org.apache.kafka.streams.processor

Interface ProcessorContext

public interface ProcessorContext

Processor context interface.

Method Summary

Modifier and Type	Method and Description
Map<String,Object>	appConfigs() Return all the application config properties as key/value pairs.
Map<String,Object>	appConfigsWithPrefix(String prefix) Return all the application config properties with the given key prefix, as key/value pairs stripping the prefix.
String	applicationId() Return the application id.
void	commit() Request a commit.
long	currentStreamTimeMs() Return the current stream-time in milliseconds.
long	currentSystemTimeMs() Return the current system timestamp (also called wall-clock time) in milliseconds.
<K,V> void	forward(K key, V value) Forward a key/value pair to all downstream processors.
<K,V> void	forward(K key, V value, To to) Forward a key/value pair to the specified downstream processors.
<S extends StateStore> S	getStateStore(String name) Get the state store given the store name.
org.apache.kafka.common.header.Headers	headers() Return the headers of the current input record; could be an empty header if it is not available.
org.apache.kafka.common.serialization.Serde<?>	keySerde() Return the default key serde.
StreamsMetrics	metrics() Return Metrics instance.
long	offset() Return the offset of the current input record; could be -1 if it is not available.
int	partition() Return the partition id of the current input record; could be -1 if it is not available.
void	register(StateStore store, StateRestoreCallback stateRestoreCallback) Register and possibly restores the specified storage engine.
Cancellable	schedule(Duration interval, PunctuationType type, Punctuator callback) Schedule a periodic operation for processors.
File	stateDir() Return the state directory for the partition.
TaskId	taskId() Return the task id.
long	timestamp() Return the current timestamp.
String	topic() Return the topic name of the current input record; could be null if it is not available.
org.apache.kafka.common.serialization.Serde<?>	valueSerde() Return the default value serde.

Method Detail

applicationId

String applicationId()

Return the application id.

Returns:

the application id

taskId

TaskId taskId()

Return the task id.

Returns:

the task id

keySerde

org.apache.kafka.common.serialization.Serde<?> keySerde()

Return the default key serde.

Returns:

the key serializer

valueSerde

org.apache.kafka.common.serialization.Serde<?> valueSerde()

Return the default value serde.

Returns:

the value serializer

stateDir

File stateDir()

Return the state directory for the partition.

Returns:

the state directory

metrics

StreamsMetrics metrics()

Return Metrics instance.

Returns:

StreamsMetrics

register

void register(StateStore store,
              StateRestoreCallback stateRestoreCallback)

Register and possibly restores the specified storage engine.

Parameters:

store - the storage engine

stateRestoreCallback - the restoration callback logic for log-backed state stores upon restart

Throws:

IllegalStateException - If store gets registered after initialized is already finished

StreamsException - if the store's change log does not contain the partition

getStateStore

<S extends StateStore> S getStateStore(String name)

Get the state store given the store name.

Type Parameters:

S - The type or interface of the store to return

Parameters:

name - The store name

Returns:

The state store instance

Throws:

ClassCastException - if the return type isn't a type or interface of the actual returned store.

schedule

Cancellable schedule(Duration interval,
                     PunctuationType type,
                     Punctuator callback)

Schedule a periodic operation for processors. A processor may call this method during initialization or processing to schedule a periodic callback — called a punctuation — to Punctuator.punctuate(long). The type parameter controls what notion of time is used for punctuation:

• PunctuationType.STREAM_TIME — uses "stream time", which is advanced by the processing of messages in accordance with the timestamp as extracted by the TimestampExtractor in use. The first punctuation will be triggered by the first record that is processed. NOTE: Only advanced if messages arrive
• PunctuationType.WALL_CLOCK_TIME — uses system time (the wall-clock time), which is advanced independent of whether new messages arrive. The first punctuation will be triggered after interval has elapsed. NOTE: This is best effort only as its granularity is limited by how long an iteration of the processing loop takes to complete

Skipping punctuations: Punctuations will not be triggered more than once at any given timestamp. This means that "missed" punctuation will be skipped. It's possible to "miss" a punctuation if:

• with PunctuationType.STREAM_TIME, when stream time advances more than interval
• with PunctuationType.WALL_CLOCK_TIME, on GC pause, too short interval, ...

Parameters:

interval - the time interval between punctuations (supported minimum is 1 millisecond)

type - one of: PunctuationType.STREAM_TIME, PunctuationType.WALL_CLOCK_TIME

callback - a function consuming timestamps representing the current stream or system time

Returns:

a handle allowing cancellation of the punctuation schedule established by this method

Throws:

IllegalArgumentException - if the interval is not representable in milliseconds

forward

<K,V> void forward(K key,
                   V value)

Forward a key/value pair to all downstream processors. Used the input record's timestamp as timestamp for the output record.

If this method is called with Punctuator.punctuate(long) the record that is sent downstream won't have any associated record metadata like topic, partition, or offset.

Parameters:

key - key

value - value

forward

<K,V> void forward(K key,
                   V value,
                   To to)

Forward a key/value pair to the specified downstream processors. Can be used to set the timestamp of the output record.

If this method is called with Punctuator.punctuate(long) the record that is sent downstream won't have any associated record metadata like topic, partition, or offset.

Parameters:

key - key

value - value

to - the options to use when forwarding

commit

void commit()

Request a commit.

topic

String topic()

Return the topic name of the current input record; could be null if it is not available.

For example, if this method is invoked within a punctuation callback, or while processing a record that was forwarded by a punctuation callback, the record won't have an associated topic. Another example is KTable.transformValues(ValueTransformerWithKeySupplier, String...) (and siblings), that do not always guarantee to provide a valid topic name, as they might be executed "out-of-band" due to some internal optimizations applied by the Kafka Streams DSL.

Returns:

the topic name

partition

int partition()

Return the partition id of the current input record; could be -1 if it is not available.

For example, if this method is invoked within a punctuation callback, or while processing a record that was forwarded by a punctuation callback, the record won't have an associated partition id. Another example is KTable.transformValues(ValueTransformerWithKeySupplier, String...) (and siblings), that do not always guarantee to provide a valid partition id, as they might be executed "out-of-band" due to some internal optimizations applied by the Kafka Streams DSL.

Returns:

the partition id

offset

long offset()

Return the offset of the current input record; could be -1 if it is not available.

For example, if this method is invoked within a punctuation callback, or while processing a record that was forwarded by a punctuation callback, the record won't have an associated offset. Another example is KTable.transformValues(ValueTransformerWithKeySupplier, String...) (and siblings), that do not always guarantee to provide a valid offset, as they might be executed "out-of-band" due to some internal optimizations applied by the Kafka Streams DSL.

Returns:

the offset

headers

org.apache.kafka.common.header.Headers headers()

Return the headers of the current input record; could be an empty header if it is not available.

For example, if this method is invoked within a punctuation callback, or while processing a record that was forwarded by a punctuation callback, the record might not have any associated headers. Another example is KTable.transformValues(ValueTransformerWithKeySupplier, String...) (and siblings), that do not always guarantee to provide valid headers, as they might be executed "out-of-band" due to some internal optimizations applied by the Kafka Streams DSL.

Returns:

the headers

timestamp

long timestamp()

Return the current timestamp.

If it is triggered while processing a record streamed from the source processor, timestamp is defined as the timestamp of the current input record; the timestamp is extracted from ConsumerRecord by TimestampExtractor. Note, that an upstream Processor might have set a new timestamp by calling forward(..., To.all().withTimestamp(...)). In particular, some Kafka Streams DSL operators set result record timestamps explicitly, to guarantee deterministic results.

If it is triggered while processing a record generated not from the source processor (for example, if this method is invoked from the punctuate call), timestamp is defined as the current task's stream time, which is defined as the largest timestamp of any record processed by the task.

Returns:

the timestamp

appConfigs

Map<String,Object> appConfigs()

Return all the application config properties as key/value pairs.

The config properties are defined in the StreamsConfig object and associated to the ProcessorContext.

The type of the values is dependent on the type of the property (e.g. the value of DEFAULT_KEY_SERDE_CLASS_CONFIG will be of type Class, even if it was specified as a String to StreamsConfig(Map)).

Returns:

all the key/values from the StreamsConfig properties

appConfigsWithPrefix

Map<String,Object> appConfigsWithPrefix(String prefix)

Return all the application config properties with the given key prefix, as key/value pairs stripping the prefix.

The config properties are defined in the StreamsConfig object and associated to the ProcessorContext.

Parameters:

prefix - the properties prefix

Returns:

the key/values matching the given prefix from the StreamsConfig properties.

currentSystemTimeMs

long currentSystemTimeMs()

Return the current system timestamp (also called wall-clock time) in milliseconds.

Note: this method returns the internally cached system timestamp from the Kafka Stream runtime. Thus, it may return a different value compared to System.currentTimeMillis().

Returns:

the current system timestamp in milliseconds

currentStreamTimeMs

long currentStreamTimeMs()

Return the current stream-time in milliseconds.

Stream-time is the maximum observed record timestamp so far (including the currently processed record), i.e., it can be considered a high-watermark. Stream-time is tracked on a per-task basis and is preserved across restarts and during task migration.

Note: this method is not supported for global processors (cf. Topology.addGlobalStore(org.apache.kafka.streams.state.StoreBuilder<?>, java.lang.String, org.apache.kafka.common.serialization.Deserializer<K>, org.apache.kafka.common.serialization.Deserializer<V>, java.lang.String, java.lang.String, org.apache.kafka.streams.processor.ProcessorSupplier<K, V>) (...) and StreamsBuilder.addGlobalStore(org.apache.kafka.streams.state.StoreBuilder<?>, java.lang.String, org.apache.kafka.streams.kstream.Consumed<K, V>, org.apache.kafka.streams.processor.ProcessorSupplier<K, V>) (...), because there is no concept of stream-time for this case. Calling this method in a global processor will result in an UnsupportedOperationException.

Returns:

the current stream-time in milliseconds