cadonna commented on a change in pull request #10851: URL: https://github.com/apache/kafka/pull/10851#discussion_r685816278
########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/StandbyTaskAssignor.java ########## @@ -0,0 +1,41 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; +import org.apache.kafka.streams.processor.internals.assignment.AssignorConfiguration.AssignmentConfigs; + +import java.util.Set; +import java.util.SortedMap; +import java.util.UUID; + +interface StandbyTaskAssignor { + + void assignStandbyTasks(final SortedMap<UUID, ClientState> clientStates, final Set<TaskId> statefulTasks); + + default boolean isValidTaskMovement(final TaskMovementAttempt taskMovementAttempt) { + return true; + } + + static StandbyTaskAssignor init(final AssignmentConfigs configs) { + if (!configs.rackAwareAssignmentTags.isEmpty()) { + return new ClientTagAwareStandbyTaskAssignor(configs); + } else { + return new DefaultStandbyTaskAssignor(configs); + } + } Review comment: I would prefer to make this interface independent of its implementations. If you put the factory method here, the interface is not independent anymore. I would prefer a factory method named `createStandbyTaskAssignor()` in `HighAvailabilityTaskAssignor` similar to the existing factory method `createTaskAssignor()` in `StreamsPartitionAssignor`. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/TaskMovementAttempt.java ########## @@ -0,0 +1,45 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; + +class TaskMovementAttempt { Review comment: I would prefer to just add two parameters -- `source` and `destination` -- to the `isValidMovement()` method in `StandbyTaskAssignor` and get rid of this class. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/ClientState.java ########## @@ -64,6 +66,7 @@ public ClientState() { previousStandbyTasks.taskIds(new TreeSet<>()); previousActiveTasks.taskIds(new TreeSet<>()); + clientTags = new HashMap<>(); Review comment: I guess the initialization in the constructor on line 79 is only temporary. This will change in one of the next PRs. Nevertheless, I agree that it would also be fine to move the initialization to the field declaration for now. I would even propose to pass the client tags to the constructor, since those are kind of constants coming from the config. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/StandbyTaskAssignor.java ########## @@ -0,0 +1,41 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; +import org.apache.kafka.streams.processor.internals.assignment.AssignorConfiguration.AssignmentConfigs; + +import java.util.Set; +import java.util.SortedMap; +import java.util.UUID; + +interface StandbyTaskAssignor { + + void assignStandbyTasks(final SortedMap<UUID, ClientState> clientStates, final Set<TaskId> statefulTasks); + + default boolean isValidTaskMovement(final TaskMovementAttempt taskMovementAttempt) { + return true; + } Review comment: nit: I think `isAllowedTaskMovement()` reflects better the meaning of this method. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/ClientTagAwareStandbyTaskAssignor.java ########## @@ -0,0 +1,212 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; +import org.apache.kafka.streams.processor.internals.assignment.AssignorConfiguration.AssignmentConfigs; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Map.Entry; +import java.util.Optional; +import java.util.Set; +import java.util.TreeMap; +import java.util.UUID; +import java.util.function.Function; + +import static java.util.stream.Collectors.toMap; + +/** + * Distributes standby tasks over different tag dimensions. + * Only tags specified via {@link AssignmentConfigs#rackAwareAssignmentTags} are taken into account. + * Standby task distribution is on a best-effort basis. For example, if there are not enough clients available + * on different tag dimensions compared to an active and corresponding standby task, + * in that case, the algorithm will fall back to distributing tasks on least-loaded clients. + */ +class ClientTagAwareStandbyTaskAssignor extends StandbyTaskAssignor { + private static final Logger log = LoggerFactory.getLogger(ClientTagAwareStandbyTaskAssignor.class); + + ClientTagAwareStandbyTaskAssignor(final AssignmentConfigs configs) { + super(configs); + } + + @Override + public void assignStandbyTasks(final Map<TaskId, UUID> statefulTasksWithClients, + final TreeMap<UUID, ClientState> clientStates) { + final int numStandbyReplicas = configs.numStandbyReplicas; + final Set<String> rackAwareAssignmentTags = new HashSet<>(configs.rackAwareAssignmentTags); + + final StandbyTaskDistributor standbyTaskDistributor = new StandbyTaskDistributor( + numStandbyReplicas, + clientStates, + rackAwareAssignmentTags, + statefulTasksWithClients + ); + + statefulTasksWithClients.forEach(standbyTaskDistributor::assignStandbyTasksForActiveTask); + } + + @Override + public boolean isValidTaskMovement(final TaskMovementAttempt taskMovementAttempt) { + final Map<String, String> sourceClientTags = taskMovementAttempt.sourceClient().clientTags(); + final Map<String, String> destinationClientTags = taskMovementAttempt.destinationClient().clientTags(); + + for (final Entry<String, String> sourceClientTagEntry : sourceClientTags.entrySet()) { + if (!sourceClientTagEntry.getValue().equals(destinationClientTags.get(sourceClientTagEntry.getKey()))) { + return false; + } + } + + return true; + } + + private static final class StandbyTaskDistributor { Review comment: I see your point, but I do also not see the need for an internal state for which we need to avoid invalidation. Variables `numStandbyReplicas` and `numStandbyReplicas` are configs that can be stored as member fields of `ClientTagAwareStandbyTaskAssignor` or passed along to the methods that need them. Variables `tagKeyToTagValuesMapping`, `clientsPerTagValue`, `standbyTaskClientsByTaskLoad`, and `clientStates` can also be passed to the methods that need them. Avoiding state makes reasoning about code simpler and here it seems possible to avoid state. See `HighAvailabilityTaskAssignor`, it does not have any state. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/StandbyTaskAssignor.java ########## @@ -0,0 +1,41 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; +import org.apache.kafka.streams.processor.internals.assignment.AssignorConfiguration.AssignmentConfigs; + +import java.util.Set; +import java.util.SortedMap; +import java.util.UUID; + +interface StandbyTaskAssignor { Review comment: Minor: You could extend interface `TaskAssignor` and remove `assignStandbyTasks()` from this interface since `assign()` in `TaskAssignor` has almost the same signature. The difference is parameters `configs` and `allTaskIds`. You will need `configs` if you will not keep the config as a member variable as mentioned in my other comment. You will not need `allTaskIds`, but that would be OK, I guess. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/ClientTagAwareStandbyTaskAssignor.java ########## @@ -0,0 +1,220 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; +import org.apache.kafka.streams.processor.internals.assignment.AssignorConfiguration.AssignmentConfigs; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Map.Entry; +import java.util.Optional; +import java.util.Set; +import java.util.SortedMap; +import java.util.UUID; +import java.util.function.Function; + +import static java.util.stream.Collectors.toMap; + +/** + * Distributes standby tasks over different tag dimensions. + * Only tags specified via {@link AssignmentConfigs#rackAwareAssignmentTags} are taken into account. + * Standby task distribution is on a best-effort basis. For example, if there are not enough clients available + * on different tag dimensions compared to an active and corresponding standby task, + * in that case, the algorithm will fall back to distributing tasks on least-loaded clients. + */ +class ClientTagAwareStandbyTaskAssignor implements StandbyTaskAssignor { + private static final Logger log = LoggerFactory.getLogger(ClientTagAwareStandbyTaskAssignor.class); + + private final AssignmentConfigs configs; + + ClientTagAwareStandbyTaskAssignor(final AssignmentConfigs configs) { + this.configs = configs; + } + + @Override + public void assignStandbyTasks(final SortedMap<UUID, ClientState> clientStates, final Set<TaskId> statefulTasks) { + final int numStandbyReplicas = configs.numStandbyReplicas; + final Set<String> rackAwareAssignmentTags = new HashSet<>(configs.rackAwareAssignmentTags); + final Map<TaskId, UUID> statefulTasksWithClients = new HashMap<>(); + + statefulTasks.forEach(statefulTaskId -> clientStates.forEach((uuid, clientState) -> { + if (clientState.activeTasks().contains(statefulTaskId)) { + statefulTasksWithClients.put(statefulTaskId, uuid); + } + })); + + final StandbyTaskDistributor standbyTaskDistributor = new StandbyTaskDistributor( + numStandbyReplicas, + clientStates, + rackAwareAssignmentTags, + statefulTasksWithClients + ); + + statefulTasksWithClients.forEach(standbyTaskDistributor::assignStandbyTasksForActiveTask); + } + + @Override + public boolean isValidTaskMovement(final TaskMovementAttempt taskMovementAttempt) { + final Map<String, String> sourceClientTags = taskMovementAttempt.sourceClient().clientTags(); + final Map<String, String> destinationClientTags = taskMovementAttempt.destinationClient().clientTags(); + + for (final Entry<String, String> sourceClientTagEntry : sourceClientTags.entrySet()) { + if (!sourceClientTagEntry.getValue().equals(destinationClientTags.get(sourceClientTagEntry.getKey()))) { + return false; + } + } + + return true; + } + + private static final class StandbyTaskDistributor { + private final int numStandbyReplicas; + private final SortedMap<UUID, ClientState> clientStates; + private final Set<String> rackAwareAssignmentTags; + private final Map<String, Set<String>> tagKeyToTagValuesMapping; + private final Map<String, Set<UUID>> clientsPerTagValue; + private final ConstrainedPrioritySet standbyTaskClientsByTaskLoad; + + private final Set<UUID> usedClients = new HashSet<>(); + private final Map<TaskId, Integer> tasksToRemainingStandbys; + + StandbyTaskDistributor(final int numStandbyReplicas, + final SortedMap<UUID, ClientState> clientStates, + final Set<String> rackAwareAssignmentTags, + final Map<TaskId, UUID> statefulTasksWithClients) { + tagKeyToTagValuesMapping = new HashMap<>(); + clientsPerTagValue = new HashMap<>(); + standbyTaskClientsByTaskLoad = new ConstrainedPrioritySet( + (client, t) -> !clientStates.get(client).hasAssignedTask(t), + client -> clientStates.get(client).assignedTaskLoad() + ); Review comment: Would it be possible to integrate the tag constraint as part of the constraint on the priority queue? ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/HighAvailabilityTaskAssignor.java ########## @@ -183,7 +164,7 @@ private static void balanceTasksOverThreads(final SortedMap<UUID, ClientState> c while (shouldMoveATask(sourceClientState, destinationClientState) && sourceIterator.hasNext()) { final TaskId taskToMove = sourceIterator.next(); final boolean canMove = !destinationClientState.hasAssignedTask(taskToMove); - if (canMove) { + if (canMove && taskMovementAttemptPredicate.test(new TaskMovementAttempt(taskToMove, sourceClientState, destinationClientState))) { Review comment: Could you move the second condition to the `canMove` assignment on line 166? I think the condition is logically a part of `canMove`. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/TaskMovementAttempt.java ########## @@ -0,0 +1,45 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.kafka.streams.processor.internals.assignment; + +import org.apache.kafka.streams.processor.TaskId; + +class TaskMovementAttempt { + private final TaskId taskId; + private final ClientState sourceClient; + private final ClientState destinationClient; + + TaskMovementAttempt(final TaskId taskId, + final ClientState sourceClient, + final ClientState destinationClient) { + this.taskId = taskId; + this.sourceClient = sourceClient; + this.destinationClient = destinationClient; + } + + public TaskId taskId() { + return taskId; + } Review comment: The task ID is never used. Could we remove it? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
