This document discusses service registration and discovery with Consul. It begins with an overview of service registration and discovery and how existing approaches like DNS can struggle in Docker environments. Consul is presented as a tool that stores information about services and supports service discovery. Registrator is introduced as a tool that automatically registers and deregisters Docker services with Consul. The document demonstrates how to run Consul and Registrator as Docker containers and have Registrator register container services with Consul. Finally, Consul Template is discussed as a tool to query services registered with Consul and apply configuration templates.

1. Service Registration
and Discovery with
Michael Richardson @m_richo

2. $whoami
• Michael Richardson
• Engineer @ odecee
• @m_richo
• http://www.mricho.com
• I like DevOps*
• Docker has grown on me in the last 6 months
* My definition of DevOps is likely different from yours

3. Agenda
• What is Service Registration & Discovery?
• Consul
– tool to store information about services
• Registrator
– tool to register Docker services
• Consul-template
– tool to query registered services and apply
configuration.
• Demo

4. Service Registration and Discovery
What is it?

5. Service Registration and Discovery
What is it?
“Service Discovery Protocols (SDP) are
network protocols which allow automatic
detection of devices and services offered by
these devices on a computer network.”
Source: http://en.wikipedia.org/wiki/Service_discovery

6. Service Registration and Discovery
What is it?
Basically… how do clients determine the
network details of desired services.

7. Service Registration and Discovery
Existing techniques?
• DNS (perhaps Dynamic DNS)
• Puppet exported resources
• Chef Search
• many others

8. Service Registration and Discovery
These approaches can struggle in a docker world
Image source: http://www.ideachampions.com/weblogs/archives/2011/09/the_top_100_lam.shtml

9. Service Registration and Discovery
These approaches can struggle in a docker world
• DNS

10. Service Registration and Discovery
These approaches can struggle in a docker world
• DNS
– TTL and caching can often be an issue

11. Service Registration and Discovery
These approaches can struggle in a docker world
• DNS
– TTL and caching can often be an issue
– Just try doing interesting DNS things in an enterprise. 

12. Service Registration and Discovery
These approaches can struggle in a docker world
• DNS
– TTL and caching can often be an issue
– Just try doing interesting DNS things in an enterprise. 
– Containers don’t have a unique IP address. Simple IP
based DNS isn’t sufficient. *
* SRV records can be an option

13. Service Registration and Discovery
These approaches can struggle in a docker world
• DNS
– TTL and caching can often be an issue
– Just try doing interesting DNS things in an enterprise. 
– Containers don’t have a unique IP address. Simple IP
based DNS isn’t sufficient. *
• Config Management agents
* SRV records can be an option

14. Service Registration and Discovery
These approaches can struggle in a docker world
• DNS
– TTL and caching can often be an issue
– Just try doing interesting DNS things in an enterprise. 
– Containers don’t have a unique IP address. Simple IP
based DNS isn’t sufficient. *
• Config Management agents
– I’m resistant to running agents within a container.
– CM agent run intervals are probably not frequent enough.
* SRV records can be an option

15. Service Registration and Discovery
Are there any new tools for Services Discovery?

16. Service Registration and Discovery
• Zookeeper
• Doozer
• Etcd
• SmartStack
• Eureka
• SkyDNS
• consul
Yep. Quite a few…

17. Service Registration and Discovery
• Zookeeper
• Doozer
• Etcd
• SmartStack
• Eureka
• SkyDNS
• consul
Yep. Quite a few…

18. Consul
“Service Discovery and
configuration made easy.
Distributed, highly available
and datacenter aware.”

19. Consul
Key features…
• Service Discovery
• Health Checking
• Key/Value Storage
• Multi Datacenter

20. Consul
Key features…
• Service Discovery
• Health Checking
• Key/Value Storage
• Multi Datacenter

21. Consul - example

22. Consul - example
Consul service definition for nginx web server

23. Consul + Docker
How should I use consul with docker?

24. Consul + Docker
How should I use consul with docker?
Option 1: run 1 Consul client agent in every
container to register its service
Or
Option 2: run 1 consul client agent per Docker
host that is responsible for all the containers on it

25. Consul + Docker
How should I use consul with docker?
Option 1: run 1 Consul client agent in every
container to register its service
Or
Option 2: run 1 consul client agent per Docker
host that is responsible for all the containers on it
Option 2 makes more sense to me

26. Consul + Docker
Docker host running some containers

27. Consul + Docker
Add a Consul Agent as a container

28. Consul + Docker
Which talks to the consul cluster

29. Consul + Docker
Next Question?
How do we register the
container services with the
consul agent?

30. Consul + Docker
Question?
How do we register the
container services with the
consul agent?
Use
Registrator!

31. Registrator
• https://github.com/gliderlabs/registrator
• Automatically registers/deregisters services for docker
containers
• Supported Registry services include consul, etcd and SkyDNS
2
• Reads events from Docker Socket (/var/run/docker.sock)
• Run on each Docker host*
* Ideally run it as a container

32. Registrator
Installation instructions

33. Registrator
Installation instructions

34. Registrator
Starting Registrator

35. Registrator
Starting Registrator

36. Registrator
Starting Registrator
pass docker socket to container
Specify service registry endpoint (eg consul)

37. How does it work

38. How does it work
• Start containers for consul
and registrator

39. How does it work
• Start containers for consul
and registrator
• Registrator watches for
container start and die
events

40. How does it work
• Start containers for consul
and registrator
• Registrator watches for
container start and die
events
• Start new container

41. How does it work
• Start containers for consul
and registrator
• Registrator watches for
container start and die
events
• Start new container
• Registrator informs consul
of service A’s metadata
(IP/port/name/tag)

42. Service information is now in
Consul. How can we access it?

43. • Consul’s HTTP API
• Consul’s DNS API
• Consul-template (via HTTP
API)
Consul Access

44. • Consul’s HTTP API
• Consul’s DNS API
• Consul-template (via HTTP
API)
Consul Access

45. Consul-template
What does it do?

46. Consul-template
What does it do?
• Populate template files with data from
Consul.
• Optionally run commands when consul
data changes.

47. Consul-template – example 1

48. Consul-template – example 1

49. Consul-template – example 2

50. Consul-template – example 2

51. Time for a Demo

52. links
• https://consul.io/
• https://github.com/hashicorp/consul-template
• https://github.com/gliderlabs/registrator
• https://github.com/CiscoCloud/microservices-
infrastructure
• http://jasonwilder.com/blog/2014/02/04/service-
discovery-in-the-cloud/

53. Questions?
Thanks for listening
@m_richo