I am new to Docker. From what I understood both Docker and Kubernetes manage multiple containers. Kubernetes is more a large-scale container management with an abstraction layer compared to Docker. Isn't it possible to duplicate this scenario of abstraction in Docker? If so, then why do we say that it is purely different from each other? How exactly does Kubernetes differ from Docker with its application?
I went through some explanations but still being confused regarding this question. Could anyone help me with a good explanation or provide some materials that would help me clear this out?
Thanks in advance.
Docker is a container runtime tool first; Kubernetes cannot be compared to Docker. The PODs are scheduled or managed by the orchestration platform known as Kubernetes.
You may compare Kubernetes with Docker swarm in several ways.
Kubernetes have some better options like
Distribution of containers based on the requirement (Run ML container on Graphics card Nodes, CPU required container on CPU intensive VMs or Node pool)
Scaling based on Metrics - HPA & VPA
Observability across platform - Easy to add/integrate other solutions
RBAC & Security options - Firewall rules, Network policies
Loadbalancing internally with Service
Traffic routing option & pluggable solutions - Istio, LinkerD
Managed services by cloud providers - EKS, GKE, OKE
Variety of Volume options - PV, PVC backed by SSD, NFS, CSI driver options
Related
I have a project to containerize several applications (Gitlab, Jenkins, Wordpress, Python Flask app...). Currently each application runs on a Compute Engine VM each at GCP. My goal would be to move everything to a cluster (Swarm or Kubernetes).
However I have different questions about Docker Swarm on Google Cloud Platform:
How can I expose my Python application on the outside (HTTP load balancer) as well as the other applications only available in my private VPC ?
From what I've seen on the internet, I have the impression that docker swarm is very little used. Should I go for a kubernetes cluster instead ? (I have good knowledge of Docker/Kubernetes)
It is difficult to find information about Docker Swarm in cloud providers. What would be an architecture with Docker Swarm on GCP?
Thanks for your help.
I'd create a template and from that an instance group for all VM, which shall host the Docker swarm. And a separate instance or instance group for said internal purposes - so that there is a strict separation, which can then be used to route the internal & external traffic accordingly (this would apply in any case). Google Kubernetes Engine is about the same as such an instance group, but Google managed infrastructure. See the tutorial, there's not much difference - except that it better integrates with gcloud & kubectl. While there is no requirement to want or need to maintain the underlying infrastructure, GKE is probably less effort.
What you are basically asking is:
Kubernetes vs. Docker Swarm: What’s the Difference?
Docker Swarm vs Kubernetes: A Helpful Guide for Picking One
Kubernetes vs. Docker: What Does it Really Mean?
Docker Swarm vs. Kubernetes: A Comparison
Kubernetes vs Docker Swarm
I am new to cluster container management, and this question is the basis for all the freshers over here.
I read some documentation, but still, my understanding is not too clear, so any leads.. helping to understand?
Somewhere it is mentioned, Minikube is used to run Kubernetes locally. So if we want to maintain cluster management in my four-node Raspberry Pi, then Minikube is not the option?
Does Minikube support only a one-node system?
Docker Compose is set of instructions and a YAML file to configure and start multiple Docker containers. Can we use this to start containers of the different hosts? Then for simple orchestration where I need to call container of the second host, I don't need any cluster management, right?
What is the link between Docker Swarm and Kubernetes? Both are independent cluster management. Is it efficient to use Kubernetes on Raspberry Pi? Any issue, because I was told that Kubernetes in single node takes the complete memory and CPU usage? Is it true?
Is there other cluster management for Raspberry Pi?
I think this 4-5 set will help me better.
Presuming that your goal here is to run a set of containers over a number of different Raspberry Pi based nodes:
Minikube isn't really appropriate. This starts a single virtual machine on a Windows, MacOS or Linux and installs a Kubernetes cluster into it. It's generally used by developers to quickly start-up a cluster on their laptops or desktops for development and testing purposes.
Docker Compose is a system for managing sets of related containers. So for example if you had a web server and database that you wanted to manage together you could put them in a single Docker Compose file.
Docker Swarm is a system for managing sets of containers across multiple hosts. It's essentially an alternative to Kubernetes. It has fewer features than Kubernetes, but it is much simpler to set up.
If you want a really simple multi-node Container cluster, I'd say that Docker swarm is a reasonable choice. If you explicitly want to experiment with Kubernetes, I'd say that kubeadm is a good option here. Kubernetes in general has higher resource requirements than Docker Swarm, so it could be somewhat less suited to it, although I know people have successfully run Kubernetes clusters on Raspberry Pis.
Docker Compose
A utility to to start multiple docker containers on a single host using a single docker-compose up. This makes it easier to start multiple containers at once, rather than having do mutliple docker run commands.
Docker swarm
A native container orchestrator for Docker. Docker swarm allows you to create a cluster of docker containers running on multiple machines. It provides features such as replication, scaling, self-healing i.e. starting a new container when one dies ...
Kubernetes
Also a container orchestrator. Kubernetes and Docker swarm can be considered as alternatives to one another. They both try to handle managing containers starting in a cluster
Minikube
Creating a real kubernetes cluster requires having multiple machines either on premise or on a cloud platform. This is not always convenient if someone is just new to Kubernetes and trying to learn by playing around with Kubernetes. To solve that minikube allows you to start a very basic Kubernetes cluster that consists of a single VM on you machine, which you can use to play around with Kubernetes.
Minikube is not for a production or multi-node cluster. There are many tools that can be used to create a multi-node Kubernetes cluster such as kubeadm
Containers are the future of application deployment. Containers are smallest unit of deployment in docker. There are three components in docker as docker engine to run a single container, docker-compose to run a multi-container application on a single host and docker-swarm to run multi-container application across hosts which also an orchestration tool.
In kubernetes, the smallest unit of deployment is Pod(which is composed of multiple container). Minikube is a single node cluster where you can install it locally and try, test and feel the kubernetes features locally. But, you can't scale this to more than a single machine. Kubernetes is an orchestration tool like Docker Swarm but more prominent than Docker Swarm with respect to features, scaling, resiliency, and security.
You can do the analysis and think about which tool will be fit for your requirements. Each one having their own pros or cons like docker swarm is good and easy to manage small clusters whereas kubernetes is much better for larger once. There is another orchestration tool Mesos which is also popular and used in largest size clusters.
Check this out, Choose your own Adventure but, it's just a general analogy and only to understand because all the three technologies are evolving rapidly.
I get the impression you're mostly looking for confirmation and am happy to help with that if I can.
Yes, minikube is local-only
Yes, minikube is intended to be single-node
Docker-compose isn't really an orchestration system like swarm and Kubernetes are. It helps with running related containers on a single host, but it is not used for multi-host.
Kubernetes and Docker Swarm are both container orchestration systems. These systems are good at managing scaling up, but they have an overhead associated with them so they're better suited to multi-node.
I don't know the range of orchestration options for Raspberry Pi, but there are Kubernetes examples out there such as Build Your Own Cloud with Kubernetes and Some Raspberry Pi.
For Pi, you can use Docker Swarm Mode on one or more Pi's. You can even run ARM emulation for testing on Docker for Windows/Mac before trying to get it all working directly on a Pi. Same goes for Kubernetes, as it's built-in to Docker for Windows/Mac now (no minikube needed).
Alex Ellis has a good blog on Pi and Docker and this post may help too.
I've been playing around with orchestrating Docker containers on a subnet of Raspberry Pis (3Bs).
I found Docker-swarm easiest to set up and work with, and adequate for my purposes. Guide: https://docs.docker.com/engine/swarm/swarm-tutorial/
For Kubernetes there are two main options; k3s and microk8s. Some guides:
k3s
https://bryanbende.com/development/2021/05/07/k3s-raspberry-pi-initial-setup
microk8s
https://ubuntu.com/tutorials/how-to-kubernetes-cluster-on-raspberry-pi#1-overview
I know that Docker and Kubernetes aren’t direct competitors. Docker is the container platform and containers are coordinated and scheduled by Kubernetes, which is a tool.
What does it really mean and how can I deploy my app on Docker for Azure ?
Short answer:
Docker (and containers in general) solve the problem of packaging an application and its dependencies. This makes it easy to ship and run everywhere.
Kubernetes is one layer of abstraction above containers. It is a distributed system that controls/manages containers.
My advice: because the landscape is huge... start learning and putting the pieces of the puzzle together by following a course. Below I have added some information from the:
Introduction to Kubernetes, free online course from The Linux Foundation.
Why do we need Kubernetes (and other orchestrators) above containers?
In the quality assurance (QA) environments, we can get away with running containers on a single host to develop and test applications. However, when we go to production, we do not have the same liberty, as we need to ensure that our applications:
Are fault-tolerant
Can scale, and do this on-demand
Use resources optimally
Can discover other applications automatically, and communicate with each other
Are accessible from the external world
Can update/rollback without any downtime.
Container orchestrators are the tools which group hosts together to form a cluster, and help us fulfill the requirements mentioned above.
Nowadays, there are many container orchestrators available, such as:
Docker Swarm: Docker Swarm is a container orchestrator provided by Docker, Inc. It is part of Docker Engine.
Kubernetes: Kubernetes was started by Google, but now, it is a part of the Cloud Native Computing Foundation project.
Mesos Marathon: Marathon is one of the frameworks to run containers at scale on Apache Mesos.
Amazon ECS: Amazon EC2 Container Service (ECS) is a hosted service provided by AWS to run Docker containers at scale on its infrastructrue.
Hashicorp Nomad: Nomad is the container orchestrator provided by HashiCorp.
Kubernetes is built on Docker technology. It is an orchestration tool for Docker container whereas Docker is a technology to create and deploy containers.
Docker, starting with a platform-as-a-service (PaaS) provider named dotCloud.
All in all, Kubernetes is related to the Docker container, allowing you to implement application portability and extensibility in container orchestration.
DOCKER
Easy and fast to install and configure
Functionality is provided and limited by the Docker API
Quick container deployment and scaling even in very large clusters
Automated internal load balancing through any node in the cluster
Simple shared local volumes
Kubernetes
Require some work to get up and running
Client, API and YAML definitions are unique to Kubernetes
Provides strong guarantees to cluster states at the expense of speed
To Enable load balancing requires manual service configuration
Volumes shared within pods
This is just a basic idea which at least explains the difference.If you want to go in depth see my posts
http://www.thecreativedev.com/an-introduction-to-kubernetes/
http://www.thecreativedev.com/learn-docker-works/
Docker and Kubernetes are complementary. Docker provides an open standard for packaging and distributing containerized applications, while Kubernetes provides for the orchestration and management of distributed, containerized applications created with Docker. In other words, Kubernetes provides the infrastructure needed to deploy and run applications built with Docker.
I'm a bit lost with some of the basic concepts. It seems like the documentation / getting started requirements are basic knowledge about docker world that I don't have yet.
A swarm is a cluster of Docker engines, or nodes, where you deploy
services. The Docker Engine CLI and API include commands to manage
swarm nodes (e.g., add or remove nodes), and deploy and orchestrate
services across the swarm.
I understand that a cluster is a group of physical/virtual computers behaving as one. What is a cluster in the context of docker?
Docker engine is what creating the docker daemon + rest api + provide CLI in the machine docker is installed. What are docker engines?
What is a node?
What is a docker node?
what is a swarm node?
what is a orchestrate service?
Finally, what is a swarm?
I'm not looking for an article for each concept, only the minimal explanation that will help understand each concept in a overall. From there, I can easily continue on my own.
Please explain any additional concept which is more advance then the mentioned ones.
Thanks.
This is a great website which I believe will answer all your questions.
A cluster in Docker context is a group of hosts on which the Docker engine is installed
The Docker engine it is the main client - server application. More on this here
A node is a physical or a virtual machine
A node is a physical or a virtual machine running the Docker engine
A swarm node it is the same as 3 and 4, however, the difference is that SWARM will be running on it alongside the Docker engine.
An orchestration service is something that will take care of container creation and their dependencies. More here
Swarm is a clustering and scheduling tool for Docker.
Also, to learn more just do a Google search for the topic that you are interested in and you will find lots of useful explanations as well as examples :)
To make a scale-able architecture with docker containers is a very attractive solutions to deal with scale-ability issue. We can auto scale docker containers in Amazon Elastic Beanstalk environment or in a vendor specific pass environments.
What is the best way to make your own scale-able docker architecture on commodity cloud servers such as Digital Ocean or Rackspace that will auto provisions containers based on loads.
The most known solution for managing scaling a docker-based infrastructure are:
docker swarm
Kubernetes
for CoreOS, Fleet
Apache Mesos
This article mentions:
In terms of scale, only Mesos has been proven to support large-scale systems of hundreds or thousands of nodes. However, when looking at small clusters of, say, less than a dozen nodes, Mesos may be an overly complex solution.
As mentioned here:
Almost everything we can do with Docker we can do with Swarm as well only on a much larger scale. There’s nothing new to do, no configurations to be duplicated and nothing new to learn.
So start with Docker Swarm first, and if particular needs arise, look for the other solutions.
See:
"Deploy and Manage Any Cluster Manager with Docker Swarm"
"Using Machine to provision Docker Swarm clusters"