Infrastructure

IARC also wants to turn off replication.

The check for potential target nodes happens in a private method under ReplicationManager.createAndQueueTasks(Identifier pid). It seems to happen near the time of the request, but, there is a shift from direct execution of mn.replicate to submitting replicate requests by targetMN. Tasks can be for Pids (make more replicas) and PID+targetNode (call mn.replicate),

in Replication repository:
pid tasks can be in : NEW or IN_PROCESS state
in the object's systemMetadata
pid+target tasks can be : QUEUED, REQUESTED, FAILED, COMPLETED

ReplicationEventListener.entryUpdated() / .entryAdded()
(a Hz systemetadata map listener)
- if the pid's authoritativeMN is listed as a replica with status COMPLETE
create new replica task in the task repository unless there already is one
(if there are more than one task for the pid, delete existing ones and submit a new one)

(triggered every two minutes, trigger set up in ReplicationManager
ReplicationTaskProcessor.run()
move a page of tasks from NEW to IN_PROCESS status
- markInProcess
- call createAndQueueTasks (pid)

createAndQueueTasks (pid)
(lockPid)
processPid
removeReplicationTasks if sysmeta disallows replication or number of replicas are sufficient
determine potential target nodes (from NodeList and sysmeta)
createAndQueueTasks(pid, potentialTargets,desiredNumber)
loop to create a few per-target-node tasks
cnReplication.updateReplicationMetadata
if success,

requeueReplicationTask(pid) #return the pid to the NEW state because we don't assume the requisite number of replicas have been created
ReplicationTaskQueue.processAllTasksForMN(targetMN)
(lock the targetNode)
get replication tasks in the QUEUED state for this target node
foreach task, requestReplication (ReplicationService.requestQueuedReplication(pid,target)
targetMn.replicate(pid)
(unlock the targetNode)
(unlockPid)