Docker- Swarm

Docker - Swarm

If we have multiple Docker Containers & which are connected together. We can’t manage one by one. To manage all this type of Multiple containers we will use Docker Swarm.

In more Detail, Docker Swarm is an Orchestration tool for Docker Containers.

Let’s take an example – we have 100 containers. You need to do

Health check on every container
Ensure all containers are up on every system
Scaling the containers up or down depending on the load
Adding updates/changes to all the containers

Installation

Check docker-machine installed or not
docker-machine -v

If not follow this
https://docs.docker.com/machine/install-machine/#installing-machine-directly

Download the Docker Machine binary and extract it to your PATH(in Linux)

base=https://github.com/docker/machine/releases/download/v0.16.0 &&
  curl -L $base/docker-machine-$(uname -s)-$(uname -m) >/tmp/docker-machine &&
  sudo mv /tmp/docker-machine /usr/local/bin/docker-machine &&
  chmod +x /usr/local/bin/docker-machine

Check the installation by displaying the Machine version:

docker-machine version
docker-machine version 0.16.0, build 9371605

Example

In this example, We need to Create one Docker Swarm & multiple Node Machines

1.Create one machine as manager

[windows]
docker-machine create --driver hyperv manager1	

[linux]
docker-machine create --driver virtualbox manager1

If you got error like
"Error with pre-create check: "VBoxManage not found. Make sure VirtualBox is installed and VBoxManage is in the path"

Run
brew cask install virtualbox;

https://stackoverflow.com/questions/38696164/docker-machineerror-with-pre-create-check-exit-status-126

2.Check machine created successfully

#>  docker-machine ls

docker-machine ip manager1 (To get IP of manager)

3.Create Worker Machines

worker1	> docker-machine create --driver virtualbox worker1
worker2 > docker-machine create --driver virtualbox worker2

Check docker-machine ls :: we should see 1 manager & 2 workers

4.SSH (connect) to docker machines

docker-machine ssh manager1

docker-machine ssh worker1

docker-machine ssh worker2

5.Initialize Docker Swarm

docker swarm init --advertise-addr MANAGER_IP

docker node ls
(this command will work only in swarm manager and not in worker)

6. Join workers with the Docker swarm
In manager node run command
docker swarm join-token worker
This will give command to join swarm as worker

Copy the generated command & run in worker nodes.Check nodes again :: it should give nodes docker node ls

7. On manager , we can run standard docker commands

docker info
docker swarm

8.Run containers on Docker Swarm

#> docker service create --replicas 3 -p 80:80 --name serviceName nginx

   # Check the status:
    docker service ls
    docker service ps serviceName

    # Check the service running on all nodes
    Check on the browser by giving ip for all nodes

9.Scale service up and down
On manager node docker service scale serviceName=2

10.Shutdown node
docker node update --availability drain worker1

11.Update service

docker service update --image imagename:version web
docker service update --image nginx:1.14.0 serviceName

12.Remove service

docker service rm serviceName
docker swarm leave : to leave the swarm
docker-machine stop machineName : to stop the machine
docker-machine rm machineName : to remove the machine

References

PPT Book http://people.irisa.fr/Anthony.Baire/docker-tutorial.pdf

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Docker - Swarm

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References

Introduction

What is Docker

Handson

Installing Docker on Ubuntu

Labs Handson