spark SupportsAdmissionControl 源码
spark SupportsAdmissionControl 代码
文件路径：/sql/catalyst/src/main/java/org/apache/spark/sql/connector/read/streaming/SupportsAdmissionControl.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.spark.sql.connector.read.streaming;
import org.apache.spark.annotation.Evolving;
/**
* A mix-in interface for {@link SparkDataStream} streaming sources to signal that they can control
* the rate of data ingested into the system. These rate limits can come implicitly from the
* contract of triggers, e.g. Trigger.Once() requires that a micro-batch process all data
* available to the system at the start of the micro-batch. Alternatively, sources can decide to
* limit ingest through data source options.
* <p>
* Through this interface, a MicroBatchStream should be able to return the next offset that it will
* process until given a {@link ReadLimit}.
*
* @since 3.0.0
*/
@Evolving
public interface SupportsAdmissionControl extends SparkDataStream {
/**
* Returns the read limits potentially passed to the data source through options when creating
* the data source.
*/
default ReadLimit getDefaultReadLimit() { return ReadLimit.allAvailable(); }
/**
* Returns the most recent offset available given a read limit. The start offset can be used
* to figure out how much new data should be read given the limit. Users should implement this
* method instead of latestOffset for a MicroBatchStream or getOffset for Source.
* <p>
* When this method is called on a `Source`, the source can return `null` if there is no
* data to process. In addition, for the very first micro-batch, the `startOffset` will be
* null as well.
* <p>
* When this method is called on a MicroBatchStream, the `startOffset` will be `initialOffset`
* for the very first micro-batch. The source can return `null` if there is no data to process.
*/
Offset latestOffset(Offset startOffset, ReadLimit limit);
/**
* Returns the most recent offset available.
* <p>
* The source can return `null`, if there is no data to process or the source does not support
* to this method.
*/
default Offset reportLatestOffset() { return null; }
}
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