Chapter 6. Overview of Red Hat Process Automation Manager on Red Hat OpenShift Container Platform
You can deploy Red Hat Process Automation Manager into a Red Hat OpenShift Container Platform environment.
In this solution, components of Red Hat Process Automation 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 Process Automation Manager are available on OpenShift:
KIE Server, also known as Execution Server, is the infrastructure element that runs decision services, process applications, and other deployable assets (collectively referred to as services) . All logic of the services runs on execution servers.
A database server is normally required for KIE Server. You can provide a database server in another OpenShift pod or configure an execution server on OpenShift to use any other database server. Alternatively, KIE Server can use an H2 database; in this case, you cannot scale the pod.
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 use the same database server and 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 and monitoring console. You can use Business Central to develop services and deploy them to KIE Servers. You can also use Business Central to monitor the execution of processes.
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.
- Business Central Monitoring is a web-based management and monitoring console. It can manage the deployment of services to KIE Servers and provide monitoring information, but does not include authoring capabilities. You can use this component to manage staging and production environments.
- Smart Router is an optional layer between KIE Servers and other components that interact with them. When your environment includes many services running on different KIE Servers, Smart Router provides a single endpoint to all client applications. A client application can make a REST API call that requires any service. Smart Router automatically calls the KIE Server that can process a particular request.
You can arrange these and other components into various environment configurations within OpenShift.
The following environment types are typical:
- Trial: an environment for demonstration and evaluation of Red Hat Process Automation Manager. This environment includes Business Central and a KIE Server. You can set it up quickly and use it to evaluate or demonstrate developing and running assets. However, the environment does not use any persistent storage and any work you do in the environment is not saved.
- Authoring: An environment for creating and modifying services using Business Central. It consists of pods that provide Business Central for the authoring work and a KIE Server for test execution of the services.
Managed deployment: An environment for running existing services for staging and production purposes. This environment includes several groups of KIE Server pods; you can deploy and undeploy services on every such group and also scale the group up or down as necessary. Use Business Central Monitoring to deploy, run, and stop the services and to monitor their execution.
You can deploy two types of managed environment. In a freeform server environment, you initially deploy Business Central Monitoring and one KIE Server. You can additionally deploy any number of KIE Servers. Business Central Monitoring can connect to all servers in the same namespace.
Alternatively, you can deploy a fixed managed server environment. A single deployment includes Business Central Monitoring, Smart Router, and a preset number of KIE Servers (by default, two servers, but you can modify the template to change the number). You cannot easily add or remove servers at a later time.
Deployment with immutable servers: An alternate environment for running existing services for staging and production purposes. In this environment, when you deploy a KIE Server pod, it builds an image that loads and starts a service or group of services. You cannot stop any service on the pod or add any new service to the pod. If you want to use another version of a service or modify the configuration in any other way, you deploy a new server image and displace the old one. In this system, the KIE Server runs like any other pod on the OpenShift environment; you can use any container-based integration workflows and do not need to use any other tools to manage the pods.
Optionally, you can use Business Central Monitoring to monitor the performance of the environment and to stop and restart some of the service instances, but not to deploy additional services to any KIE Server or undeploy any existing ones (you cannot add or remove containers).
To deploy a Red Hat Process Automation Manager environment on OpenShift, you can use the templates that are provided with Red Hat Process Automation Manager. You can modify some of the templates to ensure that the configuration suits your environment.
6.1. Architecture of an authoring environment
In Red Hat Process Automation Manager, the Business Central component provides a web-based interactive user interface for authoring services. The KIE Server component runs the services.
The KIE Server uses a database server to store the state of process 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. This KIE Server uses a built-in H2 database engine to store the state of process services.
A single authoring environment, by default, uses the controller strategy. Business Central includes the Controller, a component that can manage KIE Servers. When you configure a KIE Server to connect to Business Central, the 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 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 the KIE Server, the KIE Server receives the request through the Controller connection WebSocket. To deploy a service, the 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 the KIE Server.
Figure 6.1. 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. To scale a KIE Server, you must ensure that it uses a database server in a separate pod or an external database server, and not a built-in H2 database engine.
In a clustered deployment, several instances of the 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. Decision services and Red Hat build of OptaPlanner services that run on a clustered KIE Server 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 Servers. It can be useful if you are using several independent KIE Servers.
The client application can use services running on different KIE Servers, but always connects to the Smart Router. The Smart Router automatically passes the request to the KIE Servers 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 KIE Server configuration (for example, deploys or undeploys a service), Business Central initiates a connection to the KIE Server and sends a REST API request. The KIE Server changes the ConfigMap to reflect the new configuration state and then triggers its own redeployment, so that all instances are redeployed and reflect the new configuration.
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 6.2. Architecture diagram for a high-availability authoring environment
