Package org.apache.flink.streaming.connectors.kafka

Enum FlinkKafkaProducer.Semantic

java.lang.Object

java.lang.Enum<FlinkKafkaProducer.Semantic>

org.apache.flink.streaming.connectors.kafka.FlinkKafkaProducer.Semantic

All Implemented Interfaces:

Serializable, Comparable<FlinkKafkaProducer.Semantic>

Enclosing class:

FlinkKafkaProducer<IN>

public static enum FlinkKafkaProducer.Semantic
extends Enum<FlinkKafkaProducer.Semantic>

Semantics that can be chosen.

EXACTLY_ONCE AT_LEAST_ONCE NONE

Enum Constant Summary

Enum Constants

Enum Constant	Description
AT_LEAST_ONCE	Semantic.AT_LEAST_ONCE the Flink producer will wait for all outstanding messages in the Kafka buffers to be acknowledged by the Kafka producer on a checkpoint.
EXACTLY_ONCE	Semantic.EXACTLY_ONCE the Flink producer will write all messages in a Kafka transaction that will be committed to Kafka on a checkpoint.
NONE	Semantic.NONE means that nothing will be guaranteed.

Method Summary

Modifier and Type	Method	Description
static FlinkKafkaProducer.Semantic	valueOf(String name)	Returns the enum constant of this type with the specified name.
static FlinkKafkaProducer.Semantic[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

EXACTLY_ONCE

public static final FlinkKafkaProducer.Semantic EXACTLY_ONCE

Semantic.EXACTLY_ONCE the Flink producer will write all messages in a Kafka transaction that will be committed to Kafka on a checkpoint.

In this mode FlinkKafkaProducer sets up a pool of FlinkKafkaInternalProducer. Between each checkpoint a Kafka transaction is created, which is committed on TwoPhaseCommitSinkFunction.notifyCheckpointComplete(long). If checkpoint complete notifications are running late, FlinkKafkaProducer can run out of FlinkKafkaInternalProducers in the pool. In that case any subsequent FlinkKafkaProducer.snapshotState(FunctionSnapshotContext) requests will fail and FlinkKafkaProducer will keep using the FlinkKafkaInternalProducer from the previous checkpoint. To decrease the chance of failing checkpoints there are four options:

decrease number of max concurrent checkpoints make checkpoints more reliable (so that they complete faster) increase the delay between checkpoints increase the size of FlinkKafkaInternalProducers pool

AT_LEAST_ONCE

public static final FlinkKafkaProducer.Semantic AT_LEAST_ONCE

Semantic.AT_LEAST_ONCE the Flink producer will wait for all outstanding messages in the Kafka buffers to be acknowledged by the Kafka producer on a checkpoint.

NONE

public static final FlinkKafkaProducer.Semantic NONE

Semantic.NONE means that nothing will be guaranteed. Messages can be lost and/or duplicated in case of failure.

Method Detail

values

public static FlinkKafkaProducer.Semantic[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (FlinkKafkaProducer.Semantic c : FlinkKafkaProducer.Semantic.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static FlinkKafkaProducer.Semantic valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null