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Chapter 1. Overview of Red Hat Decision Manager on Red Hat OpenShift Container Platform
You can deploy Red Hat Decision Manager into a Red Hat OpenShift Container Platform environment.
In this solution, components of Red Hat Decision Manager are deployed as separate OpenShift pods. You can scale each of the pods up and down individually to provide as few or as many containers as required for a particular component. You can use standard OpenShift methods to manage the pods and balance the load.
The following key components of Red Hat Decision Manager are available on OpenShift:
KIE Server, also known as Execution Server, is the infrastructure element that runs decision services and other deployable assets (collectively referred to as services) . All logic of the services runs on execution servers.
In some templates, you can scale up a KIE Server pod to provide as many copies as required, running on the same host or different hosts. As you scale a pod up or down, all of its copies run the same services. OpenShift provides load balancing and a request can be handled by any of the pods.
You can deploy a separate KIE Server pod to run a different group of services. That pod can also be scaled up or down. You can have as many separate replicated KIE Server pods as required.
Business Central is a web-based interactive environment used for authoring services. It also provides a management console. You can use Business Central to develop services and deploy them to KIE Servers.
Business Central is a centralized application. However, you can configure it for high availability, where multiple pods run and share the same data.
Business Central includes a Git repository that holds the source for the services that you develop on it. It also includes a built-in Maven repository. Depending on configuration, Business Central can place the compiled services (KJAR files) into the built-in Maven repository or (if configured) into an external Maven repository.
You can arrange these and other components into various environment configurations within OpenShift.
1.1. Architecture of an authoring environment
In Red Hat Decision Manager, the Business Central component provides a web-based interactive user interface for authoring services. The KIE Server component runs the services.
You can also use Business Central to deploy services onto a KIE Server. You can use several KIE Servers to run different services and control the servers from the same Business Central.
Single authoring environment
In a single authoring environment, only one instance of Business Central is running. Multiple users can access its web interface at the same time, however the performance can be limited and there is no failover capability.
Business Central includes a built-in Maven repository that stores the built versions of the services that you develop (KJAR files/artifacts). You can use your continuous integration and continuous deployment (CICD) tools to retrieve these artifacts from the repository and move them as necessary.
Business Central saves the source code in a built-in Git repository, stored in the .niogit directory. It uses a built-in indexing mechanism to index the assets in your services.
Business Central uses persistent storage for the Maven repository and for the Git repository.
A single authoring environment, by default, includes one KIE Server instance.
A single authoring environment can use the controller strategy. Business Central includes the Controller, a component that can manage KIE Servers. When you configure KIE Server to connect to Business Central, KIE Server uses a REST API to connect to the Controller. This connection opens a persistent WebSocket. In an OpenShift deployment that uses the controller strategy, each KIE Server instance is initially configured to connect to the Business Central Controller.
When you use the Business Central user interface to deploy or manage a service on KIE Server, KIE Server receives the request through the Controller connection WebSocket. To deploy a service, KIE Server requests the necessary artifact from the Maven repository that is a part of Business Central.
Client applications use a REST API to use services that run on KIE Server.
Figure 1.1. Architecture diagram for a single authoring environment
Clustering KIE Servers and using multiple KIE Servers
You can scale a KIE Server pod to run a clustered KIE Server environment.
In a clustered deployment, several instances of KIE Server run the same services. These servers can connect to the Business Central Controller using the same server ID, so they can receive the same requests from the controller. Red Hat OpenShift Container Platform provides load-balancing between the servers. The services that run on a clustered KIE Server instance must be stateless, because requests from the same client might be processed by different instances.
You can also deploy several independent KIE Servers to run different services. In this case, the servers connect to the Business Central Controller with different server ID values. You can use the Business Central UI to deploy services to each of the servers.
Smart Router
The optional Smart Router component provides a layer between client applications and KIE Server instances. It can be useful if you are using several independent KIE Server instances.
The client application can use services running on different KIE Server instances, but always connects to the Smart Router. The Smart Router automatically passes the request to the KIE Server instances that runs the required service. The Smart Router also enables management of service versions and provides an additional load-balancing layer.
High-availability authoring environment
In a high-availability (HA) authoring environment, the Business Central pod is scaled, so several instances of Business Central are running. Red Hat OpenShift Container Platform provides load balancing for user requests. This environment provides optimal performance for multiple users and supports failover.
Each instance of Business Central includes the Maven repository for the built artifacts and uses the .niogit Git repository for source code. The instances use shared persistent storage for the repositories. A persistent volume with ReadWriteMany access is required for this storage.
An instance of Red Hat DataGrid provides indexing of all projects and assets developed in Business Central.
An instance of Red Hat AMQ propagates Java CDI messages between all instances of Business Central. For example, when a new project is created or when an asset is locked or modified on one of the instances, this information is immediately reflected in all other instances.
The controller strategy is not suitable for clustered deployment. In an OpenShift deployment, a high-availability Business Central must manage KIE Servers using the OpenShift startup strategy.
Each KIE Server deployment (which can be scaled) creates a ConfigMap that reflects its current state. The Business Central discovers all KIE Servers by reading their ConfigMaps.
When the user requests a change in the KIE Server configuration (for example, deploys or undeploys a service), Business Central initiates a connection to KIE Server and sends a REST API request. KIE Server changes the ConfigMap to reflect the new configuration state and then triggers its redeployment, so that all instances are redeployed and reflect the new configuration. For more information about ConfigMaps, see KIE configuration and ConfigMaps.
You can deploy several independent KIE Servers in your OpenShift environment. Each of the KIE Servers has a separate ConfigMap with the necessary configuration. You can scale each of the KIE Servers separately.
You can include Smart Router in the OpenShift deployment.
Figure 1.2. Architecture diagram for a high-availability authoring environment
