Cloud Computing - introSun 02 November 2014
As nobody understands the cloud, it became obvious to me I will hack something out of it. And I did. A job. My latest toy is CoreOS. It features two nice things a man doesn't need until he faces big amount of servers. First being collective consciousness, aka etcd, allowing storing information about the services, like which upstream servers for your load balancers are on which IP addresses. Second is fleetd, which uses etcd to store and read data. It starts docker containers on your CoreOS instances. Actually, it starts systemd services, which is even better! :o) Oh, did I mention cloud computing these days is all about running containers? Docker containers in my case. Lastly, in dynamic environment of the cloud, you need dynamic configuration. But what application in the world has dynamic configuration? None that I know. Despite that fact, cloud computing and docker containers are thriving. There's a secret ingredient: confd. What it does is poll etcd every 10 seconds or so, checking if there are changes on some of the keys in it and if there is, generates the configuration of your application and restarts it. Confd uses templates and etcd data to generate the configuration, so once you have your fleet running, changing master DB host is as easy as
etcdctl set /my/app/db/server 192.168.0.4
and all containers having confd will pick up the changes. Just imagine, one command and thousand services change their configuration accordingly. This is small step for cloud, but huge step for a man, because it's hard to start thinking about "configuration is in the cloud". Once you grasp that idea, you're on a great way to cloud computing.