nginx+keepalived配置高可用HTTP群集
Nginx不仅是一款优秀的WEB服务器,同时可以根据nginx的反代理可以配置成强大的负载均衡器.这里就介绍如何把nginx配置成负载均衡器,并结合keepalived配置高可用的集群.一般集群主要架构为:
前端为负载均衡器两个:主/备,两种工作方式,一种是备机待机状态,主机故障时备机接管主机工作实现故障庄毅,在主机故障恢复完成时备机继续仅需待机状态,第二种是主备同时工作,一台宕机另外一台自动接管另一台的工作实现故障转移.
第一种方式可以通过将域名解析到一个虚拟ip(vip)上,主负载均衡器绑定虚拟ip,当主负载均衡器出现故障时,通过keepalived自动将vip绑定到备用负载均衡器上同时arping网关刷新MAC地址.,避免单点故障.
第二种方式主备同时绑定一个vip,把域名通过DNS轮询的方式解析到这两个服务器上,主机出现故障,备机就将主机绑定vip绑定到备机上,同时arping网关刷新MAC地址.实现故障转移.
中间为WEB服务器作为real server,处理请求.
后端为数据库和分布式文件系统.数据库一般为主从两台.分布式文件系统有效解决WEB服务器之间的数据同步.有的还会将图片服务器单独分离出来放在后端.
本文使用环境:
CentOS 5.5 32位
nginx:nginx-1.0.11
keepalived：keepalived-1.1.19.tar.gz
主调度器:192.168.3.1
备调度器:192.168.3.2
real server:192.168.3.4/5/6
本文采用第一种方式来进行vip为:192.168.3.253
一、在主备服务器上部署nginx
1.下载
wget http://nginx.org/download/nginx-1.0.11.tar.gz
2.安装
yum -y install zlib-devel pcre-devel openssl-devel #安装依赖 tar -zxvf nginx-1.0.11.tar.gz
cd nginx-1.0.11
./configure --prefix=/usr/local/nginx --with-http_ssl_module --with-http_flv_module --with-http_gzip_static_module
make && make install
3.配置
配置主调度器的nginx,编辑nginx.conf
vi /usr/local/nginx/conf/nginx.conf
http {
include mime.types;
default_typeapplication/octet-stream;
#log_formatmain'$remote_addr - $remote_user [$time_local] "$request" '
# '$status $body_bytes_sent "$http_referer" '
# '"$http_user_agent" "$http_x_forwarded_for"';
#access_loglogs/access.logmain;
sendfile on;
#tcp_nopush on;
#keepalive_timeout0;
keepalive_timeout65;
#gzipon;
# 添加一组真实的服务器地址池
# 供proxy_pass和fastcgi_pass指令中使用的代理服务器
upstream real_server_pool {
# 后台如果有动态应用的时候,ip_hash指令可以通过hash算法
# 将客户端请求定位到同一台后端服务器上,解决session共享,
# 但建议用动态应用做session共享
# ip_hash;
# server用于指定一个后端服务器的名称和参数
# weight代表权,重默认为1,权重越高被分配的客户端越多
# max_fails 指定时间内对后端请求失败的次数
# fail_timeout 达到max_fails指定的失败次数后暂停的时间
server192.168.3.4:80 weight=1 max_fails=2 fail_timeout=30s;
# down参数用来标记为离线,不参与负载均衡.在ip_hash下使用
# 在此做演示,后面测试会去掉
server192.168.3.5:80 weight=1 max_fails=2 fail_timeout=30s down;
# backup仅仅在非backup服务器宕机或繁忙的时候使用
# (在此做演示,后面测试会去掉)
server192.168.3.6:80 weight=1 max_fails=2 fail_timeout=30s backup;
}
server {
listen 192.168.3.1:80;
server_namelocalhost;
#charset koi8-r;
#access_loglogs/host.access.logmain;
location / {
#root html;
#indexindex.html index.htm;
# 使用upstream设置的一组代理服务器
# 如果后端服务器出现502或504等执行错误时,
# 将自动将请求转发给负载均衡池中的另一台服务器.
proxy_next_upstream http_502 http_504 error timeout invalid_header;
proxy_pass http://real_server_pool;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $remote_addr;
}
}
}
http {
include mime.types;
default_typeapplication/octet-stream;
#log_formatmain'$remote_addr - $remote_user [$time_local] "$request" '
# '$status $body_bytes_sent "$http_referer" '
# '"$http_user_agent" "$http_x_forwarded_for"';
#access_loglogs/access.logmain;
sendfile on;
#tcp_nopush on;
#keepalive_timeout0;
keepalive_timeout65;
#gzipon;
upstream real_server_pool {
#ip_hash;
server192.168.3.4:80 weight=1 max_fails=2 fail_timeout=30s;
server192.168.3.5:80 weight=1 max_fails=2 fail_timeout=30s;
server192.168.3.6:80 weight=1 max_fails=2 fail_timeout=30s;
}
server {
listen 192.168.3.2:80; # 监听ip改为本地ip
server_namelocalhost;
#charset koi8-r;
#access_loglogs/host.access.logmain;
location / {
#root html;
#indexindex.html index.htm;
proxy_next_upstream http_502 http_504 error timeout invalid_header;
proxy_pass http://real_server_pool;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $remote_addr;
}
然后启动主备nginx:
/usr/local/nginx/sbin/nginx
二、在主备服务器上部署keepalived
安装
安装依赖:
yum -y install kernel-devel # 安装依赖
开启路由转发:
vi /etc/sysctl.conf
net.ipv4.ip_forward = 1 # 此参数改为1
sysctl -p # 使修改生效
首先安装ipvs:
ln -s /usr/src/kernels/2.6.18-194.el5-i686/ /usr/src/linux# ipvs需要内核文件,做一个软连接
# 下载
wget http://www.linuxvirtualserver.org/software/kernel-2.6/ipvsadm-1.24.tar.gz
tar -zxvf ipvsadm-1.24.tar.gz
cd ipvsadm-1.24
make
make install
然后安装keepalived
# 下载
wget http://www.keepalived.org/software/keepalived-1.1.19.tar.gz
tar -zxvf keepalived-1.1.19.tar.gz
cd keepalived-1.1.19
./configure --prefix=/ \ # 安装在默认位置(配置文件,二进制文件,启动脚本放到默认位置)
--mandir=/usr/local/share/man/ \
--with-kernel-dir=/usr/src/kernels/2.6.18-194.el5-i686/ # 需要内核的头文件
make && make install
配置keepalived
编辑主调度器配置文件/etc/keepalived/keepalived.conf
global_defs {
notification_email {
cold_night@linuxzen.com # 定义通知邮箱,有多个可以换行添加
}
notification_email_from root@linuxzen.com# 定义发送邮件的邮箱
smtp_server www.linuxzen.com # 定义发件服务器
smtp_connect_timeout 30 # 定义连接smtp服务器超时时间
router_id LVS_DEVEL
}
vrrp_instance VI_1 {
state MASTER # 标示主备,备机上改为BACKUP
interface eth0 # HA监测的端口
virtual_router_id 51 # 主备的virtual_router_id的值必须相同
priority 100 # 优先级,通常主要比备稍大
advert_int 1 # VRRP Multicast 广播周期秒数
authentication { # 定义认证
auth_type PASS # 认证方式
auth_pass 1111 # 认证口令字
}
virtual_ipaddress { # 定义vip
192.168.3.253 # 多个可换行添加,一行一个
}
}
virtual_server 192.168.3.253 80 {
delay_loop 6 # 每隔 6 秒查询 realserver 状态
lb_algo rr
lb_kind NAT
nat_mask 255.255.255.0
persistence_timeout 50 # 同一IP 的连接50秒内被分配到同一台realserver
protocol TCP # 用TCP监测realserver的状态
real_server 192.168.3.1 80 {
weight 3 # 权重
TCP_CHECK {
connect_timeout 10# 10秒无响应超时
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
real_server 192.168.3.2 80 {
weight 3
TCP_CHECK {
connect_timeout 3
delay_before_retry 3
connect_port 80
}
}
}
配置备用调度器的keepalived,只需要将state MASTER 改为state BACKUP,降低priority 100 的值:
global_defs {
notification_email {
cold_night@linuxzen.com
}
notification_email_from root@linuxzen.com
smtp_server www.linuxzen.com
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_instance VI_1 {
state BACKUP # 备机上改为BACKUP
interface eth0
virtual_router_id 51 # 主备的virtual_router_id的值必须相同
priority 99 # 备用优先级小于主调度器
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.3.253
}
}
virtual_server 192.168.3.253 80 {
delay_loop 6
lb_algo rr
lb_kind NAT
nat_mask 255.255.255.0
persistence_timeout 50
protocol TCP
real_server 192.168.3.1 80 {
weight 3
TCP_CHECK {
connect_timeout 10
nb_get_retry 3
delay_before_retry 3
connect_port 80
}
}
real_server 192.168.3.2 80 {
weight 3
TCP_CHECK {
connect_timeout 3
delay_before_retry 3
connect_port 80
}
}
}
主备上启动keepalived:
service keepalived start
三、测试—–部署后端服务器
在后端服务器安装nginx,这里仅部署一台然后创建3个基于ip的虚拟主机供测试:
绑定ip:
ifconfig eth0:1 192.168.3.4/24
ifconfig eth0:2 192.168.3.5/24
ifconfig eth0:3 192.168.3.6/24
安装nginx后编辑配置文件,在http块里添加:
http {
server {
listen192.168.3.4:80;
server_name 192.168.3.4;
location / {
root html/s1;
index index.html index.htm;
}
}
server {
listen192.168.3.5:80;
server_name 192.168.3.5;
location / {
root html/s2;
index index.html index.htm;
}
}
server {
listen 192.168.3.6:80;
server_name 192.168.3.5;
location / {
root html/s3;
index index.html index.htm;
}
}
}
创建虚拟主机根目录,并创建不通的首页文档:
cd /usr/local/nginx/html/
mkdir s1 s2 s3
echo server1 > s1/index.html
echo server2 > s2/index.html
echo server3 > s3/index.html
启动nginx:
/usr/local/nginx/sbin/nginx
打开浏览器访问http://192.168.3.253
刷新会看到显示不同的内容:server1,server2,server3(生产中的服务器应该是一样的)
http://www.linuxzen.com/wp-content/uploads/test2.jpg
http://www.linuxzen.com/wp-content/uploads/test1.jpg 现在停掉主调度器的keepalived
pkill keepalived
查看备调度器的日志:
cat /var/log/messages
Feb 10 16:36:27 cfhost Keepalived_vrrp: VRRP_Instance(VI_1) Transition to MASTER STATE
Feb 10 16:36:28 cfhost Keepalived_vrrp: VRRP_Instance(VI_1) Entering MASTER STATE
Feb 10 16:36:28 cfhost Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.
Feb 10 16:36:28 cfhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.3.253
Feb 10 16:36:28 cfhost Keepalived_vrrp: Netlink reflector reports IP 192.168.3.253 added
Feb 10 16:36:28 cfhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.3.253 added
Feb 10 16:36:33 cfhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.3.253
现在访问http://192.168.3.253依然可以访问.
大家也看到了备机keepalived只有检测主机的keepalived停止的时候才会切换vip,而不是检测一台real server的某一服务(比如检测80端口的HTTP)切换vip,所以在nginx进程停止的时候,如果服务器没有宕机这时候就无法实现故障转移,所以我们编写一个检测nginx状态的脚本结合keepalived实现故障转移:
#!/bin/bash
#filename:nsc.sh
ps aux | grep nginx | grep -v grep 2> /dev/null 1>&2 # 过滤nginx进程
if [[ $? -eq 0 ]] # 如果过滤有nginx进程会返回0则认为nginx存活
then
sleep 5 # 使脚本进入休眠
else
# 如果nginx没有存活尝试启动nginx,如果失败则杀死keepalived的进程
/usr/local/nginx/sbin/nginx
ps aux | grep nginx | grep -v grep 2> /dev/null 1>&2
if [[ $? -eq 0 ]]
then
pkill keepalived
fi
fi
然后后台运行此脚本:
nohup sh nsc.sh &
这样就实现了群集的高可靠和高可用.
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