Package org.apache.kafka.clients.consumer

Interface ConsumerPartitionAssignor

All Known Implementing Classes:

org.apache.kafka.clients.consumer.internals.AbstractPartitionAssignor, org.apache.kafka.clients.consumer.internals.AbstractStickyAssignor, CooperativeStickyAssignor, RangeAssignor, RoundRobinAssignor, StickyAssignor

public interface ConsumerPartitionAssignor

This interface is used to define custom partition assignment for use in 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 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 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.

The implementation can extend Configurable to get configs from consumer.

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static final class	ConsumerPartitionAssignor.Assignment
static final class	ConsumerPartitionAssignor.GroupAssignment
static final class	ConsumerPartitionAssignor.GroupSubscription
static enum	ConsumerPartitionAssignor.RebalanceProtocol	The rebalance protocol defines partition assignment and revocation semantics.
static final class	ConsumerPartitionAssignor.Subscription

Method Summary

Modifier and Type	Method	Description
ConsumerPartitionAssignor.GroupAssignment	assign(Cluster metadata, ConsumerPartitionAssignor.GroupSubscription groupSubscription)	Perform the group assignment given the member subscriptions and current cluster metadata.
static List<ConsumerPartitionAssignor>	getAssignorInstances(List<String> assignorClasses, Map<String,Object> configs)	Get a list of configured instances of ConsumerPartitionAssignor based on the class names/types specified by ConsumerConfig.PARTITION_ASSIGNMENT_STRATEGY_CONFIG
String	name()	Unique name for this assignor (e.g.
default void	onAssignment(ConsumerPartitionAssignor.Assignment assignment, ConsumerGroupMetadata metadata)	Callback which is invoked when a group member receives its assignment from the leader.
default ByteBuffer	subscriptionUserData(Set<String> topics)	Return serialized data that will be included in the ConsumerPartitionAssignor.Subscription sent to the leader and can be leveraged in assign(Cluster, GroupSubscription) ((e.g.
default List<ConsumerPartitionAssignor.RebalanceProtocol>	supportedProtocols()	Indicate which rebalance protocol this assignor works with; By default it should always work with ConsumerPartitionAssignor.RebalanceProtocol.EAGER.
default short	version()	Return the version of the assignor which indicates how the user metadata encodings and the assignment algorithm gets evolved.

Method Details

subscriptionUserData

default ByteBuffer subscriptionUserData(Set<String> topics)

Return serialized data that will be included in the ConsumerPartitionAssignor.Subscription sent to the leader and can be leveraged in assign(Cluster, GroupSubscription) ((e.g. local host/rack information)

Parameters:

topics - Topics subscribed to through KafkaConsumer.subscribe(java.util.Collection) and variants

Returns:

nullable subscription user data

assign

ConsumerPartitionAssignor.GroupAssignment assign(Cluster metadata,
 ConsumerPartitionAssignor.GroupSubscription groupSubscription)

Perform the group assignment given the member subscriptions and current cluster metadata.

Parameters:

metadata - Current topic/broker metadata known by consumer

groupSubscription - Subscriptions from all members including metadata provided through subscriptionUserData(Set)

Returns:

A map from the members to their respective assignments. This should have one entry for each member in the input subscription map.

onAssignment

default void onAssignment(ConsumerPartitionAssignor.Assignment assignment,
 ConsumerGroupMetadata metadata)

Callback which is invoked when a group member receives its assignment from the leader.

Parameters:

assignment - The local member's assignment as provided by the leader in assign(Cluster, GroupSubscription)

metadata - Additional metadata on the consumer (optional)

supportedProtocols

default List<ConsumerPartitionAssignor.RebalanceProtocol> supportedProtocols()

Indicate which rebalance protocol this assignor works with; By default it should always work with ConsumerPartitionAssignor.RebalanceProtocol.EAGER.

version

default short version()

Return the version of the assignor which indicates how the user metadata encodings and the assignment algorithm gets evolved.

name

String name()

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 ConsumerConfig.PARTITION_ASSIGNMENT_STRATEGY_CONFIG

Returns:

non-null unique name

getAssignorInstances

static List<ConsumerPartitionAssignor> getAssignorInstances(List<String> assignorClasses,
 Map<String,Object> configs)

Get a list of configured instances of ConsumerPartitionAssignor based on the class names/types specified by ConsumerConfig.PARTITION_ASSIGNMENT_STRATEGY_CONFIG