When a change is made to the desired state of components or another configuration change allows a component that has failed to activate to be retried, Rhino will initiate a series of changes to the actual state that will converge this to match the desired state. First, Rhino will calculate the changes required to make the actual state match the desired state. Once the required actions have been calculated, a series of tasks will run that update the state of individual components towards the desired state.
Convergence of components proceeds stepwise with actions ordered roughly by the desired activation state.
Typically, deactivation of components will occur first, followed by reconfiguration, then activation.
Sometimes components will be unable to transition to the desired state immediately.
For example, a service may remain in the Stopping state for some time while SBBs drain.
Tasks that depend on the state transition completing, such as removing a resource adaptor entity link name binding, will wait for a short period, then retry.
Other tasks that do not depend on a state transition will still execute.
Sometimes change to the configuration of a component requires additional state transitions to occur first. The two main cases where this is true are reconfiguration of a resource adaptor entity that does not support active reconfiguration, and removing a resource adaptor entity link name binding. In both cases, any components that must be deactivated for the configuration change to complete will first be deactivated, then the configuration change will be made. Finally, Rhino will attempt to reactivate the components. If the new configuration is missing data required for reactivation to succeed the components may fail to activate.
Rhino periodically checks that there are no outstanding differences between the actual state and the desired state. If any are found, it will start converging the actual state towards the desired state.
The management interface for importing configuration provides a single method which can be polled until the state has converged – isConvergedToDesiredState().
In rhino-console this polling is contained in the command waittilconverged.
Monitoring Convergence
Most users of the Rhino declarative configuration interfaces will want to monitor the progress of the system towards convergence. Rhino provides some basic interfaces to support this.
Checking convergence status
The following console commands can be used to monitor convergence status:
isconverged |
Reports whether convergence has been achieved. |
reportconvergencestatus |
Provides a detailed report on the convergence status of every stateful entity in the SLEE. |
waittilconverged |
Wait until the state of all components has converged. |
Poll the system using the ConfigManagementMBean method isConvergedToDesiredState().
Obtain a convergence report using the ConfigManagementMBean method getConvergenceStatus(boolean).
Checking the status of individual components
The Rhino console provides commands for querying the desired and actual state of components.
There are commands for checking the desired and actual state of a SLEE, resource adaptor entities and services. You can list these in the console by typing help declarative.
The ResourceManagementMBean, ServiceManagementMBean and SLEEManagementMBean contain methods to get the desired and actual state of components.
Tools that create and import configuration bundles can use these methods to retrieve the states and present them to the system administrator.
