MVP of AP-ALB demo with at least one way to share configurations created on run time across cluster

[fititnt]

Required by ALB v0.8.x and clustering related options #17

The drafts on the fititnt/ap-alb-cluster-demo I'm already testing Redis (thats the why Configurable HAProxy Advanced Redis Health Check #19), and one of the main reasons was share Let's Encrypt secrets (and the fact that GUI/lua-resty-autossl support Redis as just point click use).

But there is a catch here: not that Redis for our type os usage would not work, but it both could be used for real services on the same hosts (and them disincentive usage of AP-ALB) and also something I know from the start was that solutions like Etcd/Consul would be much more aligned with such needs.

So, this issue is for testing any solution that could at least work for one v0.8 demo. It also means that #17 is likely to be an release that maybe will take more time than last ones, and maybe not even archive one beta state before v0.9.

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• Comparações
  • https://technologyconversations.com/2015/09/08/service-discovery-zookeeper-vs-etcd-vs-consul/
• Consul
  • Consul Performance https://www.consul.io/docs/install/performance.html
  • https://docs.ansible.com/ansible/latest/modules/consul_module.html
  • https://github.com/brianshumate/ansible-consul
  • https://github.com/tdsacilowski/azure-consul-multi-datacenter
  • https://programmer.help/blogs/consul-remote-multi-data-center-and-cluster-deployment-scheme.html
  • https://learn.hashicorp.com/consul/getting-started/ui
• Confd
  • https://github.com/kelseyhightower/confd
  • https://github.com/jivesoftware/ansible-confd
  • https://github.com/andrewrothstein/ansible-confd
  • https://pt.slideshare.net/SeanChittenden/postgresql-highavailability-and-geographic-locality-using-consul?next_slideshow=1
• Etcd
  • https://docs.openstack.org/install-guide/environment-etcd-ubuntu.html
  • https://docs.openstack.org/install-guide/environment-etcd-ubuntu.html
  • https://launchpad.net/ubuntu/+source/etcd
  • https://www.digitalocean.com/community/tutorials/how-to-use-etcdctl-and-etcd-coreos-s-distributed-key-value-store
  • https://blog.openshift.com/metro-area-openshift-stretch-cluster-how-to-survive-an-outage-and-live-to-tell-about-it/
  • https://github.com/etcd-io/etcd/blob/master/Documentation/op-guide/clustering.md
  • https://github.com/etcd-io/etcd/blob/master/etcdctl/doc/mirror_maker.md
  • https://pt.slideshare.net/winsletts/etcd-based-postgresql-ha-cluster

[fititnt]

For the MVP demo, we will choose Consul (see https://github.com/fititnt/ap-application-load-balancer/issues/23.

Since the GUI/lua-rest-auto-ssl did not support the Consul as storage adapter, I created one at https://github.com/fititnt/ap-application-load-balancer/issues/25 and already made a Pull Request to the upstream