docker service registration and discovery

Service Registration

and Discovery with

Michael Richardson @m_richo

$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

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

Service Registration and Discovery

What is it?

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

Service Registration and Discovery

What is it?

Basically… how do clients determine the

network details of desired services.

Service Registration and Discovery

Existing techniques?

• DNS (perhaps Dynamic DNS)

• Puppet exported resources

• Chef Search

• many others

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

Service Registration and Discovery

These approaches can struggle in a docker world

• DNS

Service Registration and Discovery

These approaches can struggle in a docker world

• DNS

– TTL and caching can often be an issue

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.

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

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

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

Service Registration and Discovery

Are there any new tools for Services Discovery?

Service Registration and Discovery

• Zookeeper

• Doozer

• Etcd

• SmartStack

• Eureka

• SkyDNS

• consul

Yep. Quite a few…

Service Registration and Discovery

• Zookeeper

• Doozer

• Etcd

• SmartStack

• Eureka

• SkyDNS

• consul

Yep. Quite a few…

Consul

“Service Discovery and

configuration made easy.

Distributed, highly available

and datacenter aware.”

Consul

Key features…

• Service Discovery

• Health Checking

• Key/Value Storage

• Multi Datacenter

Consul

Key features…

• Service Discovery

• Health Checking

• Key/Value Storage

• Multi Datacenter

Consul - example

Consul - example

Consul service definition for nginx web server

Consul + Docker

How should I use consul with docker?

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

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

Consul + Docker

Docker host running some containers

Consul + Docker

Add a Consul Agent as a container

Consul + Docker

Which talks to the consul cluster

Consul + Docker

Next Question?

How do we register the

container services with the

consul agent?

Consul + Docker

Question?

How do we register the

container services with the

consul agent?

Use

Registrator!

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

Registrator

Installation instructions

Registrator

Installation instructions

Registrator

Starting Registrator

Registrator

Starting Registrator

Registrator

Starting Registrator

pass docker socket to container

Specify service registry endpoint (eg consul)

How does it work

How does it work

• Start containers for consul

and registrator

How does it work

• Start containers for consul

and registrator

• Registrator watches for

container start and die

events

How does it work

• Start containers for consul

and registrator

• Registrator watches for

container start and die

events

• Start new container

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)

Service information is now in

Consul. How can we access it?

• Consul’s HTTP API

• Consul’s DNS API

• Consul-template (via HTTP

API)

Consul Access

• Consul’s HTTP API

• Consul’s DNS API

• Consul-template (via HTTP

API)

Consul Access

Consul-template

What does it do?

Consul-template

What does it do?

• Populate template files with data from

Consul.

• Optionally run commands when consul

data changes.

Consul-template – example 1

Consul-template – example 1

Consul-template – example 2

Consul-template – example 2

Time for a Demo

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/

Questions?

Thanks for listening

@m_richo