Introduction
The Availability Management Framework (AMF) uses state models for various logical entities to manage and maintain high levels of service availability. The different states associated with service units, components, service instances, component service instances, service groups, and nodes are described in this article.
1. Service Unit States
Service unit has presence, administrative, operational, readiness, and HA states:
- Presence State: The presence state of a service unit is described in this section in terms of the presence state of its constituent components.
- Administrative State: The administrative state of a service unit can be set by the system administrator, and determines whether the service unit is administratively allowed to provide service. Valid values for the administrative state include unlocked, locked, locked-instantiation, and shutting-down.
- Operational State: The operational state determines whether a service unit is capable of taking service instance assignments. The operational state of the service unit indicates whether the components within the service unit are operable or not. Valid values for the operational state of a service unit are: enabled, and disabled.
- Readiness State: The readiness state indicates if a service unit is eligible to take service instance assignments from an administrative and health status viewpoint. It is determined by combining the operational, administrative, and presence states of a service unit, the operational state of its containing node, and the administrative states of its containing node, service group, application, and cluster. Valid values for the readiness state of a service unit are: out-of-service, in-service, and stopping.
- Service Unit’s HA State per Service Instance: HA (High Availability) states are assigned to service units on behalf of service instances. The AMF dynamically assigns the HA state to the service units for the various service instances, taking into consideration the configuration of each service group and the current value of the administrative and operational states of their service units and service instances. The HA state takes one of the following values: active, standby, quiescing, and quiesced.
2. Component States
The overall state of a component is a combination of a number of underlying states:
- Presence State: The presence state of a component reflects the component life cycle. Valid values for the presence state of a component are: uninstantiated, instantiating, instantiated, terminating, restarting, instantiation-failed, and termination-failed.
- Operational State: The operational state of a component is used by the Availability Management Framework to determine whether a component is capable of taking component service instance assignments. The operational state indicates whether the components within the service unit are operable or not. Valid values for the operational state of a component are: enabled, and disabled.
- Readiness State: The operational state of a component is combined with the readiness state of its service unit to obtain the readiness state of the component. This state indicates whether a component is available to take component service instance assignments. This state is the only state used by the Availability Management Framework to decide whether a component is eligible to receive component service instance assignments. Valid values for the readiness state of a component are: out-of-service, in-service, and stopping.
- Component’s HA State per Component Service Instance: For each component service instance assigned to a component within a service unit, the AMF assigns an HA state to the component on behalf of the component service instance. When the AMF assigns an HA state to a service unit for a particular service instance, the action is actually translated into a set of subactions on the components contained in the service unit, assigning an HA state to these components for the individual component service instances contained in the service instance. The HA state of a component for a particular component service instance takes one of the following values: active, standby, quiescing, and quiesced.
3. Service Instance States
Service instance has administrative state and assignment state:
- Administrative State: The administrative state of a service instance is manipulated by the system administrator. Valid values for the administrative state of a service instance are: unlocked, locked, and shutting-down.
- Assignment State: The assignment state of a service instance indicates whether the service represented by this service instance is being provided or not by some service unit. It is AMF that determines the value of the assignment state. Valid values for the assignment state of a service instance are: unassigned, fully-assigned, and partially-assigned.
4. Component Service Instance States
The Availability Management Framework does not define any states for a component service instance; instead, states are defined for the service instance that comprises this component service instance.
5. Service Group States
The only state defined by the AMF for service groups is the administrative state. Valid values for the administrative state of a service group are: unlocked, locked, locked-instantiation, and shutting-down. The AMF uses the administrative state of the service group to determine the readiness state of the service units of the service group.
6. Node States
Node instance has administrative state and operational state:
- Administrative State: The administrative state of a node can be set by the system administrator. Valid values for the administrative state of a node are: unlocked, locked, locked-instantiation, and shutting-down. The Availability Management Framework uses the administrative state of the node to determine the readiness state of the service units of the node.
- Operational State: The operational state of the node is used by the Availability Management Framework to determine whether a service unit within the node is capable of taking service instance assignments. The operational state of the node indicates whether the service units within the node are operable or not. Valid values for the operational state of a node are: enabled and disabled.
Conclusion
Through the seamless integration of states across various logical entities, AMF ensures efficient management and maintains high availability. For detailed information on the specific state values, their functions, and roles within the system.
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