A server-role is a parameter that is mentioned in the carbon.xml file (<PRODUCT_HOME>/repository/conf) of all WSO2 Carbon based products. 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 Gadget Server - "GadgetServer"
- WSO2 Governance Registry - "GovernanceRegistry"
- WSO2 Identity Server - "IdentityServer"
- WSO2 Mashup Server - "MashupServer"
This property value is used for the deployment of WSO2 Carbon Applications.
What is a Carbon application
In the future, the terminology used for C-App will change to Composite Application, in order to support Carbon as well as Non-Carbon applications.
A Carbon Application, abbreviated as a cApp, 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 cApp makes it easy for users to port their Web service based solution from one environment to another.
When a user deploys a cApp in a Carbon product, all its resources cannot be deployed in that particular product instance. To specify which can and which cannot be deployed, the server-role property is used. When a cApp is being deployed, it reads the ServerRoles property from the carbon.xml and deploys only the resources which match the server-role values in there. Here 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
- UserEngagementServer - jaggery app
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 they have added to a Carbon product instance. As WSO2 Stratos, which is the WSO2 Carbon based Cloud Middleware Platform, is introduced, the above action is not possible for a tenant since the tenant user is remote to the server instance.
To overcome these difficulties, the server role manager is introduced. It stores both carbon.xml file's default product roles as well as user/tenant specific server roles in the configuration registry. So, when a cApp is deployed in Carbon, the cApp deployer checks for auto-mentioned server roles from the registry instead of the carbon.xml file.
In the server roles manager, the server-roles 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.