showuon commented on a change in pull request #10851: URL: https://github.com/apache/kafka/pull/10851#discussion_r805156641
########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/DefaultStandbyTaskAssignor.java ########## @@ -0,0 +1,67 @@ +/* + * 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.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import java.util.Map; +import java.util.Set; +import java.util.UUID; + +import static org.apache.kafka.streams.processor.internals.assignment.TaskAssignmentUtils.computeTasksToRemainingStandbys; +import static org.apache.kafka.streams.processor.internals.assignment.TaskAssignmentUtils.pollClientAndMaybeAssignRemainingStandbyTasks; + +class DefaultStandbyTaskAssignor implements StandbyTaskAssignor { Review comment: I know there was no any java doc for the default least load assignor. But do you think we can add some comments to it, just like in `ClientTagAwareStandbyTaskAssignor`? I believe not everyone knows default assignor algorithm is least loaded assignor. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/ClientTagAwareStandbyTaskAssignor.java ########## @@ -0,0 +1,289 @@ +/* + * 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.Objects; +import java.util.Set; +import java.util.UUID; + +import static org.apache.kafka.streams.processor.internals.assignment.TaskAssignmentUtils.computeTasksToRemainingStandbys; +import static org.apache.kafka.streams.processor.internals.assignment.TaskAssignmentUtils.pollClientAndMaybeAssignRemainingStandbyTasks; +import static org.apache.kafka.streams.processor.internals.assignment.TaskAssignmentUtils.shouldBalanceLoad; + +/** + * 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's not enough capacity on the clients + * with 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); + + @Override + public boolean assign(final Map<UUID, ClientState> clients, Review comment: Could we add some java doc to this assign to briefly mention about the algorithm used in the assignor? Thanks. ########## File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/ClientState.java ########## @@ -59,29 +60,31 @@ private int capacity; - public ClientState() { - this(0); + public ClientState(final Map<String, String> clientTags) { + this(0, clientTags); } - ClientState(final int capacity) { + ClientState(final int capacity, final Map<String, String> clientTags) { Review comment: I'm wondering could we keep the original constructor and pass empty map into the new one? So that we don't have to make changes to the old caller. That is: ``` public ClientState() { this(0, Collections.emptyMap()); } ClientState(final int capacity) { this(capacity, Collections.emptyMap()); } ``` WDYT? -- 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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