Interesting points: Explains how each pattern
focus on key important aspects like Health monitoring and reproting,
distribution of load or even dynamic load balancing depending on the
load.
Patterns
Here are the must-know top 10 design
patterns for beginners synthesized from the
Kubernetes Patterns book. Getting familiar with these patterns will
help you understand foundational Kubernetes concepts, which in turn will help
you in discussions and when designing Kubernetes-based applications.
There are many important concepts in
Kubernetes, but these are the most important ones to start with:
To help you understand, the patterns
are organized into a few categories below, inspired by the Gang of Four's design
patterns.
These patterns represent the
principles and best practices that containerized applications must comply with
in order to become good cloud-native citizens. Regardless of the application's
nature, you should aim to follow these guidelines. Adhering to these principles
will help ensure that your applications are suitable for automation on
Kubernetes.
Health Probe dictates that every container
should implement specific APIs to help the platform observe and manage the
application in the healthiest way possible. To be fully automatable, a
cloud-native application must be highly observable by allowing its state to be
inferred so that Kubernetes can detect whether the application is up and ready
to serve requests. These observations influence the life-cycle management of
Pods and the way traffic is routed to the application.
Predictable Demands explains why every container
should declare its resource profile and stay confined to the indicated resource
requirements. The foundation of successful application deployment, management,
and coexistence on a shared cloud environment is dependent on identifying and
declaring the application's resource requirements and runtime dependencies.
This pattern describes how you should declare application requirements, whether
they are hard runtime dependencies or resource requirements. Declaring your
requirements is essential for Kubernetes to find the right place for your
application within the cluster.
Automated Placement explains how to influence
workload distribution in a multi-node cluster. Placement is the core function
of the Kubernetes scheduler for assigning new Pods to nodes satisfying
container resource requests and honoring scheduling policies. This pattern
describes the principles of Kubernetes’ scheduling algorithm and the way to
influence the placement decisions from the outside.
Having good cloud-native containers
is the first step, but not enough. Reusing containers and combining them into
Pods to achieve the desired outcome is the next step. The patterns in this
category are focused on structuring and organizing containers in a Pod to
satisfy different use cases. The forces that affect containers in Pods result
in these patterns.
Init Container introduces a separate life
cycle for initialization-related tasks and the main application containers.
Init Containers enable separation of concerns by providing a separate life
cycle for initialization-related tasks distinct from the main application containers.
This pattern introduces a fundamental Kubernetes concept that is used in many
other patterns when initialization logic is required.
Sidecar describes how to extend and
enhance the functionality of a pre-existing container without changing it. This
pattern is one of the fundamental container patterns that allows single-purpose
containers to cooperate closely together.
These patterns describe the
life-cycle guarantees of the Pods ensured by the managing platform. Depending
on the type of workload, a Pod might run until completion as a batch job or be
scheduled to run periodically. It might run as a daemon service or singleton.
Picking the right life-cycle management primitive will help you run a Pod with
the desired guarantees.
Batch Job describes how to run an
isolated, atomic unit of work until completion. This pattern is suited for
managing isolated atomic units of work in a distributed environment.
Stateful Service describes how to create and
manage distributed stateful applications with Kubernetes. Such applications
require features such as persistent identity, networking, storage, and
ordinality. The StatefulSet primitive provides these building blocks with
strong guarantees ideal for the management of stateful applications.
Service Discovery explains how clients can
access and discover the instances that are providing application services. For
this purpose, Kubernetes provides multiple mechanisms, depending on whether the
service consumers and producers are located on or off the cluster.
The patterns in this category are
more complex and represent higher-level application management patterns. Some
of the patterns here (such as Controller) are timeless, and Kubernetes itself
is built on top of them.
Controller is a pattern that actively
monitors and maintains a set of Kubernetes resources in a desired state. The
heart of Kubernetes itself consists of a fleet of controllers that regularly
watch and reconcile the current state of applications with the declared target
state. This pattern describes how to leverage this core concept for extending
the platform for our own applications.
An Operator is a Controller that uses a
CustomResourceDefinitions to encapsulate operational knowledge for a specific
application in an algorithmic and automated form. The Operator pattern allows
us to extend the Controller pattern for more flexibility and greater
expressiveness. There are an increasing number of Operators for
Kubernetes, and this pattern is turning into the major form of operating
complex distributed systems.
Today, Kubernetes is the most popular
container orchestration platform. It is jointly developed and supported by all
major software companies and offered as a service by all of the major cloud
providers. Kubernetes supports both Linux and Windows systems, plus all major
programming languages. This platform can also orchestrate and automate
stateless and stateful applications, batch jobs, periodic tasks, and serverless
workloads. The patterns described here are the most commonly used ones from a
broader set of patterns that come with Kubernetes as shown below.
Kubernetes Patters
organized in different categories
Kubernetes is the new application
portability layer and the common denominator among everybody on the cloud. If
you are a software developer or architect, the odds are that Kubernetes will
become part of your life in one form or another. Learning about the Kubernetes
patterns described here will change the way you think about this platform. I
believe that Kubernetes and the concepts originating from it will become as
fundamental as object-oriented programming concepts.
The patterns here are an attempt to
create the Gang of Four design patterns, but for container orchestration.
Reading this article must not be the end, but the beginning of your Kubernetes
journey. Happy kubectl-ing!
