As the number of docker machines increases, there needs to be a system to manage them all. Docker Orchestration is a virtual docker MANAGER and allows us to start, stop, pause, unpause or kill the docker nodes(machines).

Docker has an in-built utility called “docker swarm”.

Kubernetes is another popular and versatile docker orchestration system used. A CLUSTER of dockers is called a ‘swarm’. Swarm turns a collection of docker engines into a single virtual docker engine.

In a swarm orchestration arrangement, one machine acts as a swarm manager that controls all the other machines connected to the cluster that acts as swarm nodes.

This is how I created a swarm of dockers and managed them on my machine:

We need docker services and docker machines to run these services on.Finally, we need a docker swarm to manage the docker nodes/machines

• Commands we need:
• docker service
• docker-machine
• docker swarm
• Task
• Create docker machines(nodes) and services.

Create a docker swarm and manage the services on different nodes and port numbers.

• Step 1: Create docker machines as ‘manager’ and ‘worker’: manager, node1, node2, node3, node4
• Step 2: Create a docker swarm
• Step 3: ADD the nodes as workers(or another manager) to the swarm
• Step 4: From the manager create docker services
• Step 5: list the docker services created also use -PS flag to view the node machines these services are running on.
• Step 6: Open the <ip_address>:<port_number> in the BROWSER and confirm the services running.

Step 1: Create docker machines: manager, node1, node2, node3, node4

docker-machine create --driver virtualbox manager

Step 2: Create a docker swarm

--Initialize a swarm and add ‘manager’ to the swarm cluster using its ip address: 192.168.99.100

Step 3: Add the nodes as workers(or another manager) to the swarm

--Connect to each node and run the above swarm join command

There can be more than one ‘manager’ node in a swarm

--connect to node1 and join node1 to the swarm as a worker

docker-machine ssh node1

--List the nodes connected in the swarm

connect to manager node:

$docker-machine ssh manager

Step 4: From the ‘manager’ node create new docker services

docker-machine ssh manager

--Create service replicating them on more than 1 nodes and expose them on the mentioned port.

This command pulls the docker image from docker hub.

Step 5: list the docker services created also use -ps flag to view the node machines these services are running on.

--List the services that will be shared among different swarm nodes

Swarm randomly assigns nodes to the running services when we replicate the services.

--service ‘httpd’ running on 3 nodes: node1, node2 and node3

--service ‘couchbase’ is running on 2 nodes: node1 and manager at port: 8091

--’couchbase’ service can be accessed via ‘node1’ (ip: 192.168.99.101) and ‘manager’ (ip: 192.168.99.100) at port : 8091 as show below

• http://192.168.99.101:8091/
• http://192.168.99.100:8091
• --’httpd’ service
• http://192.168.99.101:80
• http://192.168.99.102:80
• http://192.168.99.103:80
• --’my_nginx’ service
• http://192.168.99.100:8080
• http://192.168.99.104:8080

Screenshots of the running services:

‘manager’ node can create/inspect/list/scale or remove a service.

Refer

docker service --help

Conclusion:

A number of services are balanced over different nodes(machines) in a swarm cluster.A node declared as a ‘manager’ controls the other nodes.Basic ‘docker commands’ works from within a ‘manager’ node.