Container orchestration with CoreOS at Devops Finland meetup

Development and Operations, DevOps, is one of the important things when going beyond agile. It’s boosting the agile way of working and can be seen as an incremental way to improve our development practices. And what couldn’t be a good place to improve than learning at meetups how others are doing things. This time DevOps Finland meetup was about container orchestration with CoreOS and it was held at Oppex’s lounge in central Helsinki. The talks gave a nice dive into CoreOS, covering both beginner and seasoned expert points of view. Here’s my short notes about the presentations.

CoreOS intro for beginners, by beginners

The first talk was practically an interactive Core OS tutorial by Antti Vähäkotamäki and Frans Ojala. Their 99 slides showed how to get started with CoreOS on Vagrant step by step and what difficulties they experienced. Nothing special.

CoreOS in production, lessons learned

The more interesting talk about CoreOS was “CoreOS in production, lessons learned” by Vlad Bondarenko from Oppex where he told about their software stack and how they’re running it. In short, they’re running on baremetal with CoreOS Nginx for reverse proxy, Node.js for UI and API and RethinkDB and SolrCloud clusters. Deployment is made with Ansible and makefiles and is used for Node.js. Service discovery is DNS based with docker-etcd-registrator component and they’ve also written their own DNS server. For Node.js config management with etcd they’ve made etcd-simple-config component. With Docker they use standard images with volumes and inject own data to the container.

CoreOS seemed to work quite well for them with easy cluster management, running multiple versions of 3rd party and own software and having zero downtime updates or rollbacks. But there were some cons also like maturity (bugs) and scripting systemd.

Kontena, CoreOS war stories

The last talk was about CoreOS war stories in Kontena by Jari Kolehmainen. The slides tell the story of how they use CoreOS on Kontena and what are the pain points. In story short it comes to configuration management and issues related to etcd.

For bootstrapping they use CloudInit which is de-facto way to initialize cloud instances and Integrated to CoreOS. The hard parts with etcd are discovery, security (tls certificates), using central services vs. workers and maintenance (you don’t do it). Now they run etcd inside a container, bind it only to localhost and overlay network (Weave Net) and master coordinates etcd discovery. With automatic updates they use the best-effort strategy: If etcd is running, locksmith coordinates the reboots; Otherwise just reboot when update is available.

Presentation’s summary was that the “OS” part is currently best option for containers and etcd is a must, but a little hard to handle. For the orchestrator they suggest that pick one which hides all the complexities. And automate all the things.

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