lucasbru commented on code in PR #18476: URL: https://github.com/apache/kafka/pull/18476#discussion_r1926583303
########## group-coordinator/src/main/java/org/apache/kafka/coordinator/group/streams/CurrentAssignmentBuilder.java: ########## @@ -0,0 +1,451 @@ +/* + * 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.coordinator.group.streams; + +import org.apache.kafka.common.errors.FencedMemberEpochException; + +import java.util.Collections; +import java.util.HashMap; +import java.util.HashSet; +import java.util.Map; +import java.util.Objects; +import java.util.Optional; +import java.util.Set; +import java.util.function.BiFunction; +import java.util.function.BiPredicate; + +/** + * The CurrentAssignmentBuilder class encapsulates the reconciliation engine of the streams group protocol. Given the current state of a + * member and a desired or target assignment state, the state machine takes the necessary steps to converge them. + */ +public class CurrentAssignmentBuilder { + + /** + * The streams group member which is reconciled. + */ + private final StreamsGroupMember member; + + /** + * The target assignment epoch. + */ + private int targetAssignmentEpoch; + + /** + * The target assignment. + */ + private TaskTuple targetAssignment; + + /** + * A function which returns the current process ID of an active task or null if the active task + * is not assigned. The current process ID is the process ID of the current owner. + */ + private BiFunction<String, Integer, String> currentActiveTaskProcessId; + + /** + * A function which returns the current process IDs of a standby task or null if the standby + * task is not assigned. The current process IDs are the process IDs of all current owners. + */ + private BiFunction<String, Integer, Set<String>> currentStandbyTaskProcessIds; + + /** + * A function which returns the current process IDs of a warmup task or null if the warmup task + * is not assigned. The current process IDs are the process IDs of all current owners. + */ + private BiFunction<String, Integer, Set<String>> currentWarmupTaskProcessIds; + + /** + * The tasks owned by the member. This may be provided by the member in the StreamsGroupHeartbeat request. + */ + private Optional<TaskTuple> ownedTasks = Optional.empty(); + + /** + * Constructs the CurrentAssignmentBuilder based on the current state of the provided streams group member. + * + * @param member The streams group member that must be reconciled. + */ + public CurrentAssignmentBuilder(StreamsGroupMember member) { + this.member = Objects.requireNonNull(member); + } + + /** + * Sets the target assignment epoch and the target assignment that the streams group member must be reconciled to. + * + * @param targetAssignmentEpoch The target assignment epoch. + * @param targetAssignment The target assignment. + * @return This object. + */ + public CurrentAssignmentBuilder withTargetAssignment(int targetAssignmentEpoch, + TaskTuple targetAssignment) { + this.targetAssignmentEpoch = targetAssignmentEpoch; + this.targetAssignment = Objects.requireNonNull(targetAssignment); + return this; + } + + /** + * Sets a BiFunction which allows to retrieve the current process ID of an active task. This is + * used by the state machine to determine if an active task is free or still used by another + * member, and if there is still a task on a specific process that is not yet revoked. + * + * @param currentActiveTaskProcessId A BiFunction which gets the process ID of a subtopology ID / + * partition ID pair. + * @return This object. + */ + public CurrentAssignmentBuilder withCurrentActiveTaskProcessId(BiFunction<String, Integer, String> currentActiveTaskProcessId) { + this.currentActiveTaskProcessId = Objects.requireNonNull(currentActiveTaskProcessId); + return this; + } + + /** + * Sets a BiFunction which allows to retrieve the current process IDs of a standby task. This is + * used by the state machine to determine if there is still a task on a specific process that is + * not yet revoked. + * + * @param currentStandbyTaskProcessIds A BiFunction which gets the process IDs of a subtopology + * ID / partition ID pair. + * @return This object. + */ + public CurrentAssignmentBuilder withCurrentStandbyTaskProcessIds( + BiFunction<String, Integer, Set<String>> currentStandbyTaskProcessIds + ) { + this.currentStandbyTaskProcessIds = Objects.requireNonNull(currentStandbyTaskProcessIds); + return this; + } + + /** + * Sets a BiFunction which allows to retrieve the current process IDs of a warmup task. This is + * used by the state machine to determine if there is still a task on a specific process that is + * not yet revoked. + * + * @param currentWarmupTaskProcessIds A BiFunction which gets the process IDs of a subtopology ID + * / partition ID pair. + * @return This object. + */ + public CurrentAssignmentBuilder withCurrentWarmupTaskProcessIds(BiFunction<String, Integer, Set<String>> currentWarmupTaskProcessIds) { + this.currentWarmupTaskProcessIds = Objects.requireNonNull(currentWarmupTaskProcessIds); + return this; + } + + /** + * Sets the tasks currently owned by the member. This comes directly from the last StreamsGroupHeartbeat request. This is used to + * determine if the member has revoked the necessary tasks. Passing null into this function means that the member did not provide + * its owned tasks in this heartbeat. + * + * @param ownedAssignment A collection of active, standby and warm-up tasks + * @return This object. + */ + protected CurrentAssignmentBuilder withOwnedAssignment(TaskTuple ownedAssignment) { + this.ownedTasks = Optional.ofNullable(ownedAssignment); + return this; + } + + /** + * Builds the next state for the member or keep the current one if it is not possible to move forward with the current state. + * + * @return A new StreamsGroupMember or the current one. + */ + public StreamsGroupMember build() { + switch (member.state()) { + case STABLE: + // When the member is in the STABLE state, we verify if a newer + // epoch (or target assignment) is available. If it is, we can + // reconcile the member towards it. Otherwise, we return. + if (member.memberEpoch() != targetAssignmentEpoch) { + return computeNextAssignment( + member.memberEpoch(), + member.assignedTasks() + ); + } else { + return member; + } + + case UNREVOKED_TASKS: + // When the member is in the UNREVOKED_TASKS state, we wait + // until the member has revoked the necessary tasks. They are + // considered revoked when they are not anymore reported in the + // owned tasks set in the StreamsGroupHeartbeat API. + + // If the member provides its owned tasks, we verify if it still + // owns any of the revoked tasks. If it did not provide it's + // owned tasks, or we still own some of the revoked tasks, we + // cannot progress. + if ( + ownedTasks.isEmpty() || ownedTasks.get().containsAny(member.tasksPendingRevocation()) + ) { + return member; + } + + // When the member has revoked all the pending tasks, it can + // transition to the next epoch (current + 1) and we can reconcile + // its state towards the latest target assignment. + return computeNextAssignment( + member.memberEpoch() + 1, + member.assignedTasks() + ); + + case UNRELEASED_TASKS: + // When the member is in the UNRELEASED_TASKS, we reconcile the + // member towards the latest target assignment. This will assign any + // of the unreleased tasks when they become available. + return computeNextAssignment( + member.memberEpoch(), + member.assignedTasks() + ); + + case UNKNOWN: + // We could only end up in this state if a new state is added in the + // future and the group coordinator is downgraded. In this case, the + // best option is to fence the member to force it to rejoin the group + // without any tasks and to reconcile it again from scratch. + if ((ownedTasks.isEmpty() || !ownedTasks.get().isEmpty())) { + throw new FencedMemberEpochException( + "The streams group member is in a unknown state. " + + "The member must abandon all its tasks and rejoin."); + } + + return computeNextAssignment( + targetAssignmentEpoch, + member.assignedTasks() + ); + } + + return member; + } + + /** + * Takes the current currentAssignment and the targetAssignment, and generates three + * collections: + * + * - the resultAssignedTasks: the tasks that are assigned in both the current and target + * assignments. + * - the resultTasksPendingRevocation: the tasks that are assigned in the current + * assignment but not in the target assignment. + * - the resultTasksPendingAssignment: the tasks that are assigned in the target assignment but + * not in the current assignment, and can be assigned currently (i.e., they are not owned by + * another member, as defined by the `isUnreleasedTask` predicate). + */ + private boolean computeAssignmentDifference(Map<String, Set<Integer>> currentAssignment, + Map<String, Set<Integer>> targetAssignment, + Map<String, Set<Integer>> resultAssignedTasks, + Map<String, Set<Integer>> resultTasksPendingRevocation, + Map<String, Set<Integer>> resultTasksPendingAssignment, + BiPredicate<String, Integer> isUnreleasedTask) { + boolean hasUnreleasedTasks = false; + + Set<String> allSubtopologyIds = new HashSet<>(targetAssignment.keySet()); + allSubtopologyIds.addAll(currentAssignment.keySet()); + + for (String subtopologyId : allSubtopologyIds) { + hasUnreleasedTasks |= computeAssignmentDifferenceForOneSubtopology( + subtopologyId, + currentAssignment.getOrDefault(subtopologyId, Collections.emptySet()), + targetAssignment.getOrDefault(subtopologyId, Collections.emptySet()), + resultAssignedTasks, + resultTasksPendingRevocation, + resultTasksPendingAssignment, + isUnreleasedTask + ); + } + return hasUnreleasedTasks; + } + + private static boolean computeAssignmentDifferenceForOneSubtopology(final String subtopologyId, + final Set<Integer> currentTasksForThisSubtopology, + final Set<Integer> targetTasksForThisSubtopology, + final Map<String, Set<Integer>> resultAssignedTasks, + final Map<String, Set<Integer>> resultTasksPendingRevocation, + final Map<String, Set<Integer>> resultTasksPendingAssignment, + final BiPredicate<String, Integer> isUnreleasedTask) { + // Result Assigned Tasks = Current Tasks ∩ Target Tasks + // i.e. we remove all tasks from the current assignment that are not in the target + // assignment + Set<Integer> resultAssignedTasksForThisSubtopology = new HashSet<>(currentTasksForThisSubtopology); + resultAssignedTasksForThisSubtopology.retainAll(targetTasksForThisSubtopology); + + // Result Tasks Pending Revocation = Current Tasks - Result Assigned Tasks + // i.e. we will ask the member to revoke all tasks in its current assignment that + // are not in the target assignment + Set<Integer> resultTasksPendingRevocationForThisSubtopology = new HashSet<>(currentTasksForThisSubtopology); + resultTasksPendingRevocationForThisSubtopology.removeAll(resultAssignedTasksForThisSubtopology); + + // Result Tasks Pending Assignment = Target Tasks - Result Assigned Tasks - Unreleased Tasks + // i.e. we will ask the member to assign all tasks in its target assignment, + // except those that are already assigned, and those that are unreleased + Set<Integer> resultTasksPendingAssignmentForThisSubtopology = new HashSet<>(targetTasksForThisSubtopology); + resultTasksPendingAssignmentForThisSubtopology.removeAll(resultAssignedTasksForThisSubtopology); + boolean hasUnreleasedTasks = resultTasksPendingAssignmentForThisSubtopology.removeIf(taskId -> + isUnreleasedTask.test(subtopologyId, taskId) + ); + + if (!resultAssignedTasksForThisSubtopology.isEmpty()) { + resultAssignedTasks.put(subtopologyId, resultAssignedTasksForThisSubtopology); + } + + if (!resultTasksPendingRevocationForThisSubtopology.isEmpty()) { + resultTasksPendingRevocation.put(subtopologyId, resultTasksPendingRevocationForThisSubtopology); + } + + if (!resultTasksPendingAssignmentForThisSubtopology.isEmpty()) { + resultTasksPendingAssignment.put(subtopologyId, resultTasksPendingAssignmentForThisSubtopology); + } + + return hasUnreleasedTasks; + } + + /** + * Computes the next assignment. + * + * @param memberEpoch The epoch of the member to use. This may be different from + * the epoch in {@link CurrentAssignmentBuilder#member}. + * @param memberAssignedTasks The assigned tasks of the member to use. + * @return A new StreamsGroupMember. + */ + private StreamsGroupMember computeNextAssignment(int memberEpoch, + TaskTuple memberAssignedTasks) { + Map<String, Set<Integer>> newActiveAssignedTasks = new HashMap<>(); + Map<String, Set<Integer>> newActiveTasksPendingRevocation = new HashMap<>(); + Map<String, Set<Integer>> newActiveTasksPendingAssignment = new HashMap<>(); + Map<String, Set<Integer>> newStandbyAssignedTasks = new HashMap<>(); + Map<String, Set<Integer>> newStandbyTasksPendingRevocation = new HashMap<>(); + Map<String, Set<Integer>> newStandbyTasksPendingAssignment = new HashMap<>(); + Map<String, Set<Integer>> newWarmupAssignedTasks = new HashMap<>(); + Map<String, Set<Integer>> newWarmupTasksPendingRevocation = new HashMap<>(); + Map<String, Set<Integer>> newWarmupTasksPendingAssignment = new HashMap<>(); + + boolean hasUnreleasedTasks = computeAssignmentDifference( + memberAssignedTasks.activeTasks(), + targetAssignment.activeTasks(), + newActiveAssignedTasks, + newActiveTasksPendingRevocation, + newActiveTasksPendingAssignment, + (subtopologyId, partitionId) -> + currentActiveTaskProcessId.apply(subtopologyId, partitionId) != null || + currentStandbyTaskProcessIds.apply(subtopologyId, partitionId) + .contains(member.processId()) || + currentWarmupTaskProcessIds.apply(subtopologyId, partitionId) + .contains(member.processId()) + ); + + hasUnreleasedTasks = computeAssignmentDifference( + memberAssignedTasks.standbyTasks(), + targetAssignment.standbyTasks(), + newStandbyAssignedTasks, + newStandbyTasksPendingRevocation, + newStandbyTasksPendingAssignment, + (subtopologyId, partitionId) -> + Objects.equals(currentActiveTaskProcessId.apply(subtopologyId, partitionId), + member.processId()) || + currentStandbyTaskProcessIds.apply(subtopologyId, partitionId) + .contains(member.processId()) || + currentWarmupTaskProcessIds.apply(subtopologyId, partitionId) + .contains(member.processId()) + ) || hasUnreleasedTasks; + + hasUnreleasedTasks = computeAssignmentDifference( + memberAssignedTasks.warmupTasks(), + targetAssignment.warmupTasks(), + newWarmupAssignedTasks, + newWarmupTasksPendingRevocation, + newWarmupTasksPendingAssignment, + (subtopologyId, partitionId) -> + Objects.equals(currentActiveTaskProcessId.apply(subtopologyId, partitionId), + member.processId()) || + currentStandbyTaskProcessIds.apply(subtopologyId, partitionId) + .contains(member.processId()) || + currentWarmupTaskProcessIds.apply(subtopologyId, partitionId) + .contains(member.processId()) + ) || hasUnreleasedTasks; + + return buildNewMember( + memberEpoch, + new TaskTuple( + newActiveTasksPendingRevocation, + newStandbyTasksPendingRevocation, + newWarmupTasksPendingRevocation + ), + new TaskTuple( + newActiveAssignedTasks, + newStandbyAssignedTasks, + newWarmupAssignedTasks + ), + new TaskTuple( + newActiveTasksPendingAssignment, + newStandbyTasksPendingAssignment, + newWarmupTasksPendingAssignment + ), + hasUnreleasedTasks + ); + } + + private StreamsGroupMember buildNewMember(final int memberEpoch, + final TaskTuple newTasksPendingRevocation, + final TaskTuple newAssignedTasks, + final TaskTuple newTasksPendingAssignment, + final boolean hasUnreleasedTasks) { + + final boolean hasTasksToBeRevoked = + (!newTasksPendingRevocation.isEmpty()) + && (ownedTasks.isEmpty() || ownedTasks.get().containsAny(newTasksPendingRevocation)); + + if (hasTasksToBeRevoked) { + // If there are tasks to be revoked, the member remains in its current + // epoch and requests the revocation of those tasks. It transitions to + // the UNREVOKED_TASKS state to wait until the client acknowledges the + // revocation of the tasks. + return new StreamsGroupMember.Builder(member) + .setState(MemberState.UNREVOKED_TASKS) + .updateMemberEpoch(memberEpoch) + .setAssignedTasks(newAssignedTasks) + .setTasksPendingRevocation(newTasksPendingRevocation) + .build(); + } else if (!newTasksPendingAssignment.isEmpty()) { + // If there are tasks to be assigned, the member transitions to the + // target epoch and requests the assignment of those tasks. Note that + // the tasks are directly added to the assigned tasks set. The + // member transitions to the STABLE state or to the UNRELEASED_TASKS + // state depending on whether there are unreleased tasks or not. + MemberState newState = + hasUnreleasedTasks + ? MemberState.UNRELEASED_TASKS + : MemberState.STABLE; + return new StreamsGroupMember.Builder(member) + .setState(newState) + .updateMemberEpoch(targetAssignmentEpoch) + .setAssignedTasks(newAssignedTasks.merge(newTasksPendingAssignment)) + .setTasksPendingRevocation(TaskTuple.EMPTY) + .build(); + } else if (hasUnreleasedTasks) { + // If there are no tasks to be revoked nor to be assigned but some + // tasks are not available yet, the member transitions to the target + // epoch, to the UNRELEASED_TASKS state and waits. + return new StreamsGroupMember.Builder(member) + .setState(MemberState.UNRELEASED_TASKS) Review Comment: It's a bit different. `UNREVOKED_TASKS` is used if the member needs to revoke tasks. `UNRELEASED_TASKS` is used if the member waits for other members to revoke tasks. -- 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. 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