Openshift is an open source container cloud platform, the underlying basis of the facts of the current container standard filing system Kubernetes and docker engine, companies can be based on this platform to build internal Paas platform, through the CI / CD processes, improve IT efficiency, embrace DevOps and agile development.
What is Paas
PaaS (Platform as a Service, Platform as a Service) was first presented in the cloud. As shown below, the corporate IT services are divided into nine, nine-storey traditional self-built data center facilities require companies to maintain their own, very high cost. The cloud computing architecture is equivalent to outsource part of the nine underlying architecture to the cloud computing service providers, according to the different levels of outsourcing, divided into IaaS (Infrastructure as a Service, Infrastructure as a Service), PaaS, SaaS (Software as a Service) three.
IaaS layer is infrastructure maintenance personnel services, providing computing, storage, networking and other hardware resources, the cloud platform users can deploy and run arbitrary software, including operating systems and applications, including the above, no longer need to manage infrastructure distracted.
PaaS layer to the application developer services, to provide the necessary support to run the software application run-time environment, related tools and services, such as database services, logging services, monitoring services, so that application developers can focus on delivering business value and the code without concern for the environment and basic tools needed for application.
SaaS layer for the average user (end-user) services, providing a complete set of available software system that allows general users do not care about the technical details, just through the browser, the client application can use the way application services deployed on the cloud. SaaS products such as customer relationship management systems, e-mail, virtual desktop, communications, games.
What is Kubernetes
Kubernetes is an open source container orchestration engine that automates the deployment of applications of container, expansion and management. The basic concept Kubernetes include:
- One or more worker nodes (worker node) is responsible for the workload
- One or more management node (master node) is responsible for managing the workload
- The deployment unit in a packaged called Pod using Pod additional metadata container and provides functionality for grouping a plurality of containers in a single entity in deployment
- Create a special resource. For example, a group represented Pod service and access policy, the access policy allows the container No special ip address can access. Copy controller (Replication controllers) is the number of copies Pod Another method for controlling the same time a particular resource, can use this feature to automatically extend the application to suit their current needs.
What is OKD
OKD is Kubernetes release, optimized for continuous application development and multi-tenant deployments. OKD on Kubernetes added developer tools and operations, in order to achieve rapid application development for small and large groups, easy to deploy and scale and long-term life-cycle maintenance.
OKD is embedded in the upper reaches of Kubernetes release of Red Hat OpenShift, and extended through security and other integration concept. OKD in github and document also called Origin.
openshift hierarchy
OpenShift v3 is a hierarchical system designed to open container mirror and Kubernetes concept underlying Docker format as accurately as possible, it focused on helping developers to easily composite applications. For example, the Ruby installation, and adding the code push MySQL.
Which, docker provides an abstraction based linux package and create a lightweight container mirroring; Kubernetes provides cluster management and scheduling functions containers on multiple hosts. OKD provides the following features:
- Help developers manage, build and deploy the source code
- Image management and promotion of large-scale flow into the system
- Large-scale application management
- Organize large staff organizational development team and user tracking
- Support network infrastructure cluster
OpenShift actually consists of three parts, the core part of the container is achieved scheduling Kubernetes package, in addition to a built-in image repository (Image Registry), the warehouse is optional, may be configured to use Dockerhub OpenShift or enterprise mirroring their warehouse, the outermost part is a friendly Web interface for display and operation Openshift of resources.
As shown below, OpenShift to be a complete digital platforms need to rely on the external two systems, a code base, a continuous integration services, and services are in fact two outer OpenShift can run inside. Openshift gray rectangle on the right it is the main architecture, and its top is a route (Router), and forwarding for DNS resolution, to ensure that users can call to Openshift cluster service. The intermediate portion is run on the operating system Kubernetes RHEL cluster, external storage service side, as in the cluster computing unit is floating, it is usually only provide Kubernetes clustered computing power, data need to rely on an external outer lasting example S3, EBS storage services such as cloud service providers. Infrastructure is also the lowest level provided by the cloud service provider service.
Pods
okd cited pods concept of kubernetes. pods refers to one or more containers running on the same host, it is to define, develop and deploy a minimum unit. Each pod is assigned its own internal IP address, and therefore has its entire port space, pod in the container can share their local storage and network.
pod life cycle can end when the container exit, pods can be retained in the container after the exit for easy access to the container logs.
pod can not be changed during operation, when the need to change, you need to stop and re-create the pod pod according to the configuration file, and mirror modified. When the pod will not hold exit, it is generally more advanced controller by management pods rather than the user direct management.
Reference material
https://www.duyidong.com/2017/06/14/kubernetes-and-openshift/
Official website link:
https://www.openshift.com/
https://access.redhat.com/documentation/en-us/openshift_container_platform/4.1/html/architecture/architecture
https://docs.okd.io/latest/ architecture / index.html