Docker Swarm Tutorial

Docker Swarm is the Docker native clustering solution, which can turn a group of distributed,

docker hosts into a single large virtual server.

• Docker Swarm provides the standard Docker API, and it can communicate with any tool that already works with Docker daemon allowing easy scaling to multiple hosts
• In docker swarm you create one or more managers and worker machines in the cluster .. the manager(s) take care of the orchestration of your deployed services (e.g., Creation/Replication/Assigning tasks to nodes/load balancing/service discovery )
• docker run --rm swarm --help

Step 1: Create cluster machines using docker-machine

docker-machine create --driver virtualbox --virtualbox-memory "3000" master
docker-machine create --driver virtualbox --virtualbox-memory "3000" worker1
docker-machine create --driver virtualbox --virtualbox-memory "3000" worker2

Note: Docker machine can also allow you create these machines on digital ocean, AWS, and other third party cloud services .. they have other drivers .

PS C:\Program Files\Docker Toolbox> docker-machine ls
NAME      ACTIVE   DRIVER       STATE     URL                         SWARM   DOCKER        ERRORS
master    -        virtualbox   Stopped                                       Unknown
worker1   -        virtualbox   Stopped                                       Unknown
worker2   -        virtualbox   Stopped                                       Unknown

Step 2: Start/Show machine IP/SSH into machine:

PS C:\Program Files\Docker Toolbox> docker-machine start master
PS C:\Program Files\Docker Toolbox> docker-machine ip master
192.168.99.101
PS C:\Program Files\Docker Toolbox> docker-machine ssh  master
                        ##         .
                  ## ## ##        ==
               ## ## ## ## ##    ===
           /"""""""""""""""""\___/ ===
      ~~~ {~~ ~~~~ ~~~ ~~~~ ~~~ ~ /  ===- ~~~
           \______ o           __/
             \    \         __/
              \____\_______/
 _                 _   ____     _            _
| |__   ___   ___ | |_|___ \ __| | ___   ___| | _____ _ __
| '_ \ / _ \ / _ \| __| __) / _` |/ _ \ / __| |/ / _ \ '__|
| |_) | (_) | (_) | |_ / __/ (_| | (_) | (__|   <  __/ |
|_.__/ \___/ \___/ \__|_____\__,_|\___/ \___|_|\_\___|_|
Boot2Docker version 17.05.0-ce, build HEAD : 5ed2840 - Fri May  5 21:04:09 UTC 2017
Docker version 17.05.0-ce, build 89658be
docker@master:~$ exit

Step 3: Init the swarm:You have to run this command on a manager machine.

PS C:\Program Files\Docker Toolbox> docker-machine ssh master
docker@master:~$ docker swarm init --advertise-addr 192.168.99.101

Step 4: Configure the worker machines to join the swarm
The below swarm join command is always generated after init swarm command above (include token).
In order to run on both workers I will have to SSH to each one run the command then exit.

docker-machine ssh worker1
docker swarm join \
       --token SWMTKN-1-41e2y83z8t462u4039lk0ugfwnuot5vqzbiv82ug6eadtbnbhl-2lfjygo3ic0nrnhjijffxhy47 
       192.168.99.101:2377
exit

docker-machine ssh worker2
docker swarm join \
       --token SWMTKN-1-41e2y83z8t462u4039lk0ugfwnuot5vqzbiv82ug6eadtbnbhl-2lfjygo3ic0nrnhjijffxhy47 
       192.168.99.101:2377
exit

To add a manager to this swarm, run 'docker swarm join-token manager' and follow
Step 5: Display all cluster nodes configured

PS C:\Program Files\Docker Toolbox> docker-machine ssh master
docker@master:~$ docker node ls
ID                            HOSTNAME            STATUS              AVAILABILITY        MANAGER STATUS
63izegp4x3to7cgoao1j9uqqg *   master              Ready               Active              Leader
svamypaqkur7ai3je5ob2z78t     worker2             Ready               Active
whopzq6ywt2eakrend8ji3hb8     worker1             Ready               Active

Notice the master is configured as leader and the * is because we are currently connected to it
Step 6: Create a network to make our services visible to each other

docker@master:~$ docker network create -d overlay my_network

Step 7: Create services and publish its ports
I've pushed both images to my docker hub account and now I will pull/run them on the cluster.

docker tag bipin:eureka bipingupta007/eureka
docker push bipingupta007/eureka
docker tag bipin:config bipingupta007/config
docker push bipingupta007/config

docker@master:~$ docker service create -p 8761:8761 --name eureka --network my_network bipingupta007/eureka 
docker@master:~$ docker service create -p 8888:8888 --name config --network my_network bipingupta007/config

• Here I've just deployed the services with 1 replicas .. however I could have used --replicas parameter to set the number of replicas of the service.
• You can also see that I've exposed the ports and also specified the network to make sure they can access each other using the service name

Step 8: Display all services

docker@master:~$ docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE                         PORTS
5t42nzl8bvo0        eureka              replicated          2/2                 bipingupta007/eureka:latest   *:8761->8761/tcp
uffvcped9b5o        config              replicated          1/1                 bipingupta007/config:latest   *:8888->8888/tcp

This will display the services and show you many of the replicas has been started and how many are still being prepared .. it should show something like this:
Step 9: Display tasks of a service

docker@master:~$ docker service ps eureka
ID                  NAME                IMAGE                         NODE                DESIRED STATE       CURRENT STATE           ERROR               PORTS
cvppczf7wgfw        eureka.1            bipingupta007/eureka:latest   worker1             Running             Running 2 minutes ago

Step 10: Scale a service
As I've mentioned before I could have set the number of replicas of a service at creation time .. now since I've already started it lets scale one of them to run 5 replicas.

docker@master:~$ docker service scale eureka=3
eureka scaled to 3

docker@master:~$ docker service ls
ID                  NAME                MODE                REPLICAS            IMAGE                         PORTS
5t42nzl8bvo0        eureka              replicated          3/3                 bipingupta007/eureka:latest   *:8761->8761/tcp

docker@master:~$ docker service ps eureka
ID                  NAME                IMAGE                         NODE                DESIRED STATE       CURRENT STATE                ERROR               PORTS
cvppczf7wgfw        eureka.1            bipingupta007/eureka:latest   worker1             Running             Running 8 minutes ago
86vuhj694evg        eureka.2            bipingupta007/eureka:latest   master              Running             Running about a minute ago
a6oi3gfq9pcv        eureka.3            bipingupta007/eureka:latest   worker2             Running             Running about a minute ago

Of course you can either scale up or down.

Step 11: Remove the service

docker@master:~$ docker service rm eureka
docker@master:~$ docker service ls
docker@master:~$ docker ps

and verify that the service was removed.
Step 12: Let's try calling the service
You can actually specify any of the cluster machine IPs not necessarily the manager.
http://192.168.99.101:8761/