KafkaTopicPartitionStateSentinel.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.flink.streaming.connectors.kafka.internals;

/**
 * Magic values used to represent special offset states before partitions are actually read.
 *
 * The values are all negative. Negative offsets are not used by Kafka (invalid), so we
 * pick a number that is probably (hopefully) not used by Kafka as a magic number for anything else.
 */
public class KafkaTopicPartitionStateSentinel {

	/** Magic number that defines an unset offset. */
	public static final long OFFSET_NOT_SET = -915623761776L;

	/**
	 * Magic number that defines the partition should start from the earliest offset.
	 *
	 * This is used as a placeholder so that the actual earliest offset can be evaluated lazily
	 * when the partition will actually start to be read by the consumer.
	 */
	public static final long EARLIEST_OFFSET = -915623761775L;

	/**
	 * Magic number that defines the partition should start from the latest offset.
	 *
	 * This is used as a placeholder so that the actual latest offset can be evaluated lazily
	 * when the partition will actually start to be read by the consumer.
	 */
	public static final long LATEST_OFFSET = -915623761774L;

	/**
	 * Magic number that defines the partition should start from its committed group offset in Kafka.
	 *
	 * This is used as a placeholder so that the actual committed group offset can be evaluated lazily
	 * when the partition will actually start to be read by the consumer.
	 */
	public static final long GROUP_OFFSET = -915623761773L;

}