org.apache.kafka.streams.processor.api.ProcessingContext Maven / Gradle / Ivy
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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package org.apache.kafka.streams.processor.api;
import org.apache.kafka.common.serialization.Serde;
import org.apache.kafka.streams.StreamsBuilder;
import org.apache.kafka.streams.StreamsMetrics;
import org.apache.kafka.streams.Topology;
import org.apache.kafka.streams.processor.Cancellable;
import org.apache.kafka.streams.processor.PunctuationType;
import org.apache.kafka.streams.processor.Punctuator;
import org.apache.kafka.streams.processor.StateStore;
import org.apache.kafka.streams.processor.TaskId;
import org.apache.kafka.streams.processor.TimestampExtractor;
import java.io.File;
import java.time.Duration;
import java.util.Map;
import java.util.Optional;
/**
* Processor context interface.
*/
public interface ProcessingContext {
/**
* Return the application id.
*
* @return the application id
*/
String applicationId();
/**
* Return the task id.
*
* @return the task id
*/
TaskId taskId();
/**
* Return the metadata of the current record if available. Processors may be invoked to
* process a source record from an input topic, to run a scheduled punctuation
* (see {@link ProcessingContext#schedule(Duration, PunctuationType, Punctuator)}),
* or because a parent processor called {@code forward(Record)}.
*
* In the case of a punctuation, there is no source record, so this metadata would be
* undefined. Note that when a punctuator invokes {@code forward(Record)},
* downstream processors will receive the forwarded record as a regular
* {@link Processor#process(Record)} or {@link FixedKeyProcessor#process(FixedKeyRecord)} invocation.
* In other words, it wouldn't be apparent to
* downstream processors whether the record being processed came from an input topic
* or punctuation and therefore whether this metadata is defined. This is why
* the return type of this method is {@link Optional}.
*
* If there is any possibility of punctuators upstream, any access
* to this field should consider the case of
* "recordMetadata().isPresent() == false".
* Of course, it would be safest to always guard this condition.
*/
Optional recordMetadata();
/**
* Return the default key serde.
*
* @return the key serializer
*/
Serde keySerde();
/**
* Return the default value serde.
*
* @return the value serializer
*/
Serde valueSerde();
/**
* Return the state directory for the partition.
*
* @return the state directory
*/
File stateDir();
/**
* Return Metrics instance.
*
* @return StreamsMetrics
*/
StreamsMetrics metrics();
/**
* Get the state store given the store name.
*
* @param name The store name
* @param The type or interface of the store to return
* @return The state store instance
*
* @throws ClassCastException if the return type isn't a type or interface of the actual returned store.
*/
S getStateStore(final String name);
/**
* Schedule a periodic operation for processors. A processor may call this method during
* {@link Processor#init(ProcessorContext) initialization},
* {@link Processor#process(Record) processing},
* {@link FixedKeyProcessor#init(FixedKeyProcessorContext) initialization}, or
* {@link FixedKeyProcessor#process(FixedKeyRecord) processing} to
* schedule a periodic callback — called a punctuation — to {@link Punctuator#punctuate(long)}.
* The type parameter controls what notion of time is used for punctuation:
*
* - {@link PunctuationType#STREAM_TIME} — uses "stream time", which is advanced by the processing of messages
* in accordance with the timestamp as extracted by the {@link TimestampExtractor} in use.
* The first punctuation will be triggered by the first record that is processed.
* NOTE: Only advanced if messages arrive
* - {@link 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 {@link PunctuationType#STREAM_TIME}, when stream time advances more than interval
* - with {@link PunctuationType#WALL_CLOCK_TIME}, on GC pause, too short interval, ...
*
*
* @param interval the time interval between punctuations (supported minimum is 1 millisecond)
* @param type one of: {@link PunctuationType#STREAM_TIME}, {@link PunctuationType#WALL_CLOCK_TIME}
* @param callback a function consuming timestamps representing the current stream or system time
* @return a handle allowing cancellation of the punctuation schedule established by this method
* @throws IllegalArgumentException if the interval is not representable in milliseconds
*/
Cancellable schedule(final Duration interval,
final PunctuationType type,
final Punctuator callback);
/**
* Request a commit. Note that calling {@code commit()} is only a request for a commit, but it does not execute one.
* Hence, when {@code commit()} returns, no commit was executed yet. However, Kafka Streams will commit as soon
* as possible, instead of waiting for next {@code commit.interval.ms} to pass.
*/
void commit();
/**
* Returns all the application config properties as key/value pairs.
*
* The config properties are defined in the {@link org.apache.kafka.streams.StreamsConfig}
* object and associated to the ProcessorContext.
*
*
The type of the values is dependent on the {@link org.apache.kafka.common.config.ConfigDef.Type type} of the property
* (e.g. the value of {@link org.apache.kafka.streams.StreamsConfig#DEFAULT_KEY_SERDE_CLASS_CONFIG DEFAULT_KEY_SERDE_CLASS_CONFIG}
* will be of type {@link Class}, even if it was specified as a String to
* {@link org.apache.kafka.streams.StreamsConfig#StreamsConfig(Map) StreamsConfig(Map)}).
*
* @return all the key/values from the StreamsConfig properties
*/
Map appConfigs();
/**
* 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 {@link org.apache.kafka.streams.StreamsConfig}
* object and associated to the ProcessorContext.
*
* @param prefix the properties prefix
* @return the key/values matching the given prefix from the StreamsConfig properties.
*/
Map appConfigsWithPrefix(final String prefix);
/**
* 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 {@code System.currentTimeMillis()}.
*
* @return the current system timestamp in milliseconds
*/
long currentSystemTimeMs();
/**
* Return the current stream-time in milliseconds.
*
*
Stream-time is the maximum observed {@link TimestampExtractor 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. {@link Topology#addGlobalStore} (...)
* and {@link StreamsBuilder#addGlobalStore} (...),
* because there is no concept of stream-time for this case.
* Calling this method in a global processor will result in an {@link UnsupportedOperationException}.
*
* @return the current stream-time in milliseconds
*/
long currentStreamTimeMs();
}