DevOps Classroom Series – 02/Apr/2021

In Docker Overlay network driver provides multi host networking
Refer Here to understand overlay networks
To create a overlay network in docker we use docker swarm.
Docker Swarm gives management & Orchestration features
In Docker Swarm we specify desired state (i want some application to be run in two containers and swarm will try to maintain the state)
Refer Here for docker swarm article
Lets create 3 nodes in aws and install docker in it
Lets understand some key terms in docker swarm
- Swarm: Multiple Docker hosts run in swarm mode to act as managers and workers
- Task: The manager distributes the tasks to run inside the nodes. A task consists of a Docker container and the commands to run inside the container
- Service: This defines the task
- Node: An individual system with docker installed
Manager node initializes the swarm cluster by using the ip address of manager
Now lets login into the nodes which would like to join the swarm as a worker node
now lets login into the worker node and execute the following
Lets try to create a service where we describe the number of replicas

docker service create --replicas 2 --name httpd httpd:latest

docker service scale httpd=4