ableegoldman commented on code in PR #16033: URL: https://github.com/apache/kafka/pull/16033#discussion_r1618033785
########## streams/src/main/java/org/apache/kafka/streams/processor/assignment/TaskAssignmentUtils.java: ########## @@ -74,20 +198,220 @@ public static Map<ProcessId, KafkaStreamsAssignment> optimizeRackAwareStandbyTas final ApplicationState applicationState, final Map<ProcessId, KafkaStreamsAssignment> kafkaStreamsAssignments ) { + if (!hasValidRackInformation(applicationState)) { + LOG.warn("Cannot optimize standby tasks with invalid rack information."); + return kafkaStreamsAssignments; + } + + final int crossRackTrafficCost = applicationState.assignmentConfigs().rackAwareTrafficCost(); + final int nonOverlapCost = applicationState.assignmentConfigs().rackAwareNonOverlapCost(); + final long currentCost = computeTaskCost( + applicationState.allTasks(), + applicationState.kafkaStreamsStates(false), + crossRackTrafficCost, + nonOverlapCost, + true, + true + ); + LOG.info("Assignment before standby task optimization has cost {}", currentCost); throw new UnsupportedOperationException("Not Implemented."); } + private static long computeTaskCost(final Set<TaskInfo> tasks, + final Map<ProcessId, KafkaStreamsState> clients, + final int crossRackTrafficCost, + final int nonOverlapCost, + final boolean hasReplica, + final boolean isStandby) { + if (tasks.isEmpty()) { + return 0; + } + + final List<UUID> clientIds = clients.keySet().stream().map(ProcessId::id).collect( + Collectors.toList()); + + final List<TaskId> taskIds = tasks.stream().map(TaskInfo::id).collect(Collectors.toList()); + final Map<TaskId, Set<TaskTopicPartition>> topicPartitionsByTaskId = tasks.stream().collect( + Collectors.toMap(TaskInfo::id, TaskInfo::topicPartitions)); + + final Map<UUID, Optional<String>> clientRacks = clients.values().stream().collect( + Collectors.toMap(state -> state.processId().id(), KafkaStreamsState::rackId)); + + final Map<UUID, Set<TaskId>> taskIdsByProcess = clients.values().stream().collect( + Collectors.toMap(state -> state.processId().id(), state -> { + if (isStandby) { + return state.previousStandbyTasks(); + } + return state.previousActiveTasks(); + }) + ); + + final RackAwareGraphConstructor<UUID> graphConstructor = new MinTrafficGraphConstructor<>(); + final AssignmentGraph assignmentGraph = buildTaskGraph(clientIds, clientRacks, taskIds, taskIdsByProcess, topicPartitionsByTaskId, + crossRackTrafficCost, nonOverlapCost, hasReplica, isStandby, graphConstructor); + return assignmentGraph.graph.totalCost(); + } + + private static AssignmentGraph buildTaskGraph(final List<UUID> clientIds, + final Map<UUID, Optional<String>> clientRacks, + final List<TaskId> taskIds, + final Map<UUID, Set<TaskId>> previousTaskIdsByProcess, + final Map<TaskId, Set<TaskTopicPartition>> topicPartitionsByTaskId, + final int crossRackTrafficCost, + final int nonOverlapCost, + final boolean hasReplica, + final boolean isStandby, + final RackAwareGraphConstructor<UUID> graphConstructor) { + final Map<UUID, UUID> clientsUuidByUuid = clientIds.stream().collect(Collectors.toMap(id -> id, id -> id)); + final Map<TaskId, UUID> clientByTask = new HashMap<>(); + final Map<UUID, Integer> taskCountByClient = new HashMap<>(); + final Graph<Integer> graph = graphConstructor.constructTaskGraph( + clientIds, + taskIds, + clientsUuidByUuid, + clientByTask, + taskCountByClient, + (processId, taskId) -> { + return previousTaskIdsByProcess.get(processId).contains(taskId); + }, + (taskId, processId, inCurrentAssignment, unused0, unused1, unused2) -> { + final int assignmentChangeCost = !inCurrentAssignment ? nonOverlapCost : 0; + final Optional<String> clientRack = clientRacks.get(processId); + final Set<TaskTopicPartition> topicPartitions = topicPartitionsByTaskId.get(taskId).stream().filter(tp -> { + return isStandby ? tp.isChangelog() : true; + }).collect(Collectors.toSet()); + return assignmentChangeCost + getCrossRackTrafficCost(topicPartitions, clientRack, crossRackTrafficCost); + }, + crossRackTrafficCost, + nonOverlapCost, + hasReplica, + isStandby + ); + return new AssignmentGraph(graph, clientByTask, taskCountByClient); + } + + /** + * This internal structure is used to keep track of the graph solving outputs alongside the graph + * structure itself. + */ + private static final class AssignmentGraph { + public final Graph<Integer> graph; + public final Map<TaskId, UUID> clientByTask; + public final Map<UUID, Integer> taskCountByClient; + + public AssignmentGraph(final Graph<Integer> graph, + final Map<TaskId, UUID> clientByTask, + final Map<UUID, Integer> taskCountByClient) { + this.graph = graph; + this.clientByTask = clientByTask; + this.taskCountByClient = taskCountByClient; + } + } + /** - * Return a "no-op" assignment that just copies the previous assignment of tasks to KafkaStreams clients * - * @param applicationState the metadata and other info describing the current application state + * @return the traffic cost of assigning this {@param task} to the client {@param streamsState}. + */ + private static int getCrossRackTrafficCost(final Set<TaskTopicPartition> topicPartitions, + final Optional<String> clientRack, + final int crossRackTrafficCost) { + if (!clientRack.isPresent()) { + throw new IllegalStateException("Client doesn't have rack configured."); + } + + int cost = 0; + for (final TaskTopicPartition topicPartition : topicPartitions) { + final Optional<Set<String>> topicPartitionRacks = topicPartition.rackIds(); + if (topicPartitionRacks == null || !topicPartitionRacks.isPresent()) { + throw new IllegalStateException("TopicPartition " + topicPartition + " has no rack information."); + } + + if (topicPartitionRacks.get().contains(clientRack.get())) { + continue; + } + + cost += crossRackTrafficCost; + } + return cost; + } + + /** + * This function returns whether the current application state has the required rack information + * to make assignment decisions with. + * This includes ensuring that every client has a known rack id, and that every topic partition for + * every logical task that needs to be assigned also has known rack ids. + * If a logical task has no source topic partitions, it will return false. + * If standby tasks are configured, but a logical task has no changelog topic partitions, it will return false. * - * @return a new map containing an assignment that replicates exactly the previous assignment reported - * in the applicationState + * @return whether rack-aware assignment decisions can be made for this application. */ - public static Map<ProcessId, KafkaStreamsAssignment> identityAssignment( - final ApplicationState applicationState - ) { - throw new UnsupportedOperationException("Not Implemented."); + public static boolean hasValidRackInformation(final ApplicationState applicationState) { Review Comment: needs to be private, otherwise it would be a public API which we don't want (and we don't need IIUC) ########## streams/src/main/java/org/apache/kafka/streams/processor/assignment/TaskAssignmentUtils.java: ########## @@ -16,14 +16,63 @@ */ package org.apache.kafka.streams.processor.assignment; +import java.util.ArrayList; +import java.util.Collection; +import java.util.HashMap; +import java.util.HashSet; +import java.util.List; import java.util.Map; +import java.util.Optional; +import java.util.Set; import java.util.SortedSet; +import java.util.UUID; +import java.util.stream.Collectors; import org.apache.kafka.streams.processor.TaskId; +import org.apache.kafka.streams.processor.assignment.KafkaStreamsAssignment.AssignedTask; +import org.apache.kafka.streams.processor.internals.assignment.Graph; +import org.apache.kafka.streams.processor.internals.assignment.MinTrafficGraphConstructor; +import org.apache.kafka.streams.processor.internals.assignment.RackAwareGraphConstructor; +import org.apache.kafka.streams.processor.internals.assignment.RackAwareGraphConstructorFactory; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; /** * A set of utilities to help implement task assignment via the {@link TaskAssignor} */ public final class TaskAssignmentUtils { + private static final Logger LOG = LoggerFactory.getLogger(TaskAssignmentUtils.class); + + private TaskAssignmentUtils() {} + + /** + * Return a "no-op" assignment that just copies the previous assignment of tasks to KafkaStreams clients + * + * @param applicationState the metadata and other info describing the current application state + * + * @return a new map containing an assignment that replicates exactly the previous assignment reported + * in the applicationState + */ + public static Map<ProcessId, KafkaStreamsAssignment> identityAssignment( + final ApplicationState applicationState + ) { Review Comment: Kafka Streams formatting: first parameter always on the same line (no matter how ridiculously long it gets) ```suggestion public static Map<ProcessId, KafkaStreamsAssignment> identityAssignment(final ApplicationState applicationState) { ``` ########## streams/src/main/java/org/apache/kafka/streams/processor/assignment/TaskAssignmentUtils.java: ########## @@ -58,7 +112,85 @@ public static Map<ProcessId, KafkaStreamsAssignment> optimizeRackAwareActiveTask final Map<ProcessId, KafkaStreamsAssignment> kafkaStreamsAssignments, final SortedSet<TaskId> tasks Review Comment: I think we're still missing the javadocs? -- This is an automated message from the Apache Git Service. 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