Kubernetes vs. Docker Swarm: A Complete Comparison Guide
In this comparison of two longtime rivals, we take a look at when each should be used and how they can even work together.
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There are a countless number of debates and discussions talking about Kubernetes and Docker. If you have not dived deep, you would think that both of the open-source technologies are in the fight of the container supremacy. Let’s make it clear that, Kubernetes and Docker Swarm are not rivals! Both have their own pros and cons and can be used depending on your application requirements.
In this article, more light is shed upon these questions:
How have Kubernetes and Docker changed the era of software development?
How has it revolutionized the way of DevOps consulting?
Although they are different, how they can unify the processes of development and integration?
What restrictions come to the scenario?
If you are looking to develop for modern cloud infrastructure or looking for DevOps implementation, then understanding of the full concept ofs Kubernetes and Docker is a must. This comprehensive article will take you on the journey of Kubernetes vs. Docker Swarm from scratch and will help you to answer to each of the important questions.
Container, Containerization and Container Orchestration – A Quick Intro
A container is the software package that contains an application’s code, configurations, and dependencies which delivers operational efficiency and productivity. Here, you can know exactly how it will run which means it is predictable, repeatable, and immutable. The rise of containers has been a huge enabler for DevOps as a Service and can overcome the largest security hurdles faced today.
Containerization makes the applications portable by virtualizing at the operating-system level, creating isolated, encapsulated systems which are kernel based. Containerized apps can be dropped in anywhere and run without dependencies or requiring an entire VM, eliminating dependencies.
But what if there are multiple containers?
Here container orchestration is needed!
Container orchestration is the process that can typically deploy multiple containers to implement an application through automation. Platforms like Kubernetes and Docker Swarm are the container management and container orchestration engines that enable users to guide container deployment and automate updates, health monitoring, and failover procedures.
This all sounds really nice, but how do you actually use tools and build a container?
Let’s begin with Docker.
“Build, Ship, and Run Any App Anywhere”
Docker is a container management service which helps developers to design applications and make it easier to create, deploy and run applications by using containers. Docker has a built-in mechanism for clustering containers, called “swarm mode.” With swarm mode, you can use Docker Engine to launch application across multiple machines.
Docker Swarm – Tool to Manage Docker Containers
Docker Swarm is Docker’s own native clustering solution for Docker containers which has an advantage of being tightly integrated into the ecosystem of Docker and uses its own API. It monitors the number of containers spread across clusters of servers and is the most convenient way to create clustered docker application without additional hardware. It provides you with a small-scale but useful orchestration system for the Dockerized app.
Pros of Using Docker Swarm
Runs at a faster pace: When you were using a virtual environment, you may have realized that it takes a long time and includes the tedious procedure of booting up and starting the application that you want to run. With Docker Swarm, this is no longer a problem. Docker Swarm removes the need to boot up a full virtual machine and enables the app to run in a virtual and software-defined environment quickly and helps in DevOps implementation.
Documentation provides every bit of information: The Docker team stands out when it comes to documentation! Docker is rapidly evolving and has received great applause for the entire platform. When a version gets released at a short interval of time, some platform don’t maintain documentation. But Docker Swarm never compromises with it. If the information only applies to the certain versions of Docker Swarm, the documentation makes sure that all information is updated.
Provides simple and fast configuration: One of the key benefits of Docker Swarm is that it simplifies the matter. Docker Swarm enables the user to take their own configuration, put it into a code and deploy it without any hassle. As Docker Swarm can be used in various environments, requirements are just not bound by the environment of the application.
Ensures that application is isolated: Docker Swarm takes care that each container is isolated from the other containers and has its own resources. Various containers can be deployed for running the separate application in different stacks. Apart from this, Docker Swarm cleans app removal as each application runs on its own container. If the application is no longer required, you can delete its container. It won’t leave any temporary or configuration files on your host OS.
Version control and component reuse: With Docker Swarm, you can track consecutive versions of a container, examine differences or rollback to the preceding versions. Containers reuse the components from the preceding layers which makes them noticeably lightweight.
Cons of Using Docker Swarm
Docker is platform dependent: Docker Swarm is a Linux-agonistic platform. Although Docker supports Windows and Mac OS X, it utilizes virtual machines to run on a non-Linux platform. An application which is designed to run in a Docker container on Windows can’t run on Linux and vice versa.
Doesn’t provide storage option: Docker Swarm doesn’t provide a hassle-free way to connect containers to storage and this is one of the major disadvantages. Its data volumes require a lot of improvising on the host and manual configurations. If you’re expecting Docker Swarm to solve the storage issues, it may get done but not in an efficient and user-friendly way.
Poor monitoring: Docker Swarm provides the basic information about the container and if you are looking for the basic monitoring solution than Stats command is suffice. If you are looking for the advanced monitoring then Docker Swarm is never an option. Although there are third-party tools available like CAdvisor which offers more monitoring, it is not feasible to collect more data about containers in real-time with Docker itself
To Avoid These Shortfalls, Kubernetes Can be Used
Automated Container Deployment, Scaling and Management Platform
When an application is developed with the diverse components across numerous containers on several machines, there is a need for the tool to manage and orchestrate the containers. This is only feasible with the help of Kubernetes.
Kubernetes is an open source system for managing containerized application in a clustered environment. Using Kubernetes in a right way helps the DevOps as a Service team to automatically scale up-down the application and update with the zero downtime.
Pros of using Kubernetes
Its fast: When it comes to continuously deploy new features without downtime, Kubernetes is a perfect choice. The goal of the Kubernetes is to update an application with a constant uptime. Its speed is measured through a number of features you can ship per hour while maintaining an available service.
Adheres to the principals of immutable infrastructure: In a traditional way, if anything goes wrong with multiple updates, you don’t have any record of how many updates you deployed and at which point error occurred. In immutable infrastructure, if you wish to update any application, you need to build container image with a new tag and deploy it, killing the old container with old image version. In this way, you will have a record and get an insight of what you did and in-case if there is any error; you can easily rollback to the previous image.
Provides declarative configuration: User can know in what state the system should be to avoid errors. Source control, unit tests etc. which are traditional tools can’t be used with imperative configurations but can be used with declarative configurations.
Deploy and update software at scale: Scaling is easy due to its immutable, declarative nature of Kubernetes. Kubernetes offers several useful features for scaling purpose:
Horizontal Infrastructure Scaling: Operations are done at the individual server level to apply horizontal scaling. The atest servers can be added or detached effortlessly.
Auto-scaling: Based on the usage of CPU resources or other application-metrics, you can change the number of containers that are running
Manual scaling: You can manually scale the number of running containers through a command or the interface
Replication controller: The Replication controller makes sure that cluster has a specified number of equivalent pods in a running condition. If there are too many pods, the replication controller can remove extra pods or vice-versa.
Handles the availability of the application: Kubernetes checks the health of nodes and containers as well as provides self-healing and auto-replacement if in-case pod crashes due to an error. Moreover, it distributes the load across multiple pods to balance the resources quickly during accidental traffic.
Storage Volume: In Kubernetes, data is shared across the containers, but if pods get killed volume is automatically removed. Moreover, data is stored remotely, so if the pod is moved to another node, the data will remain until it is deleted by the user.
Cons of Using Kubernetes
Initial process takes time: When a new process is created, you have to wait for the app to commence before it is available to the users. If you are migrating to Kubernetes, modifications in the code base need to be done to make a start process more efficient so that users don’t have a bad experience.
Migrating to stateless requires much effort: If your application is clustered or stateless, extra pods will not get configured and will have to rework on the configurations within your applications.
The installation process is tedious: It is difficult to set up Kubernetes on your cluster if you are not using any cloud provider like Azure, Google or Amazon.
Kubernetes vs. Docker Swarm: A Quick Summary
|Developed By||Docker Inc|
|Companies using||Bugsnag, Bluestem Brands, Hammerhead, Code Picnic, Dial once etc.||Asana, Buffer, CircleCI, Evernote, Harvest, Intel, Starbucks, Shopify etc.|
|Storage||Volumes||Persistent and Ephermal|
|Public Cloud Service Provider||Google, Azure, AWS, OTC||Azure|
|Compatibility||Less Extensive and Customizable||More Extensive and highly customizable|
|Installation||Easy to set up||Takes time for installation|
|Tolerance ratio||Low Fault Tolerance||High fault tolerance|
|Large Clusters||Speed is considered for the strong cluster states||Provides container deployment and scaling even in large clusters without considering the speed|
|Load Balancing||Provides load balancing when pods in the container are defined as service||Provides automated internal load balancing through any node in the cluster|
|Network||Overlay||Flat Networking space|
|Community||Active user base that regularly updates images for various application||Enjoys strong support from open source communities and big companies like Google, Amazon, Microsoft, and IBM|
|Weakness||No certification plan for vendors. Most organization need commercially certified version||Inclined towards developers than central IT|
|Strengths||Mostly controlled by a single vendor who can decide product direction||Clear market leader; largest adoption and interest|
|Container set up||Functionality is provided and limited by Docker API||Client API and YAML are unique in Kubernetes|
|Scalability||Quick container deployment and scaling even in large containers||
Provides strong guarantees to the cluster states at expense of speed
Docker and Kubernetes Are Different, but Not Rivals
As discussed earlier, Kubernetes and Docker both work at the different level but both can be used together. Kubernetes can be integrated with the Docker engine to carry out the scheduling and execution of Docker containers. As Docker and Kubernetes are both container orchestrators, both can help to manage the number containers and also help in DevOps implementation. Both can automate most of the tasks that are involved in running containerized infrastructure and are open source software projects, governed by an Apache License 2.0. Apart from this, both use YAML – formatted files to govern how the tools orchestrate container clusters. When both of them are used together, both Docker and Kubernetes are the best tools for deploying modern cloud architecture. With the exemption of Docker Swarm, both Kubernetes and Docker complement each other.
Kubernetes uses Docker as the main container engine solution and Docker recently announced that it can support Kubernetes as the orchestration layer of its enterprise edition. Apart from this, Docker approves certified Kubernetes program, which makes sure that all Kubernetes API functions as expected. Kubernetes uses the features of Docker Enterprise like Secure Image management, in which Docker EE provides image scanning to make sure if there is an issue in the image used in the container. Another is Secure Automation in which organizations can remove inefficiencies such as scanning image for vulnerabilities.
Kubernetes or Docker: Which is the Perfect Choice?
Use Kubernetes if:
You are looking for mature deployment and monitoring option
You are looking for fast and reliable response times
You are looking to develop a complex application and requires high resource computing without restrictions
You have a pretty big cluster
Use Docker if,
You are looking to initiate with a tool without spending much time on configuration and installation;
You are looking to develop a basic and standard application which is sufficient enough with default docker image;
Testing and running the same application on the different operating system is not an issue for you;
You want zdocker API experience and compatibility.
Final Thoughts: Kubernetes and Docker are Friends
Whether you choose Kubernetes or Docker, both are considered the best and possess considerable differences. The best way to decide between the two of them is probably to consider which one you already know better or which one fits your existing software stack. If you need to develop the complex app, use Kubernetes and if you are looking to develop the small-scale app, use Docker Swarm. Moreover, choosing the right one is a very comprehensive task and solely depends on your project requirements and target audience as well.
Published at DZone with permission of Ankit Kumar. See the original article here.
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