Merge pull request #258 from zalando-incubator/always-create-replica-service

[WIP] Always create replica service

README.md

@@ -242,6 +242,14 @@ As a preventive measure, one can restrict the minimum and the maximum number of
 If either `min_instances` or `max_instances` is set to a non-zero value, the operator may adjust the number of instances specified in the cluster manifest to match either the min or the max boundary.
 For instance, of a cluster manifest has 1 instance and the min_instances is set to 3, the cluster will be created with 3 instances. By default, both parameters are set to -1.
 
+### Load balancers 
+
+For any Postgresql/Spilo cluster an operator creates two separate k8s services: one for the master pod and one for replica pods. To expose these services to an outer network, one can attach load balancers to them by setting `enableMasterLoadBalancer` and/or `enableReplicaLoadBalancer` to `true` in the cluster manifest. In the case any of these variables is omitted from the manifest, the operator configmap's settings `enable_master_load_balancer` and `enable_replica_load_balancer` apply. Note that the operator settings affect all Postgresql services running in a namespace watched by the operator.
+
+For backward compatibility with already configured clusters we maintain in a cluster manifest older parameter names, namely `useLoadBalancer` for enabling the master service's load balancer and `replicaLoadBalancer` for the replica service. If set, these params take precedence over the newer `enableMasterLoadBalancer` and `enableReplicaLoadBalancer`. Note that in older versions of the operator (before PR #258) `replicaLoadBalancer` was responsible for both creating the replica service and attaching an LB to it; now the service is always created (since k8s service typically is free in the cloud setting), and this param only attaches an LB (that typically costs money).
+
+For the same reason of compatibility, we maintain the `enable_load_balancer` setting in the operator config map that was previously used to attach a LB to the master service. Its value is examined after the deprecated `useLoadBalancer` setting from the Postgresql manifest but before the recommended `enableMasterLoadBalancer`. There is no equivalent option for the replica service since the service used to be always created with a load balancer.
+
 # Setup development environment
 
 The following steps guide you through the setup to work on the operator itself.