What is Openshift
- Red Hat® OpenShift® Container Platform is a containerized application platform that allows enterprises to manage and scale applications utilizing container deployments.
- OpenShift provides predefined application environments, based upon Kubernetes, to support DevOps principles such as reduced time to market, infrastructure-as-code, continuous integration (CI), and continuous delivery (CD).
- RHOCP is based on the Kubernetes open source project and extends the platform with features that bring a robust, flexible, and scalable container platform t
- data centers, enabling developers to run workloads in a high availability environment.
- Red Hat OpenShift Container Platform is based on Red Hat Enterprise Linux CoreOS, the CRIO container engine, and Kubernetes.
- RHOCP 4 provides services on top of Kubernetes, such as an internal container image registry, storage, networking providers, and centralized logging and monitoring.
- Operators package applications that manage Kubernetes resources, and the Operator Lifecycle Manager (OLM) handles installation and management of operators.
- OperatorHub.io is an online catalog for discovering operators.
OpenShift Features:
High Availability:
Kubernetes has been designed with high availability in mind, for both internal components and
user applications. A highly available etcd cluster stores the state of the OpenShift cluster and its
applications. Resources stored in etcd, such as deployment configurations, provide automatic
restarting of containers to ensure that your application is always running and that faulty containers
are terminated. This applies not only to your applications, but also to containerized services that
make up the cluster, such as the web console and the internal image registry.
Lightweight Operating System:
RHOCP runs on Red Hat Enterprise Linux CoreOS, Red Hat's lightweight operating system that
focuses on agility, portability, and security.
Red Hat Enterprise Linux CoreOS (RHEL CoreOS) is an immutable operating system that is
optimized for running containerized applications. The entire operating system is updated as a
single image, instead of on a package-by-package basis, and both user applications and system
components such as network services run as containers.
RHOCP controls updates to RHEL CoreOS and its configurations, and so managing an OpenShift
cluster includes managing the operating system on cluster nodes, freeing system administrators
from these tasks and reducing the risk of human error.
Load Balancing:
Clusters provide three types of load balancers: an external load balancer, which manages access to
the OpenShift API; the HAProxy load balancer, for external access to applications; and the internal
load balancer, which uses Netfilter rules for internal access to applications and services.
Route resources use HAProxy to manage external access to the cluster. Service resources
use Netfilter rules to manage traffic from inside the cluster. The technology that external load
balancers use is dependent on the cloud provider that runs your cluster.
Automating Scaling:
OpenShift clusters can adapt to increased application traffic in real time by automatically starting
new containers, and terminating containers when the load decreases. This features ensures
that your application's access time remains optimal regardless of the number of concurrent
connections or activity.
OpenShift clusters can also add or remove more compute nodes from the cluster according to the
aggregated load from many applications, keeping responsiveness and costs down on public and
private clouds.
Logging and Monitoring:
RHOCP ships with an advanced monitoring solution, based on Prometheus, which gathers
hundreds of metrics about your cluster. This solution interacts with an alerting system that allows
you to obtain detailed information about your cluster activity and health.
RHOCP ships with an advanced aggregated logging solution, based on Elasticsearch, which allows
long-term retention of logs from cluster nodes and containers.
Services Discovery:
RHOCP runs an internal DNS service on the cluster, and configures all containers to use that
internal DNS for name resolution. This means that applications can rely on friendly names to find
other applications and services, without the overhead of an external services catalog.
Storage:
Kubernetes adds an abstraction layer between the storage back end and the storage
consumption. As such, applications can consume long-lived, short-lived, block, and file-based
storage using unified storage definitions that are independent of the storage back end. This way
your applications are not dependent on particular cloud provider storage APIs.
RHOCP embeds a number of storage providers that allow for automatic provisioning of storage on
popular cloud providers and virtualization platforms, and so cluster administrators do not need to
manage the fine details of proprietary storage arrays.
Application Management:
RHOCP empowers developers to automate the development and deployment of their
applications. Use the OpenShift Source-to-Image (S2I) feature to automatically build containers
based on your source code and run them in OpenShift. The internal registry stores application
container images, which can be reused. This decreases the time it takes to publish your
applications.
The developer catalog, accessible from the web console, is a place for publishing and accessing
application templates. It supports many runtime languages, such as Python, Ruby, Java, and
Node.js, and also database and messaging servers. You can expand the catalog by installing new
operators, which are prepackaged applications and services that embed operational intelligence
for deploying, updating, and monitoring their applications.
Cluster Extensibility:
RHOCP relies on standard extension mechanisms from Kubernetes, such as extension APIs
and custom resource definitions, to add features that are otherwise not provided by upstream
Kubernetes. OpenShift packages these extensions as operators for ease of installation, update,
and management. OpenShift also includes the Operator Lifecycle Manager (OLM), which facilitates the discovery,
installation, and update of applications and infrastructure components packaged as operators.
