Introduction to Server Roles

A ServerRoles is a parameter that is mentioned in the carbon.xml file of all WSO2 Carbon-based products, in the <PRODUCT_HOME>/repository/conf directory. Each product has a different default ServerRoles property as follows:

• WSO2 Application Server - "ApplicationServer"
• WSO2 Business Activity Monitor - "BusinessActivityMonitor"
• WSO2 Business Process Server - "BusinessProcessServer"
• WSO2 Business Rules Server - "BusinessRulesServer"
• WSO2 Data Services Server - "DataServicesServer"
• WSO2 Enterprise Service Bus - "EnterpriseServiceBus"
• WSO2 Governance Registry - "GovernanceRegistry"
• WSO2 Identity Server - "IdentityServer"
• WSO2 Cloud Gateway - "CloudGatewayServer"
• WSO2 API Manager - "APIManager"
• WSO2 Storage Server - "StorageServer"
• WSO2 Complex Event Processor - "ComplexEventProcessor"
• WSO2 Message Broker - "${default.server.role}"
• WSO2 Elastic Load Balancer - "ElasticLoadBalancer"
  
• WSO2 User Engagement Server - "JaggeryServer"
• WSO2 Enterprise Store - "EnterpriseStore"
  

This property value is used for the deployment of WSO2 Carbon Applications.

What is a Carbon application

A Carbon Application, abbreviated as a C-App, is a collection of artifacts deployable on a Carbon instance. These artifacts are usually java-based or XML configurations, designed differently for each product in the Carbon platform. In a single Carbon-based solution, there can be numerous artifacts used, such as Axis2 services, data services, synapse configurations, endpoints, proxy services, mediators, registry resources, BEPL workflows etc. Usually, these artifacts are created in a development environment and then moved one by one into staging/production environments. When moving a Carbon solution from one setup to the other, the user has to manually configure these artifacts to build up the entire solution. This is a time-consuming process. Alternatively, bundling configuration files and artifacts in a C-App makes it easy for users to port their Web service based solution from one environment to another.

When a user deploys a C-App in a Carbon based-product, all its resources cannot be deployed in that particular product instance. To specify which can and which cannot be deployed, the ServerRoles property is used. When a C-App is being deployed, it reads the ServerRoles property from the carbon.xml and deploys only the resources that match the ServerRoles values in there. The following is an example list of C-App resources that map to default server roles.

• ApplicationServer - foo.aar, jax-wx.war
• EnterpriseServiceBus - proxy.xml
• BusinessProcessServer - my_bpel.zip
• JaggeryServer - jaggery_app.jag

Server Roles Manager

Server roles manager is a component to manage the server roles property for WSO2 Carbon based products. Due to the functionality of the server roles manager, users do not have to manually modify the carbon.xml to include the server-roles related to the product feature that they have added to a Carbon product instance. The server roles manager stores both carbon.xml file's default product roles as well as the user/tenant specific server roles in the configuration registry. So, when a C-App is deployed in Carbon, the C-App deployer checks for auto-mentioned server roles from the registry instead of the carbon.xml file.

In the server roles manager, the ServerRoles properties are of two types:

• Default - All the server roles picked from that particular product instance's carbon.xml.
• Custom - All other server roles added by the users.