实现一台服务器的百万并发,服务器支撑百万连接会出现哪些问题,如何排查与解决这些问题 是本文的重点
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服务器能够同时建立连接的数量 不是 并发量,它只是并发量一个基础。
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服务器的并发量:一个服务器能够同时承载客户端的数量;
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承载:服务器能够稳定的维持这些连接,能够响应请求,在200ms内返回响应就认为是ok的,其中这200ms包括数据库的操作,网络带宽,内存操作,日志等时间。
服务器 采用 1台 centos7 12G 1核虚拟机
客户端 采用 2台 centos7 3G 1核虚拟机
服务器代码:单reactor单线程,IO多路复用使用epoll
客户端代码:IO多路复用使用epoll,每个客户端发51w个连接,每个连接发送一次数据,读取一次数据之后不再发送数据
由于fd的数量未知,这里设计ntyreactor 里面包含 eventblock ,eventblock 包含1024个fd。每个fd通过 fd/1024定位到在第几个eventblock,通过fd%1024定位到在eventblock第几个位置。
struct ntyevent {
int fd;
int events;
void *arg;
NCALLBACK callback;
int status;
char buffer[BUFFER_LENGTH];
int length;
};
struct eventblock {
struct eventblock *next;
struct ntyevent *events;
};
struct ntyreactor {
int epfd;
int blkcnt;
struct eventblock *evblk;
};
#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>
#define BUFFER_LENGTH 4096
#define MAX_EPOLL_EVENTS 1024
#define SERVER_PORT 8081
#define PORT_COUNT 100
typedef int (*NCALLBACK)(int, int, void *);
struct ntyevent {
int fd;
int events;
void *arg;
NCALLBACK callback;
int status;
char buffer[BUFFER_LENGTH];
int length;
};
struct eventblock {
struct eventblock *next;
struct ntyevent *events;
};
struct ntyreactor {
int epfd;
int blkcnt;
struct eventblock *evblk;
};
int recv_cb(int fd, int events, void *arg);
int send_cb(int fd, int events, void *arg);
struct ntyevent *ntyreactor_find_event_idx(struct ntyreactor *reactor, int 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;
}
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_find_event_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("recv[%d]:%s\n", fd, ev->buffer);
printf("recv fd=[%d\n", fd);
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_find_event_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);
printf("send fd=[%d\n]", fd);
nty_event_del(reactor->epfd, ev);
nty_event_set(ev, fd, recv_cb, reactor);
nty_event_add(reactor->epfd, EPOLLIN, ev);
}
else {
nty_event_del(reactor->epfd, ev);
close(ev->fd);
printf("send[fd=%d] error %s\n", fd, strerror(errno));
}
return len;
}
int accept_cb(int fd, int events, void *arg) {//非阻塞
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) {
printf("accept: %s\n", strerror(errno));
return -1;
}
if ((fcntl(clientfd, F_SETFL, O_NONBLOCK)) < 0) {
printf("%s: fcntl nonblocking failed, %d\n", __func__, MAX_EPOLL_EVENTS);
return -1;
}
struct ntyevent *event = ntyreactor_find_event_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;
}
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 *ntyreactor_find_event_idx(struct ntyreactor *reactor, int sockfd) {
int blkidx = sockfd / MAX_EPOLL_EVENTS;
while (blkidx >= reactor->blkcnt) {
ntyreactor_alloc(reactor);
}
int i = 0;
struct eventblock *blk = reactor->evblk;
while (i++ < blkidx && blk != NULL) {
blk = blk->next;
}
return &blk->events[sockfd % MAX_EPOLL_EVENTS];
}
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;
}
int ntyreactor_addlistener(struct ntyreactor *reactor, int sockfd, NCALLBACK *acceptor) {
if (reactor == NULL) return -1;
if (reactor->evblk == NULL) return -1;
struct ntyevent *event = ntyreactor_find_event_idx(reactor, sockfd);
nty_event_set(event, sockfd, acceptor, reactor);
nty_event_add(reactor->epfd, EPOLLIN, event);
return 0;
}
_Noreturn 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 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;
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);
}
}
}
}
// <remoteip, remoteport, localip, localport,protocol>
int main(int argc, char *argv[]) {
unsigned short port = SERVER_PORT; // listen 8081
if (argc == 2) {
port = atoi(argv[1]);
}
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++) {
sockfds[i] = init_sock(port + i);
ntyreactor_addlistener(reactor, sockfds[i], accept_cb);
}
ntyreactor_run(reactor);
ntyreactor_destory(reactor);
for (i = 0; i < PORT_COUNT; i++) {
close(sockfds[i]);
}
free(reactor);
return 0;
}
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/epoll.h>
#include <errno.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <fcntl.h>
#include <sys/time.h>
#include <unistd.h>
#define MAX_BUFFER 128
#define MAX_EPOLLSIZE (384*1024)
#define MAX_PORT 100
#define TIME_SUB_MS(tv1, tv2) ((tv1.tv_sec - tv2.tv_sec) * 1000 + (tv1.tv_usec - tv2.tv_usec) / 1000)
int isContinue = 0;
static int ntySetNonblock(int fd) {
int flags;
flags = fcntl(fd, F_GETFL, 0);
if (flags < 0) return flags;
flags |= O_NONBLOCK;
if (fcntl(fd, F_SETFL, flags) < 0) return -1;
return 0;
}
static int ntySetReUseAddr(int fd) {
int reuse = 1;
return setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse));
}
int main(int argc, char **argv) {
if (argc <= 2) {
printf("Usage: %s ip port\n", argv[0]);
exit(0);
}
const char *ip = argv[1];
int port = atoi(argv[2]);
int connections = 0;
char buffer[128] = {0};
int i = 0, index = 0;
struct epoll_event events[MAX_EPOLLSIZE];
int epoll_fd = epoll_create(MAX_EPOLLSIZE);
strcpy(buffer, " Data From MulClient\n");
struct sockaddr_in addr;
memset(&addr, 0, sizeof(struct sockaddr_in));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = inet_addr(ip);
struct timeval tv_begin;
gettimeofday(&tv_begin, NULL);
while (1) {
if (++index >= MAX_PORT) index = 0;
struct epoll_event ev;
int sockfd = 0;
if (connections < 340000 && !isContinue) {
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1) {
perror("socket");
goto err;
}
//ntySetReUseAddr(sockfd);
addr.sin_port = htons(port+index);
if (connect(sockfd, (struct sockaddr*)&addr, sizeof(struct sockaddr_in)) < 0) {
perror("connect");
goto err;
}
ntySetNonblock(sockfd);
ntySetReUseAddr(sockfd);
sprintf(buffer, "Hello Server: client --> %d\n", connections);
send(sockfd, buffer, strlen(buffer), 0);
ev.data.fd = sockfd;
ev.events = EPOLLIN | EPOLLOUT;
epoll_ctl(epoll_fd, EPOLL_CTL_ADD, sockfd, &ev);
connections ++;
}
//connections ++;
if (connections % 1000 == 999 || connections >= 340000) {
struct timeval tv_cur;
memcpy(&tv_cur, &tv_begin, sizeof(struct timeval));
gettimeofday(&tv_begin, NULL);
int time_used = TIME_SUB_MS(tv_begin, tv_cur);
printf("connections: %d, sockfd:%d, time_used:%d\n", connections, sockfd, time_used);
int nfds = epoll_wait(epoll_fd, events, connections, 100);
for (i = 0;i < nfds;i ++) {
int clientfd = events[i].data.fd;
if (events[i].events & EPOLLOUT) {
sprintf(buffer, "data from %d\n", clientfd);
send(sockfd, buffer, strlen(buffer), 0);
} else if (events[i].events & EPOLLIN) {
char rBuffer[MAX_BUFFER] = {0};
ssize_t length = recv(sockfd, rBuffer, MAX_BUFFER, 0);
if (length > 0) {
printf(" RecvBuffer:%s\n", rBuffer);
if (!strcmp(rBuffer, "quit")) {
isContinue = 0;
}
} else if (length == 0) {
printf(" Disconnect clientfd:%d\n", clientfd);
connections --;
close(clientfd);
} else {
if (errno == EINTR) continue;
printf(" Error clientfd:%d, errno:%d\n", clientfd, errno);
close(clientfd);
}
} else {
printf(" clientfd:%d, errno:%d\n", clientfd, errno);
close(clientfd);
}
}
}
usleep(1 * 1000);
}
return 0;
err:
printf("error : %s\n", strerror(errno));
return 0;
}
程序执行到一半,创建了1023个连接后,报错Too many open files
//服务端
new connect [192.168.109.101:36994], pos[1019]
new connect [192.168.109.101:55832], pos[1020]
new connect [192.168.109.101:43460], pos[1021]
new connect [192.168.109.101:59938], pos[1022]
new connect [192.168.109.101:46098], pos[1023]
accept: Too many open files
accept: Too many open files
//客户端
connect: Connection refused
error : Connection refused
怀疑是文件系统默认允许打开文件描述符数量个数(默认1024)的限制,使用ulimit -a查看open files的数量
open files:一个进程能够打开文件描述符的数量
[root@master temp]# ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 47748
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 47748
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
那么我们把open files调大一点点,看是否会停在2047,如果是,则说明问题就是open files太小的问题,实验发现就是这个原因。
[root@master temp]# ulimit -n 2048
[root@master temp]# ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 47748
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 2048
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 47748
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
new connect [192.168.109.101:53996], pos[2046]
new connect [192.168.109.101:60742], pos[2047]
accept: Too many open files
- 临时修改,只在当前这个会话有效:ulimit -n 1048576
- 永久修改,对所有会话有效:添加下面两行代码
注意这里修改的是:一个进程能够打开文件描述符的数量
[root@master temp]# vim /etc/security/limits.conf
# 修改
[root@master temp]# reboot
# 重启生效
这里还需要注意一点:file-max : 系统一共可以打开的最大文件数(所有进程加起来)
[root@master temp]# cat /proc/sys/fs/file-max
1202172
# 编辑内核参数配置文件
vim /etc/sysctl.conf
# 修改fs.file-max参数
fs.file-max = 1048576
# 重新加载配置文件
sysctl -p
另外这里建议ulimit -n 和limits.conf里nofile 设定最好不要超过/proc/sys/fs/file-max的值(虽然我测试了超过也没关系),这个小问题仁者见仁智者见智了,网上找到比较好的文章是这篇linux最大文件句柄数量之(file-max ulimit -n limit.conf)
现在的环境背景:服务器只开放一个端口,客户端不断的去请求去连接。然后客户端error : Cannot assign requested address
Cannot assign requested address这代表着客户端端口耗尽,我们先来看看如何确定一个fd,反过来说一个fd代表着什么
socket fd --- < 源IP地址 , 源端口 , 目的IP地址 , 目的端口 , 协议 > 一个fd就是一个五元组,在现在的环境中,五元组里面确定了四个,所以最多创建 1 * 源端口 * 1 * 1 * 1个fd
# 服务端
new connect [192.168.109.101:57921], pos[28234]
new connect [192.168.109.101:57923], pos[28235]
send[fd=21003] error Connection reset by peer
send[fd=22003] error Connection reset by peer
# 客户端
connections: 26999, sockfd:27002, time_used:2399
connections: 27999, sockfd:28002, time_used:2404
connect: Cannot assign requested address
error : Cannot assign requested address
我们看到大概创建了2.8w的fd , 可是我们知道端口一个有6w多个,也就是说有6w个端口,为什么我们只使用了2.8w个?
我们看到大概创建了2.8w的fd , 可是我们知道端口一个有6w多个,也就是说有6w个端口,为什么我们只使用了2.8w个?
Linux中有限定端口的使用范围:60999 - 32768 = 2.8w ,与我们上面实验结果相符。
The /proc/sys/net/ipv4/ip_local_port_range defines the local port range that is used by TCP and UDP traffic to choose the local port. You will see in the parameters of this file two numbers: The first number is the first local port allowed for TCP and UDP traffic on the server, the second is the last local port number. For high-usage systems you may change its default parameters to 32768-61000 -first-last.
proc/sys/net/ipv4/ip_local_port_range范围定义TCP和UDP通信用于选择本地端口的本地端口范围。您将在该文件的参数中看到两个数字:第一个数字是服务器上允许TCP和UDP通信的第一个本地端口,第二个是最后一个本地端口号。对于高使用率的系统,您可以将其默认参数更改为32768-61000(first-last)。
[root@master temp]# sysctl net.ipv4.ip_local_port_range
net.ipv4.ip_local_port_range = 32768 60999
修改net.ipv4.ip_local_port_range的范围,一般不这样做,我们这里研究的是服务器,怎么会去对客户端进行修改呢 之前已经说了这个问题的背景,就是只开放了一个端口,并且socket fd --- < 源IP地址 , 源端口, 目的IP地址 , 目的端口 , 运输层协议 >,在这个背景下才产生的这个问题,所以我们可以开放更多的端口,比如说100个,那么一个客户端就能连到280w了 error : Connection timed out 确定问题 我们将服务器端口开100个,按理说客户端可以连280w,但是现在只连接到13w就error : Connection timed out,与我们的预期不符
//服务端
new connect [192.168.109.101:54585], pos[131165]
new connect [192.168.109.101:48265], pos[131166]
new connect [192.168.109.101:51997], pos[131167]
new connect [192.168.109.101:43239], pos[131168]
send[fd=20102] error Connection reset by peer
send[fd=21102] error Connection reset by peer
send[fd=22102] error Connection reset by peer
//客户端
connections: 127999, sockfd:128002, time_used:7576
connections: 128999, sockfd:129002, time_used:2683
connections: 129999, sockfd:130002, time_used:2669
connections: 130999, sockfd:131002, time_used:4610
connect: Connection timed out
error : Connection timed out
网卡接收的数据,会发送到协议栈里面,通过sk_buff将数据传到协议栈,协议栈处理完再交给应用程序。由于操作系统在使用的时候,为防止被攻击,在数据发送给协议栈之前进行一个过滤,在协议栈前面加了一个小组件:过滤器,叫做netfilter。 netfilter主要是对网络数据包进行一个过滤,在netfilter的基础上我们就可以实现防火墙,在linux里面有一个就叫做iptables,iptables是基于netfilter做的,iptables分为两部分,一部分是内核实现的netfilter接口,一部分是应用程序提供给用户使用的。iptables真正实现的是netfilter提供的接口。
Connection timed out译为连接超时,也就是说,client发送的请求超时了,那么这个超时有两种情况,第一种:三次握手第一次的SYN没发出去,第二种:三次握手第二次ACK没收到。
netfilter不管对发送的数据,还是对接收的数据,都是可以过滤的。当连接数量达到一定数量的时候,netfilter就会不允许再对外发连接了。所以现在推测是情况1造成的,发送的SYN被netfilter拦截了。
事实是这样吗,我们来查看一下netfilter允许对外最大连接数量是多少。13w,与我们上面建立成功的数量一致,所以现在就可以确定是netfilter允许对外开放的最大连接数造成的了
[root@node1 temp]# cat /proc/sys/net/netfilter/nf_conntrack_max
131072
解决问题 我们可以通过设置netfilter允许对外最大连接数量,来解决这个问题
# 查看允许对外最大连接数量
[root@node1 temp]# cat /proc/sys/net/netfilter/nf_conntrack_max
131072
# 进行配置
vim /etc/sysctl.conf
# 在配置文件中把net.nf_conntrack_max参数修改为1048576(如果配置就自己添加一行)
net.nf_conntrack_max = 1048576
# 重新加载配置文件
sysctl -p
# 再次查看,发现生效了
[root@node1 temp]# cat /proc/sys/net/netfilter/nf_conntrack_max
1048576
这里我们先给客户端虚拟机2G的内存,然后发现到24w的时候,客户端进程被杀死了
connections: 239999, sockfd:240002, time_used:9837
connections: 240999, sockfd:241002, time_used:10608
connections: 241999, sockfd:242002, time_used:13109
connections: 242999, sockfd:243002, time_used:15112
connections: 243999, sockfd:244002, time_used:12606
已杀死
我们来看一下kill记录,发现是内存不足。
[root@node1 ~]# dmesg | egrep -i -B100 'killed process'
[ 2310.265218] Out of memory: Kill process 7266 (C1000Kclient) score 1 or sacrifice child
[ 2310.265962] Killed process 7266 (C1000Kclient) total-vm:8708kB, anon-rss:2960kB, file-rss:0kB, shmem-rss:0kB
这里直接说原因吧,是因为程序每个fd都有一个tcp接收缓冲区和tcp发送缓冲区。而默认的太大了,导致Linux内存不足,进程被杀死,所有我们需要适当的缩小。进程空间,代码段,堆栈都是要占用内存的。
我们只需要对net.ipv4.tcp_mem,net.ipv4.tcp_wmem,net.ipv4.tcp_rmem进行适合的修改即可
# 编辑内核参数配置文件
vim /etc/sysctl.conf
# 添加以下内容
# 最小值 默认值 最大值
net.ipv4.tcp_mem = 252144 524288 786432 # tcp协议栈的大小,单位为内存页(4K),分别是 1G 2G 3G,如果大于2G,tcp协议栈会进行一定的优化
net.ipv4.tcp_wmem = 1024 1024 2048 # tcp接收缓存区(用于tcp接受滑动窗口)的最小值,默认值和最大值(单位byte)1k 1k 2k,每一个连接fd都有一个接收缓存区
net.ipv4.tcp_rmem = 1024 1024 2048 # tcp发送缓存区(用于tcp发送滑动窗口)的最小值,默认值和最大值(单位byte)1k 1k 2k,每一个连接fd都有一个发送缓存区
# 总缓存 = (每个fd发送缓存区 + 每个fd接收缓存区) * fd数量
# (1024byte + 1024byte ) * 100w 约等于 2G
如果服务器是用来接收大文件,传输量很大的时候,就要把send buffer和read buffer调大。 如果服务器只是接收小数据字符的时候。把buffer调小是为了把fd的数量做到更多,并发数量能做到更大。如果buffer调大的话,内存会不够。
想要实现服务器百万并发:
一个进程能够打开文件描述符的数量open files 和 file-max 改成100w以上 在不同的环境下要看开放的端口够不够socket fd --- < 源IP地址 , 源端口 , 目的IP地址 , 目的端口 , 协议 > 设置netfilter允许对外最大连接数量100w以上 根据内存和场景,适当调整net.ipv4.tcp_mem,net.ipv4.tcp_wmem,net.ipv4.tcp_rmem ———————————————— 版权声明:本文为CSDN博主「cheems~」的原创文章,遵循CC 4.0 BY-SA版权协议,转载请附上原文出处链接及本声明。 原文链接:https://blog.csdn.net/qq_42956653/article/details/125653754