org.apache.beam.sdk.io.kafka

Class KafkaIO.Read<K,V>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PBegin,PCollection<KafkaRecord<K,V>>>

org.apache.beam.sdk.io.kafka.KafkaIO.Read<K,V>

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

Enclosing class:

KafkaIO

public abstract static class KafkaIO.Read<K,V>
extends PTransform<PBegin,PCollection<KafkaRecord<K,V>>>

A PTransform to read from Kafka topics. See KafkaIO for more information on usage and configuration.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	KafkaIO.Read.External Exposes KafkaIO.TypedWithoutMetadata as an external transform for cross-language usage.

Field Summary

Fields inherited from class org.apache.beam.sdk.transforms.PTransform

name

Constructor Summary

Constructors

Constructor and Description
Read()

Method Summary

Modifier and Type	Method and Description
KafkaIO.Read<K,V>	commitOffsetsInFinalize() Finalized offsets are committed to Kafka.
PCollection<KafkaRecord<K,V>>	expand(PBegin input) Override this method to specify how this PTransform should be expanded on the given InputT.
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
KafkaIO.Read<K,V>	updateConsumerProperties(java.util.Map<java.lang.String,java.lang.Object> configUpdates) Update consumer configuration with new properties.
KafkaIO.Read<K,V>	withBootstrapServers(java.lang.String bootstrapServers) Sets the bootstrap servers for the Kafka consumer.
KafkaIO.Read<K,V>	withConsumerFactoryFn(SerializableFunction<java.util.Map<java.lang.String,java.lang.Object>,org.apache.kafka.clients.consumer.Consumer<byte[],byte[]>> consumerFactoryFn) A factory to create Kafka Consumer from consumer configuration.
KafkaIO.Read<K,V>	withCreateTime(Duration maxDelay) Sets the timestamps policy based on KafkaTimestampType.CREATE_TIME timestamp of the records.
KafkaIO.Read<K,V>	withKeyDeserializer(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<K>> keyDeserializer) Sets a Kafka Deserializer to interpret key bytes read from Kafka.
KafkaIO.Read<K,V>	withKeyDeserializerAndCoder(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<K>> keyDeserializer, Coder<K> keyCoder) Sets a Kafka Deserializer for interpreting key bytes read from Kafka along with a Coder for helping the Beam runner materialize key objects at runtime if necessary.
KafkaIO.Read<K,V>	withLogAppendTime() Sets TimestampPolicy to TimestampPolicyFactory.LogAppendTimePolicy.
KafkaIO.Read<K,V>	withMaxNumRecords(long maxNumRecords) Similar to Read.Unbounded.withMaxNumRecords(long).
KafkaIO.Read<K,V>	withMaxReadTime(Duration maxReadTime) Similar to Read.Unbounded.withMaxReadTime(Duration).
KafkaIO.Read<K,V>	withOffsetConsumerConfigOverrides(java.util.Map<java.lang.String,java.lang.Object> offsetConsumerConfig) Set additional configuration for the backend offset consumer.
PTransform<PBegin,PCollection<KV<K,V>>>	withoutMetadata() Returns a PTransform for PCollection of KV, dropping Kafka metatdata.
KafkaIO.Read<K,V>	withProcessingTime() Sets TimestampPolicy to TimestampPolicyFactory.ProcessingTimePolicy.
KafkaIO.Read<K,V>	withReadCommitted() Sets "isolation_level" to "read_committed" in Kafka consumer configuration.
KafkaIO.Read<K,V>	withStartReadTime(Instant startReadTime) Use timestamp to set up start offset.
KafkaIO.Read<K,V>	withTimestampFn(SerializableFunction<KV<K,V>,Instant> timestampFn) Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.
KafkaIO.Read<K,V>	withTimestampFn2(SerializableFunction<KafkaRecord<K,V>,Instant> timestampFn) Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.
KafkaIO.Read<K,V>	withTimestampPolicyFactory(TimestampPolicyFactory<K,V> timestampPolicyFactory) Provide custom TimestampPolicyFactory to set event times and watermark for each partition.
KafkaIO.Read<K,V>	withTopic(java.lang.String topic) Sets the topic to read from.
KafkaIO.Read<K,V>	withTopicPartitions(java.util.List<org.apache.kafka.common.TopicPartition> topicPartitions) Sets a list of partitions to read from.
KafkaIO.Read<K,V>	withTopics(java.util.List<java.lang.String> topics) Sets a list of topics to read from.
KafkaIO.Read<K,V>	withValueDeserializer(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<V>> valueDeserializer) Sets a Kafka Deserializer to interpret value bytes read from Kafka.
KafkaIO.Read<K,V>	withValueDeserializerAndCoder(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<V>> valueDeserializer, Coder<V> valueCoder) Sets a Kafka Deserializer for interpreting value bytes read from Kafka along with a Coder for helping the Beam runner materialize value objects at runtime if necessary.
KafkaIO.Read<K,V>	withWatermarkFn(SerializableFunction<KV<K,V>,Instant> watermarkFn) Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.
KafkaIO.Read<K,V>	withWatermarkFn2(SerializableFunction<KafkaRecord<K,V>,Instant> watermarkFn) Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.

Methods inherited from class org.apache.beam.sdk.transforms.PTransform

compose, compose, getAdditionalInputs, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, toString, validate

Methods inherited from class java.lang.Object

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

Constructor Detail

Read

public Read()

Method Detail

withBootstrapServers

public KafkaIO.Read<K,V> withBootstrapServers(java.lang.String bootstrapServers)

Sets the bootstrap servers for the Kafka consumer.

withTopic

public KafkaIO.Read<K,V> withTopic(java.lang.String topic)

Sets the topic to read from.

See KafkaUnboundedSource.split(int, PipelineOptions) for description of how the partitions are distributed among the splits.

withTopics

public KafkaIO.Read<K,V> withTopics(java.util.List<java.lang.String> topics)

Sets a list of topics to read from. All the partitions from each of the topics are read.

See KafkaUnboundedSource.split(int, PipelineOptions) for description of how the partitions are distributed among the splits.

withTopicPartitions

public KafkaIO.Read<K,V> withTopicPartitions(java.util.List<org.apache.kafka.common.TopicPartition> topicPartitions)

Sets a list of partitions to read from. This allows reading only a subset of partitions for one or more topics when (if ever) needed.

See KafkaUnboundedSource.split(int, PipelineOptions) for description of how the partitions are distributed among the splits.

withKeyDeserializer

public KafkaIO.Read<K,V> withKeyDeserializer(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<K>> keyDeserializer)

Sets a Kafka Deserializer to interpret key bytes read from Kafka.

In addition, Beam also needs a Coder to serialize and deserialize key objects at runtime. KafkaIO tries to infer a coder for the key based on the Deserializer class, however in case that fails, you can use withKeyDeserializerAndCoder(Class, Coder) to provide the key coder explicitly.

withKeyDeserializerAndCoder

public KafkaIO.Read<K,V> withKeyDeserializerAndCoder(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<K>> keyDeserializer,
                                                     Coder<K> keyCoder)

Sets a Kafka Deserializer for interpreting key bytes read from Kafka along with a Coder for helping the Beam runner materialize key objects at runtime if necessary.

Use this method only if your pipeline doesn't work with plain withKeyDeserializer(Class).

withValueDeserializer

public KafkaIO.Read<K,V> withValueDeserializer(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<V>> valueDeserializer)

Sets a Kafka Deserializer to interpret value bytes read from Kafka.

In addition, Beam also needs a Coder to serialize and deserialize value objects at runtime. KafkaIO tries to infer a coder for the value based on the Deserializer class, however in case that fails, you can use withValueDeserializerAndCoder(Class, Coder) to provide the value coder explicitly.

withValueDeserializerAndCoder

public KafkaIO.Read<K,V> withValueDeserializerAndCoder(java.lang.Class<? extends org.apache.kafka.common.serialization.Deserializer<V>> valueDeserializer,
                                                       Coder<V> valueCoder)

Sets a Kafka Deserializer for interpreting value bytes read from Kafka along with a Coder for helping the Beam runner materialize value objects at runtime if necessary.

Use this method only if your pipeline doesn't work with plain withValueDeserializer(Class).

withConsumerFactoryFn

public KafkaIO.Read<K,V> withConsumerFactoryFn(SerializableFunction<java.util.Map<java.lang.String,java.lang.Object>,org.apache.kafka.clients.consumer.Consumer<byte[],byte[]>> consumerFactoryFn)

A factory to create Kafka Consumer from consumer configuration. This is useful for supporting another version of Kafka consumer. Default is KafkaConsumer.

updateConsumerProperties

public KafkaIO.Read<K,V> updateConsumerProperties(java.util.Map<java.lang.String,java.lang.Object> configUpdates)

Update consumer configuration with new properties.

withMaxNumRecords

public KafkaIO.Read<K,V> withMaxNumRecords(long maxNumRecords)

Similar to Read.Unbounded.withMaxNumRecords(long). Mainly used for tests and demo applications.

withStartReadTime

public KafkaIO.Read<K,V> withStartReadTime(Instant startReadTime)

Use timestamp to set up start offset. It is only supported by Kafka Client 0.10.1.0 onwards and the message format version after 0.10.0.

Note that this take priority over start offset configuration ConsumerConfig.AUTO_OFFSET_RESET_CONFIG and any auto committed offsets.

This results in hard failures in either of the following two cases : 1. If one of more partitions do not contain any messages with timestamp larger than or equal to desired timestamp. 2. If the message format version in a partition is before 0.10.0, i.e. the messages do not have timestamps.

withMaxReadTime

public KafkaIO.Read<K,V> withMaxReadTime(Duration maxReadTime)

Similar to Read.Unbounded.withMaxReadTime(Duration). Mainly used for tests and demo applications.

withLogAppendTime

public KafkaIO.Read<K,V> withLogAppendTime()

Sets TimestampPolicy to TimestampPolicyFactory.LogAppendTimePolicy. The policy assigns Kafka's log append time (server side ingestion time) to each record. The watermark for each Kafka partition is the timestamp of the last record read. If a partition is idle, the watermark advances to couple of seconds behind wall time. Every record consumed from Kafka is expected to have its timestamp type set to 'LOG_APPEND_TIME'.

In Kafka, log append time needs to be enabled for each topic, and all the subsequent records wil have their timestamp set to log append time. If a record does not have its timestamp type set to 'LOG_APPEND_TIME' for any reason, it's timestamp is set to previous record timestamp or latest watermark, whichever is larger.

The watermark for the entire source is the oldest of each partition's watermark. If one of the readers falls behind possibly due to uneven distribution of records among Kafka partitions, it ends up holding the watermark for the entire source.

withProcessingTime

public KafkaIO.Read<K,V> withProcessingTime()

Sets TimestampPolicy to TimestampPolicyFactory.ProcessingTimePolicy. This is the default timestamp policy. It assigns processing time to each record. Specifically, this is the timestamp when the record becomes 'current' in the reader. The watermark aways advances to current time. If server side time (log append time) is enabled in Kafka, withLogAppendTime() is recommended over this.

withCreateTime

public KafkaIO.Read<K,V> withCreateTime(Duration maxDelay)

Sets the timestamps policy based on KafkaTimestampType.CREATE_TIME timestamp of the records. It is an error if a record's timestamp type is not KafkaTimestampType.CREATE_TIME. The timestamps within a partition are expected to be roughly monotonically increasing with a cap on out of order delays (e.g. 'max delay' of 1 minute). The watermark at any time is '(Min(now(), Max(event timestamp so far)) - max delay)'. However, watermark is never set in future and capped to 'now - max delay'. In addition, watermark advanced to 'now - max delay' when a partition is idle.

Parameters:

maxDelay - For any record in the Kafka partition, the timestamp of any subsequent record is expected to be after current record timestamp - maxDelay.

withTimestampPolicyFactory

public KafkaIO.Read<K,V> withTimestampPolicyFactory(TimestampPolicyFactory<K,V> timestampPolicyFactory)

Provide custom TimestampPolicyFactory to set event times and watermark for each partition. TimestampPolicyFactory.createTimestampPolicy(TopicPartition, Optional) is invoked for each partition when the reader starts.

See Also:

withLogAppendTime(), withCreateTime(Duration), withProcessingTime()

withTimestampFn2

@Deprecated
public KafkaIO.Read<K,V> withTimestampFn2(SerializableFunction<KafkaRecord<K,V>,Instant> timestampFn)

Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.

A function to assign a timestamp to a record. Default is processing timestamp.

withWatermarkFn2

@Deprecated
public KafkaIO.Read<K,V> withWatermarkFn2(SerializableFunction<KafkaRecord<K,V>,Instant> watermarkFn)

Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.

A function to calculate watermark after a record. Default is last record timestamp.

See Also:

withTimestampFn(SerializableFunction)

withTimestampFn

@Deprecated
public KafkaIO.Read<K,V> withTimestampFn(SerializableFunction<KV<K,V>,Instant> timestampFn)

Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.

A function to assign a timestamp to a record. Default is processing timestamp.

withWatermarkFn

@Deprecated
public KafkaIO.Read<K,V> withWatermarkFn(SerializableFunction<KV<K,V>,Instant> watermarkFn)

Deprecated. as of version 2.4. Use withTimestampPolicyFactory(TimestampPolicyFactory) instead.

A function to calculate watermark after a record. Default is last record timestamp.

See Also:

withTimestampFn(SerializableFunction)

withReadCommitted

public KafkaIO.Read<K,V> withReadCommitted()

Sets "isolation_level" to "read_committed" in Kafka consumer configuration. This is ensures that the consumer does not read uncommitted messages. Kafka version 0.11 introduced transactional writes. Applications requiring end-to-end exactly-once semantics should only read committed messages. See JavaDoc for KafkaConsumer for more description.

commitOffsetsInFinalize

public KafkaIO.Read<K,V> commitOffsetsInFinalize()

Finalized offsets are committed to Kafka. See UnboundedSource.CheckpointMark.finalizeCheckpoint(). It helps with minimizing gaps or duplicate processing of records while restarting a pipeline from scratch. But it does not provide hard processing guarantees. There could be a short delay to commit after UnboundedSource.CheckpointMark.finalizeCheckpoint() is invoked, as reader might be blocked on reading from Kafka. Note that it is independent of 'AUTO_COMMIT' Kafka consumer configuration. Usually either this or AUTO_COMMIT in Kafka consumer is enabled, but not both.

withOffsetConsumerConfigOverrides

public KafkaIO.Read<K,V> withOffsetConsumerConfigOverrides(java.util.Map<java.lang.String,java.lang.Object> offsetConsumerConfig)

Set additional configuration for the backend offset consumer. It may be required for a secured Kafka cluster, especially when you see similar WARN log message 'exception while fetching latest offset for partition {}. will be retried'.

In KafkaIO.read(), there're two consumers running in the backend actually:
1. the main consumer, which reads data from kafka;
2. the secondary offset consumer, which is used to estimate backlog, by fetching latest offset;

By default, offset consumer inherits the configuration from main consumer, with an auto-generated ConsumerConfig.GROUP_ID_CONFIG. This may not work in a secured Kafka which requires more configurations.

withoutMetadata

public PTransform<PBegin,PCollection<KV<K,V>>> withoutMetadata()

Returns a PTransform for PCollection of KV, dropping Kafka metatdata.

expand

public PCollection<KafkaRecord<K,V>> expand(PBegin input)

Description copied from class: PTransform

Override this method to specify how this PTransform should be expanded on the given InputT.

NOTE: This method should not be called directly. Instead apply the PTransform should be applied to the InputT using the apply method.

Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

Specified by:

expand in class PTransform<PBegin,PCollection<KafkaRecord<K,V>>>

populateDisplayData

public void populateDisplayData(DisplayData.Builder builder)

Description copied from class: PTransform

Register display data for the given transform or component.

populateDisplayData(DisplayData.Builder) is invoked by Pipeline runners to collect display data via DisplayData.from(HasDisplayData). Implementations may call super.populateDisplayData(builder) in order to register display data in the current namespace, but should otherwise use subcomponent.populateDisplayData(builder) to use the namespace of the subcomponent.

By default, does not register any display data. Implementors may override this method to provide their own display data.

Specified by:

populateDisplayData in interface HasDisplayData

Overrides:

populateDisplayData in class PTransform<PBegin,PCollection<KafkaRecord<K,V>>>

Parameters:

builder - The builder to populate with display data.

See Also:

HasDisplayData