/
Source.java
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/
Source.java
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/*
* 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.api.connector.source;
import org.apache.flink.annotation.Public;
import org.apache.flink.core.io.SimpleVersionedSerializer;
/**
* The interface for Source. It acts like a factory class that helps construct the {@link
* SplitEnumerator} and {@link SourceReader} and corresponding serializers.
*
* @param <T> The type of records produced by the source.
* @param <SplitT> The type of splits handled by the source.
* @param <EnumChkT> The type of the enumerator checkpoints.
*/
@Public
public interface Source<T, SplitT extends SourceSplit, EnumChkT>
extends SourceReaderFactory<T, SplitT> {
/**
* Get the boundedness of this source.
*
* @return the boundedness of this source.
*/
Boundedness getBoundedness();
/**
* Creates a new SplitEnumerator for this source, starting a new input.
*
* @param enumContext The {@link SplitEnumeratorContext context} for the split enumerator.
* @return A new SplitEnumerator.
* @throws Exception The implementor is free to forward all exceptions directly. Exceptions
* thrown from this method cause JobManager failure/recovery.
*/
SplitEnumerator<SplitT, EnumChkT> createEnumerator(SplitEnumeratorContext<SplitT> enumContext)
throws Exception;
/**
* Restores an enumerator from a checkpoint.
*
* @param enumContext The {@link SplitEnumeratorContext context} for the restored split
* enumerator.
* @param checkpoint The checkpoint to restore the SplitEnumerator from.
* @return A SplitEnumerator restored from the given checkpoint.
* @throws Exception The implementor is free to forward all exceptions directly. Exceptions
* thrown from this method cause JobManager failure/recovery.
*/
SplitEnumerator<SplitT, EnumChkT> restoreEnumerator(
SplitEnumeratorContext<SplitT> enumContext, EnumChkT checkpoint) throws Exception;
// ------------------------------------------------------------------------
// serializers for the metadata
// ------------------------------------------------------------------------
/**
* Creates a serializer for the source splits. Splits are serialized when sending them from
* enumerator to reader, and when checkpointing the reader's current state.
*
* @return The serializer for the split type.
*/
SimpleVersionedSerializer<SplitT> getSplitSerializer();
/**
* Creates the serializer for the {@link SplitEnumerator} checkpoint. The serializer is used for
* the result of the {@link SplitEnumerator#snapshotState(long)} method.
*
* @return The serializer for the SplitEnumerator checkpoint.
*/
SimpleVersionedSerializer<EnumChkT> getEnumeratorCheckpointSerializer();
}