Configurable HAProxy Advanced Redis Health Check

[fititnt]

• Main issue: ALB v0.8.x and clustering related options #17
• Similar to: MVP of configurable HAProxy redirecting for non-localhosts OpenResty #18
• Some links
  • https://www.haproxy.com/blog/haproxy-advanced-redis-health-check/
  • https://www.serverlab.ca/tutorials/linux/network-services/how-to-configure-haproxy-health-checks/

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This issue is not about create a role to install Redis without external dependencies (...not yet) but to allow some way to, via specifications under some alb_* variables, make changes on the HAProxy component of AP-ALB to deploy already well tested HAProxy Advanced Redis Health Check.

At the https://github.com/fititnt/ap-alb-cluster-demo we're testing role davidwittman.redis and could just make ALB play very nice with this and document very well.

[fititnt]

Good to know that the official HAProxy configuration for redis have at https://www.haproxy.com/blog/haproxy-advanced-redis-health-check/ seems to not work with lastest version of HAProxy because of missings "".

So what in the documentation was

backend bk_redis
 option tcp-check
 tcp-check send PINGrn
 tcp-check expect string +PONG
 tcp-check send info replicationrn
 tcp-check expect string role:master
 tcp-check send QUITrn
 tcp-check expect string +OK
 server R1 10.0.0.11:6379 check inter 1s
 server R2 10.0.0.12:6379 check inter 1s

Should be more like

(...)
     tcp-check send PING\r\n
     tcp-check expect string +PONG
     tcp-check send info\ replication\r\n
     tcp-check expect string role:master
     tcp-check send QUIT\r\n
     tcp-check expect string +OK
     server delta 173.249.10.99:6379 check inter 5s
     server echo 167.86.127.220:6379 check inter 5s
     server foxtrot 167.86.127.225:6379 check inter 5s

[fititnt]

I put this on-hold for now.

This is not a priority for the ALB v0.8.x and clustering related options #17, in special because of this commend #22 (comment) and the MVP of Consul storage adapter to lua-resty-auto-ssl #25 have a working redis cluster is not a strong requisite.

Anyway, have this type of health check still very interesting. Maybe will do it if start to make AP-ALB also have health checks for other databases like MariaDB