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https://issues.apache.org/jira/browse/KAFKA-14386?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Grant resolved KAFKA-14386.
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Resolution: Fixed
> 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. For example, in the CreatePartitions RPC we are adding partitions
> to an existing topic and we might want to add some metadata to response
> making it clear which partition the assignment starts at which could look
> something like:
> {code:java}
> public class TopicAssignment {
> private List<PartitionAssignment> assignments;
> private Integer firstPartitionId;
>
> public TopicAssignment(List<PartitionAssignment> assignments, Integer
> firstPartitionId) {
> this.assignments = assignments;
> this.firstPartitionId = firstPartitionId;
> }
> public List<PartitionAssignment> assignments() {
> return assignments;
> }
> ...
> }
> {code}
>
> Curious to hear other folks thoughts on this.
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