通过sentinel的配置实现redis主从复制的高可用，
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一：sentinel节点配置文件的主要配置项
1.sentinel monitor [name] [host] [port] [n]
#监控主节点名称[name]
#监控主节点IP[host]
#监控主节点[port]
#[n]：至少有n个sentinel节点发现master有故障，才会自动进行sentinel故障转移
2.sentinel down-milliseconds [name] [milliseconds]
#[milliseconds]毫秒ping不同，则主观认为该节点有故障
3.sentinel parallel-syncs [name] [n]
故障转移后重新进行主从复制
#[n] = 1：代表串行，一个复制完成后，另一个才能复制
#[n] = 2或>2：代表并行，2个同时复制，或者多个同时复制
4.sentinel failover-timeout [name] [milliseconds]
#从故障转移开始milliseconds毫秒没有完成转移操作，则视为转移失败
二：配置sentinel的步骤
1.配置sentinel文件
daemonize yes
port 26379
bind 0.0.0.0
sentinel monitor mymaster 192.168.145.128 6666 2
sentinel down-after-milliseconds mymaster 30000
sentinel parallel-syncs mymaster 1
sentinel failover-timeout mymaster 15000
2.启动sentinel服务
启动sentinel服务的命令：./src/redis-sentinel [配置文件]
3.连接到sentinel的服务
./src/redis-cli -p [sentinel服务的端口号]
4.查看sentinel服务是否启动成功
在sentinel客户端输入 info 命令会出现sentinel节点的相关信息
# Server
redis_version:5.0.3
redis_git_sha1:00000000
redis_git_dirty:0
redis_build_id:129165fe599a95d
redis_mode:sentinel
os:Linux 3.10.0-862.el7.x86_64 x86_64
arch_bits:64
multiplexing_api:epoll
atomicvar_api:atomic-builtin
gcc_version:4.8.5
process_id:3852
run_id:7314d5bb4d634df94656b905b15aa4ae9ee32343
tcp_port:26379
uptime_in_seconds:537
uptime_in_days:0
hz:18
configured_hz:10
lru_clock:9993431
executable:/usr/software/redis-5.0.3/./src/redis-sentinel
config_file:/usr/software/redis-5.0.3/sentinel.custom26379.conf
# Clients
connected_clients:3
client_recent_max_input_buffer:2
client_recent_max_output_buffer:0
blocked_clients:0
# CPU
used_cpu_sys:1.650110
used_cpu_user:1.141941
used_cpu_sys_children:0.000000
used_cpu_user_children:0.000000
# Stats
total_connections_received:3
total_commands_processed:1352
instantaneous_ops_per_sec:3
total_net_input_bytes:78650
total_net_output_bytes:8155
instantaneous_input_kbps:0.28
instantaneous_output_kbps:0.02
rejected_connections:0
sync_full:0
sync_partial_ok:0
sync_partial_err:0
expired_keys:0
expired_stale_perc:0.00
expired_time_cap_reached_count:0
evicted_keys:0
keyspace_hits:0
keyspace_misses:0
pubsub_channels:0
pubsub_patterns:0
latest_fork_usec:0
migrate_cached_sockets:0
slave_expires_tracked_keys:0
active_defrag_hits:0
active_defrag_misses:0
active_defrag_key_hits:0
active_defrag_key_misses:0
# Sentinel
# 主节点
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
#主节点的描述信息，slaves=2：两个从节点，sentinels=3：三个sentinel节点
master0:name=mymaster,status=ok,address=192.168.145.128:6666,slaves=2,sentinels=3
3-1：sentinel节点是如何获取以上信息的？ →都指向master，获取master中的信息
4.再次查看sentinel配置文件(cat 配置文件名称)，会出现一些slave，其他sentinel的配置信息
daemonize yes
port 26379
bind 0.0.0.0
sentinel myid a0b40c1e998b341bfa3ed3cf4e78c5cf226fae38
sentinel deny-scripts-reconfig yes
sentinel monitor mymaster 192.168.145.128 6666 2
sentinel failover-timeout mymaster 15000
# Generated by CONFIG REWRITE
dir "/usr/software/redis-5.0.3"
protected-mode no
sentinel config-epoch mymaster 0
sentinel leader-epoch mymaster 0
# 从节点的信息
sentinel known-replica mymaster 192.168.145.128 6668
sentinel known-replica mymaster 192.168.145.128 6667
#其他sentinel的信息
sentinel known-sentinel mymaster 192.168.145.128 26381 20d86425d742e85cedd8a86e576da58d90b08b21
sentinel known-sentinel mymaster 192.168.145.128 26380 7f2886c479a783119b4bb580704ab5b8215dcb87
sentinel current-epoch 0