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# Docker Swarm (mode) cluster
This section explains how to create a multi-host docker cluster with
swarm mode using [docker-machine ](https://docs.docker.com/machine ) and
how to deploy Træfɪ
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The cluster consists of:
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- 3 servers
- 1 manager
- 2 workers
- 1 [overlay ](https://docs.docker.com/engine/userguide/networking/dockernetworks/#an-overlay-network ) network
(multi-host networking)
## Prerequisites
1. You will need to install [docker-machine ](https://docs.docker.com/machine/ )
2. You will need the latest [VirtualBox ](https://www.virtualbox.org/wiki/Downloads )
## Cluster provisioning
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First, let's create all the required nodes. It's a shorter version of
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the [swarm tutorial ](https://docs.docker.com/engine/swarm/swarm-tutorial/ ).
```sh
docker-machine create -d virtualbox manager
docker-machine create -d virtualbox worker1
docker-machine create -d virtualbox worker2
```
Then, let's setup the cluster, in order :
1. initialize the cluster
2. get the token for other host to join
3. on both workers, join the cluster with the token
```sh
docker-machine ssh manager "docker swarm init \
--listen-addr $(docker-machine ip manager) \
--advertise-addr $(docker-machine ip manager)"
export worker_token=$(docker-machine ssh manager "docker swarm \
join-token worker -q")
docker-machine ssh worker1 "docker swarm join \
--token=${worker_token} \
--listen-addr $(docker-machine ip worker1) \
--advertise-addr $(docker-machine ip worker1) \
$(docker-machine ip manager)"
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docker-machine ssh worker2 "docker swarm join \
--token=${worker_token} \
--listen-addr $(docker-machine ip worker2) \
--advertise-addr $(docker-machine ip worker2) \
$(docker-machine ip manager)"
```
Let's validate the cluster is up and running.
```sh
docker-machine ssh manager docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS
2a770ov9vixeadep674265u1n worker1 Ready Active
dbi3or4q8ii8elbws70g4hkdh * manager Ready Active Leader
esbhhy6vnqv90xomjaomdgy46 worker2 Ready Active
```
Finally, let's create a network for Træfik to use.
```sh
docker-machine ssh manager "docker network create --driver=overlay traefik-net"
```
## Deploy Træfik
Let's deploy Træfik as a docker service in our cluster. The only
requirement for Træfik to work with swarm mode is that it needs to run
on a manager node — we are going to use a
[constraint ](https://docs.docker.com/engine/reference/commandline/service_create/#/specify-service-constraints-constraint ) for
that.
```
docker-machine ssh manager "docker service create \
--name traefik \
--constraint=node.role==manager \
--publish 80:80 --publish 8080:8080 \
--mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock \
--network traefik-net \
traefik \
--docker \
--docker.swarmmode \
--docker.domain=traefik \
--docker.watch \
--web"
```
Let's explain this command:
- `--publish 80:80 --publish 8080:8080` : we publish port `80` and
`8080` on the cluster.
- `--constraint=node.role==manager` : we ask docker to schedule Træfik
on a manager node.
- `--mount type=bind,source=/var/run/docker.sock,target=/var/run/docker.sock` :
we bind mount the docker socket where Træfik is scheduled to be able
to speak to the daemon.
- `--network traefik-net` : we attach the Træfik service (and thus
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the underlying container) to the `traefik-net` network.
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- `--docker` : enable docker backend, and `--docker.swarmmode` to
enable the swarm mode on Træfik.
- `--web` : activate the webUI on port 8080
## Deploy your apps
We can now deploy our app on the cluster,
here [whoami ](https://github.com/emilevauge/whoami ), a simple web
server in Go. We start 2 services, on the `traefik-net` network.
```sh
docker-machine ssh manager "docker service create \
--name whoami0 \
--label traefik.port=80 \
--network traefik-net \
emilevauge/whoami"
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docker-machine ssh manager "docker service create \
--name whoami1 \
--label traefik.port=80 \
--network traefik-net \
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--label traefik.backend.loadbalancer.sticky=true \
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emilevauge/whoami"
```
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Note that we set whoami1 to use sticky sessions (`--label traefik.backend.loadbalancer.sticky=true`). We'll demonstrate that later.
If using `docker stack deploy` , there is [a specific way that the labels must be defined in the docker-compose file ](https://github.com/containous/traefik/issues/994#issuecomment-269095109 ).
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Check that everything is scheduled and started:
```sh
docker-machine ssh manager "docker service ls"
ID NAME REPLICAS IMAGE COMMAND
ab046gpaqtln whoami0 1/1 emilevauge/whoami
cgfg5ifzrpgm whoami1 1/1 emilevauge/whoami
dtpl249tfghc traefik 1/1 traefik --docker --docker.swarmmode --docker.domain=traefik --docker.watch --web
```
## Access to your apps through Træfɪ
```sh
curl -H Host:whoami0.traefik http://$(docker-machine ip manager)
Hostname: 8147a7746e7a
IP: 127.0.0.1
IP: ::1
IP: 10.0.9.3
IP: fe80::42:aff:fe00:903
IP: 172.18.0.3
IP: fe80::42:acff:fe12:3
GET / HTTP/1.1
Host: 10.0.9.3:80
User-Agent: curl/7.35.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 192.168.99.1
X-Forwarded-Host: 10.0.9.3:80
X-Forwarded-Proto: http
X-Forwarded-Server: 8fbc39271b4c
curl -H Host:whoami1.traefik http://$(docker-machine ip manager)
Hostname: ba2c21488299
IP: 127.0.0.1
IP: ::1
IP: 10.0.9.4
IP: fe80::42:aff:fe00:904
IP: 172.18.0.2
IP: fe80::42:acff:fe12:2
GET / HTTP/1.1
Host: 10.0.9.4:80
User-Agent: curl/7.35.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 192.168.99.1
X-Forwarded-Host: 10.0.9.4:80
X-Forwarded-Proto: http
X-Forwarded-Server: 8fbc39271b4c
```
Note that as Træfik is published, you can access it from any machine
and not only the manager.
```sh
curl -H Host:whoami0.traefik http://$(docker-machine ip worker1)
Hostname: 8147a7746e7a
IP: 127.0.0.1
IP: ::1
IP: 10.0.9.3
IP: fe80::42:aff:fe00:903
IP: 172.18.0.3
IP: fe80::42:acff:fe12:3
GET / HTTP/1.1
Host: 10.0.9.3:80
User-Agent: curl/7.35.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 192.168.99.1
X-Forwarded-Host: 10.0.9.3:80
X-Forwarded-Proto: http
X-Forwarded-Server: 8fbc39271b4c
curl -H Host:whoami1.traefik http://$(docker-machine ip worker2)
Hostname: ba2c21488299
IP: 127.0.0.1
IP: ::1
IP: 10.0.9.4
IP: fe80::42:aff:fe00:904
IP: 172.18.0.2
IP: fe80::42:acff:fe12:2
GET / HTTP/1.1
Host: 10.0.9.4:80
User-Agent: curl/7.35.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 192.168.99.1
X-Forwarded-Host: 10.0.9.4:80
X-Forwarded-Proto: http
X-Forwarded-Server: 8fbc39271b4c
```
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## Scale both services
```sh
docker-machine ssh manager "docker service scale whoami0=5"
docker-machine ssh manager "docker service scale whoami1=5"
```
Check that we now have 5 replicas of each `whoami` service:
```sh
docker-machine ssh manager "docker service ls"
ID NAME REPLICAS IMAGE COMMAND
ab046gpaqtln whoami0 5/5 emilevauge/whoami
cgfg5ifzrpgm whoami1 5/5 emilevauge/whoami
dtpl249tfghc traefik 1/1 traefik --docker --docker.swarmmode --docker.domain=traefik --docker.watch --web
```
## Access to your whoami0 through Træfɪ
Repeat the following command multiple times and note that the Hostname changes each time as Traefik load balances each request against the 5 tasks.
```sh
curl -H Host:whoami0.traefik http://$(docker-machine ip manager)
Hostname: 8147a7746e7a
IP: 127.0.0.1
IP: ::1
IP: 10.0.9.3
IP: fe80::42:aff:fe00:903
IP: 172.18.0.3
IP: fe80::42:acff:fe12:3
GET / HTTP/1.1
Host: 10.0.9.3:80
User-Agent: curl/7.35.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 192.168.99.1
X-Forwarded-Host: 10.0.9.3:80
X-Forwarded-Proto: http
X-Forwarded-Server: 8fbc39271b4c
```
Do the same against whoami1.
```sh
curl -H Host:whoami1.traefik http://$(docker-machine ip manager)
Hostname: ba2c21488299
IP: 127.0.0.1
IP: ::1
IP: 10.0.9.4
IP: fe80::42:aff:fe00:904
IP: 172.18.0.2
IP: fe80::42:acff:fe12:2
GET / HTTP/1.1
Host: 10.0.9.4:80
User-Agent: curl/7.35.0
Accept: */*
Accept-Encoding: gzip
X-Forwarded-For: 192.168.99.1
X-Forwarded-Host: 10.0.9.4:80
X-Forwarded-Proto: http
X-Forwarded-Server: 8fbc39271b4c
```
Wait, I thought we added the sticky flag to whoami1? Traefik relies on a cookie to maintain stickyness so you'll need to test this with a browser.
First you need to add whoami1.traefik to your hosts file:
```ssh
if [ -n "$(grep whoami1.traefik /etc/hosts)" ];
then
echo "whoami1.traefik already exists (make sure the ip is current)";
else
sudo -- sh -c -e "echo '$(docker-machine ip manager)\twhoami1.traefik'
>> /etc/hosts";
fi
```
Now open your browser and go to http://whoami1.traefik/
You will now see that stickyness is maintained.
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