Redis HA for System components - system-redis

System components use REDIS_URL environment variable for setting the URL for Redis (JIRA for adding this in the template – THREESCALE-1062)

This only supports a single Redis instance, the request is to support Redis HA (e.g. Sentinels, as backend component does), as when Redis is down, some components will not work, which affects the functionality of the product.

system-redis is used for job queues.

---------------------- Part 2? -----------------------
System components communicate to backend Redis to get analytics information. The location is configured via BACKEND_REDIS_URL environment variable (JIRA for adding this in the template – THREESCALE-1062).

Backend supports Redis Sentinel (see the description in the KCS, and the JIRA for adding this to the documentation).

However, system currently doesn't support the same setup, and so system can only connect to one node to pull the statistics.

The request is to make system work with Redis Sentinel as well.

Notes

See this comment for configuration instructions

Dev Notes

gem install?, some config files to add, upgrade documentation, ...
#=> Probably no gem upgrade as redis-sentinel is deprecated: https://github.com/flyerhzm/redis-sentinel
#=> We could probably add an option for sentinels in the redis yml configs though: https://github.com/redis/redis-rb#sentinel-support

Needs to be tested on OpenShift

Other thing to consider

ruby redis client accepts password for sentinels, and it needs to be implemented.

SENTINELS = [{ host: '127.0.0.1', port: 26380, password: 'mysecret' },
             { host: '127.0.0.1', port: 26381, password: 'mysecret' }]

redis = Redis.new(host: 'mymaster', sentinels: SENTINELS, role: :master)