Redis High Availability: Redis Sentinel master-slave replication failover

Redis Sentinel provides a high level of availability for Redis to monitor, notify, and fail over replication clusters.

Just right there are two servers for Centos 6.4, which has Redis 3.2 and Redis master-slave replication installed.

Server name: Centos222, ip:192.168.1.222, master-slave role: Master

Server name: Centos224, ip:192.168.1.224, master-slave role: Slave

On the basis of replication, Redis Sentinel is now configured with the following basic structure.

# 222 Configuring Redis Boot Parameters

[root@centos222 ~]# vi/etc/redis/6379.conf

bind 127.0.0.1 192.168.1.222	#redis服务器地址
Port 26379			# Sentinel Port number
daemonize Yes		#后台启动
protected-mode no	#关闭保护模式, prohibit remote direct access
Requirepass 654321	# Local access requires a password
masterauth 654321	#备端同步访问需要密码
slave-read-only Yes	#备端只读

# 224 Configuring Redis Boot Parameters

[root@centos224 ~]# vi/etc/redis/6379.conf

bind 127.0.0.1 192.168.1.224	#redis服务器地址
Port 26379			# Sentinel Port number
daemonize Yes		#后台启动
slaveof 192.168.1.222 6379		#设置为192.168.1.222 6379 from the library
Protected-mode no	#关闭保护模式, disable remote direct access to
requirepass 654321	#本地访问需要密码
masterauth 654321	# Backup sync access requires password
slave-read-only Yes	#备端只读

# Configure Redis Sentinel to configure monitoring for the primary instance only. Sentinel can obtain information from the instance through the master instance.

# Basic parameter description:

Port 26379	#Sentinel Service port
Sentinel monitor Myredis 192.168.1.xxx 6379 1	#监控 People group name/ip/Port/ The number of failure judgements (which are different from the end of the judgment is considered master disconnected)
Sentinel down-after-milliseconds Myredis 10000	#ping more than 10000 milliseconds is considered an outage
Sentinel failover-timeout Myredis 900000		#主从切换超过 30000 ms failed
Sentinel Can-failover myredis Yes				# Whether to allow failover after master disconnect
Sentinel Parallel-syncs Myredis 1				#从端继续同步新master的数量

# 222 Redis Sentinel Configuration

[root@centos222 ~]# vi/etc/redis/sentinel.conf

#ip 192.168.1.222
port 26379
bind 0.0.0.0
daemonize Yes
logfile "/var/log/sentinel_log.log"
#myredis222
Sentinel Monitor myredis222 192.168.1.222 6379 1
Sentinel Down-after-milliseconds myredis222 10000
Sentinel failover-timeout myredis222 900000
Sentinel Parallel-syncs myredis222 1
Sentinel auth-pass myredis222 654321
#myredis224
Sentinel Monitor myredis224 192.168.1.224 6379 1
Sentinel down-after-milliseconds myredis224 10000
Sentinel Failover-timeout myredis224 900000
Sentinel Parallel-syncs myredis224 1
Sentinel Auth-pass myredis224 654321

# 224 Redis Sentinel Configuration

[root@centos224 ~]#  vi/etc/redis/sentinel.conf

#ip 192.168.1.224
port 26379
bind 0.0.0.0
Daemonize Yes
logfile "/var/log/sentinel_log.log"
#myredis222
Sentinel Monitor myredis222 192.168.1.222 6379 1
Sentinel down-after-milliseconds myredis222 10000
Sentinel failover-timeout myredis222 900000
Sentinel Parallel-syncs myredis222 1
Sentinel auth-pass myredis222 654321
#myredis224
Sentinel Monitor myredis224 192.168.1.224 6379 1
Sentinel down-after-milliseconds myredis224 10000
Sentinel Failover-timeout myredis224 900000
Sentinel Parallel-syncs myredis224 1
Sentinel Auth-pass myredis224 654321

# Server 222 and 224 Firewall add inbound rules

Iptables-i input-p TCP--dport 26379-j ACCEPT

# Two methods of launching Sentinel service:

redis-sentinel/etc/redis/sentinel.conf
redis-server/etc/redis/sentinel.conf--sentinel

# 222 Launch Sentinel Service

[root@centos222 ~]# redis-sentinel/etc/redis/sentinel.conf
[root@centos222 ~]# Cat/var/log/sentinel_log.log
24630:x 18:00:50.496 # Sentinel ID is b0c01ccf191b07bc7f8f42c395b1f45ec3849258 24630:x-
Nov 18:00:50.49 6 # +monitor Master myredis224 192.168.1.224 6379 quorum 1
24630:x Nov 18:00:50.496 # +monitor Master myredis222 19 2.168.1.222 6379 Quorum 1
24630:x Nov 18:00:50.497 * +slave slave 192.168.1.224:6379 192.168.1.224 6379 @ myredis22 2 192.168.1.222 6379

# 224 Launch Sentinel Service

[root@centos224 ~]# redis-sentinel/etc/redis/sentinel.conf
[root@centos224 ~]# Cat/var/log/sentinel_log.log
29098:x 07:00:33.795 # Sentinel ID is 2303678ad7c6df83ce9c938ed9341fc33170f843 29098:x-
Nov 07:00:33.79 5 # +monitor Master myredis222 192.168.1.222 6379 quorum 1
29098:x Nov 07:00:33.795 # +monitor Master myredis224 19 2.168.1.224 6379 Quorum 1
29098:x Nov 07:00:33.797 * +slave slave 192.168.1.224:6379 192.168.1.224 6379 @ myredis22 2 192.168.1.222 6379
29098:x Nov 07:00:34.560 * +sentinel Sentinel b0c01ccf191b07bc7f8f42c395b1f45ec3849258 192.168.1.222 26379 @ myredis222 192.168.1.222 6379
29098:x Nov 07:00:34.706 * +sentinel Sentinel B0C01CCF191B07BC7 f8f42c395b1f45ec3849258 192.168.1.222 26379 @ myredis224 192.168.1.224 6379

# A message similar to the above indicates success.

# Connect Sentinel, View information (take 224 client connections as an example)

[root@centos224 ~]# redis-cli-p 26379
127.0.0.1:26379> Info Sentinel
# Sentinel
sentinel_masters:2
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_ failure_flags:0
master0:name=myredis222,status=ok,address=192.168.1.222:6379,slaves=1,sentinels=2
master1:name=myredis224,status=odown,address=192.168.1.224:6379,slaves=0,sentinels=2

# You can see Sentinel two with 2 master, where 192.168.1.22 has 1 slave. At this point, connect to 222 and 224 respectively to view the replication information.

# in 222 server connection Redis:redis role for Master

[root@centos222 ~]# redis-cli
127.0.0.1:6379> auth 654321
OK
127.0.0.1:6379> info Replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.1.224,port=6379,state=online,offset= 2088480,lag=1
master_repl_offset:2088623
repl_backlog_active:1
repl_backlog_size:1048576
repl _backlog_first_byte_offset:1040048
repl_backlog_histlen:1048576

# in 224 server connection Redis:redis role for slave

[root@centos224 ~]# redis-cli
127.0.0.1:6379> auth 654321
OK
127.0.0.1:6379> info Replication
# Replication
role:slave
master_host:192.168.1.222
master_port:6379
master_link_status:up
Master_last_io_seconds_ago:1
master_sync_in_progress:0
slave_repl_offset:2087322
slave_priority :
slave_read_only:1
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:0
repl_backlog_histlen:0

# no hurry, first introduce Redis Sentinel related commands

127.0.0.1:26379> Sentinel Masters			#列出所有master状态信息
127.0.0.1:26379> Sentinel Master myredis222	# List A master status information (myredis222 as an example)
127.0.0.1:26379> SENTINEL Slaves myredis222 # List all slave and status information for a master (myredis222 for example)
127.0.0.1:26379> SENTINEL Sentinels myredis222	# List A master's sentinels (myredis222 for example)
127.0.0.1:26379> SENTINEL get-master-addr-by-name myredis222 # Get its IP and port via a master (myredis222 as an example)
127.0.0.1:26379> SENTINEL ckquorum myredis222	# Check for a master to reach the polling and failover conditions (myredis222 as an example)
127.0.0.1:26379> Sentinel flushconfig			#强制重写 Sentinel configuration to a disk file
127.0.0.1:26379> SENTINEL failover myredis222	#这个操作就注意了. Forces a failover. Operate with caution ...

# Now test time-out failover, the server is considered to be disconnected because the profile setting Down-after-milliseconds to 10 seconds cannot be connected.
# Set the connection here for 15 seconds to see if the master-slave replication role can fail over.

[root@centos222 ~]# redis-cli-p 6379-a 654321 DEBUG sleep
OK

After the execution finishes, review the replication status.

# 222 characters changed from master to slave

127.0.0.1:6379> auth 654321
OK
127.0.0.1:6379> info Replication
# Replication
role:slave
master_host:192.168.1.224
master_port:6379
master_link_status:up
master_last_io_seconds_ago:0
master_sync_in_progress:0
slave_repl_offset:2422339
slave_priority:100
slave_read_only:1
connected_slaves:0
master_repl_offset:0
repl_backlog_active:0
repl_backlog_size:1048576
repl_backlog_first_byte_offset:1357484
repl_backlog_histlen:1048576

# 224 characters changed from slave to master

[root@centos224 ~]# redis-cli
127.0.0.1:6379> auth 654321
OK
127.0.0.1:6379> info Replication
# Replication
role:master
connected_slaves:1
slave0:ip=192.168.1.222,port=6379,state=online,offset= 2396492,lag=1
master_repl_offset:2396637
repl_backlog_active:1
repl_backlog_size:1048576
repl _backlog_first_byte_offset:2384854
repl_backlog_histlen:11784

Auto-Switch ... Get and set synchronization are normal, and 224 becomes a read-only instance. Toggle success ....

# now try forcing failover. The master is transferred to myredis222.

127.0.0.1:26379> SENTINEL Failover myredis222

The master-slave switchover is equally successful. The system is normal. The test ends here. The principle of the online search bar.

Reference: Redis Sentinel Documentation

Redis high-availability deployment and monitoring

Redis Sentinel Master-Slave Switching (failover) solution, detailed configuration