docker cluster with swarm, consul, registrator and consul-template

Docker clusterWith swarm, consul, registrator and consul-

template

jmaitrehenry

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Overview

• Create a swarm cluster

• Manage a swarm cluster

• Service discovery

• Service auto-configuration

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1 linux server…

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An host running Linux

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With docker…

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An host running Linux

Docker daemon

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2 linux servers with docker…

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An host running Linux

Docker daemon

An host running Linux

Docker daemon

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How can I manage them?

• Individually? Why not if you like that

• On a cluster with a manager? Yeah!

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Docker swarm

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Docker Swarm is native clustering for Docker. It turns a pool of Docker hosts into a single, virtual host.

https://github.com/docker/swarm

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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

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What is Consul?

Consul is a distributed, highly available system and provides:

• Service discovery

• Failure detection

• Key/Value store

• Bonus: supports multiple datacenter

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Create a swarm cluster

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Docker daemon

An host running Linux

Docker daemon

Consul host

Consuldaemon

Swarm cluster

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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

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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

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Create a swarm cluster

2015-06-15An host running Linux

Docker daemon

An host running Linux

Docker daemon

Consul host

Consuldaemon Register node to consul K/V store

Swarm cluster

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How can I manage my swarm cluster?

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• With swarm !

docker run -d -p 2375:2375 swarm manage consul://10.1.8.32:8500/dc1

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How can I manage my swarm cluster?

# export DOCKER_HOST= tcp://<manager IP>:<port>

# docker <docker cmd>

Without TLS enabled (dev only please ) : # unset DOCKER_TLS_VERIFY

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How can I manage my swarm cluster?

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Manage a swarm cluster

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An host

Docker daemo

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Consul host

Consuldaemon

Register node

My laptopDocker daemo

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Docker daemo

n

An host

manager

Swarm cluster

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Manage a swarm cluster

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An host

Docker daemo

n

Consul host

Consuldaemon

Register node

My laptopDocker daemo

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Docker daemo

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An host

managerGet node list

Swarm cluster

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Manage a swarm cluster

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An host

Docker daemo

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Consul host

Consuldaemon

Register node

My laptopDocker daemo

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Docker daemo

n

An host

manager

Manage hosts

Get node list

Swarm cluster

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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

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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?

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Oh, consul is a service discovery!

• Yes it is!

Service list: http://10.1.8.32:8500/v1/catalog/services

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Consul• Service details:

http://10.1.8.32:8500/v1/catalog/service/statsd-8125

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Consul server

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Consul• Service details:

http://10.1.8.32:8500/v1/catalog/service/statsd-8125

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Consul server

Docker node

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Consul• Service details:

http://10.1.8.32:8500/v1/catalog/service/statsd-8125

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Consul server

Docker node

Service address

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How can docker register services in consul?

• With a service registry bridge for Docker like Registrator

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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

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Registrator

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On each swarm node

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Registrator

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On each swarm node

Local docker socket

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Registrator

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Public node IP

On each swarm node

Local docker socket

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Demo

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Ok, I have some nginx running, how can I have a single entry point?

• With a load balancer (haproxy) with an auto update configuration

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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

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Consul template - command

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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

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Consul template – template file

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Service name

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Consul template – template file

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Service name

Service IP

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Consul template – template file

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Service name

Service IP

Service port

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Consul template - testing

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Consul template - testing

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Dump generated template and exit

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Thanks!