Cannot restart redis-sentinel unit - redis

Question

I'm trying to configure 3 Redis instances and 6 sentinels (3 of them running on the Redises and the rest are on the different hosts). But when I install redis-sentinel package and put my configuration under /etc/redis/sentinel.conf and restart the service using systemctl restart redis-sentinel I get this error:
Job for redis-sentinel.service failed because a timeout was exceeded.
See "systemctl status redis-sentinel.service" and "journalctl -xe" for details.
Here is the output of journalctl -u redis-sentinel:
Jan 01 08:07:07 redis1 systemd[1]: Starting Advanced key-value store...
Jan 01 08:07:07 redis1 redis-sentinel[16269]: 16269:X 01 Jan 2020 08:07:07.263 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
Jan 01 08:07:07 redis1 redis-sentinel[16269]: 16269:X 01 Jan 2020 08:07:07.263 # Redis version=5.0.7, bits=64, commit=00000000, modified=0, pid=16269, just started
Jan 01 08:07:07 redis1 redis-sentinel[16269]: 16269:X 01 Jan 2020 08:07:07.263 # Configuration loaded
Jan 01 08:07:07 redis1 systemd[1]: redis-sentinel.service: Can't open PID file /var/run/sentinel/redis-sentinel.pid (yet?) after start: No such file or directory
Jan 01 08:08:37 redis1 systemd[1]: redis-sentinel.service: Start operation timed out. Terminating.
Jan 01 08:08:37 redis1 systemd[1]: redis-sentinel.service: Failed with result 'timeout'.
Jan 01 08:08:37 redis1 systemd[1]: Failed to start Advanced key-value store.
Jan 01 08:08:37 redis1 systemd[1]: redis-sentinel.service: Service hold-off time over, scheduling restart.
Jan 01 08:08:37 redis1 systemd[1]: redis-sentinel.service: Scheduled restart job, restart counter is at 5.
Jan 01 08:08:37 redis1 systemd[1]: Stopped Advanced key-value store.
Jan 01 08:08:37 redis1 systemd[1]: Starting Advanced key-value store...
Jan 01 08:08:37 redis1 redis-sentinel[16307]: 16307:X 01 Jan 2020 08:08:37.738 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
Jan 01 08:08:37 redis1 redis-sentinel[16307]: 16307:X 01 Jan 2020 08:08:37.739 # Redis version=5.0.7, bits=64, commit=00000000, modified=0, pid=16307, just started
Jan 01 08:08:37 redis1 redis-sentinel[16307]: 16307:X 01 Jan 2020 08:08:37.739 # Configuration loaded
Jan 01 08:08:37 redis1 systemd[1]: redis-sentinel.service: Can't open PID file /var/run/sentinel/redis-sentinel.pid (yet?) after start: No such file or directory
and my sentinel.conf file:
port 26379
daemonize yes
sentinel myid 851994c7364e2138e03ee1cd346fbdc4f1404e4c
sentinel deny-scripts-reconfig yes
sentinel monitor mymaster 172.28.128.11 6379 2
sentinel down-after-milliseconds mymaster 5000
# Generated by CONFIG REWRITE
dir "/"
protected-mode no
sentinel failover-timeout mymaster 60000
sentinel config-epoch mymaster 0
sentinel leader-epoch mymaster 0
sentinel current-epoch 0

Answer 1

If you are trying to run your Redis servers on Debian based distribution, add below to your Redis configurations:
pidfile /var/run/redis/redis-sentinel.pid to /etc/redis/sentinel.conf
pidfile /var/run/redis/redis-server.pid to /etc/redis/redis.conf

Answer 2

What's the output in the sentinel log file?
I had a similar issue where Sentinel received a lot of sigterms.
In that case you need to make sure that if you use the daemonize yes setting, the systemd unit file must be using Type=forking.
Also make sure that the location of the PID file specified in the sentinel config matches the location specified in the systemd unit file.

Answer 3

If you face below error in journalctl or systemctl logs,
Jun 26 10:13:02 x systemd[1]: redis-server.service: Failed with result 'exit-code'.
Jun 26 10:13:02 x systemd[1]: redis-server.service: Scheduled restart job, restart counter is at 5.
Jun 26 10:13:02 x systemd[1]: Stopped Advanced key-value store.
Jun 26 10:13:02 x systemd[1]: redis-server.service: Start request repeated too quickly.
Jun 26 10:13:02 x systemd[1]: redis-server.service: Failed with result 'exit-code'.
Jun 26 10:13:02 x systemd[1]: Failed to start Advanced key-value store.
Then check /var/log/redis/redis-server.log for more information
In most cases issue is mentioned there.
i.e if a dump.rdb file is placed in /var/lib/redis then the issue might be with database count or redis version.
or in another scenario disabled IPV6 might be the issue.