apoorvmittal10 commented on code in PR #18864:
URL: https://github.com/apache/kafka/pull/18864#discussion_r1957427989
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/assignor/SimpleAssignor.java:
##########
@@ -72,36 +77,178 @@ private GroupAssignment assignHomogenous(
if (subscribeTopicIds.isEmpty())
return new GroupAssignment(Collections.emptyMap());
- Map<Uuid, Set<Integer>> targetPartitions = computeTargetPartitions(
+ // Subscribed topic partitions for the share group.
+ List<TargetPartition> targetPartitions = computeTargetPartitions(
subscribeTopicIds, subscribedTopicDescriber);
- return new
GroupAssignment(groupSpec.memberIds().stream().collect(Collectors.toMap(
- Function.identity(), memberId -> new
MemberAssignmentImpl(targetPartitions))));
+ // The current assignment from topic partition to members.
+ Map<TargetPartition, List<String>> currentAssignment =
currentAssignment(groupSpec);
+ return newAssignmentHomogeneous(groupSpec, subscribeTopicIds,
targetPartitions, currentAssignment);
}
private GroupAssignment assignHeterogeneous(
GroupSpec groupSpec,
SubscribedTopicDescriber subscribedTopicDescriber
) {
- Map<String, MemberAssignment> members = new HashMap<>();
+ Map<String, List<TargetPartition>> memberToPartitionsSubscription =
new HashMap<>();
for (String memberId : groupSpec.memberIds()) {
MemberSubscription spec = groupSpec.memberSubscription(memberId);
if (spec.subscribedTopicIds().isEmpty())
continue;
- Map<Uuid, Set<Integer>> targetPartitions = computeTargetPartitions(
+ // Subscribed topic partitions for the share group member.
+ List<TargetPartition> targetPartitions = computeTargetPartitions(
spec.subscribedTopicIds(), subscribedTopicDescriber);
+ memberToPartitionsSubscription.put(memberId, targetPartitions);
+ }
+
+ // The current assignment from topic partition to members.
+ Map<TargetPartition, List<String>> currentAssignment =
currentAssignment(groupSpec);
+ return newAssignmentHeterogeneous(groupSpec,
memberToPartitionsSubscription, currentAssignment);
+ }
- members.put(memberId, new MemberAssignmentImpl(targetPartitions));
+ // Get the current assignment for subscribed topic partitions to share
group members.
+ private Map<TargetPartition, List<String>> currentAssignment(GroupSpec
groupSpec) {
+ Map<TargetPartition, List<String>> assignment = new HashMap<>();
+
+ for (String member : groupSpec.memberIds()) {
+ Map<Uuid, Set<Integer>> assignedTopicPartitions =
groupSpec.memberAssignment(member).partitions();
+ assignedTopicPartitions.forEach((topicId, partitions) ->
partitions.forEach(
+ partition -> assignment.computeIfAbsent(new
TargetPartition(topicId, partition), k -> new ArrayList<>()).add(member)));
}
+ return assignment;
+ }
+
+ private GroupAssignment newAssignmentHomogeneous(
+ GroupSpec groupSpec,
+ Set<Uuid> subscribeTopicIds,
+ List<TargetPartition> targetPartitions,
+ Map<TargetPartition, List<String>> currentAssignment) {
+
+ Map<TargetPartition, List<String>> newAssignment = new HashMap<>();
+ // Step 1: Hash member IDs to partitions.
+ memberHashAssignment(targetPartitions, groupSpec.memberIds(),
newAssignment);
+
+ // Step 2: Round-robin assignment for unassigned partitions which do
not have members already assigned in the current assignment.
+ Set<TargetPartition> assignedPartitions = new
HashSet<>(newAssignment.keySet());
+ List<TargetPartition> unassignedPartitions = targetPartitions.stream()
+ .filter(targetPartition ->
!assignedPartitions.contains(targetPartition))
+ .filter(targetPartition ->
!currentAssignment.containsKey(targetPartition))
+ .collect(Collectors.toList());
+
+ roundRobinAssignment(groupSpec.memberIds(), unassignedPartitions,
newAssignment);
+
+ Map<String, Set<TargetPartition>> finalAssignment = new HashMap<>();
+
+ // When combining current assignment, we need to only consider the
topics in current assignment that are also being
+ // subscribed in the new assignment as well.
+ currentAssignment.forEach((targetPartition, members) -> {
+ if (subscribeTopicIds.contains(targetPartition.topicId))
+ members.forEach(member -> {
+ if (groupSpec.memberIds().contains(member))
+ finalAssignment.computeIfAbsent(member, k -> new
HashSet<>()).add(targetPartition);
+ });
+ });
+ newAssignment.forEach((targetPartition, members) ->
members.forEach(member ->
+ finalAssignment.computeIfAbsent(member, k -> new
HashSet<>()).add(targetPartition)));
+
+ return groupAssignment(finalAssignment, groupSpec.memberIds());
+ }
+
+ private GroupAssignment newAssignmentHeterogeneous(
+ GroupSpec groupSpec,
+ Map<String, List<TargetPartition>> memberToPartitionsSubscription,
+ Map<TargetPartition, List<String>> currentAssignment) {
+
+ // Exhaustive set of all subscribed topic partitions.
+ Set<TargetPartition> targetPartitions = new LinkedHashSet<>();
+
memberToPartitionsSubscription.values().forEach(targetPartitions::addAll);
+
+ // Create a map for topic to members subscription.
+ Map<Uuid, Set<String>> topicToMemberSubscription = new HashMap<>();
+ memberToPartitionsSubscription.forEach((member, partitions) ->
+ partitions.forEach(partition ->
topicToMemberSubscription.computeIfAbsent(partition.topicId(), k -> new
LinkedHashSet<>()).add(member)));
+
+ Map<TargetPartition, List<String>> newAssignment = new HashMap<>();
+ // Step 1: Hash member IDs to partitions.
+ memberToPartitionsSubscription.forEach((member, partitions) ->
+ memberHashAssignment(partitions,
Collections.singletonList(member), newAssignment));
+
+ // Step 2: Round-robin assignment for unassigned partitions which do
not have members already assigned in the current assignment.
+ Set<TargetPartition> assignedPartitions = new
LinkedHashSet<>(newAssignment.keySet());
+ Map<Uuid, List<TargetPartition>> unassignedPartitions = new
HashMap<>();
+ targetPartitions.forEach(targetPartition -> {
+ if (!assignedPartitions.contains(targetPartition) &&
!currentAssignment.containsKey(targetPartition))
+
unassignedPartitions.computeIfAbsent(targetPartition.topicId(), k -> new
ArrayList<>()).add(targetPartition);
+ });
+
+ unassignedPartitions.keySet().forEach(unassignedTopic ->
+
roundRobinAssignment(topicToMemberSubscription.get(unassignedTopic),
unassignedPartitions.get(unassignedTopic), newAssignment));
+
+ // Step 3: We combine current assignment and new assignment.
+ Map<String, Set<TargetPartition>> finalAssignment = new HashMap<>();
+
+ // When combining current assignment, we need to only consider the
member topic subscription in current assignment
+ // which is being subscribed in the new assignment as well.
+ currentAssignment.forEach((targetPartition, members) ->
members.forEach(member -> {
+ if
(topicToMemberSubscription.getOrDefault(targetPartition.topicId(),
Collections.emptySet()).contains(member))
+ finalAssignment.computeIfAbsent(member, k -> new
HashSet<>()).add(targetPartition);
+ }));
+ newAssignment.forEach((targetPartition, members) ->
members.forEach(member ->
+ finalAssignment.computeIfAbsent(member, k -> new
HashSet<>()).add(targetPartition)));
+
+ return groupAssignment(finalAssignment, groupSpec.memberIds());
+ }
+
+ private GroupAssignment groupAssignment(
+ Map<String, Set<TargetPartition>> assignmentByMember,
+ Collection<String> allGroupMembers) {
+ Map<String, MemberAssignment> members = new HashMap<>();
+ for (Map.Entry<String, Set<TargetPartition>> entry :
assignmentByMember.entrySet()) {
+ Map<Uuid, Set<Integer>> targetPartitions = new HashMap<>();
+ entry.getValue().forEach(targetPartition ->
targetPartitions.computeIfAbsent(targetPartition.topicId(), k -> new
HashSet<>()).add(targetPartition.partition()));
+ members.put(entry.getKey(), new
MemberAssignmentImpl(targetPartitions));
+ }
+ allGroupMembers.forEach(member -> {
+ if (!members.containsKey(member))
+ members.put(member, new MemberAssignmentImpl(new HashMap<>()));
+ });
+
return new GroupAssignment(members);
}
- private Map<Uuid, Set<Integer>> computeTargetPartitions(
+ // Visible for testing.
+ void memberHashAssignment(
+ List<TargetPartition> targetPartitions,
+ Collection<String> memberIds,
+ Map<TargetPartition, List<String>> assignment) {
+ if (!targetPartitions.isEmpty())
+ for (String memberId : memberIds) {
+ int topicPartitionIndex = Math.abs(memberId.hashCode() %
targetPartitions.size());
+ TargetPartition topicPartition =
targetPartitions.get(topicPartitionIndex);
+ assignment.computeIfAbsent(topicPartition, k -> new
ArrayList<>()).add(memberId);
+ }
+ }
+
+ // Visible for testing.
+ void roundRobinAssignment(
+ Collection<String> members,
+ List<TargetPartition> partitions,
+ Map<TargetPartition, List<String>> assignment) {
+ Iterator<String> memberIterator = members.iterator();
+ for (TargetPartition targetPartition : partitions) {
+ if (!memberIterator.hasNext()) {
+ memberIterator = members.iterator();
+ }
+ String member = memberIterator.next();
Review Comment:
What we are trying to do here, can you please write comments.
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