C++基於reactor的服務器百萬並發實現與講解
reactor實現的原理請參考：
https://www.jb51.net/article/253794.htm
本次百萬並發的代碼實現也是基於上面代碼進行更改而來
並發量和承載的概念
並發量：一個服務器能同時承載客戶端的數量
承載：客戶端發送給服務器的請求(http或tcp等)在200ms內可以返回正確的結果
一、服務器的代碼實現與講解
結構體代碼主要構建的結構如圖所示
鏈表結構，每個eventblock結點，包括一個ntyevent數組，數組中存儲fd
/*結構體定義鏈表數組*/
struct ntyevent {
int fd;//要監聽的文件描述符
int events;//對應的監聽事件， EPOLLIN和EPOLLOUT（不同的事件，走不同的回調函數）
void *arg;//指向自己結構體指針
int (*callback)(int fd, int events, void *arg);
int status;//是否在監聽：1->在紅黑樹上（監聽），0->不在（不監聽）
char buffer[BUFFER_LENGTH];
int length;
long last_active;
};
struct eventblock {
struct eventblock *next;
struct ntyevent *events;//數組
};
struct ntyreactor {
//句柄
int epfd;
//結點個數
int blkcnt;
struct eventblock *evblk; //fd --> 100w
};
初始化fd 上樹、下樹代碼
//nty_event_set(event, sockfd, acceptor, reactor);
//初始化sockfd
void 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);
//對監聽的epoll紅黑樹上的結點的修改
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;
}
回調函數代碼的書寫
註意看recv_cb的回調函數中，recv之後，立馬下樹，然後又重新初始化fd，上樹。這樣做的目的是因為代碼邏輯是recv收到數據後，立即原樣send,所以需要對fd的屬性進行更改，需要重新初始化賦值，然後上樹
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;
}
/*存儲*/
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;
}
鏈表的初始化與銷毀
//初始化鏈表
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應在鏈表數組中存儲的位置並返回
//新增塊數(eventblock結點個數)
//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;
//如果塊數(eventblock結點個數)不能滿足新的sockfd的存放
while (blkidx >= reactor->blkcnt) {
//新增塊數(eventblock結點個數)
ntyreactor_alloc(reactor);
}
//找到存放sockfd的塊(eventblock對應的結點)
int i = 0;
struct eventblock *blk = reactor->evblk;
while(i ++ < blkidx && blk != NULL) {
blk = blk->next;
}
//返回對應塊(eventblock對應的結點)的存放sockfd數組的那個具體位置
return &blk->events[sockfd % MAX_EPOLL_EVENTS];
}
上樹，並初始化鏈表數組上對應的fd
//ntyreactor_addlistener(reactor, sockfds[i], accept_cb);
//上樹，並初始化鏈表數組上對應的fd
int 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所在的具體位置
struct ntyevent *event = ntyreactor_idx(reactor, sockfd);
初始化sockfd
nty_event_set(event, sockfd, acceptor, reactor);
//對監聽的epoll紅黑樹上的結點的修改
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) {
/*
long now = time(NULL);
for (i = 0;i < 100;i ++, checkpos ++) {
if (checkpos == MAX_EPOLL_EVENTS) {
checkpos = 0;
}
if (reactor->events[checkpos].status != 1) {
continue;
}
long duration = now - reactor->events[checkpos].last_active;
if (duration >= 60) {
close(reactor->events[checkpos].fd);
printf("[fd=%d] timeout\n", reactor->events[checkpos].fd);
nty_event_del(reactor->epfd, &reactor->events[checkpos]);
}
}
*/
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連接是否發生變化
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函數；此服務器代碼開設瞭100個監聽的端口，目的是因為客戶端測試程序也是運行在虛擬機的Ubuntu上，通過開三臺來充當客戶端來進行測試。有因為一臺Ubuntu最多有6w個端口，3臺有18w端口。如果服務器隻開設一個監聽端口，則最多有18w端口。因此要達到100w並發則應多開設端口
// 3, 6w, 1, 100 ==
// <remoteip, remoteport, localip, localport>
int main(int argc, char *argv[]) {
unsigned short port = SERVER_PORT; // listen 8888
if (argc == 2) {
port = atoi(argv[1]);//把參數 str 所指向的字符串轉換為一個整數（類型為 int 型）
}
struct ntyreactor *reactor = (struct ntyreactor*)malloc(sizeof(struct ntyreactor));
/*初始化三個結構體，建立鏈表*/
ntyreactor_init(reactor);
int i = 0;
int sockfds[PORT_COUNT] = {0};
for (i = 0;i < PORT_COUNT;i ++) {
//端口號的監聽
sockfds[i] = init_sock(port+i);
//上樹
ntyreactor_addlistener(reactor, sockfds[i], accept_cb);
}
// epoll_wait
ntyreactor_run(reactor);
//
ntyreactor_destory(reactor);
for (i = 0;i < PORT_COUNT;i ++) {
close(sockfds[i]);
}
free(reactor);
return 0;
}
完整服務器代碼展示
/*鏈表存儲數組，把epoll變成對事件的管理,用鏈表數組的目的就是為瞭回調函數*/
/*recv寫法：代碼邏輯是收到數據後，立即原樣返回所以才那樣寫*/
#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_LENGTH 4096
#define MAX_EPOLL_EVENTS 1024
#define SERVER_PORT 8888
#define PORT_COUNT 100
typedef int NCALLBACK(int ,int, void*);
//struct ntyevent *evs = (struct ntyevent*)malloc((MAX_EPOLL_EVENTS) * sizeof(struct ntyevent));
struct ntyevent {
int fd;//要監聽的文件描述符
int events;//對應的監聽事件， EPOLLIN和EPOLLOUT（不同的事件，走不同的回調函數）
void *arg;//指向自己結構體指針
int (*callback)(int fd, int events, void *arg);
int status;//是否在監聽：1->在紅黑樹上（監聽），0->不在（不監聽）
char buffer[BUFFER_LENGTH];
int length;
long last_active;
};
struct eventblock {
struct eventblock *next;
struct ntyevent *events;//數組
};
struct ntyreactor {
//句柄
int epfd;
//結點個數
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sockfd
void 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);
//對監聽的epoll紅黑樹上的結點的修改
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;
}
/*存儲*/
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;
}
//新增塊數(eventblock結點個數)
//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;
//如果塊數(eventblock結點個數)不能滿足新的sockfd的存放
while (blkidx >= reactor->blkcnt) {
//新增塊數(eventblock結點個數)
ntyreactor_alloc(reactor);
}
//找到存放sockfd的塊(eventblock對應的結點)
int i = 0;
struct eventblock *blk = reactor->evblk;
while(i ++ < blkidx && blk != NULL) {
blk = blk->next;
}
//返回對應塊(eventblock對應的結點)的存放sockfd數組的那個具體位置
return &blk->events[sockfd % MAX_EPOLL_EVENTS];
}
//初始化鏈表
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);
//上樹，並初始化鏈表數組上對應的fd
int 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所在的具體位置
struct ntyevent *event = ntyreactor_idx(reactor, sockfd);
初始化sockfd
nty_event_set(event, sockfd, acceptor, reactor);
//對監聽的epoll紅黑樹上的結點的修改
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) {
/*
long now = time(NULL);
for (i = 0;i < 100;i ++, checkpos ++) {
if (checkpos == MAX_EPOLL_EVENTS) {
checkpos = 0;
}
if (reactor->events[checkpos].status != 1) {
continue;
}
long duration = now - reactor->events[checkpos].last_active;
if (duration >= 60) {
close(reactor->events[checkpos].fd);
printf("[fd=%d] timeout\n", reactor->events[checkpos].fd);
nty_event_del(reactor->epfd, &reactor->events[checkpos]);
}
}
*/
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連接是否發生變化
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 8888
if (argc == 2) {
port = atoi(argv[1]);//把參數 str 所指向的字符串轉換為一個整數（類型為 int 型）
}
struct ntyreactor *reactor = (struct ntyreactor*)malloc(sizeof(struct ntyreactor));
/*初始化三個結構體，建立鏈表*/
ntyreactor_init(reactor);
int i = 0;
int sockfds[PORT_COUNT] = {0};
for (i = 0;i < PORT_COUNT;i ++) {
//端口號的監聽
sockfds[i] = init_sock(port+i);
//上樹
ntyreactor_addlistener(reactor, sockfds[i], accept_cb);
}
// epoll_wait
ntyreactor_run(reactor);
//
ntyreactor_destory(reactor);
for (i = 0;i < PORT_COUNT;i ++) {
close(sockfds[i]);
}
free(reactor);
return 0;
}
reactor的寫法感覺和epoll的普通寫法，感覺差別就是reactor多瞭個回調函數，具體沒啥優點？
epoll是針對io的管理。 reactor對針對事件的管理
不同的事件，針對不同的回調函數
性能上沒啥差異，但提高瞭代碼的復用性。具體需要自己慢慢體會體會，嗚嗚嗚嗚還有體會到，編程思想不過關。
二、環境設置
限制是fd的限制，系統默認fd最多有1024個，按照一個連接一個fd的做法，那就需要百萬個fd。這裡有兩種修改方法，一是使用ulimit -n命令，這個命令重啟就失效；二是修改/etc/security/limits.conf文件，這是永久有效的，重啟或sysctl -p生效。
* hard nofile 1048576 * soft nofile 1048576
hard是硬限制，不能超過該值，soft是軟限制，可以超過，超過後就開始回收。
這個文件裡還有一些其他的參數可以瞭解一下，fs.file_max是fd可取到的最大值，註意與fd最大個數區分。
突破這兩個限制後，還會遇到一個問題，客戶端會報錯：connection timedout。連接超時，即是客戶端未收到服務器對客戶端connect()的回應包。這裡有兩種可能，客戶端為收到服務器的包或是服務器未收到客戶端的connect包。事實上，是因為系統有個防火墻iotables，這個防火墻是基於網卡和協議棧之間的過濾機制netfilter實現的。netfilter當連接數到達一定程度時，會不允許再向外發送connect包。修改也是通過/etc/security/limits.conf文件
net.nf_conntrack_max=1048576
突破這些限制，就可以實現百萬並發瞭。
這裡再介紹/etc/security/limits.conf中幾個參數
net.ipv4.tcp_mem=262144 524288 786432是所有TCP協議棧所占空間的大小，單位是頁（4KB）。介紹一下後面寫的三個值，當所占空間大小超過第二個值時，系統會進行優化，此時如果占用空間降到第一個值以下，不再優化，第三個值是上限，不允許分配超過比大小的空間。
net.ipv4.tcp_wmem=2048 2048 4096是每個socket對應的寫緩沖區大小，三個值分別是最小值、默認值、最大值，單位是B。
net.ipv4.tcp_rmem=2048 2048 4096是每個socket對應的讀緩沖區大小，三個值分別是最小值、默認值、最大值，單位是B。
做百萬並發時，如果內存不大，可以相應調小。在實際應用中，如果傳輸大文件，調大；如果傳輸的都是字符，調小，就可以接收更多fd。
到此這篇關於C++基於reactor的服務器百萬並發實現的文章就介紹到這瞭,更多相關reactor服務器百萬並發內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet！
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