactor_idx(reactor, sockfd);初始化sockfdnty_event_set(event, sockfd, acceptor, reactor);//对监听的epoll红黑树上的结点的修改nty_event_add(reactor->epfd, EPOLLIN, event);return 0;}//ntyreactor_run(reactor);int ntyreactor_run(struct ntyreactor *reactor) {if (reactor == NULL) return -1;if (reactor->epfd < 0) return -1;if (reactor->evblk == NULL) return -1;struct epoll_event events[MAX_EPOLL_EVENTS+1];int checkpos = 0, i;while (1) {int nready = epoll_wait(reactor->epfd, events, MAX_EPOLL_EVENTS, 1000);if (nready < 0) {printf("epoll_wait error, exit\n");continue;}for (i = 0;i < nready;i ++) {struct ntyevent *ev = (struct ntyevent*)events[i].data.ptr;//看fd连接是否发生变化if ((events[i].events & EPOLLIN) && (ev->events & EPOLLIN)) {ev->callback(ev->fd, events[i].events, ev->arg);}if ((events[i].events & EPOLLOUT) && (ev->events & EPOLLOUT)) {ev->callback(ev->fd, events[i].events, ev->arg);}}}}// 3, 6w, 1, 100 == // <remoteip, remoteport, localip, localport>int main(int argc, char *argv[]) {unsigned short port = SERVER_PORT; // listen 8888if (argc == 2) {port = atoi(argv[1]);//把参数 str 所指向的字符串转换为一个整数（类型为 int 型）}struct ntyreactor *reactor = (struct ntyreactor*)malloc(sizeof(struct ntyreactor));ntyreactor_init(reactor);int i = 0;int sockfds[PORT_COUNT] = {0};for (i = 0;i < PORT_COUNT;i ++) {//端口号的监听sockfds[i] = init_sock(port+i);//上树ntyreactor_addlistener(reactor, sockfds[i], accept_cb);}// epoll_waitntyreactor_run(reactor);//ntyreactor_destory(reactor);for (i = 0;i < PORT_COUNT;i ++) {close(sockfds[i]);}free(reactor);return 0;}reactor的写法感觉和epoll的普通写法，感觉差别就是reactor多了个回调函数，具体没啥优点？
epoll是针对io的管理。 reactor对针对事件的管理
不同的事件，针对不同的回调函数
性能上没啥差异，但提高了代码的复用性。具体需要自己慢慢体会体会，呜呜呜呜还有体会到，编程思想不过关。
二、环境设置
限制是fd的限制，系统默认fd最多有1024个，按照一个连接一个fd的做法，那就需要百万个fd。这里有两种修改方法，一是使用ulimit -n命令，这个命令重启就失效；二是修改/etc/security/limits.conf文件，这是永久有效的，重启或sysctl -p生效。
* hard nofile 1048576* soft nofile 1048576hard是硬限制，不能超过该值，soft是软限制，可以超过，超过后就开始回收。
这个文件里还有一些其他的参数可以了解一下，fs.file_max是fd可取到的最大值，注意与fd最大个数区分。
突破这两个限制后，还会遇到一个问题，客户端会报错：connection timedout。连接超时，即是客户端未收到服务器对客户端connect()的回应包。这里有两种可能，客户端为收到服务器的包或是服务器未收到客户端的connect包。事实上，是因为系统有个防火墙iotables，这个防火墙是基于网卡和协议栈之间的过滤机制netfilter实现的。netfilter当连接数到达一定程度时，会不允许再向外发送connect包。修改也是通过/etc/security/limits.conf文件
net.nf_conntrack_max=1048576突破这些限制，就可以实现百万并发了。
这里再介绍/etc/security/limits.conf中几个参数
net.ipv4.tcp_mem=262144 524288 786432是所有TCP协议栈所占空间的大小，单位是页（4KB）。介绍一下后面写的三个值，当所占空间大小超过第二个值时，系统会进行优化，此时如果占用空间降到第一个值以下，不再优化，第三个值是上限，不允许分配超过比大小的空间。
net.ipv4.tcp_wmem=2048 2048 4096是每个socket对应的写缓冲区大小，三个值分别是最小值、默认值、最大值，单位是B。
net.ipv4.tcp_rmem=2048 2048 4096是每个socket对应的读缓冲区大小，三个值分别是最小值、默认值、最大值，单位是B。
做百万并发时，如果内存不大，可以相应调小。在实际应用中，如果传输大文件，调大；如果传输的都是字符，调小，就可以接收更多fd。
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