PlacementPlanFactory (Solr 9.0.0 core API)

All Known Implementing Classes:

PlacementPlanFactoryImpl
```
public interface PlacementPlanFactory
```
Allows plugins to create PlacementPlans telling the Solr layer where to create replicas following the processing of a PlacementRequest. The Solr layer can (and will) check that the PlacementPlan conforms to the PlacementRequest (and if it does not, the requested operation will fail).

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`PlacementPlan`	`createPlacementPlan(PlacementRequest request, Set<ReplicaPlacement> replicaPlacements)`	Creates a `PlacementPlan` for adding replicas to a given shard(s) of an existing collection.
`ReplicaPlacement`	`createReplicaPlacement(SolrCollection solrCollection, String shardName, Node node, Replica.ReplicaType replicaType)`	Creates a `ReplicaPlacement` to be passed to `PlacementPlan` factory methods.

- Method Detail
  - createPlacementPlan
```
PlacementPlan createPlacementPlan(PlacementRequest request,
                                  Set<ReplicaPlacement> replicaPlacements)
```
    Creates a PlacementPlan for adding replicas to a given shard(s) of an existing collection. Note this is also used for creating new collections since such a creation first creates the collection, then adds the replicas.
    This is in support (directly or indirectly) of AddReplicaCmd, CreateShardCmd, ReplaceNodeCmd, MoveReplicaCmd, SplitShardCmd, RestoreCmd, MigrateCmd as well as of CreateCollectionCmd.
  - createReplicaPlacement
```
ReplicaPlacement createReplicaPlacement(SolrCollection solrCollection,
                                        String shardName,
                                        Node node,
                                        Replica.ReplicaType replicaType)
```
    Creates a ReplicaPlacement to be passed to PlacementPlan factory methods.
    Note the plugin can also build its own instances implementing ReplicaPlacement instead of using this call (but using this method makes it easier).