While I know how to configure and run Redis master and slave on two different servers, I would like to whether my Webserver will be able to connect to slave redis server if the master redis server goes down?
If that is not the case, May I know how can I achieve that?
Thanks
Balaji
At the server side, for a simple failover, you can do it by using Nagios and NRPE.
On the Nagios server:
define service{ use critical-service host_name B service_description redis:2302 check_command check_tcp!2302 event_handler promote_redis!C!2302 contact_groups admin-sms,admin } define command{ command_name promote_redis command_line $USER1$/eventhandlers/promote_redis.sh $SERVICESTATE$ $SERVICESTATETYPE$ $SERVICEATTEMPT$ $ARG1$ $ARG2$ } promote_redis.sh
#!/bin/bash case "$1" in OK) ;; WARNING) ;; UNKNOWN) /usr/local/nagios/libexec/check_nrpe -H $4 -c promote_redis -a $5 ;; CRITICAL) /usr/local/nagios/libexec/check_nrpe -H $4 -c promote_redis -a $5 ;; esac exit 0 On the slave:
nrpe.cfg
command[promote_slave_redis]=/usr/lib64/nagios/plugins/promote_redis.sh $ARG1$ promote_redis.sh
#!/bin/bash echo 'slaveof no one' | /usr/local/redis/bin/redis-cli -h C -p $1 Virtual IP can be set up by using keepalived, something like this:
/etc/keepalived/keepalived.conf
vrrp_script chk_redis { script "killall -0 redis-server" interval 2 weight 2 } vrrp_instance VI_1 { state MASTER #nopreempt interface eth0 lvs_sync_daemon_interface eth0 virtual_router_id 51 priority 101 advert_int 1 authentication { auth_type PASS auth_pass pa$$w0rd } virtual_ipaddress { x.y.z.t } track_script { chk_redis } } But what happens if you want to run multiple instances?
Yves Trudeau and Percona wrote a great resource agent to failover MySQL. Based on that, Martin Walter rewrite for the Redis service. Give it a try!
crm configure show
node master_629 node svr200-632.localdomain primitive VIP ocf:heartbeat:IPaddr2 \ params ip="192.168.6.179" cidr_netmask="24" \ meta target-role="Started" primitive redis_6380 ocf:heartbeat:redis \ params config="/usr/local/redis/etc/redis.conf" ms ms_redis_6380 redis_6380 \ meta master-max="1" master-node-max="1" clone-max="2" clone-node-max="1" notify="true" target-role="Started" location REDIS-PREFER-master_629 ms_redis_12345 100: master_629 colocation vip_on_ms_redis_6380 inf: VIP:Started ms_redis_6380:Master order vip_after_ms_redis_6380 inf: ms_redis_6380:promote VIP:start property $id="cib-bootstrap-options" \ no-quorum-policy="ignore" \ default-action-timeout="60s" \ stonith-enabled="false" \ startup-fencing="false" \ dc-version="1.0.12-unknown" \ cluster-infrastructure="openais" \ expected-quorum-votes="2" crm status
============ Last updated: Tue Aug 21 22:12:11 2012 Stack: openais Current DC: master_629 - partition with quorum Version: 1.0.12-unknown 2 Nodes configured, 2 expected votes 6 Resources configured. ============ Online: [ svr200-632.localdomain master_629 ] Master/Slave Set: ms_redis_12345 Masters: [ master_629 ] Slaves: [ svr200-632.localdomain ] VIP (ocf::heartbeat:IPaddr2): Started master_629 Master/Slave Set: ms_redis_6380 Masters: [ master_629 ] Slaves: [ svr200-632.localdomain ] You either handle it in the client or use something like
