[jira] [Updated] (KAFKA-14386) Change ReplicaPlacer place method to return a class instead of list of list of integers

["Andrew Grant (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-14386?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Grant updated KAFKA-14386:
---------------------------------
    Summary: Change ReplicaPlacer place method to return a class instead of list of list of integers  (was: Change ReplicaPlacer to return a class instead of list of list of integers)

> Change ReplicaPlacer place method to return a class instead of list of list of integers
> ---------------------------------------------------------------------------------------
>
>                 Key: KAFKA-14386
>                 URL: https://issues.apache.org/jira/browse/KAFKA-14386
>             Project: Kafka
>          Issue Type: Improvement
>            Reporter: Andrew Grant
>            Assignee: Andrew Grant
>            Priority: Major
>
> In KRaft mode, a new interface was introduced, [ReplicaPlacer|https://github.com/apache/kafka/blob/trunk/metadata/src/main/java/org/apache/kafka/metadata/placement/ReplicaPlacer.java], that is used by ReplicationControlManager to create partition assignments during both CreateTopics and CreatePartitions RPCs. Right now it has one implementation, StripedReplicaPlacer.
> Currently, it has a method called place that returns a list of list of integers:
> {code:java}
> List<List<Integer>> place(
> PlacementSpec placement,
> ClusterDescriber cluster
> ) throws InvalidReplicationFactorException;{code}
> The index corresponds to the partition ID and the integers are the replicas of the assignment. The suggestion is to update the interface so that it models topic and partitions more explicitly. I'm thinking something like:
> {code:java}
> TopicAssignment place(
> PlacementSpec placement,
> ClusterDescriber cluster
> ) throws InvalidReplicationFactorException;{code}
> where we have
> {code:java}
> public class TopicAssignment {
>     private List<PartitionAssignment> assignments;
>     public TopicAssignment(List<PartitionAssignment> assignments) {
>      this.assignments = assignments;
>     }
>     public List<PartitionAssignment> assignments() {
>      return assignments;
>     }
> }{code}
> and
> {code:java}
> public class PartitionAssignment {
>     private List<Integer> replicas;
>     public PartitionAssignment(List<Integer> replicas) {
>      this.replicas = replicas;
>     }
>     public List<Integer> replicas() {
>      return replicas;
>     }
> }{code}
> There are two reasons for the suggestion. First, as mentioned above, it will make the interface, arguably, a bit more readable and understandable by explicitly modeling the idea of topic and partition. Second and more importantly, it makes the interface more extendable in the future. Right now it would be challenging to add more metadata to the response. By having classes, we can easily add fields to them without breaking/changing the interface.
> Curious to hear other folks thoughts on this.



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