Docker Swarm or Swarm offers its clients a multitude of features. This management tool helps its end-users to create and deploy a cluster of nodes. Clients that require an orchestrated environment and have multiple cloud platforms often prefer Swarm.

Before we jump into Docker Swarm, we need to first understand Docker and Docker containers.

What is Docker and Docker Container?

Docker: it provides developers the freedom to simplify their workflow and restyle the tools as well as deployment environments for each project. Applications can be automatically deployed across different environments using Docker.

Docker containers: This open-source, light-weight software, launched in 2013, contained all the dependencies, for example-code, framework, libraries, etc. , required by an application to run efficiently between computing environments. Containers allowed developers to separate their apps from the environment.

In this blog, we will learn the following:

• What are the key concepts one needs to familiarize themselves with?
• What are Docker Swarm nodes?
• A list of important features of Docker Swarm
• Difference between Kubernetes and Docker swarm
• An installation guide for beginners

What are the key concepts one needs to familiarize themselves with?

1. Docker daemon: In addition to waiting for API requests it also manages docker objects like images, networks, containers, etc. The daemon issues a site for shared space and manages the content, for example- networks, volumes, that might be shared across multiple containers.

2. Docker Images: It is a read-only template that has a collection of instructions on how to create a container that can run smoothly on a Docker platform. The images contain OS libraries and important tools that are moreover required to run an application. In addition, it provides an opportune method to package up applications and server environments that have already been configured. Docker users can choose to either share it with others or keep it private.

3. Docker Client: it is a primary method of interaction, therefore the Docker and clients can communicate with multiple daemons easily. We can manage the entire lifecycle of a container using the Docker client inside the terminal. Moreover, the client provides an interface through which the user uses the product.

4. Docker registry: The registry is an open-sourced platform under the Apache License. The application allows us to store and distribute Docker images. As a result, we have a certain degree of control as to where the images are being stored. That is to say, we own the image distribution pipeline. The Registry is compatible with the Docker engine version 1.6.0 or higher.

What are Docker Swarm nodes?

A group of physical and virtual machines that work together in a cluster creates a Docker Swarm. In this swarm, when a machine joins a cluster, it becomes a node. There are three different types of nodes and each of them has a unique role to play:

1. Manager Node: As the name suggests, its main role is to distribute tasks among the other nodes in the swarm. In addition, they also perform “managerial tasks” needed to operate the swarm. The general recommendation is seven manager nodes for one swarm.
2. Leader Node: To assign a leader, after the formation of a cluster, Raft Consensus Algorithm is used. The leader node undertakes task management and orchestration decisions. During the unavailability of a leader node, for instance, a power failure, a new one can be created.
3. Worker Node: There are numerous hosts within a swarm. Each worker node receives and executes the duty assigned to them by the Manager node. By default, all manager modes are also worker nodes. In other words, they too perform the tasks depending on the availability of the resources.

A list of important features of Docker Swarm

1. High security
2. Ease with a user can easily roll-back a task
3. A decentralized access
4. Automated Load Balancing
5. High service availability.

Difference between Kubernetes and Docker swarm

Kubernetes and Docker Swarm are capable of running several similar services that may vary a little in terms of approach. In addition to difference in approaches, there are several more dissimilarities between these two open-source software.

1. The process of installation in Kubernetes is quite a time consuming and complex. On the other hand, the installation is fairly simple in the case of Docker swarm.
2. Load balancing in Docker Swarm is automated. On the other hand, manual intervention is required during the process of load balancing for Kubernetes.
3. The scalability and deployment of containers are comparatively faster in the case of Swarm.
4. In a swarm, the availability of applications is increased via redundancy.
5. In Kubernetes, data volumes can be shared with containers that are within the same pod. However, in the case of a swarm, data volumes can be shared with any containers.
6. Docker Swarm does not require tools for logging and monitoring. On the other hand, Kubernetes requires built-in tools to perform both functions.

A brief installation guide for beginners

Pre-requisities:

1. Ubuntu 64-bit operating system
2. An ubuntu  account with Sudo privileges
3. Command-line terminal
4. Docker software repositories (optional)

Procedure:

1. Update software repositories( sudo apt-get update ) and uninstall old versions of Docker( sudo apt-get remove docker docker-engine docker.io ).
2. Install Docker on Ubuntu using the command line: sudo apt install docker.io
3. Set-up and run the service by entering the following lines in the terminal window. First, sudo systemctl start docker and second, sudo systemctl enable docker.
4. Verify the docker version with the following command: sudo docker –version
5. Run a Docker Container and remember to pull an Image. We can list down the available images on the machines using the following command: sudo docker ps -a
6. Use the IP address of the manager node to create a cluster.
7. Once the manager node is successfully configured, add the worker node by copying the command of the “swarm init” and paste the output onto the worker node: sudo Docker Swarm join –token SWMTKN-1- xxxxx
8. Now, go back to the manager node and execute the following command to list the worker node: sudo docker node ls
9. As a result, a Swarm cluster is created and the service is launched in swarm mode.

Conclusion

To sum it up, Docker Swarm is extremely popular among developers as offers a simple solution. In addition, it proposes simplicity and fast deployment of applications.