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KAFKA-19478 [3/N]: Use heaps to discover the least loaded process (#20172) 

The original implementation uses a linear search to find the least
loaded process in O(n), and we can replace this by look-ups in a heap is
O(log(n)), as described below

Active tasks: For active tasks, we can do exactly the same assignment as
in the original algorithm by first building a heap (by load) of all
processes. When we assign a task, we pick the head off the heap, assign
the task to it, update the load, and re-insert it into the heap in
O(log(n)).

Standby tasks: For standby tasks, we cannot do this optimization
directly, because of the order in which we assign tasks:

1. We first try to assign task A to a process that previously owned A.
2. If we did not find such a process, we assign A to the least loaded
node.
3. We now try to assign task B to a process that previously owned B
4. If we did not find such a process, we assign B to the least loaded
node
   ...

The problem is that we cannot efficiently keep a heap (by load)
throughout this process, because finding and removing process that
previously owned A (and B and…) in the heap is O(n). We therefore need
to change the order of evaluation to be able to use a heap:

1. Try to assign all tasks A, B.. to a process that previously owned the
task
2. Build a heap.
3. Assign all remaining tasks to the least-loaded process that does not
yet own the task. Since at most NumStandbyReplicas already own the task,
we can do it by removing up to NumStandbyReplicas from the top of the
heap in O(log(n)), so we get O(log(NumProcesses)*NumStandbyReplicas).

Note that the change in order changes the resulting standby assignments
(although this difference does not show up in the existing unit tests).
I would argue that the new order of assignment will actually yield
better assignments, since the assignment will be more sticky, which has
the potential to reduce the amount of store we have to restore from the
changelog topic after assingments.

In our worst-performing benchmark, this improves the runtime by ~107x.

Reviewers: Bill Bejeck<bbejeck@apache.org>
This commit is contained in:
Lucas Brutschy 2025-09-03 17:13:01 +02:00 committed by GitHub
parent 4b9075b506
commit 6247fd9eb3
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6 changed files with 451 additions and 111 deletions
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247
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java
View File

@ -20,12 +20,14 @@ package org.apache.kafka.coordinator.group.streams.assignor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Optional;
import java.util.PriorityQueue;
import java.util.Set;
import java.util.stream.Collectors;
@ -45,14 +47,14 @@ public class StickyTaskAssignor implements TaskAssignor {
@Override
public GroupAssignment assign(final GroupSpec groupSpec, final TopologyDescriber topologyDescriber) throws TaskAssignorException {
initialize(groupSpec, topologyDescriber);
GroupAssignment assignments = doAssign(groupSpec, topologyDescriber);
final GroupAssignment assignments = doAssign(groupSpec, topologyDescriber);
localState = null;
return assignments;
}
private GroupAssignment doAssign(final GroupSpec groupSpec, final TopologyDescriber topologyDescriber) {
//active
Set<TaskId> activeTasks = taskIds(topologyDescriber, true);
final Set<TaskId> activeTasks = taskIds(topologyDescriber, true);
assignActive(activeTasks);
//standby
@ -60,7 +62,7 @@ public class StickyTaskAssignor implements TaskAssignor {
groupSpec.assignmentConfigs().isEmpty() ? 0
: Integer.parseInt(groupSpec.assignmentConfigs().get("num.standby.replicas"));
if (numStandbyReplicas > 0) {
Set<TaskId> statefulTasks = taskIds(topologyDescriber, false);
final Set<TaskId> statefulTasks = taskIds(topologyDescriber, false);
assignStandby(statefulTasks, numStandbyReplicas);
}
@ -68,10 +70,10 @@ public class StickyTaskAssignor implements TaskAssignor {
}
private Set<TaskId> taskIds(final TopologyDescriber topologyDescriber, final boolean isActive) {
Set<TaskId> ret = new HashSet<>();
for (String subtopology : topologyDescriber.subtopologies()) {
final Set<TaskId> ret = new HashSet<>();
for (final String subtopology : topologyDescriber.subtopologies()) {
if (isActive || topologyDescriber.isStateful(subtopology)) {
int numberOfPartitions = topologyDescriber.maxNumInputPartitions(subtopology);
final int numberOfPartitions = topologyDescriber.maxNumInputPartitions(subtopology);
for (int i = 0; i < numberOfPartitions; i++) {
ret.add(new TaskId(subtopology, i));
}
@ -83,8 +85,8 @@ public class StickyTaskAssignor implements TaskAssignor {
private void initialize(final GroupSpec groupSpec, final TopologyDescriber topologyDescriber) {
localState = new LocalState();
localState.allTasks = 0;
for (String subtopology : topologyDescriber.subtopologies()) {
int numberOfPartitions = topologyDescriber.maxNumInputPartitions(subtopology);
for (final String subtopology : topologyDescriber.subtopologies()) {
final int numberOfPartitions = topologyDescriber.maxNumInputPartitions(subtopology);
localState.allTasks += numberOfPartitions;
}
localState.totalCapacity = groupSpec.members().size();
@ -93,7 +95,7 @@ public class StickyTaskAssignor implements TaskAssignor {
localState.processIdToState = new HashMap<>();
localState.activeTaskToPrevMember = new HashMap<>();
localState.standbyTaskToPrevMember = new HashMap<>();
for (Map.Entry<String, AssignmentMemberSpec> memberEntry : groupSpec.members().entrySet()) {
for (final Map.Entry<String, AssignmentMemberSpec> memberEntry : groupSpec.members().entrySet()) {
final String memberId = memberEntry.getKey();
final String processId = memberEntry.getValue().processId();
final Member member = new Member(processId, memberId);
@ -103,19 +105,19 @@ public class StickyTaskAssignor implements TaskAssignor {
localState.processIdToState.get(processId).addMember(memberId);
// prev active tasks
for (Map.Entry<String, Set<Integer>> entry : memberSpec.activeTasks().entrySet()) {
Set<Integer> partitionNoSet = entry.getValue();
for (int partitionNo : partitionNoSet) {
for (final Map.Entry<String, Set<Integer>> entry : memberSpec.activeTasks().entrySet()) {
final Set<Integer> partitionNoSet = entry.getValue();
for (final int partitionNo : partitionNoSet) {
localState.activeTaskToPrevMember.put(new TaskId(entry.getKey(), partitionNo), member);
}
}
// prev standby tasks
for (Map.Entry<String, Set<Integer>> entry : memberSpec.standbyTasks().entrySet()) {
Set<Integer> partitionNoSet = entry.getValue();
for (int partitionNo : partitionNoSet) {
TaskId taskId = new TaskId(entry.getKey(), partitionNo);
localState.standbyTaskToPrevMember.putIfAbsent(taskId, new HashSet<>());
for (final Map.Entry<String, Set<Integer>> entry : memberSpec.standbyTasks().entrySet()) {
final Set<Integer> partitionNoSet = entry.getValue();
for (final int partitionNo : partitionNoSet) {
final TaskId taskId = new TaskId(entry.getKey(), partitionNo);
localState.standbyTaskToPrevMember.putIfAbsent(taskId, new ArrayList<>());
localState.standbyTaskToPrevMember.get(taskId).add(member);
}
}
@ -139,15 +141,15 @@ public class StickyTaskAssignor implements TaskAssignor {
return set1;
}));
for (String memberId : members) {
Map<String, Set<Integer>> activeTasks = new HashMap<>();
for (final String memberId : members) {
final Map<String, Set<Integer>> activeTasks = new HashMap<>();
if (activeTasksAssignments.containsKey(memberId)) {
activeTasks = toCompactedTaskIds(activeTasksAssignments.get(memberId));
activeTasks.putAll(toCompactedTaskIds(activeTasksAssignments.get(memberId)));
}
Map<String, Set<Integer>> standByTasks = new HashMap<>();
final Map<String, Set<Integer>> standByTasks = new HashMap<>();
if (standbyTasksAssignments.containsKey(memberId)) {
standByTasks = toCompactedTaskIds(standbyTasksAssignments.get(memberId));
standByTasks.putAll(toCompactedTaskIds(standbyTasksAssignments.get(memberId)));
}
memberAssignments.put(memberId, new MemberAssignment(activeTasks, standByTasks, new HashMap<>()));
}
@ -156,8 +158,8 @@ public class StickyTaskAssignor implements TaskAssignor {
}
private Map<String, Set<Integer>> toCompactedTaskIds(final Set<TaskId> taskIds) {
Map<String, Set<Integer>> ret = new HashMap<>();
for (TaskId taskId : taskIds) {
final Map<String, Set<Integer>> ret = new HashMap<>();
for (final TaskId taskId : taskIds) {
ret.putIfAbsent(taskId.subtopologyId(), new HashSet<>());
ret.get(taskId.subtopologyId()).add(taskId.partition());
}
@ -167,42 +169,47 @@ public class StickyTaskAssignor implements TaskAssignor {
private void assignActive(final Set<TaskId> activeTasks) {
// 1. re-assigning existing active tasks to clients that previously had the same active tasks
for (Iterator<TaskId> it = activeTasks.iterator(); it.hasNext();) {
for (final Iterator<TaskId> it = activeTasks.iterator(); it.hasNext();) {
final TaskId task = it.next();
final Member prevMember = localState.activeTaskToPrevMember.get(task);
if (prevMember != null && hasUnfulfilledQuota(prevMember)) {
localState.processIdToState.get(prevMember.processId).addTask(prevMember.memberId, task, true);
updateHelpers(prevMember, true);
final ProcessState processState = localState.processIdToState.get(prevMember.processId);
processState.addTask(prevMember.memberId, task, true);
maybeUpdateTasksPerMember(processState.activeTaskCount());
it.remove();
}
}
// 2. re-assigning tasks to clients that previously have seen the same task (as standby task)
for (Iterator<TaskId> it = activeTasks.iterator(); it.hasNext();) {
for (final Iterator<TaskId> it = activeTasks.iterator(); it.hasNext();) {
final TaskId task = it.next();
final Set<Member> prevMembers = localState.standbyTaskToPrevMember.get(task);
final Member prevMember = findMemberWithLeastLoad(prevMembers, task, true);
final ArrayList<Member> prevMembers = localState.standbyTaskToPrevMember.get(task);
final Member prevMember = findPrevMemberWithLeastLoad(prevMembers, null);
if (prevMember != null && hasUnfulfilledQuota(prevMember)) {
localState.processIdToState.get(prevMember.processId).addTask(prevMember.memberId, task, true);
updateHelpers(prevMember, true);
final ProcessState processState = localState.processIdToState.get(prevMember.processId);
processState.addTask(prevMember.memberId, task, true);
maybeUpdateTasksPerMember(processState.activeTaskCount());
it.remove();
}
}
// 3. assign any remaining unassigned tasks
for (Iterator<TaskId> it = activeTasks.iterator(); it.hasNext();) {
final PriorityQueue<ProcessState> processByLoad = new PriorityQueue<>(Comparator.comparingDouble(ProcessState::load));
processByLoad.addAll(localState.processIdToState.values());
for (final Iterator<TaskId> it = activeTasks.iterator(); it.hasNext();) {
final TaskId task = it.next();
final Set<Member> allMembers = localState.processIdToState.entrySet().stream().flatMap(entry -> entry.getValue().memberToTaskCounts().keySet().stream()
.map(memberId -> new Member(entry.getKey(), memberId))).collect(Collectors.toSet());
final Member member = findMemberWithLeastLoad(allMembers, task, false);
final ProcessState processWithLeastLoad = processByLoad.poll();
if (processWithLeastLoad == null) {
throw new TaskAssignorException("No process available to assign active task {}." + task);
}
final String member = memberWithLeastLoad(processWithLeastLoad);
if (member == null) {
log.error("Unable to assign active task {} to any member.", task);
throw new TaskAssignorException("No member available to assign active task {}." + task);
}
localState.processIdToState.get(member.processId).addTask(member.memberId, task, true);
processWithLeastLoad.addTask(member, task, true);
it.remove();
updateHelpers(member, true);
maybeUpdateTasksPerMember(processWithLeastLoad.activeTaskCount());
processByLoad.add(processWithLeastLoad); // Add it back to the queue after updating its state
}
}
@ -214,29 +221,75 @@ public class StickyTaskAssignor implements TaskAssignor {
}
}
private Member findMemberWithLeastLoad(final Set<Member> members, TaskId taskId, final boolean returnSameMember) {
private boolean assignStandbyToMemberWithLeastLoad(PriorityQueue<ProcessState> queue, TaskId taskId) {
final ProcessState processWithLeastLoad = queue.poll();
if (processWithLeastLoad == null) {
return false;
}
boolean found = false;
if (!processWithLeastLoad.hasTask(taskId)) {
final String memberId = memberWithLeastLoad(processWithLeastLoad);
if (memberId != null) {
processWithLeastLoad.addTask(memberId, taskId, false);
found = true;
}
} else if (!queue.isEmpty()) {
found = assignStandbyToMemberWithLeastLoad(queue, taskId);
}
queue.add(processWithLeastLoad); // Add it back to the queue after updating its state
return found;
}
/**
* Finds the previous member with the least load for a given task.
*
* @param members The list of previous members owning the task.
* @param taskId The taskId, to check if the previous member already has the task. Can be null, if we assign it
* for the first time (e.g., during active task assignment).
*
* @return Previous member with the least load that deoes not have the task, or null if no such member exists.
*/
private Member findPrevMemberWithLeastLoad(final ArrayList<Member> members, final TaskId taskId) {
if (members == null || members.isEmpty()) {
return null;
}
Optional<ProcessState> processWithLeastLoad = members.stream()
.map(member -> localState.processIdToState.get(member.processId))
.min(Comparator.comparingDouble(ProcessState::load));
// if the same exact former member is needed
if (returnSameMember) {
return localState.standbyTaskToPrevMember.get(taskId).stream()
.filter(standby -> standby.processId.equals(processWithLeastLoad.get().processId()))
.findFirst()
.orElseGet(() -> memberWithLeastLoad(processWithLeastLoad.get()));
Member candidate = members.get(0);
final ProcessState candidateProcessState = localState.processIdToState.get(candidate.processId);
double candidateProcessLoad = candidateProcessState.load();
double candidateMemberLoad = candidateProcessState.memberToTaskCounts().get(candidate.memberId);
for (int i = 1; i < members.size(); i++) {
final Member member = members.get(i);
final ProcessState processState = localState.processIdToState.get(member.processId);
final double newProcessLoad = processState.load();
if (newProcessLoad < candidateProcessLoad && (taskId == null || !processState.hasTask(taskId))) {
final double newMemberLoad = processState.memberToTaskCounts().get(member.memberId);
if (newMemberLoad < candidateMemberLoad) {
candidateProcessLoad = newProcessLoad;
candidateMemberLoad = newMemberLoad;
candidate = member;
}
}
return memberWithLeastLoad(processWithLeastLoad.get());
}
private Member memberWithLeastLoad(final ProcessState processWithLeastLoad) {
Optional<String> memberWithLeastLoad = processWithLeastLoad.memberToTaskCounts().entrySet().stream()
if (taskId == null || !candidateProcessState.hasTask(taskId)) {
return candidate;
}
return null;
}
private String memberWithLeastLoad(final ProcessState processWithLeastLoad) {
final Map<String, Integer> members = processWithLeastLoad.memberToTaskCounts();
if (members.isEmpty()) {
return null;
}
if (members.size() == 1) {
return members.keySet().iterator().next();
}
final Optional<String> memberWithLeastLoad = processWithLeastLoad.memberToTaskCounts().entrySet().stream()
.min(Map.Entry.comparingByValue())
.map(Map.Entry::getKey);
return memberWithLeastLoad.map(memberId -> new Member(processWithLeastLoad.processId(), memberId)).orElse(null);
return memberWithLeastLoad.orElse(null);
}
private boolean hasUnfulfilledQuota(final Member member) {
@ -244,55 +297,49 @@ public class StickyTaskAssignor implements TaskAssignor {
}
private void assignStandby(final Set<TaskId> standbyTasks, final int numStandbyReplicas) {
for (TaskId task : standbyTasks) {
final ArrayList<StandbyToAssign> toLeastLoaded = new ArrayList<>(standbyTasks.size() * numStandbyReplicas);
for (final TaskId task : standbyTasks) {
for (int i = 0; i < numStandbyReplicas; i++) {
final Set<String> availableProcesses = localState.processIdToState.values().stream()
.filter(process -> !process.hasTask(task))
.map(ProcessState::processId)
.collect(Collectors.toSet());
if (availableProcesses.isEmpty()) {
log.warn("{} There is not enough available capacity. " +
"You should increase the number of threads and/or application instances to maintain the requested number of standby replicas.",
errorMessage(numStandbyReplicas, i, task));
break;
}
Member standby = null;
// prev active task
Member prevMember = localState.activeTaskToPrevMember.get(task);
if (prevMember != null && availableProcesses.contains(prevMember.processId) && isLoadBalanced(prevMember.processId)) {
standby = prevMember;
final Member prevMember = localState.activeTaskToPrevMember.get(task);
if (prevMember != null) {
final ProcessState prevMemberProcessState = localState.processIdToState.get(prevMember.processId);
if (!prevMemberProcessState.hasTask(task) && isLoadBalanced(prevMemberProcessState)) {
prevMemberProcessState.addTask(prevMember.memberId, task, false);
continue;
}
}
// prev standby tasks
if (standby == null) {
final Set<Member> prevMembers = localState.standbyTaskToPrevMember.get(task);
final ArrayList<Member> prevMembers = localState.standbyTaskToPrevMember.get(task);
if (prevMembers != null && !prevMembers.isEmpty()) {
prevMembers.removeIf(member -> !availableProcesses.contains(member.processId));
prevMember = findMemberWithLeastLoad(prevMembers, task, true);
if (prevMember != null && isLoadBalanced(prevMember.processId)) {
standby = prevMember;
final Member prevMember2 = findPrevMemberWithLeastLoad(prevMembers, task);
if (prevMember2 != null) {
final ProcessState prevMemberProcessState = localState.processIdToState.get(prevMember2.processId);
if (isLoadBalanced(prevMemberProcessState)) {
prevMemberProcessState.addTask(prevMember2.memberId, task, false);
continue;
}
}
}
// others
if (standby == null) {
final Set<Member> availableMembers = availableProcesses.stream()
.flatMap(pId -> localState.processIdToState.get(pId).memberToTaskCounts().keySet().stream()
.map(mId -> new Member(pId, mId))).collect(Collectors.toSet());
standby = findMemberWithLeastLoad(availableMembers, task, false);
if (standby == null) {
log.warn("{} Error in standby task assignment!", errorMessage(numStandbyReplicas, i, task));
toLeastLoaded.add(new StandbyToAssign(task, numStandbyReplicas - i));
break;
}
}
localState.processIdToState.get(standby.processId).addTask(standby.memberId, task, false);
updateHelpers(standby, false);
}
final PriorityQueue<ProcessState> processByLoad = new PriorityQueue<>(Comparator.comparingDouble(ProcessState::load));
processByLoad.addAll(localState.processIdToState.values());
for (final StandbyToAssign toAssign : toLeastLoaded) {
for (int i = 0; i < toAssign.remainingReplicas; i++) {
if (!assignStandbyToMemberWithLeastLoad(processByLoad, toAssign.taskId)) {
log.warn("{} There is not enough available capacity. " +
"You should increase the number of threads and/or application instances to maintain the requested number of standby replicas.",
errorMessage(numStandbyReplicas, i, toAssign.taskId));
break;
}
}
}
}
@ -301,21 +348,13 @@ public class StickyTaskAssignor implements TaskAssignor {
" of " + numStandbyReplicas + " standby tasks for task [" + task + "].";
}
private boolean isLoadBalanced(final String processId) {
final ProcessState process = localState.processIdToState.get(processId);
private boolean isLoadBalanced(final ProcessState process) {
final double load = process.load();
boolean isLeastLoadedProcess = localState.processIdToState.values().stream()
final boolean isLeastLoadedProcess = localState.processIdToState.values().stream()
.allMatch(p -> p.load() >= load);
return process.hasCapacity() || isLeastLoadedProcess;
}
private void updateHelpers(final Member member, final boolean isActive) {
if (isActive) {
// update task per process
maybeUpdateTasksPerMember(localState.processIdToState.get(member.processId).activeTaskCount());
}
}
private static int computeTasksPerMember(final int numberOfTasks, final int numberOfMembers) {
if (numberOfMembers == 0) {
return 0;
@ -327,6 +366,16 @@ public class StickyTaskAssignor implements TaskAssignor {
return tasksPerMember;
}
static class StandbyToAssign {
private final TaskId taskId;
private final int remainingReplicas;
public StandbyToAssign(final TaskId taskId, final int remainingReplicas) {
this.taskId = taskId;
this.remainingReplicas = remainingReplicas;
}
}
static class Member {
private final String processId;
private final String memberId;
@ -340,7 +389,7 @@ public class StickyTaskAssignor implements TaskAssignor {
private static class LocalState {
// helper data structures:
Map<TaskId, Member> activeTaskToPrevMember;
Map<TaskId, Set<Member>> standbyTaskToPrevMember;
Map<TaskId, ArrayList<Member>> standbyTaskToPrevMember;
Map<String, ProcessState> processIdToState;
int allTasks;

259
group-coordinator/src/test/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignorTest.java
View File

@ -833,6 +833,265 @@ public class StickyTaskAssignorTest {
assertEquals(2, getAllActiveTaskIds(result, "newMember").size());
}
@Test
public void shouldHandleLargeNumberOfTasksWithStandbyAssignment() {
final int numTasks = 100;
final int numClients = 5;
final int numStandbyReplicas = 2;
Map<String, AssignmentMemberSpec> members = new HashMap<>();
for (int i = 0; i < numClients; i++) {
members.put("member" + i, createAssignmentMemberSpec("process" + i));
}
GroupAssignment result = assignor.assign(
new GroupSpecImpl(members, mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, String.valueOf(numStandbyReplicas)))),
new TopologyDescriberImpl(numTasks, true, List.of("test-subtopology"))
);
// Verify all active tasks are assigned
Set<Integer> allActiveTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberActiveTasks = getAllActiveTaskIds(result, memberId);
allActiveTasks.addAll(memberActiveTasks);
}
assertEquals(numTasks, allActiveTasks.size());
// Verify standby tasks are assigned (should be numTasks * numStandbyReplicas total)
Set<Integer> allStandbyTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberStandbyTasks = getAllStandbyTaskIds(result, memberId);
allStandbyTasks.addAll(memberStandbyTasks);
}
// With 5 clients and 2 standby replicas, we should have at least some standby tasks
assertTrue(allStandbyTasks.size() > 0, "Should have some standby tasks assigned");
// Maximum possible = numTasks * min(numStandbyReplicas, numClients - 1) = 100 * 2 = 200
int maxPossibleStandbyTasks = numTasks * Math.min(numStandbyReplicas, numClients - 1);
assertTrue(allStandbyTasks.size() <= maxPossibleStandbyTasks,
"Should not exceed maximum possible standby tasks: " + maxPossibleStandbyTasks);
// Verify no client has both active and standby for the same task
for (String memberId : result.members().keySet()) {
Set<Integer> memberActiveTasks = new HashSet<>(getAllActiveTaskIds(result, memberId));
Set<Integer> memberStandbyTasks = new HashSet<>(getAllStandbyTaskIds(result, memberId));
memberActiveTasks.retainAll(memberStandbyTasks);
assertTrue(memberActiveTasks.isEmpty(), "Client " + memberId + " has both active and standby for same task");
}
// Verify load distribution is reasonable
int minActiveTasks = Integer.MAX_VALUE;
int maxActiveTasks = 0;
for (String memberId : result.members().keySet()) {
int activeTaskCount = getAllActiveTaskCount(result, memberId);
minActiveTasks = Math.min(minActiveTasks, activeTaskCount);
maxActiveTasks = Math.max(maxActiveTasks, activeTaskCount);
}
// With 100 tasks and 5 clients, each should have 20 tasks
assertEquals(20, minActiveTasks);
assertEquals(20, maxActiveTasks);
// Verify standby task distribution is reasonable
int minStandbyTasks = Integer.MAX_VALUE;
int maxStandbyTasks = 0;
for (String memberId : result.members().keySet()) {
int standbyTaskCount = getAllStandbyTaskIds(result, memberId).size();
minStandbyTasks = Math.min(minStandbyTasks, standbyTaskCount);
maxStandbyTasks = Math.max(maxStandbyTasks, standbyTaskCount);
}
// Each client should have some standby tasks, but not necessarily equal distribution
assertTrue(minStandbyTasks >= 0);
assertTrue(maxStandbyTasks > 0);
}
@Test
public void shouldHandleOddNumberOfClientsWithStandbyTasks() {
// Test with odd number of clients (7) and even number of tasks (14)
final int numTasks = 14;
final int numClients = 7;
final int numStandbyReplicas = 1;
Map<String, AssignmentMemberSpec> members = new HashMap<>();
for (int i = 0; i < numClients; i++) {
members.put("member" + i, createAssignmentMemberSpec("process" + i));
}
GroupAssignment result = assignor.assign(
new GroupSpecImpl(members, mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, String.valueOf(numStandbyReplicas)))),
new TopologyDescriberImpl(numTasks, true, List.of("test-subtopology"))
);
// Verify all active tasks are assigned
Set<Integer> allActiveTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberActiveTasks = getAllActiveTaskIds(result, memberId);
allActiveTasks.addAll(memberActiveTasks);
}
assertEquals(numTasks, allActiveTasks.size());
// Verify standby tasks are assigned
Set<Integer> allStandbyTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberStandbyTasks = getAllStandbyTaskIds(result, memberId);
allStandbyTasks.addAll(memberStandbyTasks);
}
assertEquals(numTasks * numStandbyReplicas, allStandbyTasks.size());
// With 14 tasks and 7 clients, each client should have 2 active tasks
int expectedTasksPerClient = numTasks / numClients; // 14 / 7 = 2
int remainder = numTasks % numClients; // 14 % 7 = 0
int clientsWithExpectedTasks = 0;
int clientsWithOneMoreTask = 0;
for (String memberId : result.members().keySet()) {
int activeTaskCount = getAllActiveTaskCount(result, memberId);
if (activeTaskCount == expectedTasksPerClient) {
clientsWithExpectedTasks++;
} else if (activeTaskCount == expectedTasksPerClient + 1) {
clientsWithOneMoreTask++;
}
}
assertEquals(numClients - remainder, clientsWithExpectedTasks); // 7 clients should have 2 tasks
assertEquals(remainder, clientsWithOneMoreTask); // 0 clients should have 3 tasks
}
@Test
public void shouldHandleHighStandbyReplicaCount() {
// Test with high number of standby replicas (5) and limited clients (3)
final int numTasks = 6;
final int numClients = 3;
final int numStandbyReplicas = 5;
Map<String, AssignmentMemberSpec> members = new HashMap<>();
for (int i = 0; i < numClients; i++) {
members.put("member" + i, createAssignmentMemberSpec("process" + i));
}
GroupAssignment result = assignor.assign(
new GroupSpecImpl(members, mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, String.valueOf(numStandbyReplicas)))),
new TopologyDescriberImpl(numTasks, true, List.of("test-subtopology"))
);
// Verify all active tasks are assigned
Set<Integer> allActiveTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberActiveTasks = getAllActiveTaskIds(result, memberId);
allActiveTasks.addAll(memberActiveTasks);
}
assertEquals(numTasks, allActiveTasks.size());
// With only 3 clients and 5 standby replicas, not all standby replicas can be assigned
// since each client can only hold standby tasks for tasks it doesn't have active
Set<Integer> allStandbyTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberStandbyTasks = getAllStandbyTaskIds(result, memberId);
allStandbyTasks.addAll(memberStandbyTasks);
}
// Maximum possible = numTasks * min(numStandbyReplicas, numClients - 1) = 6 * 2 = 12
int maxPossibleStandbyTasks = numTasks * Math.min(numStandbyReplicas, numClients - 1);
assertTrue(allStandbyTasks.size() <= maxPossibleStandbyTasks);
assertTrue(allStandbyTasks.size() > 0); // Should assign at least some standby tasks
}
@Test
public void shouldHandleLargeNumberOfSubtopologiesWithStandbyTasks() {
// Test with many subtopologies (10) each with different numbers of tasks
final int numSubtopologies = 10;
final int numClients = 4;
final int numStandbyReplicas = 1;
List<String> subtopologies = new ArrayList<>();
for (int i = 0; i < numSubtopologies; i++) {
subtopologies.add("subtopology-" + i);
}
Map<String, AssignmentMemberSpec> members = new HashMap<>();
for (int i = 0; i < numClients; i++) {
members.put("member" + i, createAssignmentMemberSpec("process" + i));
}
GroupAssignment result = assignor.assign(
new GroupSpecImpl(members, mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, String.valueOf(numStandbyReplicas)))),
new TopologyDescriberImpl(5, true, subtopologies) // 5 tasks per subtopology
);
// Verify all subtopologies have tasks assigned
Set<String> subtopologiesWithTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
MemberAssignment member = result.members().get(memberId);
subtopologiesWithTasks.addAll(member.activeTasks().keySet());
}
assertEquals(numSubtopologies, subtopologiesWithTasks.size());
// Verify standby tasks are assigned across subtopologies
Set<String> subtopologiesWithStandbyTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
MemberAssignment member = result.members().get(memberId);
subtopologiesWithStandbyTasks.addAll(member.standbyTasks().keySet());
}
assertEquals(numSubtopologies, subtopologiesWithStandbyTasks.size());
}
@Test
public void shouldHandleEdgeCaseWithSingleClientAndMultipleStandbyReplicas() {
// Test edge case: single client with multiple standby replicas
final int numTasks = 10;
final int numStandbyReplicas = 3;
Map<String, AssignmentMemberSpec> members = mkMap(
mkEntry("member1", createAssignmentMemberSpec("process1"))
);
GroupAssignment result = assignor.assign(
new GroupSpecImpl(members, mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, String.valueOf(numStandbyReplicas)))),
new TopologyDescriberImpl(numTasks, true, List.of("test-subtopology"))
);
// Single client should get all active tasks
assertEquals(numTasks, getAllActiveTaskCount(result, "member1"));
// No standby tasks should be assigned since there's only one client
// (standby tasks can't be assigned to the same client as active tasks)
assertTrue(getAllStandbyTaskIds(result, "member1").isEmpty());
}
@Test
public void shouldHandleEdgeCaseWithMoreStandbyReplicasThanAvailableClients() {
// Test edge case: more standby replicas than available clients
final int numTasks = 4;
final int numClients = 2;
final int numStandbyReplicas = 5; // More than available clients
Map<String, AssignmentMemberSpec> members = new HashMap<>();
for (int i = 0; i < numClients; i++) {
members.put("member" + i, createAssignmentMemberSpec("process" + i));
}
GroupAssignment result = assignor.assign(
new GroupSpecImpl(members, mkMap(mkEntry(NUM_STANDBY_REPLICAS_CONFIG, String.valueOf(numStandbyReplicas)))),
new TopologyDescriberImpl(numTasks, true, List.of("test-subtopology"))
);
// Verify all active tasks are assigned
Set<Integer> allActiveTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberActiveTasks = getAllActiveTaskIds(result, memberId);
allActiveTasks.addAll(memberActiveTasks);
}
assertEquals(numTasks, allActiveTasks.size());
// With only 2 clients, maximum standby tasks per task = 1 (since each client has active tasks)
Set<Integer> allStandbyTasks = new HashSet<>();
for (String memberId : result.members().keySet()) {
List<Integer> memberStandbyTasks = getAllStandbyTaskIds(result, memberId);
allStandbyTasks.addAll(memberStandbyTasks);
}
// Maximum possible = numTasks * 1 = 4
assertEquals(numTasks, allStandbyTasks.size());
}
private int getAllActiveTaskCount(GroupAssignment result, String... memberIds) {
int size = 0;
for (String memberId : memberIds) {

2
streams/integration-tests/src/test/java/org/apache/kafka/streams/integration/RestoreIntegrationTest.java
View File

@ -573,7 +573,7 @@ public class RestoreIntegrationTest {
createStateForRestoration(inputStream, 0);
if (useNewProtocol) {
CLUSTER.setStandbyReplicas(appId, 1);
CLUSTER.setGroupStandbyReplicas(appId, 1);
}
final Properties props1 = props(stateUpdaterEnabled);

12
streams/integration-tests/src/test/java/org/apache/kafka/streams/integration/SmokeTestDriverIntegrationTest.java
View File

@ -140,15 +140,19 @@ public class SmokeTestDriverIntegrationTest {
final Properties props = new Properties();
final String appId = safeUniqueTestName(testInfo);
props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, bootstrapServers);
props.put(StreamsConfig.APPLICATION_ID_CONFIG, safeUniqueTestName(testInfo));
props.put(StreamsConfig.APPLICATION_ID_CONFIG, appId);
props.put(InternalConfig.STATE_UPDATER_ENABLED, stateUpdaterEnabled);
props.put(InternalConfig.PROCESSING_THREADS_ENABLED, processingThreadsEnabled);
// decrease the session timeout so that we can trigger the rebalance soon after old client left closed
props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 10000);
props.put(ConsumerConfig.HEARTBEAT_INTERVAL_MS_CONFIG, 500);
if (streamsProtocolEnabled) {
props.put(StreamsConfig.GROUP_PROTOCOL_CONFIG, GroupProtocol.STREAMS.name().toLowerCase(Locale.getDefault()));
// decrease the session timeout so that we can trigger the rebalance soon after old client left closed
CLUSTER.setGroupSessionTimeout(appId, 10000);
CLUSTER.setGroupHeartbeatTimeout(appId, 1000);
} else {
// decrease the session timeout so that we can trigger the rebalance soon after old client left closed
props.put(ConsumerConfig.SESSION_TIMEOUT_MS_CONFIG, 10000);
}
// cycle out Streams instances as long as the test is running.

2
streams/integration-tests/src/test/java/org/apache/kafka/streams/integration/StandbyTaskCreationIntegrationTest.java
View File

@ -99,7 +99,7 @@ public class StandbyTaskCreationIntegrationTest {
streamsConfiguration.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.IntegerSerde.class);
if (streamsProtocolEnabled) {
streamsConfiguration.put(StreamsConfig.GROUP_PROTOCOL_CONFIG, GroupProtocol.STREAMS.name().toLowerCase(Locale.getDefault()));
CLUSTER.setStandbyReplicas("app-" + safeTestName, 1);
CLUSTER.setGroupStandbyReplicas("app-" + safeTestName, 1);
} else {
streamsConfiguration.put(StreamsConfig.NUM_STANDBY_REPLICAS_CONFIG, 1);
}

30
streams/integration-tests/src/test/java/org/apache/kafka/streams/integration/utils/EmbeddedKafkaCluster.java
View File

@ -401,6 +401,8 @@ public class EmbeddedKafkaCluster {
private void addDefaultBrokerPropsIfAbsent(final Properties brokerConfig) {
brokerConfig.putIfAbsent(CleanerConfig.LOG_CLEANER_DEDUPE_BUFFER_SIZE_PROP, 2 * 1024 * 1024L);
brokerConfig.putIfAbsent(GroupCoordinatorConfig.STREAMS_GROUP_MIN_SESSION_TIMEOUT_MS_CONFIG, "100");
brokerConfig.putIfAbsent(GroupCoordinatorConfig.STREAMS_GROUP_MIN_HEARTBEAT_INTERVAL_MS_CONFIG, "100");
brokerConfig.putIfAbsent(GroupCoordinatorConfig.GROUP_MIN_SESSION_TIMEOUT_MS_CONFIG, "0");
brokerConfig.putIfAbsent(GroupCoordinatorConfig.GROUP_INITIAL_REBALANCE_DELAY_MS_CONFIG, "0");
brokerConfig.putIfAbsent(GroupCoordinatorConfig.OFFSETS_TOPIC_PARTITIONS_CONFIG, "5");
@ -439,7 +441,33 @@ public class EmbeddedKafkaCluster {
}
}
public void setStandbyReplicas(final String groupId, final int numStandbyReplicas) {
public void setGroupSessionTimeout(final String groupId, final int sessionTimeoutMs) {
try (final Admin adminClient = createAdminClient()) {
adminClient.incrementalAlterConfigs(
Map.of(
new ConfigResource(ConfigResource.Type.GROUP, groupId),
List.of(new AlterConfigOp(new ConfigEntry(GroupConfig.STREAMS_SESSION_TIMEOUT_MS_CONFIG, String.valueOf(sessionTimeoutMs)), AlterConfigOp.OpType.SET))
)
).all().get();
} catch (final InterruptedException | ExecutionException e) {
throw new RuntimeException(e);
}
}
public void setGroupHeartbeatTimeout(final String groupId, final int heartbeatTimeoutMs) {
try (final Admin adminClient = createAdminClient()) {
adminClient.incrementalAlterConfigs(
Map.of(
new ConfigResource(ConfigResource.Type.GROUP, groupId),
List.of(new AlterConfigOp(new ConfigEntry(GroupConfig.STREAMS_HEARTBEAT_INTERVAL_MS_CONFIG, String.valueOf(heartbeatTimeoutMs)), AlterConfigOp.OpType.SET))
)
).all().get();
} catch (final InterruptedException | ExecutionException e) {
throw new RuntimeException(e);
}
}
public void setGroupStandbyReplicas(final String groupId, final int numStandbyReplicas) {
try (final Admin adminClient = createAdminClient()) {
adminClient.incrementalAlterConfigs(
Map.of(