kafka ExtractRecordMetadataTimestamp 源码

kafka ExtractRecordMetadataTimestamp 代码

文件路径：/streams/src/main/java/org/apache/kafka/streams/processor/ExtractRecordMetadataTimestamp.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * 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,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.kafka.streams.processor;

import org.apache.kafka.clients.consumer.ConsumerRecord;

/**
 * Retrieves embedded metadata timestamps from Kafka messages.
 * If a record has a negative (invalid) timestamp value, an error handler method is called.
 * <p>
 * Embedded metadata timestamp was introduced in "KIP-32: Add timestamps to Kafka message" for the new
 * 0.10+ Kafka message format.
 * <p>
 * Here, "embedded metadata" refers to the fact that compatible Kafka producer clients automatically and
 * transparently embed such timestamps into message metadata they send to Kafka, which can then be retrieved
 * via this timestamp extractor.
 * <p>
 * If the embedded metadata timestamp represents <i>CreateTime</i> (cf. Kafka broker setting
 * {@code message.timestamp.type} and Kafka topic setting {@code log.message.timestamp.type}),
 * this extractor effectively provides <i>event-time</i> semantics.
 * If <i>LogAppendTime</i> is used as broker/topic setting to define the embedded metadata timestamps,
 * using this extractor effectively provides <i>ingestion-time</i> semantics.
 * <p>
 * If you need <i>processing-time</i> semantics, use {@link WallclockTimestampExtractor}.
 *
 * @see FailOnInvalidTimestamp
 * @see LogAndSkipOnInvalidTimestamp
 * @see UsePartitionTimeOnInvalidTimestamp
 * @see WallclockTimestampExtractor
 */
abstract class ExtractRecordMetadataTimestamp implements TimestampExtractor {

    /**
     * Extracts the embedded metadata timestamp from the given {@link ConsumerRecord}.
     *
     * @param record a data record
     * @param partitionTime the highest extracted valid timestamp of the current record's partition˙ (could be -1 if unknown)
     * @return the embedded metadata timestamp of the given {@link ConsumerRecord}
     */
    @Override
    public long extract(final ConsumerRecord<Object, Object> record, final long partitionTime) {
        final long timestamp = record.timestamp();

        if (timestamp < 0) {
            return onInvalidTimestamp(record, timestamp, partitionTime);
        }

        return timestamp;
    }

    /**
     * Called if no valid timestamp is embedded in the record meta data.
     *
     * @param record a data record
     * @param recordTimestamp the timestamp extractor from the record
     * @param partitionTime the highest extracted valid timestamp of the current record's partition˙ (could be -1 if unknown)
     * @return a new timestamp for the record (if negative, record will not be processed but dropped silently)
     */
    public abstract long onInvalidTimestamp(final ConsumerRecord<Object, Object> record,
                                            final long recordTimestamp,
                                            final long partitionTime);
}

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