cadonna commented on code in PR #18551: URL: https://github.com/apache/kafka/pull/18551#discussion_r1937615571
########## clients/src/main/java/org/apache/kafka/clients/consumer/internals/StreamsMembershipManager.java: ########## @@ -0,0 +1,1249 @@ +/* + * 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.clients.consumer.internals; + +import org.apache.kafka.clients.consumer.internals.events.StreamsOnAllTasksLostCallbackCompletedEvent; +import org.apache.kafka.clients.consumer.internals.events.StreamsOnTasksAssignedCallbackCompletedEvent; +import org.apache.kafka.clients.consumer.internals.events.StreamsOnTasksRevokedCallbackCompletedEvent; +import org.apache.kafka.clients.consumer.internals.metrics.ConsumerRebalanceMetricsManager; +import org.apache.kafka.clients.consumer.internals.metrics.RebalanceMetricsManager; +import org.apache.kafka.common.KafkaException; +import org.apache.kafka.common.TopicPartition; +import org.apache.kafka.common.Uuid; +import org.apache.kafka.common.message.StreamsGroupHeartbeatResponseData; +import org.apache.kafka.common.metrics.Metrics; +import org.apache.kafka.common.protocol.Errors; +import org.apache.kafka.common.requests.StreamsGroupHeartbeatRequest; +import org.apache.kafka.common.requests.StreamsGroupHeartbeatResponse; +import org.apache.kafka.common.utils.LogContext; +import org.apache.kafka.common.utils.Time; + +import org.slf4j.Logger; + +import java.util.ArrayList; +import java.util.Collections; +import java.util.List; +import java.util.Map; +import java.util.Objects; +import java.util.Optional; +import java.util.SortedSet; +import java.util.TreeSet; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.atomic.AtomicBoolean; +import java.util.stream.Collectors; +import java.util.stream.Stream; + +/** + * Tracks state the state of a single member in relationship to a group: + * <p/> + * Responsible for: + * <ul> + * <li>Keeping member state</li> + * <li>Keeping assignment for the member</li> + * <li>Reconciling assignment, for example if tasks need to be revoked before other tasks can be assigned</li> + * <li>Calling the assignment and revocation callbacks on the Streams client</li> + * </ul> + */ +public class StreamsMembershipManager implements RequestManager { + + /** + * A data structure to represent the current task assignment, and current target task assignment of a member in a + * streams group. + * <p/> + * Besides the assigned tasks, it contains a local epoch that is bumped whenever the assignment changes, to ensure + * that two assignments with the same tasks but different local epochs are not considered equal. + */ + private static class LocalAssignment { + public static final long NONE_EPOCH = -1; + public static final LocalAssignment NONE = new LocalAssignment( + NONE_EPOCH, + Collections.emptyMap(), + Collections.emptyMap(), + Collections.emptyMap() + ); + + public final long localEpoch; + public final Map<String, SortedSet<Integer>> activeTasks; + public final Map<String, SortedSet<Integer>> standbyTasks; + public final Map<String, SortedSet<Integer>> warmupTasks; + + public LocalAssignment(final long localEpoch, + final Map<String, SortedSet<Integer>> activeTasks, + final Map<String, SortedSet<Integer>> standbyTasks, + final Map<String, SortedSet<Integer>> warmupTasks) { + this.localEpoch = localEpoch; + this.activeTasks = activeTasks; + this.standbyTasks = standbyTasks; + this.warmupTasks = warmupTasks; + if (localEpoch == NONE_EPOCH && + (!activeTasks.isEmpty() || !standbyTasks.isEmpty() || !warmupTasks.isEmpty())) { + throw new IllegalArgumentException("Local epoch must be set if tasks are assigned."); + } + } + + Optional<LocalAssignment> updateWith(final Map<String, SortedSet<Integer>> activeTasks, + final Map<String, SortedSet<Integer>> standbyTasks, + final Map<String, SortedSet<Integer>> warmupTasks) { + if (localEpoch != NONE_EPOCH && + activeTasks.equals(this.activeTasks) && + standbyTasks.equals(this.standbyTasks) && + warmupTasks.equals(this.warmupTasks)) { + return Optional.empty(); + } + + long nextLocalEpoch = localEpoch + 1; + return Optional.of(new LocalAssignment(nextLocalEpoch, activeTasks, standbyTasks, warmupTasks)); + } + + @Override + public String toString() { + return "LocalAssignment{" + + "localEpoch=" + localEpoch + + ", activeTasks=" + activeTasks + + ", standbyTasks=" + standbyTasks + + ", warmupTasks=" + warmupTasks + + '}'; + } + + @Override + public boolean equals(Object o) { + if (this == o) return true; + if (o == null || getClass() != o.getClass()) return false; + LocalAssignment that = (LocalAssignment) o; + return localEpoch == that.localEpoch && + Objects.equals(activeTasks, that.activeTasks) && + Objects.equals(standbyTasks, that.standbyTasks) && + Objects.equals(warmupTasks, that.warmupTasks); + } + + @Override + public int hashCode() { + return Objects.hash(localEpoch, activeTasks, standbyTasks, warmupTasks); + } + } + + /** + * TopicPartition comparator based on topic name and partition. + */ + static final Utils.TopicPartitionComparator TOPIC_PARTITION_COMPARATOR = new Utils.TopicPartitionComparator(); + + private final Logger log; + + /** + * The processor that handles events of the Streams rebalance protocol. + * For example, requests for invocation of assignment/revocation callbacks. + */ + private final StreamsRebalanceEventsProcessor streamsRebalanceEventsProcessor; + + /** + * Data needed to participate in the Streams rebalance protocol. + */ + private final StreamsRebalanceData streamsRebalanceData; + + /** + * Subscription state object holding the current assignment the member has for the topology + * of the Streams application. + */ + private final SubscriptionState subscriptionState; + + /** + * Current state of this member as part of the consumer group, as defined in {@link MemberState} + */ + private MemberState state; + + /** + * Group ID of the Streams group the member will be part of, provided when creating the current + * membership manager. + */ + private final String groupId; + + /** + * Member ID generated by the consumer at startup, which is unique within the group and remains consistent + * for the entire lifetime of the process. This ID acts as an incarnation identifier for the consumer process + * and does not reset or change, even if the consumer leaves and rejoins the group. + * The Member ID remains the same until the process is completely stopped or terminated. + */ + private final String memberId = Uuid.randomUuid().toString(); + + /** + * Group instance ID to be used by a static member, provided when creating the current membership manager. + */ + private final Optional<String> groupInstanceId = Optional.empty(); + + /** + * Current epoch of the member. It will be set to 0 by the member, and provided to the server + * on the heartbeat request, to join the group. It will be then maintained by the server, + * incremented as the member reconciles and acknowledges the assignments it receives. It will + * be reset to 0 if the member gets fenced. + */ + private int memberEpoch = 0; + + /** + * If the member is currently leaving the group after a call to {@link #leaveGroup()} or + * {@link #leaveGroupOnClose()}, this will have a future that will complete when the ongoing leave operation + * completes (callbacks executed and heartbeat request to leave is sent out). This will be empty if the + * member is not leaving. + */ + private Optional<CompletableFuture<Void>> leaveGroupInProgress = Optional.empty(); + + /** + * Future that will complete when a stale member completes releasing its assignment after + * leaving the group due to poll timer expired. Used to make sure that the member rejoins + * when the timer is reset, only when it completes releasing its assignment. + */ + private CompletableFuture<Void> staleMemberAssignmentRelease; + + /** + * If there is a reconciliation running (callbacks). + * This will be true if {@link #maybeReconcile()} has been triggered + * after receiving a heartbeat response, or a metadata update. + */ + private boolean reconciliationInProgress; + + /** + * True if a reconciliation is in progress and the member rejoined the group since the start + * of the reconciliation. Used to know that the reconciliation in progress should be + * interrupted and not be applied. + */ + private boolean rejoinedWhileReconciliationInProgress; + + /** + * Registered listeners that will be notified whenever the member epoch gets updated + * (valid values received from the broker, or values cleared due to member leaving + * the group, getting fenced or failing). + */ + private final List<MemberStateListener> stateUpdatesListeners = new ArrayList<>(); + + /** + * Tasks received in the last target assignment, together with its local epoch. + * + * This member variable is reassigned every time a new assignment is received. + * It is equal to LocalAssignment.NONE whenever we are not in a group. + */ + private LocalAssignment targetAssignment = LocalAssignment.NONE; + + /** + * Assignment that the member received from the server and successfully processed, together with + * its local epoch. + * + * This is equal to LocalAssignment.NONE when we are not in a group, or we haven't reconciled any assignment yet. + */ + private LocalAssignment currentAssignment = LocalAssignment.NONE; + + /** + * AtomicBoolean to track whether the subscription is updated. + * If it's true and subscription state is UNSUBSCRIBED, the next {@link #onConsumerPoll()} will change member state to JOINING. + */ + private final AtomicBoolean subscriptionUpdated = new AtomicBoolean(false); + + /** + * Measures successful rebalance latency and number of failed rebalances. + */ + private final RebalanceMetricsManager metricsManager; + + private final Time time; + + /** + * True if the poll timer has expired, signaled by a call to + * {@link #transitionToSendingLeaveGroup(boolean)} with dueToExpiredPollTimer param true. This + * will be used to determine that the member should transition to STALE after leaving the + * group, to release its assignment and wait for the timer to be reset. + */ + private boolean isPollTimerExpired; + + /** + * Constructs the Streams membership manager. + * + * @param groupId The ID of the group. + * @param streamsRebalanceEventsProcessor The processor that handles Streams rebalance events like requests for + * invocation of assignment/revocation callbacks. + * @param streamsRebalanceData Data needed to participate in the Streams rebalance protocol. + * @param subscriptionState The subscription state of the member. + * @param logContext The log context. + * @param time The time. + * @param metrics The metrics. + */ + public StreamsMembershipManager(final String groupId, + final StreamsRebalanceEventsProcessor streamsRebalanceEventsProcessor, + final StreamsRebalanceData streamsRebalanceData, + final SubscriptionState subscriptionState, + final LogContext logContext, + final Time time, + final Metrics metrics) { + log = logContext.logger(StreamsMembershipManager.class); + this.state = MemberState.UNSUBSCRIBED; + this.groupId = groupId; + this.streamsRebalanceEventsProcessor = streamsRebalanceEventsProcessor; + this.streamsRebalanceData = streamsRebalanceData; + this.subscriptionState = subscriptionState; + metricsManager = new ConsumerRebalanceMetricsManager(metrics); + this.time = time; + } + + /** + * @return Group ID of the group the member is part of (or wants to be part of). + */ + public String groupId() { + return groupId; + } + + /** + * @return Member ID that is generated at startup and remains unchanged for the entire lifetime of the process. + */ + public String memberId() { + return memberId; + } + + /** + * @return Instance ID used by the member when joining the group. If non-empty, it will indicate that + * this is a static member. + */ + public Optional<String> groupInstanceId() { + return groupInstanceId; + } + + /** + * @return Current epoch of the member, maintained by the server. + */ + public int memberEpoch() { + return memberEpoch; + } + + /** + * @return Current state of this member in relationship to a group, as defined in + * {@link MemberState}. + */ + public MemberState state() { + return state; + } + + /** + * @return True if the member is preparing to leave the group (waiting for callbacks), or + * leaving (sending last heartbeat). This is used to skip proactively leaving the group when + * the poll timer expires. + */ + public boolean isLeavingGroup() { + return state == MemberState.PREPARE_LEAVING || state == MemberState.LEAVING; + } + + private boolean isNotInGroup() { + return state == MemberState.UNSUBSCRIBED || + state == MemberState.FENCED || + state == MemberState.FATAL || + state == MemberState.STALE; + } + + /** + * Register a new listener that will be invoked whenever the member state changes, or a new + * member ID or epoch is received. + * + * @param listener Listener to invoke. + */ + public void registerStateListener(MemberStateListener listener) { + Objects.requireNonNull(listener, "State updates listener cannot be null"); + for (MemberStateListener registeredListener : stateUpdatesListeners) { + if (registeredListener == listener) { + throw new IllegalArgumentException("Listener is already registered."); + } + } + stateUpdatesListeners.add(listener); + } + + /** + * Call all listeners that are registered to get notified when the member epoch is updated. + * This also includes the member ID in the notification. If the member fails or leaves + * the group, this will be invoked with empty epoch. + */ + private void notifyEpochChange(Optional<Integer> epoch) { + stateUpdatesListeners.forEach(stateListener -> stateListener.onMemberEpochUpdated(epoch, memberId)); + } + + /** + * Transition to the {@link MemberState#JOINING} state, indicating that the member will + * try to join the group on the next heartbeat request. This is expected to be invoked when + * the user calls the subscribe API, or when the member wants to rejoin after getting fenced. + * Visible for testing. + */ + private void transitionToJoining() { + if (state == MemberState.FATAL) { + log.warn("No action taken to join the group with the updated subscription because " + + "the member is in FATAL state"); + return; + } + if (reconciliationInProgress) { + rejoinedWhileReconciliationInProgress = true; + } + resetEpoch(); + transitionTo(MemberState.JOINING); + clearCurrentTaskAssignment(); + } + + /** + * Reset member epoch to the value required for the leave the group heartbeat request, and + * transition to the {@link MemberState#LEAVING} state so that a heartbeat request is sent + * out with it. + * + * @param dueToExpiredPollTimer True if the leave group is due to an expired poll timer. This + * will indicate that the member must remain STALE after leaving, + * until it releases its assignment and the timer is reset. + */ + private void transitionToSendingLeaveGroup(boolean dueToExpiredPollTimer) { + if (state == MemberState.FATAL) { + log.warn("Member {} with epoch {} won't send leave group request because it is in " + + "FATAL state", memberId, memberEpoch); + return; + } + if (state == MemberState.UNSUBSCRIBED) { + log.warn("Member {} won't send leave group request because it is already out of the group.", + memberId); + return; + } + + if (dueToExpiredPollTimer) { + isPollTimerExpired = true; + // Briefly transition through prepare leaving. The member does not have to release + // any assignment before sending the leave group given that is stale. It will invoke + // onAllTasksLost after sending the leave group on the STALE state. + transitionTo(MemberState.PREPARE_LEAVING); + } + finalizeLeaving(); + transitionTo(MemberState.LEAVING); + } + + private void finalizeLeaving() { + updateMemberEpoch(StreamsGroupHeartbeatRequest.LEAVE_GROUP_MEMBER_EPOCH); + clearCurrentTaskAssignment(); + } + + /** + * Transition to STALE to release assignments because the member has left the group due to + * expired poll timer. This will trigger the onAllTasksLost callback. Once the callback + * completes, the member will remain stale until the poll timer is reset by an application + * poll event. See {@link #maybeRejoinStaleMember()}. + */ + private void transitionToStale() { + transitionTo(MemberState.STALE); + + final CompletableFuture<Void> onAllTasksLostCallbackExecution = + streamsRebalanceEventsProcessor.requestOnAllTasksLostCallbackInvocation(); + staleMemberAssignmentRelease = onAllTasksLostCallbackExecution.whenComplete((result, error) -> { + if (error != null) { + log.error("Task revocation callback invocation failed " + + "after member left group due to expired poll timer.", error); + } + clearTaskAndPartitionAssignment(); + log.debug("Member {} sent leave group heartbeat and released its assignment. It will remain " + + "in {} state until the poll timer is reset, and it will then rejoin the group", + memberId, MemberState.STALE); + }); + } + + /** + * Transition the member to the FATAL state and update the member info as required. This is + * invoked when un-recoverable errors occur (ex. when the heartbeat returns a non-retriable + * error) + */ + public void transitionToFatal() { + MemberState previousState = state; + transitionTo(MemberState.FATAL); + log.error("Member {} with epoch {} transitioned to fatal state", memberId, memberEpoch); + notifyEpochChange(Optional.empty()); + + if (previousState == MemberState.UNSUBSCRIBED) { + log.debug("Member {} with epoch {} got fatal error from the broker but it already " + + "left the group, so onAllTasksLost callback won't be triggered.", memberId, memberEpoch); + return; + } + + if (previousState == MemberState.LEAVING || previousState == MemberState.PREPARE_LEAVING) { + log.info("Member {} with epoch {} was leaving the group with state {} when it got a " + + "fatal error from the broker. It will discard the ongoing leave and remain in " + + "fatal state.", memberId, memberEpoch, previousState); + maybeCompleteLeaveInProgress(); + return; + } + + CompletableFuture<Void> onAllTasksLostCallbackExecuted = streamsRebalanceEventsProcessor.requestOnAllTasksLostCallbackInvocation(); + onAllTasksLostCallbackExecuted.whenComplete((result, error) -> { + if (error != null) { + log.error("onAllTasksLost callback invocation failed while releasing assignment " + + "after member failed with fatal error.", error); + } + clearTaskAndPartitionAssignment(); + }); + } + + /** + * Notify when the heartbeat request is skipped. + * Transition out of the {@link MemberState#LEAVING} state even if the heartbeat was not sent. + * This will ensure that the member is not blocked on {@link MemberState#LEAVING} (best + * effort to send the request, without any response handling or retry logic) + */ + public void onHeartbeatRequestSkipped() { + if (state == MemberState.LEAVING) { + log.warn("Heartbeat to leave group cannot be sent (most probably due to coordinator " + + "not known/available). Member {} with epoch {} will transition to {}.", + memberId, memberEpoch, MemberState.UNSUBSCRIBED); + transitionTo(MemberState.UNSUBSCRIBED); + maybeCompleteLeaveInProgress(); + } + } + + /** + * Update the member state, setting it to the nextState only if it is a valid transition. + * + * @throws IllegalStateException If transitioning from the member {@link #state} to the + * nextState is not allowed as defined in {@link MemberState}. + */ + private void transitionTo(MemberState nextState) { + if (!state.equals(nextState) && !nextState.getPreviousValidStates().contains(state)) { + throw new IllegalStateException(String.format("Invalid state transition from %s to %s", + state, nextState)); + } + + if (isCompletingRebalance(state, nextState)) { + metricsManager.recordRebalanceEnded(time.milliseconds()); + } + if (isStartingRebalance(state, nextState)) { + metricsManager.recordRebalanceStarted(time.milliseconds()); + } + + log.info("Member {} with epoch {} transitioned from {} to {}.", memberId, memberEpoch, state, nextState); + this.state = nextState; + } + + private static boolean isCompletingRebalance(MemberState currentState, MemberState nextState) { + return currentState == MemberState.RECONCILING && + (nextState == MemberState.STABLE || nextState == MemberState.ACKNOWLEDGING); + } + + private static boolean isStartingRebalance(MemberState currentState, MemberState nextState) { + return currentState != MemberState.RECONCILING && nextState == MemberState.RECONCILING; + } + + private void resetEpoch() { + updateMemberEpoch(StreamsGroupHeartbeatRequest.JOIN_GROUP_MEMBER_EPOCH); + } + + private void updateMemberEpoch(int newEpoch) { + boolean newEpochReceived = this.memberEpoch != newEpoch; + this.memberEpoch = newEpoch; + if (newEpochReceived) { + if (memberEpoch > 0) { + notifyEpochChange(Optional.of(memberEpoch)); + } else { + notifyEpochChange(Optional.empty()); + } + } + } + + /** + * Discard assignments received that have not been reconciled yet (waiting for metadata + * or the next reconciliation loop). + */ + private void clearCurrentTaskAssignment() { + currentAssignment = LocalAssignment.NONE; + } + + /** + * Clear the assigned partitions in the member subscription, pending assignments and metadata cache. + */ + private void clearTaskAndPartitionAssignment() { + subscriptionState.assignFromSubscribed(Collections.emptySet()); + currentAssignment = LocalAssignment.NONE; + targetAssignment = LocalAssignment.NONE; + } + + /** + * @return True if the member should not send heartbeats, which is the case when it is in a + * state where it is not an active member of the group. + */ + public boolean shouldSkipHeartbeat() { + return isNotInGroup(); + } + + /** + * @return True if the member should send heartbeat to the coordinator without waiting for + * the interval. + */ + public boolean shouldHeartbeatNow() { + return state == MemberState.ACKNOWLEDGING || state == MemberState.LEAVING || state == MemberState.JOINING; + } + + /** + * Set {@link #subscriptionUpdated} to true to indicate that the subscription has been updated. + * The next {@link #onConsumerPoll()} will join the group with the updated subscription, if the member is not part of it yet. + * If the member is already part of the group, this will only ensure that the updated subscription + * is included in the next heartbeat request. + * <p/> + * Note that list of topics of the subscription is taken from the shared subscription state. 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