First released in 2014, Kubernetes is an open-source container orchestration tool that can automatically scale, distribute and manage fault-tolerance on containers. Originally created by Google and then donated to Cloud Native Computing Foundation, Kubernetes is widely used in production environments to handle Docker containers and other container tools in a fault-tolerant manner. As an open-source product, it is available on various platforms and systems. Google Cloud, Microsoft Azure, and Amazon AWS offer official support for Kubernetes, so configuration changes to the cluster itself are not necessary.
The popularity of Kubernetes has steadily increased, with more than four major releases in 2017. K8s also was the most discussed project in GitHub during 2017 and was the project with the second most reviews.
Container orchestration systems like Kubernetes (nicknamed K8S) ensure high availability, disaster recovery, or scalability. The systems are responsible for handling one or multiple clusters of machines and detect the availability of each image running on it. The size of the clusters can range from three machines to more than thousands of machines and containers, distributed among different cloud providers if needed. If a machine breaks down, the tool should be able to shift its containers to another node while keeping the entire cluster operational.
We have selected some common use cases to demonstrate Kubernetes’ capabilities. The use cases can be utilized together for different setups.
Self-Healing and Scaling Services
For simplicity, K8s process units can be detailed as pods and services. A pod is the smaller deployment unit available on Kubernetes. A pod can contain several containers that will have some related communication — such as network and storage. Services are the interface that provides accessibility to a set of containers. These services can be for internal or public access and can load balance several container instances.
Serverless, with Server
Serverless architecture has taken the world by a storm since AWS launched Lambda. The principle is simple: just develop the code, and don’t worry about anything else. Server and scalability are handled by the cloud provider and code just have to be developed as functions that handle specific events: from HTTP requests to queue messages.
Vendor lock-in is the major disadvantage of this solution. It is almost impossible to change cloud providers without refactoring most of the code. There are some solutions like Serverless that seek to standardize function code across clouds. Another solution is to use a Kubernetes cluster to create a vendor-free serverless platform. As mentioned above, K8S abstracts away the difference between cloud servers. Currently, two popular frameworks virtualize the cluster as a serverless platform: Kubeless and Fission.
Optimized Resource Usage with Namespaces
A K8s namespace is also known as a virtual cluster. Namespaces create a virtually separated cluster inside the real cluster. Clusters without namespaces probably have test, staging and production clusters. Virtual clusters usually waste some resources because they do not undergo continuous testing and because staging is used from time to time to validate the work of a new feature. By using a virtual cluster, or a namespace, an operations team can use the same set of physical machines for different sets depending on a given workload.
Namespaces are closely related to DNS because services located within the same namespace are accessible through their names. Namespaces offer a good solution for creating similar environments that locate services through network names: instances from different namespaces will find their dependencies without having to take into account which namespace they are located in.
In addition, namespaces can have resource quotas: each virtual cluster can receive a defined allocation in order to avoid a resource competition between namespaces. This is particularly useful to avoid a production environment sharing computing resources with just a few priority environments. Finally, different permissions can be created with roles for each namespace in order to limit the number of individuals with access to production environments.
Hybrid and Multiclouds
A hybrid cloud utilizes computing resources from a local, conventional data centre, and from a cloud provider. A hybrid cloud is normally used when a company has some servers in an on-premise data centre and wants to use the cloud’s unlimited computing resources to expand or substitute company resources. A multi-cloud, on the other hand, refers to a cloud that uses multiple cloud providers to handle computing resources. Multi clouds are generally used to avoid vendor lock-in, and to reduce the risk from a cloud provider going down while performing mission-critical operations.
Both solutions are addressed by Kubernetes Federation. Multiple clusters — one for each cloud or on-premise data centre — are created that are managed by the Federation. The Federation synchronizes computing resources, and even allows cross-cluster discovery: virtually any pod can communicate with a pod in another cluster without knowing the infrastructure.
The Federation setup is not simple, and there is a caveat: for obvious reasons, the solution doesn’t work on managed services like Google Kubernetes Engine, Azure Container Service or AWS EKS.
Pinterest’s Kubernetes Story
With over 250 million monthly active users and serving over 10 billion recommendations every single day, the engineers at Pinterest knew these numbers are going to grow day by day, and they began to realize the pain of scalability and performance issues.
Their initial strategy was to move their workload from EC2 instances to Docker containers; they first moved their services to Docker to free up engineering time spent on Puppet and to have an immutable infrastructure.
The next strategy was to move to Kubernetes. Now they can take ideas from ideation to production in a matter of minutes, whereas earlier they used to take hours or even days. They have cut down so much overhead cost by utilizing Kubernetes and have removed a lot of manual work without making engineers worry about the underlying infrastructure.
Airbnb’s Kubernetes Story
Airbnb’s transition from a monolithic to a microservices architecture is pretty amazing. They needed to scale continuous delivery horizontally, and the goal was to make continuous delivery available to the company’s 1,000 or so engineers so they could add new services. Airbnb adopted Kubernetes to support over 1,000 engineers concurrently configuring and deploying over 250 critical services to Kubernetes (at a frequency of about 500 deploys per day on average). I want you to see this excellent presentation from Melanie Cebula, the infrastructure engineer at Airbnb.
The New York Times’s Journey to Kubernetes
Today the majority of the NYT’s customer-facing applications are running on Kubernetes. What an amazing story. The biggest impact has been an increase in the speed of deployment and productivity. Legacy deployments that took up to 45 minutes are now pushed in just a few. It’s also given developers more freedom and fewer bottlenecks. The New York Times has gone from a ticket-based system for requesting resources and weekly deploy schedules to allowing developers to push updates independently.
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