Docker Swarm

Docker swarm is a container orchestration tool. Swarm Mode in Docker was introduced in version 1.12 which enables the ability to deploy multiple containers on multiple Docker hosts. For this Docker uses an overlay network for the service discovery and with a built-in load balancer for scaling the services. One of the key advantages of docker swarm is that the configuration of the docker services such as volume and network can be modified without the need to manually restart the service Docker will update the configuration, stop the service tasks with the out-of-date configuration, and create new ones matching the desired configuration.

What is Docker and Docker Container?

Docker is an open-source container platform that helps in packing an appliation with all its dependencies in on one bundle i.e., Docker Image. On using this docker image assigning the resources such as RAM, CPU executing it as process known as Docker Container. Docker platform make the application containerized and portable to the all systems that supports docker.

What is Docker Swarm?

Docker Swarm is a native clustering and orchestrating tool that helps in managing the a docker engines. In this the group of docker engines turned into as single virtual docker host. It facilitates the users to deploy, manage and scale the applications seamlessly across multiple docker nodes. It comes with providing the features such as service discovery, load balancing, scaling, and rolling updates. It provides an easy and integrated way to manage the containerized applications in a cluster.

What are the Task and Service in Docker Swarm?

In Docker Swarm, a Service is a higher-level abstraction used to define how containers should be deployed, managed, and scaled across a swarm of Docker nodes. It includes specifications like the number of replicas, networking, and load balancing.

A Task is an individual instance of a container that is created and managed by a service. Each task represents a single unit of work and is scheduled to run on one of the nodes in the swarm. Tasks are the actual running containers that fulfill the requirements specified by the service.

How Does Docker Swarm Work?

When you want to deploy a container in the swarm first, you have to launch services. Service consists of multiple containers of the same image. These services are deployed inside a node so to deploy a swarm at least one node has to be deployed. As you see below diagram the manager node is responsible for the allocation of the task, dispatch the tasks, and schedule the tasks. API in the manager is the medium between the manager node and the worker node to communicate with each other by using the HTTP protocol. The service of one cluster can be used by the other. All the execution of the task is performed by the worker node.

Docker Swarm Init

To initialize the docker swarm cluster we use the command called “docker swarm init”. For converting the docker engine to the swarm manager we will use this command after converting into the swarm mode then you will able the manager and the worker nodes then the swarm will distribute the work across them.

After Initializing The Swarm Mode

• After initializing the docker swarm init it will bring the swarm into existence.
• After bringing the swarm into existence know it will turn the current node into a manager node. And also it will generate one token.
• The token that is generated will be used for the further joining of the worker nodes and master nodes.

Docker Swarm Architecture

There are two types of nodes in Docker Swarm:

1. Manager node: Carries out and oversees cluster-level duties.?
2. Worker node: Receives and completes the tasks set by the manager node.
3. Features of Docker Swarm

The following are the features of Docker Swarm:

1. Cluster management: To create Swarm you can use the Docker engine CLI where you can deploy the applications. Additional orchestration software is not required to manage a swarm.
2. Multi-host networking: Swarm can contain multiple overlay networks so while deploying the service you can specify the network on which you want to deploy your service. The swarm manager automatically assigns addresses to the containers on the overlay network when it initializes or updates the application.
3. Load balancing: While deploying any service on a particular port the swarm automatically balances the load of these ports.
4. Scaling: When you scale up or down, the swarm manager automatically adapts by adding or removing tasks to maintain the desired state.