Keepalived學習筆記二:keepalived實現nginx的高可用
本文所需環境 tomcat + nginx + keepalived 。關於tomcat和nginx請自行學習。
一.主節點:修改keepalived.conf 的內容（keepalived的配置檔案預設放在/etc/keeplived下，安裝的時候啟動不了，後來手動建立了keeplived和keepalived.conf檔案，才啟動成功。）內容如下：
global_defs { notification_email { [email protected] } notification_email_from [email protected]smtp_server smtp.hysec.com smtp_connection_timeout 30 router_id nginx_master # 設定nginx master的id，在一個網路應該是唯一的 } vrrp_script chk_http_port { script "/usr/local/src/check_nginx_pid.sh" #最後手動執行下此指令碼，以確保此指令碼能夠正常執行 interval 2 #（檢測指令碼執行的間隔，單位是秒） weight 2 } vrrp_instance VI_1 { state MASTER # 指定keepalived的角色，MASTER為主，BACKUP為備 interface eth0 # 當前進行vrrp通訊的網路介面卡(當前centos的網絡卡) virtual_router_id 66 # 虛擬路由編號，主從要一直 priority 100 # 優先順序，數值越大，獲取處理請求的優先順序越高 advert_int 1 # 檢查間隔，預設為1s(vrrp組播週期秒數) authentication { auth_type PASS auth_pass 1111 } track_script { chk_http_port #（呼叫檢測指令碼） } virtual_ipaddress { 192.168.30.200 # 定義虛擬ip(VIP)，可多設，每行一個，且需要和nginx在同一個網段 } }
nginx檢測指令碼check_nginx_pid.sh內容如下：
#!/bin/bash A=`ps -C nginx --no-header |wc -l` if [ $A -eq 0 ];then /usr/local/nginx/sbin/nginx #重啟nginx if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then #nginx重啟失敗，則停掉keepalived服務，進行VIP轉移 killall keepalived fi fi
此時完成了keepalived對nginx的監控。keepalived會每兩秒(通過interval 2配置時間間隔) 傳送心跳檢查nginx埠是否能正常訪問。如果不能則執行指令碼重啟nginx（見check_nginx_pid.sh）。
驗證步驟：
啟動nginx，啟動keepalived。
3，將 interval （檢測指令碼執行的間隔，單位是秒）設定為10秒,停止nginx（./nginx -s stop）
5.啟動keepalived，此時keepalived傳送心跳發現nginx埠不通，執行指令碼啟動nginx 此時http://192.168.30.130/architecture1web/訪問正常
以上測試說明keepalived會監控nginx的埠狀態。如果nginx掛了會自動執行指令碼啟動nginx。
上面的操作只是單臺keeplived對nginx的監控。下面的是對keeplived做主從，當主節點掛了之後，從節點自動接管虛擬ip。
二.從節點:修改keepalived.conf 的內容如下：注意interface eth1 必須是真是的網絡卡地址通過ip addr查詢
global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
smtp_server smtp.hysec.com
smtp_connection_timeout 30
router_id nginx_backup # 設定nginx backup的id，在一個網路應該是唯一的
}
vrrp_script chk_http_port {
script "/usr/local/keepalived/sh/check_nginx_pid.sh"
interval 2 #（檢測指令碼執行的間隔）
weight 2
}
vrrp_instance VI_1 {
state BACKUP # 指定keepalived的角色，MASTER為主，BACKUP為備
interface eth1 # 當前進行vrrp通訊的網路介面卡(當前centos的網絡卡)
virtual_router_id 66 # 虛擬路由編號，主從要一直
priority 99 # 優先順序，數值越大，獲取處理請求的優先順序越高
advert_int 1 # 檢查間隔，預設為1s(vrrp組播週期秒數)
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
chk_http_port #（呼叫檢測指令碼）
}
virtual_ipaddress {
192.168.30.200 # 定義虛擬ip(VIP)，可多設，每行一個
}
}
啟動主節點的 keepalived （./keepalived），檢視啟動日誌如下：
Oct 7 02:26:16 yuyivie Keepalived_vrrp[9930]: Unknown keyword 'smtp_connection_timeout'
Oct 7 02:26:17 yuyivie Keepalived_vrrp[9930]: Using LinkWatch kernel netlink reflector...
Oct 7 02:26:17 yuyivie Keepalived_vrrp[9930]: VRRP_Script(chk_http_port) succeeded
Oct 7 02:26:18 yuyivie Keepalived_vrrp[9930]: VRRP_Instance(VI_1) Transition to MASTER STATE
Oct 7 02:26:18 yuyivie Keepalived_vrrp[9930]: VRRP_Instance(VI_1) Effective priority = 102
Oct 7 02:26:19 yuyivie Keepalived_vrrp[9930]: VRRP_Instance(VI_1) Entering MASTER STATE
Oct 7 02:26:21 yuyivie Keepalived_healthcheckers[9929]: Unknown keyword 'smtp_connection_timeout'
Oct 7 02:26:22 yuyivie Keepalived_healthcheckers[9929]: Using LinkWatch kernel netlink reflector啟動從節點的keepalived,檢視日誌如下：
[[email protected] sbin]# tail -f /var/log/messages
Oct 7 02:26:41 yuyivie Keepalived_vrrp[8995]: Opening file '/etc/keepalived/keepalived.conf'.
Oct 7 02:26:41 yuyivie Keepalived_healthcheckers[8994]: Registering Kernel netlink command channel
Oct 7 02:26:41 yuyivie Keepalived_healthcheckers[8994]: Opening file '/etc/keepalived/keepalived.conf'.
Oct 7 02:26:41 yuyivie Keepalived_vrrp[8995]: Unknown keyword 'smtp_connection_timeout'
Oct 7 02:26:41 yuyivie Keepalived_healthcheckers[8994]: Unknown keyword 'smtp_connection_timeout'
Oct 7 02:26:42 yuyivie Keepalived_vrrp[8995]: Using LinkWatch kernel netlink reflector...
Oct 7 02:26:42 yuyivie Keepalived_vrrp[8995]: VRRP_Instance(VI_1) Entering BACKUP STATE
Oct 7 02:26:42 yuyivie Keepalived_healthcheckers[8994]: Using LinkWatch kernel netlink reflector...
關閉主節點的keepalived，（此時從節點會自動頂上來做主節點）檢視下圖從節點日誌發現從節點自動變成主節點了。
Oct 7 02:43:18 yuyivie Keepalived_vrrp[8995]: pid 10034 exited with status 32256
Oct 7 02:43:20 yuyivie Keepalived_vrrp[8995]: pid 10036 exited with status 32256
Oct 7 02:43:21 yuyivie Keepalived_vrrp[8995]: VRRP_Instance(VI_1) Transition to MASTER STATE
Oct 7 02:43:22 yuyivie Keepalived_vrrp[8995]: VRRP_Instance(VI_1) Entering MASTER STATE
Oct 7 02:43:22 yuyivie Keepalived_vrrp[8995]: pid 10038 exited with status 32256
Oct 7 02:43:24 yuyivie Keepalived_vrrp[8995]: pid 10040 exited with status 32256
重新啟動主節點的keepalived,此時主節點會將重新託管虛擬ip，此時檢視從節點（因為主節點失效此時之前的從節點變成了主節點）日誌如下：
Oct 7 02:47:25 yuyivie Keepalived_vrrp[8995]: VRRP_Instance(VI_1) Received higher prio advert 100
Oct 7 02:47:25 yuyivie Keepalived_vrrp[8995]: VRRP_Instance(VI_1) Entering BACKUP STATE
Oct 7 02:47:27 yuyivie Keepalived_vrrp[8995]: pid 10283 exited with status 32256
Oct 7 02:47:29 yuyivie Keepalived_vrrp[8995]: pid 10285 exited with status 32256
以上測試說明主節點失效後從節點會變成主節點來託管虛擬ip，當重啟失效的主節點之後，主節點會重新重新託管虛擬ip，之前變為主節點的從節點，依舊為從節點。
總結：keepalived主備 + nginx 做服務高可用，。
託管一個虛擬ip：
a.主節點監控nginx，nginx掛了嘗試重啟。重啟失敗則自己pkill停止自己。
b.從節點監控主節點，主節點掛了，則自己頂上來做主節點。
c. 主節點重啟後，從節點讓出託管的主節點。。