kafka ConsumerPartitionAssignor 源码

  • 2022-10-20
  • 浏览 (508)

kafka ConsumerPartitionAssignor 代码

文件路径:/clients/src/main/java/org/apache/kafka/clients/consumer/ConsumerPartitionAssignor.java

/*
 * 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;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Optional;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.kafka.common.Cluster;
import org.apache.kafka.common.Configurable;
import org.apache.kafka.common.KafkaException;
import org.apache.kafka.common.TopicPartition;
import org.apache.kafka.common.utils.Utils;

/**
 * This interface is used to define custom partition assignment for use in
 * {@link org.apache.kafka.clients.consumer.KafkaConsumer}. Members of the consumer group subscribe
 * to the topics they are interested in and forward their subscriptions to a Kafka broker serving
 * as the group coordinator. The coordinator selects one member to perform the group assignment and
 * propagates the subscriptions of all members to it. Then {@link #assign(Cluster, GroupSubscription)} is called
 * to perform the assignment and the results are forwarded back to each respective members
 *
 * In some cases, it is useful to forward additional metadata to the assignor in order to make
 * assignment decisions. For this, you can override {@link #subscriptionUserData(Set)} and provide custom
 * userData in the returned Subscription. For example, to have a rack-aware assignor, an implementation
 * can use this user data to forward the rackId belonging to each member.
 */
public interface ConsumerPartitionAssignor {

    /**
     * Return serialized data that will be included in the {@link Subscription} sent to the leader
     * and can be leveraged in {@link #assign(Cluster, GroupSubscription)} ((e.g. local host/rack information)
     *
     * @param topics Topics subscribed to through {@link org.apache.kafka.clients.consumer.KafkaConsumer#subscribe(java.util.Collection)}
     *               and variants
     * @return nullable subscription user data
     */
    default ByteBuffer subscriptionUserData(Set<String> topics) {
        return null;
    }

    /**
     * Perform the group assignment given the member subscriptions and current cluster metadata.
     * @param metadata Current topic/broker metadata known by consumer
     * @param groupSubscription Subscriptions from all members including metadata provided through {@link #subscriptionUserData(Set)}
     * @return A map from the members to their respective assignments. This should have one entry
     *         for each member in the input subscription map.
     */
    GroupAssignment assign(Cluster metadata, GroupSubscription groupSubscription);

    /**
     * Callback which is invoked when a group member receives its assignment from the leader.
     * @param assignment The local member's assignment as provided by the leader in {@link #assign(Cluster, GroupSubscription)}
     * @param metadata Additional metadata on the consumer (optional)
     */
    default void onAssignment(Assignment assignment, ConsumerGroupMetadata metadata) {
    }

    /**
     * Indicate which rebalance protocol this assignor works with;
     * By default it should always work with {@link RebalanceProtocol#EAGER}.
     */
    default List<RebalanceProtocol> supportedProtocols() {
        return Collections.singletonList(RebalanceProtocol.EAGER);
    }

    /**
     * Return the version of the assignor which indicates how the user metadata encodings
     * and the assignment algorithm gets evolved.
     */
    default short version() {
        return (short) 0;
    }

    /**
     * Unique name for this assignor (e.g. "range" or "roundrobin" or "sticky"). Note, this is not required
     * to be the same as the class name specified in {@link ConsumerConfig#PARTITION_ASSIGNMENT_STRATEGY_CONFIG}
     * @return non-null unique name
     */
    String name();

    final class Subscription {
        private final List<String> topics;
        private final ByteBuffer userData;
        private final List<TopicPartition> ownedPartitions;
        private Optional<String> groupInstanceId;

        public Subscription(List<String> topics, ByteBuffer userData, List<TopicPartition> ownedPartitions) {
            this.topics = topics;
            this.userData = userData;
            this.ownedPartitions = ownedPartitions;
            this.groupInstanceId = Optional.empty();
        }

        public Subscription(List<String> topics, ByteBuffer userData) {
            this(topics, userData, Collections.emptyList());
        }

        public Subscription(List<String> topics) {
            this(topics, null, Collections.emptyList());
        }

        public List<String> topics() {
            return topics;
        }

        public ByteBuffer userData() {
            return userData;
        }

        public List<TopicPartition> ownedPartitions() {
            return ownedPartitions;
        }

        public void setGroupInstanceId(Optional<String> groupInstanceId) {
            this.groupInstanceId = groupInstanceId;
        }

        public Optional<String> groupInstanceId() {
            return groupInstanceId;
        }

        @Override
        public String toString() {
            return "Subscription(" +
                "topics=" + topics +
                (userData == null ? "" : ", userDataSize=" + userData.remaining()) +
                ", ownedPartitions=" + ownedPartitions +
                ", groupInstanceId=" + (groupInstanceId.map(String::toString).orElse("null")) +
                ")";
        }
    }

    final class Assignment {
        private List<TopicPartition> partitions;
        private ByteBuffer userData;

        public Assignment(List<TopicPartition> partitions, ByteBuffer userData) {
            this.partitions = partitions;
            this.userData = userData;
        }

        public Assignment(List<TopicPartition> partitions) {
            this(partitions, null);
        }

        public List<TopicPartition> partitions() {
            return partitions;
        }

        public ByteBuffer userData() {
            return userData;
        }

        @Override
        public String toString() {
            return "Assignment(" +
                "partitions=" + partitions +
                (userData == null ? "" : ", userDataSize=" + userData.remaining()) +
                ')';
        }
    }

    final class GroupSubscription {
        private final Map<String, Subscription> subscriptions;

        public GroupSubscription(Map<String, Subscription> subscriptions) {
            this.subscriptions = subscriptions;
        }

        public Map<String, Subscription> groupSubscription() {
            return subscriptions;
        }

        @Override
        public String toString() {
            return "GroupSubscription(" +
                "subscriptions=" + subscriptions +
                ")";
        }
    }

    final class GroupAssignment {
        private final Map<String, Assignment> assignments;

        public GroupAssignment(Map<String, Assignment> assignments) {
            this.assignments = assignments;
        }

        public Map<String, Assignment> groupAssignment() {
            return assignments;
        }

        @Override
        public String toString() {
            return "GroupAssignment(" +
                "assignments=" + assignments +
                ")";
        }
    }

    /**
     * The rebalance protocol defines partition assignment and revocation semantics. The purpose is to establish a
     * consistent set of rules that all consumers in a group follow in order to transfer ownership of a partition.
     * {@link ConsumerPartitionAssignor} implementors can claim supporting one or more rebalance protocols via the
     * {@link ConsumerPartitionAssignor#supportedProtocols()}, and it is their responsibility to respect the rules
     * of those protocols in their {@link ConsumerPartitionAssignor#assign(Cluster, GroupSubscription)} implementations.
     * Failures to follow the rules of the supported protocols would lead to runtime error or undefined behavior.
     *
     * The {@link RebalanceProtocol#EAGER} rebalance protocol requires a consumer to always revoke all its owned
     * partitions before participating in a rebalance event. It therefore allows a complete reshuffling of the assignment.
     *
     * {@link RebalanceProtocol#COOPERATIVE} rebalance protocol allows a consumer to retain its currently owned
     * partitions before participating in a rebalance event. The assignor should not reassign any owned partitions
     * immediately, but instead may indicate consumers the need for partition revocation so that the revoked
     * partitions can be reassigned to other consumers in the next rebalance event. This is designed for sticky assignment
     * logic which attempts to minimize partition reassignment with cooperative adjustments.
     */
    enum RebalanceProtocol {
        EAGER((byte) 0), COOPERATIVE((byte) 1);

        private final byte id;

        RebalanceProtocol(byte id) {
            this.id = id;
        }

        public byte id() {
            return id;
        }

        public static RebalanceProtocol forId(byte id) {
            switch (id) {
                case 0:
                    return EAGER;
                case 1:
                    return COOPERATIVE;
                default:
                    throw new IllegalArgumentException("Unknown rebalance protocol id: " + id);
            }
        }
    }

    /**
     * Get a list of configured instances of {@link org.apache.kafka.clients.consumer.ConsumerPartitionAssignor}
     * based on the class names/types specified by {@link org.apache.kafka.clients.consumer.ConsumerConfig#PARTITION_ASSIGNMENT_STRATEGY_CONFIG}
     */
    static List<ConsumerPartitionAssignor> getAssignorInstances(List<String> assignorClasses, Map<String, Object> configs) {
        List<ConsumerPartitionAssignor> assignors = new ArrayList<>();
        // a map to store assignor name -> assignor class name
        Map<String, String> assignorNameMap = new HashMap<>();

        if (assignorClasses == null)
            return assignors;

        for (Object klass : assignorClasses) {
            // first try to get the class if passed in as a string
            if (klass instanceof String) {
                try {
                    klass = Class.forName((String) klass, true, Utils.getContextOrKafkaClassLoader());
                } catch (ClassNotFoundException classNotFound) {
                    throw new KafkaException(klass + " ClassNotFoundException exception occurred", classNotFound);
                }
            }

            if (klass instanceof Class<?>) {
                Object assignor = Utils.newInstance((Class<?>) klass);
                if (assignor instanceof Configurable)
                    ((Configurable) assignor).configure(configs);

                if (assignor instanceof ConsumerPartitionAssignor) {
                    String assignorName = ((ConsumerPartitionAssignor) assignor).name();
                    if (assignorNameMap.containsKey(assignorName)) {
                        throw new KafkaException("The assignor name: '" + assignorName + "' is used in more than one assignor: " +
                            assignorNameMap.get(assignorName) + ", " + assignor.getClass().getName());
                    }
                    assignorNameMap.put(assignorName, assignor.getClass().getName());
                    assignors.add((ConsumerPartitionAssignor) assignor);
                } else {
                    throw new KafkaException(klass + " is not an instance of " + ConsumerPartitionAssignor.class.getName());
                }
            } else {
                throw new KafkaException("List contains element of type " + klass.getClass().getName() + ", expected String or Class");
            }
        }
        return assignors;
    }

}

相关信息

kafka 源码目录

相关文章

kafka CommitFailedException 源码

kafka Consumer 源码

kafka ConsumerConfig 源码

kafka ConsumerGroupMetadata 源码

kafka ConsumerInterceptor 源码

kafka ConsumerRebalanceListener 源码

kafka ConsumerRecord 源码

kafka ConsumerRecords 源码

kafka CooperativeStickyAssignor 源码

kafka InvalidOffsetException 源码

0  赞