NetPlane Core Services | Message Queue Service |
|
|
2.5.2.2.2Checkpoint Node Director
The Checkpoint Node Director (CPND) runs as process both on payload blades and on the two system manager nodes. Its tasks are:
z Accepting checkpoint requests from Checkpoint Agents and streamline requests from applications to checkpoints
z Maintaining and controlling the state information pertaining to checkpoints
z Coordinating read and write accesses to/from checkpoint applications across the cluster
z Keeping track of CPNDs on other nodes in order to update the local data if a CPND that is managing the active checkpoint goes down
z Maintaining local replicas in shared memory
z Storing checkpoint control information in the shared memory so that it may be retrieved after a CPND restart
z Managing accesses to sister replicas and coordinating accesses from other applications to the replicas within the scope of the CPND
2.5.2.2.3Checkpoint Agent
The Checkpoint Agent (CPA) is a linkable library available to applications that want to use checkpoint services.
2.5.3Message Queue Service
The Message Queue Service (MQSv) implements the SAF Message service API.
2.5.3.1Basic Functionality
Sender application(s) which use this service, send messages to queues and queue groups managed by MQSv and not to receiving application(s) directly. This means, if a process dies, the message persists in the queue and can be read by the restarted application or by another process.
Applications may create and destroy queues, where each queue has a globally unique name. Multiple senders may then direct messages to a queue, while a single receiver may read messages from the named queue.
Applications may group several queues into a
2.5.3.2Architecture
The MQSv service consists of the following three subparts:
zMessage Queue Director
zMessage Queue Node Director
zMessage Queue Agent
30 | NetPlane Core Services Overview User’s Guide (6806800C08B) |
