Kontena is an open source container platform that aims to maximize developer happiness. It uses CoreOS as the underlying OS and handles orchestration of containerized workloads across multiple nodes through tools like etcd for service discovery, Weave Net for the overlay network, and automated updates. Initially setting up etcd and the overlay network posed challenges, but Kontena's implementation addresses these by running etcd in containers only accessible via localhost/overlay network and having the master coordinate etcd discovery and network configuration. CoreOS and its bundled tools provide an ideal minimal base for containers, but Kontena abstracts away its complexity through automation and orchestration.

1. CoreOS Battle Stories
Jari Kolehmainen, Founder

2. Background

3. © 2015 Kontena, Inc.
What is Kontena?
Open Source container platform built to
maximize developer happiness. Works on
any cloud, easy to setup, simple to use.

4. How does it work?
Kontena Grid
A number of physical or virtual machines – Kontena Nodes –
create a Kontena Grid. The nodes may be located anywhere;
in single data center, different AZs or different cloud
providers.
Overlay Network
Kontena will automatically create an overlay network
powered by Weave and connect all nodes of a Grid. Overlay
network enable services to communicate with each other in
multi-host, multi-AZ environment.
Service Discovery
Kontena has a built-in service discovery powered by etcd. It is
used to automatically assign DNS addresses for any services
running in Kontena. It is also used by Kontena’s load
balancer for zero-downtime operation.
Orchestration
Kontena’s orchestrator is distributing, running and
monitoring all Kontena Services in a Grid. Services may be
stateless or stateful, and they are automatically distributed
across Nodes in a Grid.
Containerized Workloads
With Kontena, all containerized workloads are described as
Services. Kontena Service is composed of containers based
on the same image file. Services may be scaled and linked
together to create complex elastic apps.
OS
Docker
Kontena Nodes & Agent
Kontena Agent may be installed to any
machine capable of running Docker. It
is running as a privileged container in a
machine.
Kontena Master
Kontena Master is orchestrating the
entire Kontena system. It provides APIs
used by Kontena CLI, Web UI and third
party integrations.
Kontena Master may be installed as
high-availability setup if needed.

5. What about OS?

6. © 2016 Kontena, Inc.
Perfect OS: Requirements
• Minimal footprint
• Container native
• Zero maintenance
• Stable
• Secure

7. © 2016 Kontena, Inc.
Why Container OS?
• Our expectation from an OS has changed
• “Pets vs Cattle”
• Maintaining the system should be easy
• It needs to be more secure than traditional OS

8. Finding the
Right OS

9. © 2016 Kontena, Inc.
Choices (Back Then)
• Boot2Docker
• CoreOS
• Project Atomic
• DIY (not an option, really)

10. © 2016 Kontena, Inc.
Boot2Docker
• Based on Tiny Core Linux
• Small (24MB download, 5s to boot)
• No automatic updates
• Not recommended for production use

11. © 2016 Kontena, Inc.
CoreOS
• Based on Gentoo
• Minimal (~100MB)
• Designed for containers
• Focus on security and stability
• Automatic updates

12. © 2016 Kontena, Inc.
Project Atomic
• Not a new Linux distribution
• Framework to create on OS from RHEL, CentOS
and Fedora
• Designed for containers
• Focus on security and stability

13. CoreOS

14. Is not just an OS…

15. © 2016 Kontena, Inc.
CoreOS Project
• etcd
• rkt
• fleet
• locksmith
• flannel
• many more…

16. © 2016 Kontena, Inc.
CoreOS Host

17. Automation

18. © 2016 Kontena, Inc.
Kontena Provisioning Goals
• single command that “just works”
• register host to etcd cluster
• register host to Kontena Grid
• should work on any infrastructure

19. © 2016 Kontena, Inc.
CoreOS Problems
• configuration management
• etcd cluster / discovery
• etcd security
• coordinated auto-updates

20. © 2016 Kontena, Inc.
CoreOS & Configuration Management
• Chef
• Puppet
• Ansible
• Saltstack
• ??

22. CloudInit

23. © 2016 Kontena, Inc.
Bootstrapping with CloudInit
• de-facto way to initialize cloud instances
• integrated to CoreOS
• only sane way to bootstrap

24. etcd

25. © 2016 Kontena, Inc.
Etcd: The Hard Parts
• discovery
• security (tls certificates)
• central services vs workers
• maintenance

27. © 2016 Kontena, Inc.
Initial Implementation
• run etcd inside a container
• bind etcd only to localhost & overlay network
• use public discovery service

29. © 2016 Kontena, Inc.
Etcd: Current Implementation
• run etcd inside a container
• bind etcd only to localhost & overlay network
• master coordicates etcd discovery
• static ip’s

30. © 2016 Kontena, Inc.
Etcd: Future Improvements
• automatic failover with magic
• support for external etcd cluster
• compose.io

31. Automatic Updates

32. © 2016 Kontena, Inc.
Automatic Updates
• several update strategies
• best-effort, etcd-lock, reboot, off
• our pick: best-effort
• if etcd is running, locksmith coordinates the
reboots
• otherwise just reboot once update is available

33. © 2016 Kontena, Inc.
Automatic Updates
• chaos monkey for free!
• updates also kontena-agent
• works like a charm

34. Overlay Network

35. © 2016 Kontena, Inc.
Overlay Network Options
• Flannel by CoreOS
• Weave Net by Weaveworks
• Calico
• Docker Overlay Network
• Most likely you need one of these

36. © 2016 Kontena, Inc.
Flannel
• bundled with CoreOS
• depends on working etcd
• has multiple backends to choose from

37. © 2016 Kontena, Inc.
Weave Net
• simple setup
• optional encryption
• multicast, multi-hop, fast datapath
• dns
• requires “some” external coordination
• needs information about other peers

38. © 2016 Kontena, Inc.
Our Pick: Weave Net
• can start before etcd
• makes it possible to expose etcd only to overlay net
• secure communication between nodes
• not dependant on infrastructure features
• easy-ish to orchestrate
• “just works”

39. Demo!

40. Summary

41. © 2016 Kontena, Inc.
CoreOS Summary
• the “OS” part is currently best option for containers
• etcd is a must, but a little hard to handle
• pick orchestrator that hides all the complexities
• automate everything

42. Thank You!www.kontena.io