1. Docker cluster
With swarm, consul, registrator and consul-template
jmaitrehenry

2. Overview
• Create a swarm cluster
• Manage a swarm cluster
• Service discovery
• Service auto-configuration
2015-06-15 2

3. 1 linux server…
2015-06-15 3
An host running Linux

4. With docker…
2015-06-15 4
An host running Linux
Docker daemon

5. 2 linux servers with docker…
2015-06-15 5
An host running Linux
Docker daemon
An host running Linux
Docker daemon

6. How can I manage them?
• Individually? Why not if you like that
• On a cluster with a manager?Yeah!
2015-06-15 6

7. Docker swarm
2015-06-15 7
Docker Swarm is native clustering for Docker. It turns a pool of Docker hosts into a single, virtual host.
https://github.com/docker/swarm

8. How do I add a node to swarm ?
• Swarm need to register node IP and docker tcp port somewhere
• Consul have a Key/Value store and swarm can register node on it
2015-06-15 8

9. What is Consul?
Consul is a distributed, highly available system and provides:
• Service discovery
• Failure detection
• Key/Value store
• Bonus: supports multiple datacenter
2015-06-15 9

10. Create a swarm cluster
2015-06-15 10An host running Linux
Docker daemon
An host running Linux
Docker daemon
Consul host
Consul
daemon
Swarm cluster

11. How do I register an node to consul ?
• With swarm !
docker run -d swarm:0.3.0-rc2 join --
addr=10.1.1.231:2375 consul://10.1.8.32:8500/dc1
2015-06-15 11

12. How do I register an node to consul ?
• swarm:0.3.0-rc2 ? Support docker login
• --addr=<public host IP>:<port of docker http API>
• consul://<IP of consul server>:<port>/<datacenter>
docker run -d swarm:0.3.0-rc2 join --
addr=10.1.1.231:2375 consul://10.1.8.32:8500/dc1
2015-06-15 12

13. Create a swarm cluster
2015-06-15 13An host running Linux
Docker daemon
An host running Linux
Docker daemon
Consul host
Consul
daemon Register node to consul K/V store
Swarm cluster

14. How can I manage my swarm cluster?
• With swarm !
docker run -d -p 2375:2375 swarm manage
consul://10.1.8.32:8500/dc1
2015-06-15 14

15. How can I manage my swarm cluster?
# export DOCKER_HOST= tcp://<manager IP>:<port>
# docker <docker cmd>
WithoutTLS enabled (dev only please ) :
# unset DOCKER_TLS_VERIFY
2015-06-15 15

16. How can I manage my swarm cluster?
2015-06-15 16

17. Manage a swarm cluster
2015-06-15 17
An host
Docker
daemon
Consul host
Consul
daemon
Register node
My laptop
Docker
daemon
Docker
daemon
An host
manager
Swarm cluster

18. Manage a swarm cluster
2015-06-15 18
An host
Docker
daemon
Consul host
Consul
daemon
Register node
My laptop
Docker
daemon
Docker
daemon
An host
manager
Get node list
Swarm cluster

19. Manage a swarm cluster
2015-06-15 19
An host
Docker
daemon
Consul host
Consul
daemon
Register node
My laptop
Docker
daemon
Docker
daemon
An host
manager
Manage hosts
Get node list
Swarm cluster

20. Ok, fine, I have 3 docker containers but how
they know each other?
• First, we need to register service somewhere
• Second, each service can ask somewhere where are other service
2015-06-15 20

21. Service discovery
Service discovery is a key component of most distributed systems and
service oriented architectures.The problem seems simple at first: How do
clients determine the IP and port for a service that exist on multiple hosts?
2015-06-15 21

22. Oh, consul is a service discovery!
• Yes it is!
Service list: http://10.1.8.32:8500/v1/catalog/services
2015-06-15 22

23. Consul
• Service details: http://10.1.8.32:8500/v1/catalog/service/statsd-8125
2015-06-15 23
Consul server

24. Consul
• Service details: http://10.1.8.32:8500/v1/catalog/service/statsd-8125
2015-06-15 24
Consul server
Docker node

25. Consul
• Service details: http://10.1.8.32:8500/v1/catalog/service/statsd-8125
2015-06-15 25
Consul server
Docker node
Service address

26. How can docker register services in consul?
• With a service registry bridge for Docker like Registrator
2015-06-15 26

27. Registrator
• Service registry bridge for Docker
• « Registrator automatically register/deregisters services for Docker
containers based on published ports and metadata from the container
environment. »
• https://github.com/gliderlabs/registrator
2015-06-15 27

28. Registrator
2015-06-15 28
On each swarm node

29. Registrator
2015-06-15 29
On each swarm node
Local docker socket

30. Registrator
2015-06-15 30
Public node IP
On each swarm node
Local docker socket

31. Demo
2015-06-15 31

32. 2015-06-15 32

33. 2015-06-15 33

34. Ok, I have some nginx running, how can I have
a single entry point?
• With a load balancer (haproxy) with an auto update configuration
2015-06-15 34

35. Consul template
«The daemon consul-template queries a Consul instance and updates any
number of specified templates on the filesystem. As an added bonus, consul-
template can optionally run arbitrary commands when the update process
completes »
https://github.com/hashicorp/consul-template
2015-06-15 35

36. Consul template - command
2015-06-15 36

37. Consul template – where to run it?
• Where you want, the only condition is to have access to consul server.
• You could have it in a container
• You could have it somewhere else
2015-06-15 37

38. Consul template – template file
2015-06-15 38
Service name

39. Consul template – template file
2015-06-15 39
Service name
Service IP

40. Consul template – template file
2015-06-15 40
Service name
Service IP
Service port

41. Consul template - testing
2015-06-15 41

42. Consul template - testing
2015-06-15 42
Dump generated template and exit

43. Thanks!
2015-06-15 43