lucasbru commented on code in PR #20172:
URL: https://github.com/apache/kafka/pull/20172#discussion_r2219107453
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -115,7 +117,7 @@ private void initialize(final GroupSpec groupSpec, final
TopologyDescriber topol
Set<Integer> partitionNoSet = entry.getValue();
for (int partitionNo : partitionNoSet) {
TaskId taskId = new TaskId(entry.getKey(), partitionNo);
- localState.standbyTaskToPrevMember.putIfAbsent(taskId, new
HashSet<>());
+ localState.standbyTaskToPrevMember.putIfAbsent(taskId, new
ArrayList<>());
Review Comment:
minor: no need to deduplicate here, so I'd rather just use arrays
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -171,38 +173,43 @@ private void assignActive(final Set<TaskId> activeTasks) {
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);
+ ProcessState processState =
localState.processIdToState.get(prevMember.processId);
+ processState.addTask(prevMember.memberId, task, true);
+ maybeUpdateTasksPerMember(processState.activeTaskCount());
Review Comment:
Just inlining `updateHelpers`
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -171,38 +173,43 @@ private void assignActive(final Set<TaskId> activeTasks) {
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);
+ 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();) {
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);
+ ProcessState processState =
localState.processIdToState.get(prevMember.processId);
+ processState.addTask(prevMember.memberId, task, true);
+ maybeUpdateTasksPerMember(processState.activeTaskCount());
it.remove();
}
}
// 3. assign any remaining unassigned tasks
+ PriorityQueue<ProcessState> processByLoad = new
PriorityQueue<>(Comparator.comparingDouble(ProcessState::load));
+ processByLoad.addAll(localState.processIdToState.values());
for (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);
+ ProcessState processWithLeastLoad = processByLoad.poll();
+ if (processWithLeastLoad == null) {
+ throw new TaskAssignorException("No process available to
assign active task {}." + task);
+ }
+ String member = memberWithLeastLoad(processWithLeastLoad);
Review Comment:
`memberWithLeastLoad` still uses linear search within the process, as before.
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -301,21 +348,13 @@ private String errorMessage(final int numStandbyReplicas,
final int i, final Tas
" 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) {
Review Comment:
minor: passing the process in here saves us from looking it up in the
hashmap again.
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -171,38 +173,43 @@ private void assignActive(final Set<TaskId> activeTasks) {
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);
+ 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();) {
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);
+ ProcessState processState =
localState.processIdToState.get(prevMember.processId);
+ processState.addTask(prevMember.memberId, task, true);
+ maybeUpdateTasksPerMember(processState.activeTaskCount());
it.remove();
}
}
// 3. assign any remaining unassigned tasks
+ PriorityQueue<ProcessState> processByLoad = new
PriorityQueue<>(Comparator.comparingDouble(ProcessState::load));
+ processByLoad.addAll(localState.processIdToState.values());
Review Comment:
Initial build of the priority queue by load
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -214,85 +221,125 @@ private void maybeUpdateTasksPerMember(final int
activeTasksNo) {
}
}
- private Member findMemberWithLeastLoad(final Set<Member> members, TaskId
taskId, final boolean returnSameMember) {
+ private boolean
assignStandbyToMemberWithLeastLoad(PriorityQueue<ProcessState> queue, TaskId
taskId) {
+ ProcessState processWithLeastLoad = queue.poll();
+ if (processWithLeastLoad == null) {
+ return false;
+ }
+ boolean found = false;
+ if (!processWithLeastLoad.hasTask(taskId)) {
+ String memberId = memberWithLeastLoad(processWithLeastLoad);
+ if (memberId != null) {
+ processWithLeastLoad.addTask(memberId, taskId, false);
+ found = true;
+ }
+ } else if (!queue.isEmpty()) {
+ found = assignStandbyToMemberWithLeastLoad(queue, taskId);
Review Comment:
We are using recursion here. If the least loaded member already has the
task, we recurse to find the next least loaded member. The point is that the
least-loaded process is not added back to the queue at this point.
Recursion is fine here, because we know that we get only `numStandbyTasks +
1` recursions, since only `numStandbyTasks` processes can have the task
already. By default, we only allow 2 standby replicas, so we'd get at most 3
recursive calls here.
##########
streams/integration-tests/src/test/java/org/apache/kafka/streams/integration/SmokeTestDriverIntegrationTest.java:
##########
@@ -140,15 +140,19 @@ public void shouldWorkWithRebalance(
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);
Review Comment:
The integration test set the session timeout and the heartbeat interval
incorrectly before in the new protocol. We need to set it on the group level.
This sometimes made the test flaky with the new assignment algorithm, since
we iteratively cycle out the "oldest" member, and tend to assign the tasks from
the next-oldest member. But, due to the high session timeout and heartbeat
timeout, it could sometimes take too long for the new member to get the new
tasks assigned, before being cycled out as well.
I don't see a problem in the assignment logic here - actually, it seems
useful to assign tasks to "old" members, since they are stable. We are just
cycling out the tasks to quickly in this integration test.
##########
streams/integration-tests/src/test/java/org/apache/kafka/streams/integration/utils/EmbeddedKafkaCluster.java:
##########
@@ -401,6 +401,8 @@ public KafkaConsumer<byte[], byte[]>
createConsumerAndSubscribeTo(final Map<Stri
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");
Review Comment:
For integration tests, we want to use rather extreme values so that they run
quickly.
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -171,38 +173,43 @@ private void assignActive(final Set<TaskId> activeTasks) {
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);
+ 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();) {
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);
+ ProcessState processState =
localState.processIdToState.get(prevMember.processId);
+ processState.addTask(prevMember.memberId, task, true);
+ maybeUpdateTasksPerMember(processState.activeTaskCount());
it.remove();
}
}
// 3. assign any remaining unassigned tasks
+ PriorityQueue<ProcessState> processByLoad = new
PriorityQueue<>(Comparator.comparingDouble(ProcessState::load));
+ processByLoad.addAll(localState.processIdToState.values());
for (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);
+ ProcessState processWithLeastLoad = processByLoad.poll();
Review Comment:
replace iteration to find least loaded member in `findMemberWithLeastLoad`
by polling the priority queue.
##########
streams/integration-tests/src/test/java/org/apache/kafka/streams/integration/StandbyTaskCreationIntegrationTest.java:
##########
@@ -99,7 +99,7 @@ private Properties streamsConfiguration(final boolean
streamsProtocolEnabled) {
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);
Review Comment:
Just renamed
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -171,38 +173,43 @@ private void assignActive(final Set<TaskId> activeTasks) {
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);
+ 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();) {
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);
+ ProcessState processState =
localState.processIdToState.get(prevMember.processId);
+ processState.addTask(prevMember.memberId, task, true);
+ maybeUpdateTasksPerMember(processState.activeTaskCount());
it.remove();
}
}
// 3. assign any remaining unassigned tasks
+ PriorityQueue<ProcessState> processByLoad = new
PriorityQueue<>(Comparator.comparingDouble(ProcessState::load));
+ processByLoad.addAll(localState.processIdToState.values());
for (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);
+ ProcessState processWithLeastLoad = processByLoad.poll();
+ if (processWithLeastLoad == null) {
+ throw new TaskAssignorException("No process available to
assign active task {}." + task);
+ }
+ 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
Review Comment:
After we have changed the load, we need to add it back to the priority
queue, so that it is inserted at the correct position
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -214,85 +221,125 @@ private void maybeUpdateTasksPerMember(final int
activeTasksNo) {
}
}
- private Member findMemberWithLeastLoad(final Set<Member> members, TaskId
taskId, final boolean returnSameMember) {
+ private boolean
assignStandbyToMemberWithLeastLoad(PriorityQueue<ProcessState> queue, TaskId
taskId) {
+ ProcessState processWithLeastLoad = queue.poll();
+ if (processWithLeastLoad == null) {
+ return false;
+ }
+ boolean found = false;
+ if (!processWithLeastLoad.hasTask(taskId)) {
+ 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);
+ 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++) {
+ Member member = members.get(i);
+ ProcessState processState =
localState.processIdToState.get(member.processId);
+ double newProcessLoad = processState.load();
+ if (newProcessLoad < candidateProcessLoad && (taskId == null ||
!processState.hasTask(taskId))) {
+ double newMemberLoad =
processState.memberToTaskCounts().get(member.memberId);
+ if (newMemberLoad < candidateMemberLoad) {
+ candidateProcessLoad = newProcessLoad;
+ candidateMemberLoad = newMemberLoad;
+ candidate = member;
+ }
+ }
}
- return memberWithLeastLoad(processWithLeastLoad.get());
+
+ if (taskId == null || !candidateProcessState.hasTask(taskId)) {
+ return candidate;
+ }
+ return null;
}
- private Member memberWithLeastLoad(final ProcessState
processWithLeastLoad) {
+ private String memberWithLeastLoad(final ProcessState
processWithLeastLoad) {
+ Map<String, Integer> members =
processWithLeastLoad.memberToTaskCounts();
+ if (members.isEmpty()) {
+ return null;
+ }
+ if (members.size() == 1) {
+ return members.keySet().iterator().next();
+ }
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) {
return
localState.processIdToState.get(member.processId).memberToTaskCounts().get(member.memberId)
< localState.tasksPerMember;
}
private void assignStandby(final Set<TaskId> standbyTasks, final int
numStandbyReplicas) {
+ ArrayList<StandbyToAssign> toLeastLoaded = new
ArrayList<>(standbyTasks.size() * numStandbyReplicas);
Review Comment:
This arrayList is used to store all standby tasks that we couldn't assign to
a member that previously owned that task, and needs to be assigned to the
"least loaded" node.
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -301,21 +348,13 @@ private String errorMessage(final int numStandbyReplicas,
final int i, final Tas
" 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()
.allMatch(p -> p.load() >= load);
return process.hasCapacity() || isLeastLoadedProcess;
}
- private void updateHelpers(final Member member, final boolean isActive) {
Review Comment:
I just inlined this function
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -214,85 +221,125 @@ private void maybeUpdateTasksPerMember(final int
activeTasksNo) {
}
}
- private Member findMemberWithLeastLoad(final Set<Member> members, TaskId
taskId, final boolean returnSameMember) {
+ private boolean
assignStandbyToMemberWithLeastLoad(PriorityQueue<ProcessState> queue, TaskId
taskId) {
+ ProcessState processWithLeastLoad = queue.poll();
+ if (processWithLeastLoad == null) {
+ return false;
+ }
+ boolean found = false;
+ if (!processWithLeastLoad.hasTask(taskId)) {
+ 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) {
Review Comment:
`findPrevMemberWithLeastLoad` works very similar to the old
`findMemberWithLeastLoad` - that is, it does a linear search among a collection
of candidates.
However, since we don't use it anymore to find the least loaded node among
all members anymore - we use a priority queue there.
This is only used to select the least loaded node among all members that
previously owned the task. I replaced the Java Streams based iteration with a
loop, since it's more efficient.
##########
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/assignor/StickyTaskAssignor.java:
##########
@@ -214,85 +221,125 @@ private void maybeUpdateTasksPerMember(final int
activeTasksNo) {
}
}
- private Member findMemberWithLeastLoad(final Set<Member> members, TaskId
taskId, final boolean returnSameMember) {
+ private boolean
assignStandbyToMemberWithLeastLoad(PriorityQueue<ProcessState> queue, TaskId
taskId) {
Review Comment:
This is the same as the active case assignment above. The difference is that
there may be processes that already have the task, so consider more than one
candidate process here (see recursion below).
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