org.apache.kafka.streams.processor.ProcessorContext Maven / Gradle / Ivy
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* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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* See the License for the specific language governing permissions and
* limitations under the License.
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package org.apache.kafka.streams.processor;
import org.apache.kafka.common.header.Headers;
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.errors.StreamsException;
import org.apache.kafka.streams.kstream.ValueTransformerWithKeySupplier;
import java.io.File;
import java.time.Duration;
import java.util.Map;
/**
* Processor context interface.
*/
@SuppressWarnings("deprecation") // Not deprecating the old context, since it is used by Transformers. See KAFKA-10603.
public interface ProcessorContext {
/**
* Return the application id.
*
* @return the application id
*/
String applicationId();
/**
* Return the task id.
*
* @return the task id
*/
TaskId taskId();
/**
* 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();
/**
* Register and possibly restores the specified storage engine.
*
* @param store the storage engine
* @param stateRestoreCallback the restoration callback logic for log-backed state stores upon restart
*
* @throws IllegalStateException If store gets registered after initialized is already finished
* @throws StreamsException if the store's change log does not contain the partition
*/
void register(final StateStore store,
final StateRestoreCallback stateRestoreCallback);
/**
* 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} or
* {@link Processor#process(Object, Object) 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);
/**
* 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 {@link Punctuator#punctuate(long)} the record that
* is sent downstream won't have any associated record metadata like topic, partition, or offset.
*
* @param key key
* @param value value
*/
void forward(final K key, final V value);
/**
* 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 {@link Punctuator#punctuate(long)} the record that
* is sent downstream won't have any associated record metadata like topic, partition, or offset.
*
* @param key key
* @param value value
* @param to the options to use when forwarding
*/
void forward(final K key, final V value, final To to);
/**
* Request a commit.
*/
void commit();
/**
* Return the topic name of the current input record; could be {@code null} if it is not
* available.
*
* For example, if this method is invoked within a {@link Punctuator#punctuate(long)
* 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
* {@link org.apache.kafka.streams.kstream.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.
*
* @return the topic name
*/
String topic();
/**
* Return the partition id of the current input record; could be {@code -1} if it is not
* available.
*
*
For example, if this method is invoked within a {@link Punctuator#punctuate(long)
* 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
* {@link org.apache.kafka.streams.kstream.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.
*
* @return the partition id
*/
int partition();
/**
* Return the offset of the current input record; could be {@code -1} if it is not
* available.
*
*
For example, if this method is invoked within a {@link Punctuator#punctuate(long)
* 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
* {@link org.apache.kafka.streams.kstream.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.
*
* @return the offset
*/
long offset();
/**
* 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 {@link Punctuator#punctuate(long)
* 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
* {@link org.apache.kafka.streams.kstream.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.
*
* @return the headers
*/
Headers headers();
/**
* 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
* {@link org.apache.kafka.clients.consumer.ConsumerRecord ConsumerRecord} by {@link TimestampExtractor}.
* Note, that an upstream {@link Processor} might have set a new timestamp by calling
* {@link ProcessorContext#forward(Object, Object, To) 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.
*
* @return the timestamp
*/
long timestamp();
/**
* Return 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();
}