Redis Sentinel Load Balancing with HAProxy

For installing and configuring HAProxy, the APPUiO HAProxy Helm Chart is being used. It contains a ConfigMap (redisk8s) which configures the details.

HAProxy will check the 3 Sentinel instances which are available via the redis-headless service on port 26379. This service points to the master redis-node-X Pod. These Pods are also available through the redis-headless service on port 6379.

Using a custom TCP health check, the role of each Redis instance is checked and only instances which return role:master will be counted as healthy.

This approach has the small caveat that a restarted instance of Redis might come up in a master state until Sentinel reconfigured it to be a slave of the actual master. This could be solved by configuring each Redis instance with slaveof 0.0.0.0 6739 so on startup it will never be a slave. See selivan.github.io/2016/06/10/redis-no-splitbrain-on-network-partition.html