squah-confluent commented on code in PR #22487: URL: https://github.com/apache/kafka/pull/22487#discussion_r3398118462
########## group-coordinator/src/main/java/org/apache/kafka/coordinator/group/TargetAssignmentRecordsBuilder.java: ########## @@ -0,0 +1,483 @@ +/* + * 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; + +import org.apache.kafka.common.utils.internals.LogContext; +import org.apache.kafka.coordinator.common.runtime.CoordinatorRecord; +import org.apache.kafka.coordinator.group.modern.Assignment; +import org.apache.kafka.coordinator.group.streams.StreamsCoordinatorRecordHelpers; +import org.apache.kafka.coordinator.group.streams.TasksTuple; + +import org.slf4j.Logger; + +import java.util.ArrayList; +import java.util.HashMap; +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.Set; + +/** + * Builds the records to persist a new target assignment for a group. + * + * Records are only created for members which have a new target assignment. If + * their assignment did not change, no new record is needed. + * + * @param <A> The member's target assignment type. + */ +public abstract class TargetAssignmentRecordsBuilder<A> { + + /** + * The logger. + */ + private final Logger log; + + /** + * The group id. + */ + private final String groupId; + + /** + * The target assignment epoch. + */ + private int assignmentEpoch; + + /** + * The time at which the target assignment calculation finished. + */ + private long assignmentTimestampMs; + + /** + * The static members in the group at the time the new target assignment was computed. + */ + private Map<String, String> previousStaticMembers = Map.of(); + + /** + * The current member ids in the group. + */ + private Set<String> currentMemberIds; + + /** + * The current static members in the group. + */ + private Map<String, String> currentStaticMembers = Map.of(); + + /** + * The current target assignment. + */ + private Map<String, A> currentTargetAssignment = Map.of(); + + /** + * The new target assignment. + */ + private Map<String, A> newTargetAssignment = Map.of(); + + /** + * Constructs the object. + * + * @param logContext The log context. + * @param groupId The group id. + */ + public TargetAssignmentRecordsBuilder( + LogContext logContext, + String groupId + ) { + this.log = logContext.logger(this.getClass()); + this.groupId = Objects.requireNonNull(groupId); + } + + /** + * Sets the target assignment epoch. + * + * @param assignmentEpoch The target assignment epoch. + * @return This object. + */ + public TargetAssignmentRecordsBuilder<A> withAssignmentEpoch(int assignmentEpoch) { + this.assignmentEpoch = assignmentEpoch; + return this; + } + + /** + * Sets the time at which the target assignment calculation finished. + * + * @param assignmentTimestampMs The time at which the target assignment calculation finished. + * @return This object. + */ + public TargetAssignmentRecordsBuilder<A> withAssignmentTimestampMs(long assignmentTimestampMs) { + this.assignmentTimestampMs = assignmentTimestampMs; + return this; + } + + /** + * Sets the static members in the group at the time the new target assignment was computed. + * + * @param previousStaticMembers The static members in the group at the time the new target assignment was computed. + * @return This object. + */ + public TargetAssignmentRecordsBuilder<A> withPreviousStaticMembers(Map<String, String> previousStaticMembers) { + this.previousStaticMembers = previousStaticMembers; + return this; + } + + /** + * Sets the current member ids in the group. + * + * @param currentMemberIds The current member ids in the group. + * @return This object. + */ + public TargetAssignmentRecordsBuilder<A> withCurrentMemberIds(Set<String> currentMemberIds) { + this.currentMemberIds = currentMemberIds; + return this; + } + + /** + * Sets the current static members in the group. + * + * @param currentStaticMembers The current static members in the group. + * @return This object. + */ + public TargetAssignmentRecordsBuilder<A> withCurrentStaticMembers(Map<String, String> currentStaticMembers) { + this.currentStaticMembers = currentStaticMembers; + return this; + } + + /** + * Sets the current target assignment. + * + * @param currentTargetAssignment The current target assignment. + * @return This object. + */ + public TargetAssignmentRecordsBuilder<A> withCurrentTargetAssignment(Map<String, A> currentTargetAssignment) { + this.currentTargetAssignment = currentTargetAssignment; + return this; + } + + /** + * Sets the new target assignment. + * + * @param newTargetAssignment The new target assignment. + * @return This object. + */ + public TargetAssignmentRecordsBuilder<A> withNewTargetAssignment(Map<String, A> newTargetAssignment) { + this.newTargetAssignment = newTargetAssignment; + return this; + } + + /** + * Builds the records for the new target assignment. + * + * @return The records for the new target assignment. + */ + public List<CoordinatorRecord> build() { + List<CoordinatorRecord> records = new ArrayList<>(); + build(records); + return records; + } + + /** + * Builds the records for the new target assignment. + * + * @param records The list to accumulate records. + */ + @SuppressWarnings({"CyclomaticComplexity", "NPathComplexity"}) + public void build(List<CoordinatorRecord> records) { + // The members in the group may have changed while the target assignment was computed. + // We want to act as if concurrent member operations such as leaves and static member + // replacements happened *after* the target assignment was computed. + // + // * When members leave the group, we tombstone their target assignment. + // * When static members are replaced, we move the assignment from the old member id to the + // new member id. + // * When members rejoin with the same member id but a different instance id, they keep + // their existing assignment. + // + // Thus, when building the new target assignment records, + // * we should not emit records for members that have left the group + // * we should relabel records with the latest member id for static members + // * we should match up members using member ids first, then fall back to instance ids. + + // Build map of replacement member ids for static members that have churned. + Map<String, String> staticMemberIdRemapping = new HashMap<>(); + for (Map.Entry<String, String> entry : previousStaticMembers.entrySet()) { + String instanceId = entry.getKey(); + String oldMemberId = entry.getValue(); + String newMemberId = currentStaticMembers.get(instanceId); + + if (currentMemberIds.contains(oldMemberId)) { + // The member id is still in the group. We must not create a remapping entry, + // otherwise we could give the same assignment to two different members. + continue; + } + + if (newMemberId != null) { + staticMemberIdRemapping.put(newMemberId, oldMemberId); + } + + if (log.isDebugEnabled()) { + if (newMemberId == null) { + log.debug("[GroupId {}] Previous static member {} with instance id {} has no replacement, discarding their target assignment.", + groupId, oldMemberId, instanceId); + } else { + log.debug("[GroupId {}] Previous static member {} with instance id {} has been replaced by {}, transferring target assignment.", + groupId, oldMemberId, instanceId, newMemberId); + } + } + } + + if (log.isDebugEnabled()) { + // Log current static members with no previous static member. + for (Map.Entry<String, String> entry : currentStaticMembers.entrySet()) { + String instanceId = entry.getKey(); + String newMemberId = entry.getValue(); + + if (newTargetAssignment.containsKey(newMemberId)) { + // The member has been in the group the whole time. + continue; + } + + if (!previousStaticMembers.containsKey(instanceId)) { + log.debug("[GroupId {}] Current static member {} with instance id {} has no previous static member and will receive an empty target assignment.", + groupId, newMemberId, instanceId); + } + } + + // Log previous members that have left the group. + for (String memberId : newTargetAssignment.keySet()) { + if (currentMemberIds.contains(memberId)) { + // The member has been in the group the whole time. + continue; + } + + log.debug("[GroupId {}] Member {} has left the group, discarding their target assignment unless they were static and a corresponding static member exists.", + groupId, memberId); + } + + // Log current members that have joined the group. + for (String memberId : currentMemberIds) { + if (newTargetAssignment.containsKey(memberId)) { + // The member has been in the group the whole time. + continue; + } + + if (!staticMemberIdRemapping.containsKey(memberId)) { + log.debug("[GroupId {}] Member {} is new and will receive an empty target assignment or has no target assignment.", + groupId, memberId); + } + } + } Review Comment: Most of this method is debug logging. I'm unsure if we should add 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
