flink-libraries/flink-sql-client/src/main/java/org/apache/flink/table/client/gateway/local/result/ChangelogCollectStreamResult.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.table.client.gateway.local.result;

import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.table.api.types.DataType;
import org.apache.flink.table.client.gateway.TypedResult;
import org.apache.flink.types.Row;

import java.net.InetAddress;
import java.util.ArrayList;
import java.util.List;

/**
 * Collects results and returns them as a changelog.
 *
 * @param <C> cluster id to which this result belongs to
 */
public class ChangelogCollectStreamResult<C> extends CollectStreamResult<C> implements ChangelogResult<C> {

	private List<Tuple2<Boolean, Row>> changeRecordBuffer;
	private static final int CHANGE_RECORD_BUFFER_SIZE = 5_000;

	public ChangelogCollectStreamResult(
			DataType outputType, ExecutionConfig config, InetAddress gatewayAddress, int gatewayPort) {
		super(outputType, config, gatewayAddress, gatewayPort);

		// prepare for changelog
		changeRecordBuffer = new ArrayList<>();
	}

	@Override
	public boolean isMaterialized() {
		return false;
	}

	@Override
	public TypedResult<List<Tuple2<Boolean, Row>>> retrieveChanges() {
		synchronized (resultLock) {
			// retrieval thread is alive return a record if available
			// but the program must not have failed
			if (isRetrieving() && executionException == null) {
				if (changeRecordBuffer.isEmpty()) {
					return TypedResult.empty();
				} else {
					final List<Tuple2<Boolean, Row>> change = new ArrayList<>(changeRecordBuffer);
					changeRecordBuffer.clear();
					resultLock.notify();
					return TypedResult.payload(change);
				}
			}
			// retrieval thread is dead but there is still a record to be delivered
			else if (!isRetrieving() && !changeRecordBuffer.isEmpty()) {
				final List<Tuple2<Boolean, Row>> change = new ArrayList<>(changeRecordBuffer);
				changeRecordBuffer.clear();
				return TypedResult.payload(change);
			}
			// no results can be returned anymore
			else {
				return handleMissingResult();
			}
		}
	}

	// --------------------------------------------------------------------------------------------

	@Override
	protected void processRecord(Tuple2<Boolean, Row> change) {
		synchronized (resultLock) {
			// wait if the buffer is full
			if (changeRecordBuffer.size() >= CHANGE_RECORD_BUFFER_SIZE) {
				try {
					resultLock.wait();
				} catch (InterruptedException e) {
					// ignore
				}
			} else {
				changeRecordBuffer.add(change);
			}
		}
	}
}