org.apache.kafka.clients.consumer

Class RoundRobinAssignor

java.lang.Object

org.apache.kafka.clients.consumer.internals.AbstractPartitionAssignor

org.apache.kafka.clients.consumer.RoundRobinAssignor

All Implemented Interfaces:

org.apache.kafka.clients.consumer.internals.PartitionAssignor

public class RoundRobinAssignor
extends org.apache.kafka.clients.consumer.internals.AbstractPartitionAssignor

The round robin assignor lays out all the available partitions and all the available consumers. It then proceeds to do a round robin assignment from partition to consumer. If the subscriptions of all consumer instances are identical, then the partitions will be uniformly distributed. (i.e., the partition ownership counts will be within a delta of exactly one across all consumers.)

For example, suppose there are two consumers C0 and C1, two topics t0 and t1, and each topic has 3 partitions, resulting in partitions t0p0, t0p1, t0p2, t1p0, t1p1, and t1p2.

The assignment will be:

• C0: [t0p0, t0p2, t1p1]
• C1: [t0p1, t1p0, t1p2]

When subscriptions differ across consumer instances, the assignment process still considers each consumer instance in round robin fashion but skips over an instance if it is not subscribed to the topic. Unlike the case when subscriptions are identical, this can result in imbalanced assignments. For example, we have three consumers C0, C1, C2, and three topics t0, t1, t2, with 1, 2, and 3 partitions, respectively. Therefore, the partitions are t0p0, t1p0, t1p1, t2p0, t2p1, t2p2. C0 is subscribed to t0; C1 is subscribed to t0, t1; and C2 is subscribed to t0, t1, t2.

That assignment will be:

• C0: [t0p0]
• C1: [t1p0]
• C2: [t1p1, t2p0, t2p1, t2p2]

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.kafka.clients.consumer.internals.PartitionAssignor

org.apache.kafka.clients.consumer.internals.PartitionAssignor.Assignment, org.apache.kafka.clients.consumer.internals.PartitionAssignor.Subscription

Constructor Summary

Constructors

Constructor and Description
RoundRobinAssignor()

Method Summary

Modifier and Type	Method and Description
java.util.List<TopicPartition>	allPartitionsSorted(java.util.Map<java.lang.String,java.lang.Integer> partitionsPerTopic, java.util.Map<java.lang.String,org.apache.kafka.clients.consumer.internals.PartitionAssignor.Subscription> subscriptions)
java.util.Map<java.lang.String,java.util.List<TopicPartition>>	assign(java.util.Map<java.lang.String,java.lang.Integer> partitionsPerTopic, java.util.Map<java.lang.String,org.apache.kafka.clients.consumer.internals.PartitionAssignor.Subscription> subscriptions)
java.lang.String	name()

Methods inherited from class org.apache.kafka.clients.consumer.internals.AbstractPartitionAssignor

assign, onAssignment, partitions, put, subscription

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RoundRobinAssignor

public RoundRobinAssignor()

Method Detail

assign

public java.util.Map<java.lang.String,java.util.List<TopicPartition>> assign(java.util.Map<java.lang.String,java.lang.Integer> partitionsPerTopic,
                                                                             java.util.Map<java.lang.String,org.apache.kafka.clients.consumer.internals.PartitionAssignor.Subscription> subscriptions)

Specified by:

assign in class org.apache.kafka.clients.consumer.internals.AbstractPartitionAssignor

allPartitionsSorted

public java.util.List<TopicPartition> allPartitionsSorted(java.util.Map<java.lang.String,java.lang.Integer> partitionsPerTopic,
                                                          java.util.Map<java.lang.String,org.apache.kafka.clients.consumer.internals.PartitionAssignor.Subscription> subscriptions)

name

public java.lang.String name()