{{tag>db replication redis}}

====== redis replication setup ======

In order for replication to work, you need to have at least 3 instance on redis on different servers preferrably. 2 of those server have to have 

  ...
  replicaof <master redis server ip or dns> 6379
  ...

in their config files. The master must not have that line when starting.

This setup also uses redis-sentinel for failover. Here's an example of sentinel config file

<code>
port 26379
pidfile "/run/redis/redis-sentinel-dns.pid"
dir "/var/lib/redis-sentinel-dns"
logfile "/var/log/redis/sentinel-dns.log"

sentinel monitor master-dns 10.0.0.1 6379 2

sentinel auth-user master-dns yourauthuser
sentinel auth-pass master-dns passwored12345
sentinel down-after-milliseconds master-dns 5000

sentinel failover-timeout master-dns 10000

user default on nopass sanitize-payload ~* &* +@all
</code>

The above must be the same on all sentinel instances.

Example output from redis-sentinel which shows 2 replicas
<code>
127.0.0.1:26379> SENTINEL replicas master-dns
1)  1) "name"
    2) "10.0.0.2:6379"
    3) "ip"
    4) "10.0.0.2"
    5) "port"
    6) "6379"
    7) "runid"
    8) "db734ef0bd69a043632efad123dff5a6f4292b64"
    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) "625"
   19) "last-ping-reply"
   20) "625"
   21) "down-after-milliseconds"
   22) "5000"
   23) "info-refresh"
   24) "3101"
   25) "role-reported"
   26) "slave"
   27) "role-reported-time"
   28) "13207"
   29) "master-link-down-time"
   30) "0"
   31) "master-link-status"
   32) "ok"
   33) "master-host"
   34) "10.0.0.1"
   35) "master-port"
   36) "6379"
   37) "slave-priority"
   38) "100"
   39) "slave-repl-offset"
   40) "6405"
   41) "replica-announced"
   42) "1"
2)  1) "name"
    2) "10.0.0.3:6379"
    3) "ip"
    4) "10.0.0.3"
    5) "port"
    6) "6379"
    7) "runid"
    8) "a588edcbbd8f914000c341531da818617471c5a5"
    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) "251"
   19) "last-ping-reply"
   20) "251"
   21) "down-after-milliseconds"
   22) "5000"
   23) "info-refresh"
   24) "2973"
   25) "role-reported"
   26) "slave"
   27) "role-reported-time"
   28) "13208"
   29) "master-link-down-time"
   30) "0"
   31) "master-link-status"
   32) "ok"
   33) "master-host"
   34) "10.0.0.1"
   35) "master-port"
   36) "6379"
   37) "slave-priority"
   38) "100"
   39) "slave-repl-offset"
   40) "6419"
   41) "replica-announced"
   42) "1"
127.0.0.1:26379>

</code>

In above case the master is at IP 10.0.0.1 as shown:

<code>
127.0.0.1:26379> SENTINEL master master-dns
 1) "name"
 2) "master-dns"
 3) "ip"
 4) "10.0.0.1"
 5) "port"
 6) "6379"
 7) "runid"
 8) "fef19e25fd8fed69b64f9733fe276889455171ce"
 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) "170"
19) "last-ping-reply"
20) "170"
21) "down-after-milliseconds"
22) "5000"
23) "info-refresh"
24) "6640"
25) "role-reported"
26) "master"
27) "role-reported-time"
28) "414310"
29) "config-epoch"
30) "0"
31) "num-slaves"
32) "2"
33) "num-other-sentinels"
34) "2"
35) "quorum"
36) "2"
37) "failover-timeout"
38) "10000"
39) "parallel-syncs"
40) "1"
127.0.0.1:26379>
</code>
====== Tested on ======
  * redis 6.2.17
  * AlmaLinux release 9.5 (Teal Serval)

====== See also ======

====== References ======
  * https://redis.io/docs/latest/operate/oss_and_stack/management/sentinel/#a-quick-tutorial
  * https://redis.io/learn/howtos/quick-start/cheat-sheet