Task Manager

The replica manager holds two task manager instances: one for updating and one for marshaling replicas. Updating tasks are executed within the replica manager's UpdateFromReplica step, while marshaling tasks are executed in the Marshal step. Tasks can execute other tasks while running. TaskManager::Add queues the tasks in an ordered list. TaskManager::Wait executes a task and waits until it finishes. When an event fires in the replica system, replica manager adds the corresponding task into TaskSystem.

Here are few examples of this behavior:

• A user changes a dataset's value within a replica. The change needs to be marshaled to other peers. The OnReplicaChanged event is called on ReplicaManager, and ReplicaMarshalTask is queued for execution. Because replicas must be sent in the order of their creation, the task's priority is based on the replica's creation time. The queued task is executed at the appropriate time within the Marshal step.

• A new proxy replica is unmarshaled. When this happens, OnReplicaUnmarshaled() is called and ReplicaUpdateTask is queued. This task's priority is always zero because the order of execution is not important. UpdateFromReplica is called to notify the user of the new replica's data.