Redis碎碎念
Redis Sentinel是Redis的高可用方案。是Redis 2.8中正式引入的。
在之前的主從復制方案中，如果主節點出現問題，需要手動將一個從節點升級為主節點，然后將其它從節點指向新的主節點，并且需要修改應用方主節點的地址。整個過程都需要人工干預。
?
Sentinel的相關參數
# bind 127.0.0.1 192.168.1.1 # protected-mode no port 26379 # sentinel announce-ip <ip> # sentinel announce-port <port> dir /tmp sentinel monitor mymaster 127.0.0.1 6379 2 # sentinel auth-pass <master-name> <password> sentinel down-after-milliseconds mymaster 30000 sentinel parallel-syncs mymaster 1 sentinel failover-timeout mymaster 180000 # sentinel notification-script mymaster /var/redis/notify.sh # sentinel client-reconfig-script mymaster /var/redis/reconfig.sh sentinel deny-scripts-reconfig yes其中，
dir：設置Sentinel的工作目錄。
sentinel monitor mymaster 127.0.0.1 6379 2：其中2是quorum，即權重，代表至少需要兩個Sentinel節點認為主節點主觀下線，才可判定主節點為客觀下線。一般建議將其設置為Sentinel節點的一半加1。不僅如此，quorum還與Sentinel節點的領導者選舉有關。為了選出Sentinel的領導者，至少需要max(quorum, num(sentinels) / 2 + 1)個Sentinel節點參與選舉。
?
sentinel down-after-milliseconds mymaster 30000：每個Sentinel節點都要通過定期發送ping命令來判斷Redis節點和其余Sentinel節點是否可達。
如果在指定的時間內，沒有收到主節點的有效回復，則判斷其為主觀下線。需要注意的是，該參數不僅用來判斷主節點狀態，同樣也用來判斷該主節點下面的從節點及其它Sentinel的狀態。其默認值為30s。
?
sentinel parallel-syncs mymaster 1：在failover期間，允許多少個slave同時指向新的主節點。如果numslaves設置較大的話，雖然復制操作并不會阻塞主節點，但多個節點同時指向新的主節點，會增加主節點的網絡和磁盤IO負載。
?
sentinel failover-timeout mymaster 180000：定義故障轉移超時時間。默認180000，單位秒，即3min。需要注意的是，該時間不是總的故障轉移的時間，而是適用于故障轉移的多個場景。
# Specifies the failover timeout in milliseconds. It is used in many ways: # # - The time needed to re-start a failover after a previous failover was # already tried against the same master by a given Sentinel, is two # times the failover timeout. # # - The time needed for a slave replicating to a wrong master according # to a Sentinel current configuration, to be forced to replicate # with the right master, is exactly the failover timeout (counting since # the moment a Sentinel detected the misconfiguration). # # - The time needed to cancel a failover that is already in progress but # did not produced any configuration change (SLAVEOF NO ONE yet not # acknowledged by the promoted slave). # # - The maximum time a failover in progress waits for all the slaves to be # reconfigured as slaves of the new master. However even after this time # the slaves will be reconfigured by the Sentinels anyway, but not with # the exact parallel-syncs progression as specified.第一種場景：
?
sentinel notification-script：定義通知腳本，當Sentinel出現WARNING級別的事件時，會調用該腳本，其會傳入兩個參數：事件類型，事件描述。
sentinel client-reconfig-script：當主節點發生切換時，會調用該參數定義的腳本，其會傳入以下參數：<master-name> <role> <state> <from-ip> <from-port> <to-ip> <to-port>
關于腳本，其必須遵循一定的規則。
# SCRIPTS EXECUTION # # sentinel notification-script and sentinel reconfig-script are used in order # to configure scripts that are called to notify the system administrator # or to reconfigure clients after a failover. The scripts are executed # with the following rules for error handling: # # If script exits with "1" the execution is retried later (up to a maximum # number of times currently set to 10). # # If script exits with "2" (or an higher value) the script execution is # not retried. # # If script terminates because it receives a signal the behavior is the same # as exit code 1. # # A script has a maximum running time of 60 seconds. After this limit is # reached the script is terminated with a SIGKILL and the execution retried.?
sentinel deny-scripts-reconfig：不允許使用SENTINEL SET設置notification-script和client-reconfig-script。
?
Sentinel的常見操作
- PING This command simply returns PONG.
- SENTINEL masters Show a list of monitored masters and their state.
- SENTINEL master <master name> Show the state and info of the specified master.
- SENTINEL slaves <master name> Show a list of slaves for this master, and their state.
- SENTINEL sentinels <master name> Show a list of sentinel instances for this master, and their state.
- SENTINEL get-master-addr-by-name <master name> Return the ip and port number of the master with that name. If a failover is in progress or terminated successfully for this master it returns the address and port of the promoted slave.
- SENTINEL reset <pattern> This command will reset all the masters with matching name. The pattern argument is a glob-style pattern. The reset process clears any previous state in a master (including a failover in progress), and removes every slave and sentinel already discovered and associated with the master.
- SENTINEL failover <master name> Force a failover as if the master was not reachable, and without asking for agreement to other Sentinels (however a new version of the configuration will be published so that the other Sentinels will update their configurations).
- SENTINEL ckquorum <master name> Check if the current Sentinel configuration is able to reach the quorum needed to failover a master, and the majority needed to authorize the failover. This command should be used in monitoring systems to check if a Sentinel deployment is ok.
- SENTINEL flushconfig Force Sentinel to rewrite its configuration on disk, including the current Sentinel state. Normally Sentinel rewrites the configuration every time something changes in its state (in the context of the subset of the state which is persisted on disk across restart). However sometimes it is possible that the configuration file is lost because of operation errors, disk failures, package upgrade scripts or configuration managers. In those cases a way to to force Sentinel to rewrite the configuration file is handy. This command works even if the previous configuration file is completely missing.
sentinel masters
輸出被監控的主節點的狀態信息
127.0.0.1:26379> sentinel masters 1) 1) "name"2) "mymaster"3) "ip"4) "127.0.0.1"5) "port"6) "6379"7) "runid"8) "6ab2be5db3a37c10f2473c8fb9daed147a32df3e"9) "flags"10) "master"11) "link-pending-commands"12) "0"13) "link-refcount"14) "1"15) "last-ping-sent"16) "0"17) "last-ok-ping-reply"18) "639"19) "last-ping-reply"20) "639"21) "down-after-milliseconds"22) "30000"23) "info-refresh"24) "2075"25) "role-reported"26) "master"27) "role-reported-time"28) "759682"29) "config-epoch"30) "0"31) "num-slaves"32) "2"33) "num-other-sentinels"34) "2"35) "quorum"36) "2"37) "failover-timeout"38) "180000"39) "parallel-syncs"40) "1" View Code?
也可單獨查看某個主節點的狀態
sentinel master mymaster
?
sentinel slaves mymaster?
查看某個主節點slave的狀態
127.0.0.1:26379> sentinel slaves mymaster 1) 1) "name"2) "127.0.0.1:6380"3) "ip"4) "127.0.0.1"5) "port"6) "6380"7) "runid"8) "983b87fd070c7f052b26f5135bbb30fdeb170a54"9) "flags"10) "slave"11) "link-pending-commands"12) "0"13) "link-refcount"14) "1"15) "last-ping-sent"16) "0"17) "last-ok-ping-reply"18) "178"19) "last-ping-reply"20) "178"21) "down-after-milliseconds"22) "30000"23) "info-refresh"24) "6160"25) "role-reported"26) "slave"27) "role-reported-time"28) "489019"29) "master-link-down-time"30) "0"31) "master-link-status"32) "ok"33) "master-host"34) "127.0.0.1"35) "master-port"36) "6379"37) "slave-priority"38) "100"39) "slave-repl-offset"40) "70375" 2) 1) "name"2) "127.0.0.1:6381"3) "ip"4) "127.0.0.1"5) "port"6) "6381"7) "runid"8) "b88059cce9104dd4e0366afd6ad07a163dae8b15"9) "flags"10) "slave"11) "link-pending-commands"12) "0"13) "link-refcount"14) "1"15) "last-ping-sent"16) "0"17) "last-ok-ping-reply"18) "178"19) "last-ping-reply"20) "178"21) "down-after-milliseconds"22) "30000"23) "info-refresh"24) "2918"25) "role-reported"26) "slave"27) "role-reported-time"28) "489019"29) "master-link-down-time"30) "0"31) "master-link-status"32) "ok"33) "master-host"34) "127.0.0.1"35) "master-port"36) "6379"37) "slave-priority"38) "100"39) "slave-repl-offset"40) "71040" View Code?
sentinel sentinels mymaster
查看其它Sentinel的狀態
127.0.0.1:26379> sentinel sentinels mymaster 1) 1) "name"2) "738ccbddaa0d4379d89a147613d9aecfec765bcb"3) "ip"4) "127.0.0.1"5) "port"6) "26381"7) "runid"8) "738ccbddaa0d4379d89a147613d9aecfec765bcb"9) "flags"10) "sentinel"11) "link-pending-commands"12) "0"13) "link-refcount"14) "1"15) "last-ping-sent"16) "0"17) "last-ok-ping-reply"18) "475"19) "last-ping-reply"20) "475"21) "down-after-milliseconds"22) "30000"23) "last-hello-message"24) "79"25) "voted-leader"26) "?"27) "voted-leader-epoch"28) "0" 2) 1) "name"2) "7251bb129ca373ad0d8c7baf3b6577ae2593079f"3) "ip"4) "127.0.0.1"5) "port"6) "26380"7) "runid"8) "7251bb129ca373ad0d8c7baf3b6577ae2593079f"9) "flags"10) "sentinel"11) "link-pending-commands"12) "0"13) "link-refcount"14) "1"15) "last-ping-sent"16) "0"17) "last-ok-ping-reply"18) "475"19) "last-ping-reply"20) "475"21) "down-after-milliseconds"22) "30000"23) "last-hello-message"24) "985"25) "voted-leader"26) "?"27) "voted-leader-epoch"28) "0" View Code?
sentinel get-master-addr-by-name <master name>
返回指定<master name>主節點的IP地址和端口。如果在進行故障轉移，則顯示的是新主的信息。
127.0.0.1:26379> sentinel get-master-addr-by-name mymaster 1) "127.0.0.1" 2) "6379"?
sentinel reset <pattern>
對符合<pattern>（通配符風格）主節點的配置進行重置。
如果某個slave宕機了，其依然處于sentinel的管理中，所以，在其恢復正常后，其依然會加入到之前的復制環境中，即使配置文件中沒有指定slaveof選項。不僅如此，如果主節點宕機了，在其重啟后，其默認會作為從節點接入到之前的復制環境中。
但很多時候，我們可能就是想移除old master，slave，這個時候，sentinel reset就派上用場了。其會基于當前主節點的狀態，重置其配置（they'll refresh the list of slaves within the next 10 seconds, only adding the ones listed as correctly replicating from the current master INFO output）。關鍵的是，對于非正常狀態的slave，會從當前的配置中剔除。這樣，被剔除節點在恢復正常后（注意此時的配置文件，需剔除slaveof的配置），也不會自動加入到之前的復制環境中。
需要注意的是，該命令僅對當前sentinel節點有效，如果要剔除某個節點，需要在所有的sentinel節點上執行reset操作。
?
sentinel failover <master name>
對指定 <master name> 主節點進行強制故障轉移。相對于常規的故障轉移，其無需
?
sentinel ckquorum <master name>
檢測當前可達的Sentinel節點總數是否達到<quorum>的個數
127.0.0.1:26379> sentinel ckquorum mymaster OK 3 usable Sentinels. Quorum and failover authorization can be reached?
sentinel flushconfig
將Sentinel節點的配置信息強制刷到磁盤上，這個命令Sentinel節點自身用得比較多，對于開發和運維人員只有當外部原因（例如磁盤損壞）造成配置文件損壞或者丟失時，才會用上。
?
sentinel remove <master name>
取消當前Sentinel節點對于指定<master name>主節點的監控。
[root@slowtech redis-4.0.11]# grep -Ev "^#|^$" sentinel_26379.conf port 26379 dir "/tmp" sentinel myid 2467530fa249dbbc435c50fbb0dc2a4e766146f8 sentinel deny-scripts-reconfig yes sentinel monitor mymaster 127.0.0.1 6381 2 sentinel config-epoch mymaster 12 sentinel leader-epoch mymaster 0 sentinel known-slave mymaster 127.0.0.1 6380 sentinel known-slave mymaster 127.0.0.1 6379 sentinel known-sentinel mymaster 127.0.0.1 26381 738ccbddaa0d4379d89a147613d9aecfec765bcb sentinel known-sentinel mymaster 127.0.0.1 26380 7251bb129ca373ad0d8c7baf3b6577ae2593079f sentinel current-epoch 12[root@slowtech redis-4.0.11]# redis-cli -p 26379 127.0.0.1:26379> sentinel remove mymaster OK 127.0.0.1:26379> quit[root@slowtech redis-4.0.11]# grep -Ev "^#|^$" sentinel_26379.conf port 26379 dir "/tmp" sentinel myid 2467530fa249dbbc435c50fbb0dc2a4e766146f8 sentinel deny-scripts-reconfig yes sentinel current-epoch 12 View Code?
總結
- 上一篇： docker 介绍
- 下一篇： Android重写菜单增加系统自带返回键