Andrew Grant created KAFKA-14386:
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Summary: Change ReplicaPlacer 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
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 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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