Docker swarm Logo

Docker Swarm allows orchestrating and managing container clusters easily, providing high availability and scalability. In this chapter, we will explore how to set up a cluster in Docker Swarm, deploy services, and manage the cluster.

What is Docker Swarm?

Docker Swarm is a built-in orchestration tool in Docker that allows you to manage multiple containers distributed across several hosts. Docker Swarm simplifies the creation and management of container clusters, permitting applications to scale and be fault tolerant.

Setting Up a Docker Swarm Cluster

To create a Docker Swarm cluster, we first need to initiate the Swarm on a primary node and then add additional nodes as workers or managers.

Initialize a Swarm

On the node that will act as the main manager of the cluster, execute the following command:

bash

Add Nodes to the Swarm

Once the Swarm is initialized, Docker provides a command to add additional nodes as workers. Run the following command on the node you wish to add:

bash

This image shows how Docker Swarm works with the nodes

Deploying Services in Docker Swarm

In Docker Swarm, applications run as services, which are automatically distributed across the cluster nodes. A service is similar to a container but is designed to run in a distributed and scalable manner.

Create a Service

To create a service in the cluster, use the following command:

bash

Scale a Service

Docker Swarm facilitates the scalability of services, allowing for real-time adjustment of the number of replicas.

bash

Managing Services in Docker Swarm

Docker Swarm allows managing services and checking their status in the cluster using the docker service ls command, which lists all running services.

View Service Status

bash

Inspect a Service

To get detailed information about a specific service, use the docker service inspect command:

bash

High Availability in Docker Swarm

Docker Swarm automatically distributes services among the cluster nodes. If a node fails, Docker Swarm reassigns the tasks of the fallen node to other available nodes to ensure service continuity.

Conclusion

Docker Swarm allows creating distributed container clusters, providing scalability and high availability for applications. With a simple setup, Docker Swarm facilitates managing services and nodes in a production environment. In the next chapter, we will address Kubernetes and compare its features with Docker Swarm to understand their differences and advantages in container orchestration.