OpenShift on Azure for Beginners | Architecture and Features

In this post, I am sharing the overview of Azure OpenShift. Microsoft Azure Red Hat OpenShift is a fully managed offering that runs on Azure. This service is jointly managed and supported by Microsoft and Red Hat. As you know, Red Hat OpenShift provides a consistent application platform for modernized and cloud-native applications. Combining OpenShift and Azure together helps you to deploy Containerized Apps much more faster and reliably with no downtime.

Let’s quickly go through the topics of discussion:

Azure Red Hat OpenShift follows a simple architecture that depends on smaller decoupled entities called Microservices. These decoupled entities work together and run on the Kubernetes cluster. All of the data about objects is stored in a trusted clustered key-value store. These services are split into two components:

• Rest API: These are responsible for exposing every single core object.
• Controller: It is responsible for reading the above APIs, make necessary changes in other objects if required, report the status, and finally write back to the object. 

Source: Red Hat Docs

The cluster runs on Microsoft Azure cloud resources. It is managed by the Azure Red Hat OpenShift site reliability engineers who, among other things, follow the cluster maintenance processes. Users call REST API to change the system state. The controllers use the REST API to read the desired state from the user and then try to synchronize the other parts of the system.

Example: When a user requests a build, they create a “Build” object. The build controller sees that a new build has taken place and runs a process on the cluster to run that build. When the build is complete, the controller will update the build object via REST API, and the user will see that their build is complete. 

Check out: Deploy Application Using OpenShift

Azure OpenShift Access, Security, and Monitoring

Azure Red Hat OpenShift offers its users to integrate with Azure Active Directory (Azure AD) and use Kubernetes role-based access control (Kubernetes RBAC) for better security and management. Users can easily monitor the health of their clusters and resources.

If we talk about security, the Azure Red Hat OpenShift and Kubernetes APIs authenticate users presenting credentials through Azure Active Directory (Azure AD) integration and then authorize based on their role. The authentication layer identifies the user associated with requests to the Azure Red Hat OpenShift API. The authorization layer then uses information about the user to find if the request can be granted or not.

Check out: Kubernetes Prometheus Monitoring

Azure OpenShift Master, Infrastructure and Application Nodes

Master nodes are hosts that contain the components of the control plane, including the API server, the controller manager server, and so on. The nodes are managed in their Kubernetes cluster and schedule the pods to run on those nodes. A node provides the runtime environments for containers.

Each node in a Kubernetes cluster has the necessary services to be managed by the master. The nodes also have the services required to run Pods, including the container runtime, a kubelet, and a service proxy.

Each node also runs a simple network proxy that reflects the services defined in API on that node. This allows the node to perform simple TCP and UDP stream forwarding over to multiple backends. Azure Red Hat OpenShift creates nodes that run in Azure virtual machines attached to Azure Premium SSD.

Check out: OpenShift vs Kubernetes

Service Level Agreement

Azure Red Hat OpenShift offers an SLA (Service Level Agreement) to ensure that the service will be available 99.95% of the time. This Service Level Agreement for Azure Red Hat OpenShift comes under the Microsoft volume licensing agreement. Microsoft Azure gives you the surety that if they are not able to achieve and maintain the Service Level Agreement and high availability, as mentioned, customers can get the credits in their monthly service fee. Hence, you use can OpenShift on Azure by considering that there will be zero downtime and your applications will be up and running. 

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