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Posted to jira@kafka.apache.org by GitBox <gi...@apache.org> on 2022/02/14 07:14:38 UTC
[GitHub] [kafka] showuon commented on a change in pull request #11493: KAFKA-12959: Prioritise assigning standby tasks to threads without any active tasks
showuon commented on a change in pull request #11493:
URL: https://github.com/apache/kafka/pull/11493#discussion_r805534017
##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -784,21 +784,33 @@ private void populatePartitionsByHostMaps(final Map<HostInfo, Set<TopicPartition
final ClientMetadata clientMetadata = clientEntry.getValue();
final ClientState state = clientMetadata.state;
final SortedSet<String> consumers = clientMetadata.consumers;
+ final Map<String, Integer> threadTaskCounts = new HashMap<>();
- final Map<String, List<TaskId>> activeTaskAssignment = assignTasksToThreads(
+ final Map<String, List<TaskId>> activeTaskStatefulAssignment = assignStatefulTasksToThreads(
state.statefulActiveTasks(),
- state.statelessActiveTasks(),
consumers,
- state
+ state,
+ threadTaskCounts
);
- final Map<String, List<TaskId>> standbyTaskAssignment = assignTasksToThreads(
+ final Map<String, List<TaskId>> standbyTaskAssignment = assignStatefulTasksToThreads(
state.standbyTasks(),
- Collections.emptySet(),
consumers,
- state
+ state,
+ threadTaskCounts
+ );
+
+ final Map<String, List<TaskId>> activeTaskStatelessAssignment = assignStatelessTasksToThreads(
+ state.statelessActiveTasks(),
+ consumers,
+ threadTaskCounts
);
+ final Map<String, List<TaskId>> activeTaskAssignment = activeTaskStatefulAssignment;
Review comment:
could we add comment here to mention this is to combine active stateful assignment + active stateless assignmet...?
##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -1029,104 +1041,148 @@ private boolean addClientAssignments(final Set<TaskId> statefulTasks,
/**
* Generate an assignment that tries to preserve thread-level stickiness of stateful tasks without violating
- * balance. The stateful and total task load are both balanced across threads. Tasks without previous owners
- * will be interleaved by group id to spread subtopologies across threads and further balance the workload.
+ * balance. The tasks are balanced across threads. Tasks without previous owners will be interleaved by
+ * group id to spread subtopologies across threads and further balance the workload.
+ * threadLoad is a map that keeps track of task load per thread across multiple calls so actives and standbys
+ * are evenly distributed
*/
- static Map<String, List<TaskId>> assignTasksToThreads(final Collection<TaskId> statefulTasksToAssign,
- final Collection<TaskId> statelessTasksToAssign,
- final SortedSet<String> consumers,
- final ClientState state) {
+ static Map<String, List<TaskId>> assignStatefulTasksToThreads(final Collection<TaskId> tasksToAssign,
+ final SortedSet<String> consumers,
+ final ClientState state,
+ final Map<String, Integer> threadLoad) {
final Map<String, List<TaskId>> assignment = new HashMap<>();
for (final String consumer : consumers) {
assignment.put(consumer, new ArrayList<>());
}
- final List<TaskId> unassignedStatelessTasks = new ArrayList<>(statelessTasksToAssign);
- Collections.sort(unassignedStatelessTasks);
-
- final Iterator<TaskId> unassignedStatelessTasksIter = unassignedStatelessTasks.iterator();
+ int totalTasks = tasksToAssign.size();
+ for (final Integer threadTaskCount : threadLoad.values()) {
+ totalTasks += threadTaskCount;
+ }
- final int minStatefulTasksPerThread = (int) Math.floor(((double) statefulTasksToAssign.size()) / consumers.size());
- final PriorityQueue<TaskId> unassignedStatefulTasks = new PriorityQueue<>(statefulTasksToAssign);
+ final int minTasksPerThread = (int) Math.floor(((double) totalTasks) / consumers.size());
+ final PriorityQueue<TaskId> unassignedTasks = new PriorityQueue<>(tasksToAssign);
final Queue<String> consumersToFill = new LinkedList<>();
// keep track of tasks that we have to skip during the first pass in case we can reassign them later
// using tree-map to make sure the iteration ordering over keys are preserved
final Map<TaskId, String> unassignedTaskToPreviousOwner = new TreeMap<>();
- if (!unassignedStatefulTasks.isEmpty()) {
- // First assign stateful tasks to previous owner, up to the min expected tasks/thread
+ if (!unassignedTasks.isEmpty()) {
+ // First assign tasks to previous owner, up to the min expected tasks/thread
for (final String consumer : consumers) {
final List<TaskId> threadAssignment = assignment.get(consumer);
for (final TaskId task : state.prevTasksByLag(consumer)) {
- if (unassignedStatefulTasks.contains(task)) {
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ if (unassignedTasks.contains(task)) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
Review comment:
`threadLoad` is not changed before the end of the `assignTasksToThreads` method. Could we get the value: `threadLoad.getOrDefault(consumer, 0);` at the beginning of the consumers loop?
##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -1029,104 +1041,148 @@ private boolean addClientAssignments(final Set<TaskId> statefulTasks,
/**
* Generate an assignment that tries to preserve thread-level stickiness of stateful tasks without violating
- * balance. The stateful and total task load are both balanced across threads. Tasks without previous owners
- * will be interleaved by group id to spread subtopologies across threads and further balance the workload.
+ * balance. The tasks are balanced across threads. Tasks without previous owners will be interleaved by
+ * group id to spread subtopologies across threads and further balance the workload.
+ * threadLoad is a map that keeps track of task load per thread across multiple calls so actives and standbys
+ * are evenly distributed
*/
- static Map<String, List<TaskId>> assignTasksToThreads(final Collection<TaskId> statefulTasksToAssign,
- final Collection<TaskId> statelessTasksToAssign,
- final SortedSet<String> consumers,
- final ClientState state) {
+ static Map<String, List<TaskId>> assignStatefulTasksToThreads(final Collection<TaskId> tasksToAssign,
+ final SortedSet<String> consumers,
+ final ClientState state,
+ final Map<String, Integer> threadLoad) {
final Map<String, List<TaskId>> assignment = new HashMap<>();
for (final String consumer : consumers) {
assignment.put(consumer, new ArrayList<>());
}
- final List<TaskId> unassignedStatelessTasks = new ArrayList<>(statelessTasksToAssign);
- Collections.sort(unassignedStatelessTasks);
-
- final Iterator<TaskId> unassignedStatelessTasksIter = unassignedStatelessTasks.iterator();
+ int totalTasks = tasksToAssign.size();
+ for (final Integer threadTaskCount : threadLoad.values()) {
+ totalTasks += threadTaskCount;
+ }
- final int minStatefulTasksPerThread = (int) Math.floor(((double) statefulTasksToAssign.size()) / consumers.size());
- final PriorityQueue<TaskId> unassignedStatefulTasks = new PriorityQueue<>(statefulTasksToAssign);
+ final int minTasksPerThread = (int) Math.floor(((double) totalTasks) / consumers.size());
+ final PriorityQueue<TaskId> unassignedTasks = new PriorityQueue<>(tasksToAssign);
final Queue<String> consumersToFill = new LinkedList<>();
// keep track of tasks that we have to skip during the first pass in case we can reassign them later
// using tree-map to make sure the iteration ordering over keys are preserved
final Map<TaskId, String> unassignedTaskToPreviousOwner = new TreeMap<>();
- if (!unassignedStatefulTasks.isEmpty()) {
- // First assign stateful tasks to previous owner, up to the min expected tasks/thread
+ if (!unassignedTasks.isEmpty()) {
+ // First assign tasks to previous owner, up to the min expected tasks/thread
for (final String consumer : consumers) {
final List<TaskId> threadAssignment = assignment.get(consumer);
for (final TaskId task : state.prevTasksByLag(consumer)) {
- if (unassignedStatefulTasks.contains(task)) {
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ if (unassignedTasks.contains(task)) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
threadAssignment.add(task);
- unassignedStatefulTasks.remove(task);
+ unassignedTasks.remove(task);
} else {
unassignedTaskToPreviousOwner.put(task, consumer);
}
}
}
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
consumersToFill.offer(consumer);
}
}
// Next interleave remaining unassigned tasks amongst unfilled consumers
while (!consumersToFill.isEmpty()) {
- final TaskId task = unassignedStatefulTasks.poll();
+ final TaskId task = unassignedTasks.poll();
if (task != null) {
final String consumer = consumersToFill.poll();
final List<TaskId> threadAssignment = assignment.get(consumer);
threadAssignment.add(task);
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
consumersToFill.offer(consumer);
}
} else {
throw new TaskAssignmentException("Ran out of unassigned stateful tasks but some members were not at capacity");
}
}
- // At this point all consumers are at the min capacity, so there may be up to N - 1 unassigned
- // stateful tasks still remaining that should now be distributed over the consumers
- if (!unassignedStatefulTasks.isEmpty()) {
- consumersToFill.addAll(consumers);
+ // At this point all consumers are at the min or min + 1 capacity,
+ // the tasks still remaining that should now be distributed over the consumers that are still
+ // at min capacity
+ if (!unassignedTasks.isEmpty()) {
+ for (final String consumer : consumers) {
+ final int taskCount = assignment.get(consumer).size() + threadLoad.getOrDefault(consumer, 0);
+ if (taskCount == minTasksPerThread) {
+ consumersToFill.add(consumer);
Review comment:
I think the original algorithm assumes that when reaching this step, all consumers are at the min capacity. So that it could just do this to set `comsuersToFill`:
```java
if (!unassignedStatefulTasks.isEmpty())
consumersToFill.addAll(consumers);
```
But I didn't see the where we change this algorithm. Please let me know where I missed. Thanks.
##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -1029,104 +1041,148 @@ private boolean addClientAssignments(final Set<TaskId> statefulTasks,
/**
* Generate an assignment that tries to preserve thread-level stickiness of stateful tasks without violating
- * balance. The stateful and total task load are both balanced across threads. Tasks without previous owners
- * will be interleaved by group id to spread subtopologies across threads and further balance the workload.
+ * balance. The tasks are balanced across threads. Tasks without previous owners will be interleaved by
+ * group id to spread subtopologies across threads and further balance the workload.
+ * threadLoad is a map that keeps track of task load per thread across multiple calls so actives and standbys
+ * are evenly distributed
*/
- static Map<String, List<TaskId>> assignTasksToThreads(final Collection<TaskId> statefulTasksToAssign,
- final Collection<TaskId> statelessTasksToAssign,
- final SortedSet<String> consumers,
- final ClientState state) {
+ static Map<String, List<TaskId>> assignStatefulTasksToThreads(final Collection<TaskId> tasksToAssign,
+ final SortedSet<String> consumers,
+ final ClientState state,
+ final Map<String, Integer> threadLoad) {
final Map<String, List<TaskId>> assignment = new HashMap<>();
for (final String consumer : consumers) {
assignment.put(consumer, new ArrayList<>());
}
- final List<TaskId> unassignedStatelessTasks = new ArrayList<>(statelessTasksToAssign);
- Collections.sort(unassignedStatelessTasks);
-
- final Iterator<TaskId> unassignedStatelessTasksIter = unassignedStatelessTasks.iterator();
+ int totalTasks = tasksToAssign.size();
+ for (final Integer threadTaskCount : threadLoad.values()) {
+ totalTasks += threadTaskCount;
+ }
- final int minStatefulTasksPerThread = (int) Math.floor(((double) statefulTasksToAssign.size()) / consumers.size());
- final PriorityQueue<TaskId> unassignedStatefulTasks = new PriorityQueue<>(statefulTasksToAssign);
+ final int minTasksPerThread = (int) Math.floor(((double) totalTasks) / consumers.size());
+ final PriorityQueue<TaskId> unassignedTasks = new PriorityQueue<>(tasksToAssign);
final Queue<String> consumersToFill = new LinkedList<>();
// keep track of tasks that we have to skip during the first pass in case we can reassign them later
// using tree-map to make sure the iteration ordering over keys are preserved
final Map<TaskId, String> unassignedTaskToPreviousOwner = new TreeMap<>();
- if (!unassignedStatefulTasks.isEmpty()) {
- // First assign stateful tasks to previous owner, up to the min expected tasks/thread
+ if (!unassignedTasks.isEmpty()) {
+ // First assign tasks to previous owner, up to the min expected tasks/thread
for (final String consumer : consumers) {
final List<TaskId> threadAssignment = assignment.get(consumer);
for (final TaskId task : state.prevTasksByLag(consumer)) {
- if (unassignedStatefulTasks.contains(task)) {
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ if (unassignedTasks.contains(task)) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
Review comment:
Also, to compute the `threadTaskCount`, we always need to add `threadLoad.getOrDefault(consumer, 0)` each time. Could we just make the `minTasksPerThread = minTasksPerThread - threadLoad.getOrDefault(consumer, 0)`, and add comments to it to make it clear, so that we don't need to do this adding `threadLoad.getOrDefault(consumer, 0)` each time? WDYT?
##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -1140,6 +1196,13 @@ private boolean addClientAssignments(final Set<TaskId> statefulTasks,
consumersToFill.offer(consumer);
}
+ // Update threadLoad
+ for (final Map.Entry<String, List<TaskId>> taskEntry : assignment.entrySet()) {
+ final String consumer = taskEntry.getKey();
+ final int totalCount = threadLoad.getOrDefault(consumer, 0) + taskEntry.getValue().size();
+ threadLoad.put(consumer, totalCount);
+ }
+
Review comment:
should we keep the `threadLoad` at the end of `assignStatelessTasksToThreads`. We don't need it after `assignStatelessTasksToThreads`, right?
##########
File path: streams/src/test/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignorTest.java
##########
@@ -997,6 +997,77 @@ public void testAssignWithStandbyReplicas() {
assertEquals(standbyPartitionsByHost, info20.standbyPartitionByHost());
}
+ @Test
+ public void testAssignWithStandbyReplicasBalance() {
+ builder.addSource(null, "source1", null, null, null, "topic1");
+ builder.addProcessor("processor", new MockApiProcessorSupplier<>(), "source1");
+ builder.addStateStore(new MockKeyValueStoreBuilder("store1", false), "processor");
+
+ final List<String> topics = asList("topic1");
+
+ final Set<TaskId> prevTasks00 = mkSet(TASK_0_0);
+ final Set<TaskId> standbyTasks = mkSet(TASK_0_0, TASK_0_1, TASK_0_2);
+
+ createMockTaskManager(prevTasks00, standbyTasks);
Review comment:
The `prevTasks00` and `standbyTasks` are meaningless in this test. If we just want to create a mock taskManager, could we use `createMockTaskManager(EMPTY_TASKS, EMPTY_TASKS);` instead?
##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -1029,104 +1041,148 @@ private boolean addClientAssignments(final Set<TaskId> statefulTasks,
/**
* Generate an assignment that tries to preserve thread-level stickiness of stateful tasks without violating
- * balance. The stateful and total task load are both balanced across threads. Tasks without previous owners
- * will be interleaved by group id to spread subtopologies across threads and further balance the workload.
+ * balance. The tasks are balanced across threads. Tasks without previous owners will be interleaved by
+ * group id to spread subtopologies across threads and further balance the workload.
+ * threadLoad is a map that keeps track of task load per thread across multiple calls so actives and standbys
+ * are evenly distributed
*/
- static Map<String, List<TaskId>> assignTasksToThreads(final Collection<TaskId> statefulTasksToAssign,
- final Collection<TaskId> statelessTasksToAssign,
- final SortedSet<String> consumers,
- final ClientState state) {
+ static Map<String, List<TaskId>> assignStatefulTasksToThreads(final Collection<TaskId> tasksToAssign,
+ final SortedSet<String> consumers,
+ final ClientState state,
+ final Map<String, Integer> threadLoad) {
final Map<String, List<TaskId>> assignment = new HashMap<>();
for (final String consumer : consumers) {
assignment.put(consumer, new ArrayList<>());
}
- final List<TaskId> unassignedStatelessTasks = new ArrayList<>(statelessTasksToAssign);
- Collections.sort(unassignedStatelessTasks);
-
- final Iterator<TaskId> unassignedStatelessTasksIter = unassignedStatelessTasks.iterator();
+ int totalTasks = tasksToAssign.size();
+ for (final Integer threadTaskCount : threadLoad.values()) {
+ totalTasks += threadTaskCount;
+ }
- final int minStatefulTasksPerThread = (int) Math.floor(((double) statefulTasksToAssign.size()) / consumers.size());
- final PriorityQueue<TaskId> unassignedStatefulTasks = new PriorityQueue<>(statefulTasksToAssign);
+ final int minTasksPerThread = (int) Math.floor(((double) totalTasks) / consumers.size());
+ final PriorityQueue<TaskId> unassignedTasks = new PriorityQueue<>(tasksToAssign);
final Queue<String> consumersToFill = new LinkedList<>();
// keep track of tasks that we have to skip during the first pass in case we can reassign them later
// using tree-map to make sure the iteration ordering over keys are preserved
final Map<TaskId, String> unassignedTaskToPreviousOwner = new TreeMap<>();
- if (!unassignedStatefulTasks.isEmpty()) {
- // First assign stateful tasks to previous owner, up to the min expected tasks/thread
+ if (!unassignedTasks.isEmpty()) {
+ // First assign tasks to previous owner, up to the min expected tasks/thread
for (final String consumer : consumers) {
final List<TaskId> threadAssignment = assignment.get(consumer);
for (final TaskId task : state.prevTasksByLag(consumer)) {
- if (unassignedStatefulTasks.contains(task)) {
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ if (unassignedTasks.contains(task)) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
threadAssignment.add(task);
- unassignedStatefulTasks.remove(task);
+ unassignedTasks.remove(task);
} else {
unassignedTaskToPreviousOwner.put(task, consumer);
}
}
}
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
consumersToFill.offer(consumer);
}
}
// Next interleave remaining unassigned tasks amongst unfilled consumers
while (!consumersToFill.isEmpty()) {
- final TaskId task = unassignedStatefulTasks.poll();
+ final TaskId task = unassignedTasks.poll();
if (task != null) {
final String consumer = consumersToFill.poll();
final List<TaskId> threadAssignment = assignment.get(consumer);
threadAssignment.add(task);
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
consumersToFill.offer(consumer);
}
} else {
throw new TaskAssignmentException("Ran out of unassigned stateful tasks but some members were not at capacity");
}
}
- // At this point all consumers are at the min capacity, so there may be up to N - 1 unassigned
- // stateful tasks still remaining that should now be distributed over the consumers
- if (!unassignedStatefulTasks.isEmpty()) {
- consumersToFill.addAll(consumers);
+ // At this point all consumers are at the min or min + 1 capacity,
+ // the tasks still remaining that should now be distributed over the consumers that are still
+ // at min capacity
+ if (!unassignedTasks.isEmpty()) {
+ for (final String consumer : consumers) {
+ final int taskCount = assignment.get(consumer).size() + threadLoad.getOrDefault(consumer, 0);
+ if (taskCount == minTasksPerThread) {
+ consumersToFill.add(consumer);
+ }
+ }
// Go over the tasks we skipped earlier and assign them to their previous owner when possible
for (final Map.Entry<TaskId, String> taskEntry : unassignedTaskToPreviousOwner.entrySet()) {
final TaskId task = taskEntry.getKey();
final String consumer = taskEntry.getValue();
- if (consumersToFill.contains(consumer) && unassignedStatefulTasks.contains(task)) {
+ if (consumersToFill.contains(consumer) && unassignedTasks.contains(task)) {
assignment.get(consumer).add(task);
- unassignedStatefulTasks.remove(task);
+ unassignedTasks.remove(task);
// Remove this consumer since we know it is now at minCapacity + 1
consumersToFill.remove(consumer);
}
}
// Now just distribute the remaining unassigned stateful tasks over the consumers still at min capacity
- for (final TaskId task : unassignedStatefulTasks) {
+ for (final TaskId task : unassignedTasks) {
final String consumer = consumersToFill.poll();
final List<TaskId> threadAssignment = assignment.get(consumer);
threadAssignment.add(task);
}
+ }
+ }
+ // Update threadLoad
+ for (final Map.Entry<String, List<TaskId>> taskEntry : assignment.entrySet()) {
+ final String consumer = taskEntry.getKey();
+ final int totalCount = threadLoad.getOrDefault(consumer, 0) + taskEntry.getValue().size();
+ threadLoad.put(consumer, totalCount);
+ }
+ return assignment;
+ }
- // There must be at least one consumer still at min capacity while all the others are at min
- // capacity + 1, so start distributing stateless tasks to get all consumers back to the same count
- while (unassignedStatelessTasksIter.hasNext()) {
- final String consumer = consumersToFill.poll();
- if (consumer != null) {
- final TaskId task = unassignedStatelessTasksIter.next();
- unassignedStatelessTasksIter.remove();
- assignment.get(consumer).add(task);
- } else {
- break;
- }
- }
+ static Map<String, List<TaskId>> assignStatelessTasksToThreads(final Collection<TaskId> statelessTasksToAssign,
+ final SortedSet<String> consumers,
+ final Map<String, Integer> threadLoad) {
+ final List<TaskId> tasksToAssign = new ArrayList<>(statelessTasksToAssign);
+ Collections.sort(tasksToAssign);
+ final Map<String, List<TaskId>> assignment = new HashMap<>();
+ for (final String consumer : consumers) {
+ assignment.put(consumer, new ArrayList<>());
+ }
+
+ int maxThreadLoad = 0;
+ for (final int load : threadLoad.values()) {
+ maxThreadLoad = Integer.max(maxThreadLoad, load);
Review comment:
I was thinking we don't need these loops to get the maxThreadLoad and `consumersToFill`. Do you think if we can put `assignStatelessTasksToThreads` at the end of `assignStatefulTasksToThreads`. So that we will have `maxThreadLoad` and `consumersToFill` directly. So in the `assignStatefulTasksToThreads` method signature, we will have one more parameter like: `boolean shouldAssignStatelessTasks`, or `isActiveTasksAssignment`... something like that. WDYT?
##########
File path: streams/src/test/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignorTest.java
##########
@@ -997,6 +997,77 @@ public void testAssignWithStandbyReplicas() {
assertEquals(standbyPartitionsByHost, info20.standbyPartitionByHost());
}
+ @Test
+ public void testAssignWithStandbyReplicasBalance() {
+ builder.addSource(null, "source1", null, null, null, "topic1");
+ builder.addProcessor("processor", new MockApiProcessorSupplier<>(), "source1");
+ builder.addStateStore(new MockKeyValueStoreBuilder("store1", false), "processor");
+
+ final List<String> topics = asList("topic1");
+
+ final Set<TaskId> prevTasks00 = mkSet(TASK_0_0);
+ final Set<TaskId> standbyTasks = mkSet(TASK_0_0, TASK_0_1, TASK_0_2);
+
+ createMockTaskManager(prevTasks00, standbyTasks);
+ adminClient = createMockAdminClientForAssignor(getTopicPartitionOffsetsMap(
+ singletonList(APPLICATION_ID + "-store1-changelog"),
+ singletonList(3))
+ );
+ configurePartitionAssignorWith(Collections.singletonMap(StreamsConfig.NUM_STANDBY_REPLICAS_CONFIG, 1));
+
+ subscriptions.put("consumer10",
+ new Subscription(
+ topics,
+ getInfo(UUID_1, EMPTY_TASKS, EMPTY_TASKS, USER_END_POINT).encode()));
+ subscriptions.put("consumer11",
+ new Subscription(
+ emptyList(),
+ getInfo(UUID_1, EMPTY_TASKS, EMPTY_TASKS, USER_END_POINT).encode()));
+ subscriptions.put("consumer12",
+ new Subscription(
+ emptyList(),
+ getInfo(UUID_1, EMPTY_TASKS, EMPTY_TASKS, USER_END_POINT).encode()));
+ subscriptions.put("consumer13",
+ new Subscription(
+ emptyList(),
+ getInfo(UUID_1, EMPTY_TASKS, EMPTY_TASKS, USER_END_POINT).encode()));
+ subscriptions.put("consumer20",
+ new Subscription(
+ topics,
+ getInfo(UUID_2, EMPTY_TASKS, EMPTY_TASKS, OTHER_END_POINT).encode()));
+ subscriptions.put("consumer21",
+ new Subscription(
+ topics,
+ getInfo(UUID_2, EMPTY_TASKS, EMPTY_TASKS, OTHER_END_POINT).encode()));
+ subscriptions.put("consumer22",
+ new Subscription(
+ topics,
+ getInfo(UUID_2, EMPTY_TASKS, EMPTY_TASKS, OTHER_END_POINT).encode()));
+
+
+ final Map<String, Assignment> assignments =
+ partitionAssignor.assign(metadata, new GroupSubscription(subscriptions)).groupAssignment();
+
+ // Consumers
+ final AssignmentInfo info10 = AssignmentInfo.decode(assignments.get("consumer10").userData());
+ final AssignmentInfo info11 = AssignmentInfo.decode(assignments.get("consumer11").userData());
+ final AssignmentInfo info12 = AssignmentInfo.decode(assignments.get("consumer12").userData());
+ final AssignmentInfo info13 = AssignmentInfo.decode(assignments.get("consumer13").userData());
+ final AssignmentInfo info20 = AssignmentInfo.decode(assignments.get("consumer20").userData());
+ final AssignmentInfo info21 = AssignmentInfo.decode(assignments.get("consumer21").userData());
+ final AssignmentInfo info22 = AssignmentInfo.decode(assignments.get("consumer22").userData());
+
+ // Check each consumer has no more than 1 task
+ // (client 1 has more consumers than needed so consumer13 won't get a task)
+ assertEquals(1, info10.activeTasks().size() + info10.standbyTasks().size());
+ assertEquals(1, info11.activeTasks().size() + info11.standbyTasks().size());
+ assertEquals(1, info12.activeTasks().size() + info12.standbyTasks().size());
+ assertEquals(0, info13.activeTasks().size() + info13.standbyTasks().size());
+ assertEquals(1, info20.activeTasks().size() + info20.standbyTasks().size());
+ assertEquals(1, info21.activeTasks().size() + info21.standbyTasks().size());
+ assertEquals(1, info22.activeTasks().size() + info22.standbyTasks().size());
Review comment:
I'm thinking we can just verify the assignment size is `< 2`. We don't care about the exact number, right?
##########
File path: streams/src/test/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignorTest.java
##########
@@ -997,6 +997,77 @@ public void testAssignWithStandbyReplicas() {
assertEquals(standbyPartitionsByHost, info20.standbyPartitionByHost());
}
+ @Test
+ public void testAssignWithStandbyReplicasBalance() {
Review comment:
Could we add some tests to cover the are less than total tasks (active + standby), but we can still distribute them evenly, ex:
tasks: TASK_0_0, TASK_0_1, TASK_0_2
consumers: 2 in thread1, 3 in thread2
We expected each thread should have 3 tasks, and distribute evenly.
##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
##########
@@ -1029,104 +1041,148 @@ private boolean addClientAssignments(final Set<TaskId> statefulTasks,
/**
* Generate an assignment that tries to preserve thread-level stickiness of stateful tasks without violating
- * balance. The stateful and total task load are both balanced across threads. Tasks without previous owners
- * will be interleaved by group id to spread subtopologies across threads and further balance the workload.
+ * balance. The tasks are balanced across threads. Tasks without previous owners will be interleaved by
+ * group id to spread subtopologies across threads and further balance the workload.
+ * threadLoad is a map that keeps track of task load per thread across multiple calls so actives and standbys
+ * are evenly distributed
*/
- static Map<String, List<TaskId>> assignTasksToThreads(final Collection<TaskId> statefulTasksToAssign,
- final Collection<TaskId> statelessTasksToAssign,
- final SortedSet<String> consumers,
- final ClientState state) {
+ static Map<String, List<TaskId>> assignStatefulTasksToThreads(final Collection<TaskId> tasksToAssign,
+ final SortedSet<String> consumers,
+ final ClientState state,
+ final Map<String, Integer> threadLoad) {
final Map<String, List<TaskId>> assignment = new HashMap<>();
for (final String consumer : consumers) {
assignment.put(consumer, new ArrayList<>());
}
- final List<TaskId> unassignedStatelessTasks = new ArrayList<>(statelessTasksToAssign);
- Collections.sort(unassignedStatelessTasks);
-
- final Iterator<TaskId> unassignedStatelessTasksIter = unassignedStatelessTasks.iterator();
+ int totalTasks = tasksToAssign.size();
+ for (final Integer threadTaskCount : threadLoad.values()) {
+ totalTasks += threadTaskCount;
+ }
- final int minStatefulTasksPerThread = (int) Math.floor(((double) statefulTasksToAssign.size()) / consumers.size());
- final PriorityQueue<TaskId> unassignedStatefulTasks = new PriorityQueue<>(statefulTasksToAssign);
+ final int minTasksPerThread = (int) Math.floor(((double) totalTasks) / consumers.size());
+ final PriorityQueue<TaskId> unassignedTasks = new PriorityQueue<>(tasksToAssign);
final Queue<String> consumersToFill = new LinkedList<>();
// keep track of tasks that we have to skip during the first pass in case we can reassign them later
// using tree-map to make sure the iteration ordering over keys are preserved
final Map<TaskId, String> unassignedTaskToPreviousOwner = new TreeMap<>();
- if (!unassignedStatefulTasks.isEmpty()) {
- // First assign stateful tasks to previous owner, up to the min expected tasks/thread
+ if (!unassignedTasks.isEmpty()) {
+ // First assign tasks to previous owner, up to the min expected tasks/thread
for (final String consumer : consumers) {
final List<TaskId> threadAssignment = assignment.get(consumer);
for (final TaskId task : state.prevTasksByLag(consumer)) {
- if (unassignedStatefulTasks.contains(task)) {
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ if (unassignedTasks.contains(task)) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
threadAssignment.add(task);
- unassignedStatefulTasks.remove(task);
+ unassignedTasks.remove(task);
} else {
unassignedTaskToPreviousOwner.put(task, consumer);
}
}
}
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
consumersToFill.offer(consumer);
}
}
// Next interleave remaining unassigned tasks amongst unfilled consumers
while (!consumersToFill.isEmpty()) {
- final TaskId task = unassignedStatefulTasks.poll();
+ final TaskId task = unassignedTasks.poll();
if (task != null) {
final String consumer = consumersToFill.poll();
final List<TaskId> threadAssignment = assignment.get(consumer);
threadAssignment.add(task);
- if (threadAssignment.size() < minStatefulTasksPerThread) {
+ final int threadTaskCount = threadAssignment.size() + threadLoad.getOrDefault(consumer, 0);
+ if (threadTaskCount < minTasksPerThread) {
consumersToFill.offer(consumer);
}
} else {
throw new TaskAssignmentException("Ran out of unassigned stateful tasks but some members were not at capacity");
}
}
- // At this point all consumers are at the min capacity, so there may be up to N - 1 unassigned
- // stateful tasks still remaining that should now be distributed over the consumers
- if (!unassignedStatefulTasks.isEmpty()) {
- consumersToFill.addAll(consumers);
+ // At this point all consumers are at the min or min + 1 capacity,
Review comment:
Where does the `min + 1` case come from? Could you elaborate more?
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