RDB creates point-in-time snapshots of your dataset at specified intervals. It is efficient in terms of I\/O and allows fast restarts, making it suitable for backup and disaster recovery. On the other hand, AOF logs every write operation received by the server, ensuring higher durability. You can configure AOF to sync to disk every second, on every command, or let the OS manage it. This flexibility allows to balance between performance and reliability.<\/p>\n
In many production environments, both RDB and AOF are enabled simultaneously to leverage the strengths of both methods. When both are enabled, Redis creates regular snapshots and logs every operation. This hybrid model increases data safety but also demands careful tuning of parameters to prevent excessive disk I\/O.<\/p>\n
Another powerful feature of Redis is its support for high availability and automatic failover through Redis Sentinel. Sentinel continuously monitors your Redis deployment to detect failures and automatically promotes a replica to master in case the primary server becomes unreachable. It also updates the configurations of other Sentinel instances and clients to reflect the new master, ensuring minimal downtime. Sentinel helps Redis maintain strong consistency and availability in distributed environments, making it an essential component in production-grade Redis clusters.<\/p>\n
![\"\"](\"https:\/\/www.fatihacar.com\/blog\/resimler\/redis_sentinel-1024x604.png\")
<\/p>\n
In this article, I will mention how to set up Redis, Redis Sentinel and Keepalived<\/strong> services consisting of 1 master and 2 replica nodes in detail. I will use Redis 7.2.x version.<\/p>\n Hostname and IP<\/b><\/p>\n Master Node : rds1 – 192.168.1.12<\/p>\n Replica Node 1 : rds2 – 192.168.1.13<\/p>\n Replica Node 2 : rds3 – 192.168.1.14<\/p>\n Virtual Service IP – 192.168.1.11<\/p><\/blockquote>\n 1. Upgrade Packages<\/strong><\/p>\n yum upgrade<\/p><\/blockquote>\n 2. Selinux Disable or Permissive<\/strong><\/p>\n You can do disabled or permissive<\/p>\n vi \/etc\/selinux\/config<\/p>\n SELINUX=permissive<\/p>\n setenforce permissive<\/p><\/blockquote>\n 3. Firewall Close and Disable<\/strong><\/p>\n You can open after installation,but you have to give permission to necessary ports and services for Redis<\/p>\n systemctl stop firewalld.service<\/p>\n systemctl disable firewalld.service<\/p><\/blockquote>\n 4. Chrony NTP Configuration<\/strong><\/p>\n You can write your ntp server information in \/etc\/chrony.conf file to time sync.<\/p>\n vi \/etc\/chrony.conf<\/p>\n server yourntpaddress iburst<\/p>\n systemctl restart chronyd.service<\/p>\n systemctl enable chronyd.service<\/p><\/blockquote>\n 5. sysctl.conf Configuration<\/strong><\/p>\n You can add below parameters to sysctl.conf for Redis performance as your needs.<\/p>\n vi \/etc\/sysctl.conf<\/p>\n # Redis Official # Redis Community Recommended 6. limits.conf Configuration<\/strong><\/p>\n You can add below parameters to limits.conf for Redis performance as your needs.<\/p>\n vi \/etc\/security\/limits.conf<\/p>\n # Redis Recommended Limits root soft nofile 100000 7. Disable Transparent Huge Pages<\/strong><\/p>\n Redis recommend disable transparent huge pages feature. I will create a service to disable THP.<\/p>\n Create service<\/strong><\/p>\n vi \/etc\/systemd\/system\/disable-thp.service<\/p>\n [Unit] [Service] [Install] Activate disable-thp service<\/strong><\/p>\n systemctl daemon-reload<\/p>\n systemctl enable disable-thp.service<\/p>\n systemctl start disable-thp.service<\/p>\n Control THP status<\/strong><\/p>\n You can check THP status with below commands. If you see as [never], THP is disable.<\/p>\n cat \/sys\/kernel\/mm\/transparent_hugepage\/enabled<\/p>\n cat \/sys\/kernel\/mm\/transparent_hugepage\/defrag<\/p><\/blockquote>\n 1. Install Redis<\/strong><\/p>\n We can install Redis with several different ways. I will use remi repo to installation. Also if you want, you can download Redis last version from redis.io by creating a account.<\/p>\n Linux version is OEL 9.5. so I find suitable redis version as redis-7.2.7-1.el9.remi.x86_64.rpm<\/p>\n cd \/tmp\/<\/p>\n wget https:\/\/rpms.remirepo.net\/enterprise\/9.5\/modular\/x86_64\/redis-7.2.7-1.el9.remi.x86_64.rpm<\/p>\n rpm -ivh redis-7.2.7-1.el9.remi.x86_64.rpm<\/p><\/blockquote>\n 2. Create Directories<\/strong><\/p>\n I will use \/data directory for redis data directory.<\/p>\n mkdir -p \/data\/redis<\/p>\n chown -R redis.redis \/data<\/p><\/blockquote>\n 1. Configure redis.conf<\/strong><\/p>\n You can find redis configuration file at \/etc\/redis\/redis.conf<\/p>\n I will configure below parameters. Some parameters will be different node by node.<\/p>\n vi \/etc\/redis\/redis.conf<\/p>\n Master Node – 192.168.1.12<\/strong><\/p>\n bind * -::* Replica Node 1 – 192.168.1.13<\/strong><\/p>\n bind * -::* Replica Node 2 – 192.168.1.14<\/strong><\/p>\n bind * -::* chown redis.redis redis.conf<\/p><\/blockquote>\n 2. Configure sentinel.conf<\/strong><\/p>\n You can find sentinel configuration file at \/etc\/redis\/sentinel.conf<\/p>\n I will remove # for more readable file. Firstly, I will take a backup as sentinel.conf.orginal<\/p>\n cd \/etc\/redis<\/p>\n cp sentinel.conf sentinel.conf.orginal<\/p>\n grep -Ev ‘^#|^$’ sentinel.conf.orginal > sentinel.conf<\/p>\n vi sentinel.conf<\/p>\n All Nodes<\/strong><\/p>\n protected-mode no chown redis.redis sentinel.conf<\/p>\n chmod 640 sentinel.conf<\/p><\/blockquote>\n 3. Create users.acl<\/strong><\/p>\n users.acl will provide password authentication for login.<\/p>\n touch \/etc\/redis\/users.acl<\/p>\n chown redis.redis \/etc\/redis\/users.acl<\/p>\n chmod 640 \/etc\/redis\/users.acl<\/p><\/blockquote>\n 1. Start and Enable Redis Service on All Nodes<\/strong><\/p>\n systemctl start redis.service<\/p>\n systemctl enable redis.service<\/p><\/blockquote>\n 2. Start and Enable Sentinel Service on All Nodes<\/strong><\/p>\n I will create a redis-sentinel.service file because there is not redis-sentinel.service file on my servers.<\/p>\n vi \/etc\/systemd\/system\/redis-sentinel.service<\/p>\n [Unit] [Service] [Install] <\/p>\n systemctl daemon-reexec<\/p>\n systemctl daemon-reload<\/p>\n systemctl start redis-sentinel.service<\/p>\n systemctl enable redis-sentinel.service<\/p><\/blockquote>\n 1. Create Users on All Nodes<\/strong><\/p>\n [root@rds1 redis]# redis-cli Also, you can see users at \/etc\/redis\/users.acl file.<\/p><\/blockquote>\n 1. Check sentinel.conf<\/strong><\/p>\n Master Node<\/strong><\/p>\n more \/etc\/redis\/sentinel.conf<\/p>\n protected-mode no sentinel failover-timeout mymaster 5000 # Generated by CONFIG REWRITE sentinel known-sentinel mymaster 192.168.1.13 26379 ab94b82a7bc368de19aafb63513ccb2380d243b4<\/p>\n sentinel known-sentinel mymaster 192.168.1.14 26379 23a2bfdc79fa7d96a3e830e89ef3b24290b2fefa<\/p>\n sentinel known-replica mymaster 192.168.1.13 6379<\/p>\n sentinel known-replica mymaster 192.168.1.14 6379<\/p>\n Replica Node 1<\/strong><\/p>\n protected-mode no sentinel failover-timeout mymaster 5000 # Generated by CONFIG REWRITE sentinel known-replica mymaster 192.168.1.14 6379<\/p>\n sentinel known-sentinel mymaster 192.168.1.12 26379 f03686f91106b6173c30cdcc517527df5fa38943<\/p>\n sentinel known-sentinel mymaster 192.168.1.14 26379 23a2bfdc79fa7d96a3e830e89ef3b24290b2fefa<\/p>\n sentinel known-replica mymaster 192.168.1.13 6379<\/p>\n Replica Node 2<\/strong><\/p>\n protected-mode no sentinel failover-timeout mymaster 5000 # Generated by CONFIG REWRITE sentinel known-sentinel mymaster 192.168.1.13 26379 ab94b82a7bc368de19aafb63513ccb2380d243b4<\/p>\n sentinel known-replica mymaster 192.168.1.14 6379<\/p>\n sentinel known-sentinel mymaster 192.168.1.12 26379 f03686f91106b6173c30cdcc517527df5fa38943<\/p>\n sentinel known-replica mymaster 192.168.1.13 6379<\/p><\/blockquote>\n 2. Check Replication<\/strong><\/p>\n Master Node<\/strong><\/p>\n [root@rds1 redis]# redis-cli Replica Node 1<\/strong><\/p>\n [root@rds2 redis]# redis-cli Replica Node 2<\/strong><\/p>\n [root@rds3 redis]# redis-cli 3. Check Sentinel<\/strong><\/p>\n [root@rds1 redis]# redis-cli -p 26379 127.0.0.1:26379> SENTINEL get-master-addr-by-name mymaster 127.0.0.1:26379> SENTINEL slaves mymaster 4. Check Log Files<\/strong><\/p>\n tail -100f \/var\/log\/redis\/redis.log<\/p>\n tail -100f \/var\/log\/redis\/sentinel.log<\/p>\n tail -100f \/var\/log\/messages<\/p><\/blockquote>\n 5. Check Latency<\/strong><\/p>\n [root@rds1 redis]# redis-cli –latency We will use a virtual IP which is 192.168.1.11 for connecting to redis from applications. So, I configure keepalived service on all nodes regarding to redis.<\/p>\n 1.Keepalived Package Install<\/strong><\/p>\n dnf install keepalived<\/p><\/blockquote>\n 2.Create redis master check bash script<\/strong><\/p>\n cd \/etc\/keepalived<\/p>\n vi check_redis_master.sh<\/p>\n #!\/bin\/bash<\/p>\n ROLE=$(redis-cli -a Password123 INFO replication 2>\/dev\/null | grep -v “Warning” | grep role | cut -d’:’ -f2 | tr -d ‘\\r’)<\/p>\n if [ “$ROLE” == “master” ]; then chmod +x check_redis_master.sh<\/p><\/blockquote>\n 3.Configure keepalived.conf<\/strong><\/p>\n vi keepalived.conf<\/p>\n vrrp_script chk_redis { vrrp_instance VI_1 { First node keepalived.conf will be like above. Second node keepalived.conf some parameters will change like that state BACKUP and priority 90. Third node keepalived.conf some parameters will change like that state BACKUP and priority 80.<\/p><\/blockquote>\n 4. Start Keepalived Service<\/strong><\/p>\n systemctl start keepalived.service<\/p>\n systemctl enable keepalived.service<\/p><\/blockquote>\n 5. Check IP<\/strong><\/p>\n You can check IP with ip a command<\/p><\/blockquote>\n Redis Sentinel manages failover operations and chooses new master from candidates. Redis Sentinel make failover automatically when reboot or interruption on master node. Also you can make failover manually with below commands.<\/p>\n 1.Check Status Before Failover<\/strong><\/p>\n [root@rds1 redis]# redis-cli connected_slaves count has to be suitable. 2.Failover<\/strong><\/p>\n [root@rds1 redis]# redis-cli -p 26379 SENTINEL failover mymaster As you see second node is new master now.<\/p><\/blockquote>\n 1.DML<\/strong><\/p>\n SET key value<\/strong> Sets a key to hold the specified value 2.List<\/strong><\/p>\n LPUSH key value<\/strong> Inserts value at the head of the list 3.Set<\/strong><\/p>\n SADD key value<\/strong> Adds a value to a set 4.Hash<\/strong><\/p>\n HSET key field value<\/strong> Sets a field in a hash 5.DDL<\/strong><\/p>\n KEYS *<\/strong> Lists all keys (not recommended for production) 6.Config<\/strong><\/p>\n SAVE<\/strong> Performs a synchronous save to disk 7.Control & Monitor<\/strong><\/p>\n INFO replication<\/strong> Shows replication role and status <\/p>\n","protected":false},"excerpt":{"rendered":" Redis is an open-source, in-memory data structure store, widely used as a database, cache, and message broker. Known for its lightning-fast performance, Redis operates by keeping data in memory rather than on disk, which allows for incredibly quick read and write operations. It supports a variety of data structures such as strings, hashes, lists, sets,…<\/p>\n","protected":false},"author":37,"featured_media":3012,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[129],"tags":[131,132,130],"class_list":["post-2995","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-redis","tag-database","tag-nosql","tag-redis"],"jetpack_featured_media_url":"http:\/\/www.fatihacar.com\/blog\/resimler\/redis_sentinel.png","jetpack_shortlink":"https:\/\/wp.me\/p39NFI-Mj","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/posts\/2995","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/users\/37"}],"replies":[{"embeddable":true,"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/comments?post=2995"}],"version-history":[{"count":22,"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/posts\/2995\/revisions"}],"predecessor-version":[{"id":3014,"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/posts\/2995\/revisions\/3014"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/media\/3012"}],"wp:attachment":[{"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/media?parent=2995"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/categories?post=2995"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.fatihacar.com\/blog\/wp-json\/wp\/v2\/tags?post=2995"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Redis Servers Information<\/h3>\n
First Step : Configure Operating System on Each Node<\/h3>\n
\nvm.overcommit_memory = 1 # Allows memory overcommitment, helps Redis avoid fork failures<\/p>\n
\nvm.swappiness = 1 # Controls how aggressively the kernel uses swap
\nnet.core.somaxconn = 65535 # Max connections queued before being refused
\nnet.ipv4.tcp_tw_reuse = 1 # Allows reuse of TIME-WAIT sockets for new connections
\nnet.ipv4.tcp_max_syn_backlog = 4096 # Max pending TCP connections in SYN state
\nfs.file-max = 100000 # Max number of open files allowed by the system<\/p><\/blockquote>\n
\nredis soft nofile 100000
\nredis hard nofile 100000
\nredis soft nproc 65535
\nredis hard nproc 65535
\nredis soft memlock unlimited
\nredis hard memlock unlimited<\/p>\n
\nroot hard nofile 100000
\nroot soft nproc 65535
\nroot hard nproc 65535
\nroot soft memlock unlimited
\nroot hard memlock unlimited<\/p><\/blockquote>\n
\nDescription=Disable Transparent Huge Pages (THP)
\nAfter=network.target<\/p>\n
\nType=oneshot
\nExecStart=\/bin\/bash -c “echo never > \/sys\/kernel\/mm\/transparent_hugepage\/enabled”
\nExecStartPost=\/bin\/bash -c “echo never > \/sys\/kernel\/mm\/transparent_hugepage\/defrag”
\nRemainAfterExit=true<\/p>\n
\nWantedBy=multi-user.target<\/p>\nSecond Step : Install Redis Package on Each Node<\/h3>\n
Third Step : Configure Redis and Sentinel Configuration Files<\/h3>\n
\nprotected-mode no
\nloglevel verbose
\ndir \/data\/redis
\nmasterauth “Password123”
\nreplica-priority 1
\naclfile \/etc\/redis\/users.acl
\nappendonly yes<\/p>\n
\nprotected-mode no
\nloglevel verbose
\ndir \/data\/redis
\nreplicaof 192.168.1.12 6379
\nmasterauth “Password123”
\nreplica-priority 2
\naclfile \/etc\/redis\/users.acl
\nappendonly yes<\/p>\n
\nprotected-mode no
\nloglevel verbose
\ndir \/data\/redis
\nreplicaof 192.168.1.12 6379
\nmasterauth “Password123”
\nreplica-priority 3
\naclfile \/etc\/redis\/users.acl
\nappendonly yes<\/p>\n
\nport 26379
\ndaemonize no
\npidfile \/var\/run\/redis-sentinel.pid
\nloglevel verbose
\nlogfile \/var\/log\/redis\/sentinel.log
\ndir \/data\/redis
\nsentinel monitor mymaster 192.168.1.12 6379 2
\nsentinel down-after-milliseconds mymaster 3000
\nsentinel parallel-syncs mymaster 1
\nsentinel failover-timeout mymaster 5000
\nsentinel auth-pass mymaster “Password123”
\nsentinel deny-scripts-reconfig yes<\/p>\nFourth Step : Start Redis and Sentinel Service<\/h3>\n
\nDescription=Redis Sentinel
\nAfter=network.target<\/p>\n
\nExecStart=\/usr\/bin\/redis-sentinel \/etc\/redis\/sentinel.conf –supervised systemd
\nExecStop=\/bin\/kill -s TERM $MAINPID
\nUser=redis
\nGroup=redis
\nRestart=always<\/p>\n
\nWantedBy=multi-user.target<\/p>\nFifth Step : Create Users<\/h3>\n
\n127.0.0.1:6379> auth default Password123
\nOK
\n127.0.0.1:6379> ACL SETUSER default on >Password123 allcommands allkeys allchannels
\nOK
\n127.0.0.1:6379> ACL SETUSER user1 on >Password123 allcommands allkeys allchannels
\nOK
\n127.0.0.1:6379> ACL SAVE
\nOK
\n127.0.0.1:6379> ACL LIST
\n1) “user default on sanitize-payload #008c70392e3abfbd0fa47bbc2ed96aa99bd49e159727fcba0f2e6abeb3a9d601 ~* &* +@all”
\n2) “user user1 on sanitize-payload #008c70392e3abfbd0fa47bbc2ed96aa99bd49e159727fcba0f2e6abeb3a9d601 ~* &* +@all”<\/p>\nSixth Step : Cluster Status Check<\/h3>\n
\nport 26379
\ndaemonize no
\npidfile “\/var\/run\/redis-sentinel.pid”
\nloglevel verbose
\nlogfile “\/var\/log\/redis\/sentinel.log”
\ndir “\/data\/redis”
\nsentinel monitor mymaster 192.168.1.12 6379 2
\nsentinel down-after-milliseconds mymaster 3000<\/p>\n
\nsentinel auth-pass mymaster Password123
\nsentinel deny-scripts-reconfig yes<\/p>\n
\nlatency-tracking-info-percentiles 50 99 99.9
\nsupervised systemd
\nuser default on nopass sanitize-payload ~* &* +@all
\nsentinel myid f03686f91106b6173c30cdcc517527df5fa38943
\nsentinel config-epoch mymaster 0
\nsentinel leader-epoch mymaster 0
\nsentinel current-epoch 0<\/p>\n
\nport 26379
\ndaemonize no
\npidfile “\/var\/run\/redis-sentinel.pid”
\nloglevel verbose
\nlogfile “\/var\/log\/redis\/sentinel.log”
\ndir “\/data\/redis”
\nsentinel monitor mymaster 192.168.1.12 6379 2
\nsentinel down-after-milliseconds mymaster 3000<\/p>\n
\nsentinel auth-pass mymaster Password123
\nsentinel deny-scripts-reconfig yes<\/p>\n
\nsupervised systemd
\nlatency-tracking-info-percentiles 50 99 99.9
\nuser default on nopass sanitize-payload ~* &* +@all
\nsentinel myid ab94b82a7bc368de19aafb63513ccb2380d243b4
\nsentinel config-epoch mymaster 0
\nsentinel leader-epoch mymaster 0
\nsentinel current-epoch 0<\/p>\n
\nport 26379
\ndaemonize no
\npidfile “\/var\/run\/redis-sentinel.pid”
\nloglevel verbose
\nlogfile “\/var\/log\/redis\/sentinel.log”
\ndir “\/data\/redis”
\nsentinel monitor mymaster 192.168.1.12 6379 2
\nsentinel down-after-milliseconds mymaster 3000<\/p>\n
\nsentinel auth-pass mymaster Password123
\nsentinel deny-scripts-reconfig yes<\/p>\n
\nsupervised systemd
\nlatency-tracking-info-percentiles 50 99 99.9
\nuser default on nopass sanitize-payload ~* &* +@all
\nsentinel myid 23a2bfdc79fa7d96a3e830e89ef3b24290b2fefa
\nsentinel config-epoch mymaster 0
\nsentinel leader-epoch mymaster 0
\nsentinel current-epoch 0<\/p>\n
\n127.0.0.1:6379> auth default Password123
\nOK
\n127.0.0.1:6379> info replication
\n# Replication
\nrole:master
\nconnected_slaves:2
\nslave0:ip=192.168.1.14,port=6379,state=online,offset=325224,lag=1
\nslave1:ip=192.168.1.13,port=6379,state=online,offset=325224,lag=1
\nmaster_failover_state:no-failover
\nmaster_replid:a0185047c72a48c65d3ff584865dc3675b1d03af
\nmaster_replid2:0000000000000000000000000000000000000000
\nmaster_repl_offset:325502
\nsecond_repl_offset:-1
\nrepl_backlog_active:1
\nrepl_backlog_size:1048576
\nrepl_backlog_first_byte_offset:1
\nrepl_backlog_histlen:325502<\/p>\n
\n127.0.0.1:6379> auth default Password123
\nOK
\n127.0.0.1:6379> info replication
\n# Replication
\nrole:slave
\nmaster_host:192.168.1.12
\nmaster_port:6379
\nmaster_link_status:up
\nmaster_last_io_seconds_ago:1
\nmaster_sync_in_progress:0
\nslave_read_repl_offset:361185
\nslave_repl_offset:361185
\nslave_priority:2
\nslave_read_only:1
\nreplica_announced:1
\nconnected_slaves:0
\nmaster_failover_state:no-failover
\nmaster_replid:a0185047c72a48c65d3ff584865dc3675b1d03af
\nmaster_replid2:0000000000000000000000000000000000000000
\nmaster_repl_offset:361185
\nsecond_repl_offset:-1
\nrepl_backlog_active:1
\nrepl_backlog_size:1048576
\nrepl_backlog_first_byte_offset:9337
\nrepl_backlog_histlen:351849<\/p>\n
\n127.0.0.1:6379> auth default Password123
\nOK
\n127.0.0.1:6379> info replication
\n# Replication
\nrole:slave
\nmaster_host:192.168.1.12
\nmaster_port:6379
\nmaster_link_status:up
\nmaster_last_io_seconds_ago:1
\nmaster_sync_in_progress:0
\nslave_read_repl_offset:371263
\nslave_repl_offset:371263
\nslave_priority:3
\nslave_read_only:1
\nreplica_announced:1
\nconnected_slaves:0
\nmaster_failover_state:no-failover
\nmaster_replid:a0185047c72a48c65d3ff584865dc3675b1d03af
\nmaster_replid2:0000000000000000000000000000000000000000
\nmaster_repl_offset:371263
\nsecond_repl_offset:-1
\nrepl_backlog_active:1
\nrepl_backlog_size:1048576
\nrepl_backlog_first_byte_offset:9337
\nrepl_backlog_histlen:361927<\/p><\/blockquote>\n
\n127.0.0.1:26379> auth default Password123
\nOK
\n127.0.0.1:26379> sentinel masters
\n1) 1) “name”
\n2) “mymaster”
\n3) “ip”
\n4) “192.168.1.12”
\n5) “port”
\n6) “6379”
\n7) “runid”
\n8) “fd52c7129201e03249df7b579b5ac75b8d1b5886”
\n9) “flags”
\n10) “master”
\n11) “link-pending-commands”
\n12) “0”
\n13) “link-refcount”
\n14) “1”
\n15) “last-ping-sent”
\n16) “0”
\n17) “last-ok-ping-reply”
\n18) “118”
\n19) “last-ping-reply”
\n20) “118”
\n21) “down-after-milliseconds”
\n22) “3000”
\n23) “info-refresh”
\n24) “6876”
\n25) “role-reported”
\n26) “master”
\n27) “role-reported-time”
\n28) “2326059”
\n29) “config-epoch”
\n30) “0”
\n31) “num-slaves”
\n32) “2”
\n33) “num-other-sentinels”
\n34) “2”
\n35) “quorum”
\n36) “2”
\n37) “failover-timeout”
\n38) “5000”
\n39) “parallel-syncs”
\n40) “1”<\/p>\n
\n1) “192.168.1.12”
\n2) “6379”<\/p>\n
\n1) 1) “name”
\n2) “192.168.1.14:6379”
\n3) “ip”
\n4) “192.168.1.14”
\n5) “port”
\n6) “6379”
\n7) “runid”
\n8) “19083afb2af517c11dd12d52366f52b605f11898”
\n9) “flags”
\n10) “slave”
\n11) “link-pending-commands”
\n12) “0”
\n13) “link-refcount”
\n14) “1”
\n15) “last-ping-sent”
\n16) “0”
\n17) “last-ok-ping-reply”
\n18) “130”
\n19) “last-ping-reply”
\n20) “130”
\n21) “down-after-milliseconds”
\n22) “3000”
\n23) “info-refresh”
\n24) “5673”
\n25) “role-reported”
\n26) “slave”
\n27) “role-reported-time”
\n28) “2465451”
\n29) “master-link-down-time”
\n30) “0”
\n31) “master-link-status”
\n32) “ok”
\n33) “master-host”
\n34) “192.168.1.12”
\n35) “master-port”
\n36) “6379”
\n37) “slave-priority”
\n38) “3”
\n39) “slave-repl-offset”
\n40) “526637”
\n41) “replica-announced”
\n42) “1”
\n2) 1) “name”
\n2) “192.168.1.13:6379”
\n3) “ip”
\n4) “192.168.1.13”
\n5) “port”
\n6) “6379”
\n7) “runid”
\n8) “a3304c327c08fc35b58b45820fde6c86dc3eb396”
\n9) “flags”
\n10) “slave”
\n11) “link-pending-commands”
\n12) “0”
\n13) “link-refcount”
\n14) “1”
\n15) “last-ping-sent”
\n16) “0”
\n17) “last-ok-ping-reply”
\n18) “130”
\n19) “last-ping-reply”
\n20) “130”
\n21) “down-after-milliseconds”
\n22) “3000”
\n23) “info-refresh”
\n24) “5673”
\n25) “role-reported”
\n26) “slave”
\n27) “role-reported-time”
\n28) “2465451”
\n29) “master-link-down-time”
\n30) “0”
\n31) “master-link-status”
\n32) “ok”
\n33) “master-host”
\n34) “192.168.1.12”
\n35) “master-port”
\n36) “6379”
\n37) “slave-priority”
\n38) “2”
\n39) “slave-repl-offset”
\n40) “526637”
\n41) “replica-announced”
\n42) “1”<\/p><\/blockquote>\n
\nmin: 0, max: 1, avg: 0.02 (176 samples)<\/p><\/blockquote>\nSeventh Step : Keepalived Virtual IP Configuration<\/h3>\n
\nexit 0
\nelse
\nexit 1
\nfi<\/p>\n
\nscript “\/etc\/keepalived\/check_redis_master.sh”
\ninterval 2
\nweight 10
\n}<\/p>\n
\nstate MASTER
\ninterface ens160
\nvirtual_router_id 51
\npriority 100
\nadvert_int 1
\nauthentication {
\nauth_type PASS
\nauth_pass Pass1234
\n}
\nvirtual_ipaddress {
\n192.168.1.11
\n}
\ntrack_script {
\nchk_redis
\n}
\n}<\/p>\nEighth Step : Failover Operations<\/h3>\n
\n127.0.0.1:6379> auth default Password123
\nOK
\n127.0.0.1:6379> info replication
\n# Replication
\nrole:master
\nconnected_slaves:2
\nslave0:ip=192.168.1.14,port=6379,state=online,offset=754198,lag=0
\nslave1:ip=192.168.1.13,port=6379,state=online,offset=754198,lag=0
\nmaster_failover_state:no-failover
\nmaster_replid:03026581141f83e6224b3ad1a15b982b8b5854dc
\nmaster_replid2:e6be901b80683835a598cee49dfed0b412d62ed7
\nmaster_repl_offset:754198
\nsecond_repl_offset:739868
\nrepl_backlog_active:1
\nrepl_backlog_size:1048576
\nrepl_backlog_first_byte_offset:653194
\nrepl_backlog_histlen:101005<\/p>\n
\nlag has to be 0 or max 1.
\noffset has to be the same or near.
\nstate has to be online.<\/p><\/blockquote>\n
\nOK
\n[root@rds1 redis]# redis-cli -p 26379 SENTINEL get-master-addr-by-name mymaster
\n1) “192.168.1.13”
\n2) “6379”<\/p>\nBonus : Useful Commands<\/h3>\n
\nGET key<\/strong> Gets the value of a key
\nDEL key<\/strong> Deletes a key
\nEXISTS key<\/strong> Checks if a key exists (returns 1 or 0)
\nEXPIRE key seconds<\/strong> Sets a time-to-live (TTL) for a key
\nTTL key<\/strong> Gets remaining TTL for a key
\nINCR key<\/strong> Increments the integer value of a key by one
\nDECR key<\/strong> Decrements the integer value of a key by one
\nAPPEND key value<\/strong> Appends value to an existing key<\/p><\/blockquote>\n
\nRPUSH key value<\/strong> Inserts value at the end of the list
\nLPOP key<\/strong> Removes and returns the first element
\nRPOP key<\/strong> Removes and returns the last element
\nLRANGE key 0 -1<\/strong> Returns elements between given indexes<\/p><\/blockquote>\n
\nSREM key value<\/strong> Removes a value from a set
\nSMEMBERS key<\/strong> Gets all members of the set
\nSISMEMBER key value<\/strong> Checks if a value exists in the set<\/p><\/blockquote>\n
\nHGET key field<\/strong> Gets the value of a field in a hash
\nHDEL key field<\/strong> Deletes a field from a hash
\nHGETALL key<\/strong> Gets all fields and values in a hash<\/p><\/blockquote>\n
\nFLUSHDB<\/strong> Deletes all keys in the current DB
\nFLUSHALL<\/strong> Deletes all keys in all databases
\nRENAME old new<\/strong> Renames a key
\nTYPE key<\/strong> Returns the data type of the key<\/p><\/blockquote>\n
\nBGSAVE<\/strong> Performs an asynchronous background save
\nLASTSAVE<\/strong> Shows the last successful save time
\nCONFIG GET <pattern><\/strong> Gets configuration parameters
\nCONFIG SET <param> <value><\/strong> Dynamically sets a configuration value<\/p><\/blockquote>\n
\nINFO persistence<\/strong> Shows persistence status
\nSLAVEOF host port<\/strong> Makes the server a replica of another instance
\nSENTINEL get-master-addr-by-name name<\/strong> Returns IP\/Port of monitored master
\nMONITOR<\/strong> Streams all received commands in real-time
\nSLOWLOG get<\/strong> Shows list of slow commands
\nINFO<\/strong> Displays detailed information about Redis server<\/p><\/blockquote>\n