Jiabao-Sun commented on code in PR #1: URL: https://github.com/apache/flink-connector-mongodb/pull/1#discussion_r1017645688
########## flink-connector-mongodb/src/main/java/org/apache/flink/connector/mongodb/source/enumerator/MongoSourceEnumStateSerializer.java: ########## @@ -0,0 +1,114 @@ +/* + * 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.connector.mongodb.source.enumerator; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.connector.mongodb.source.split.MongoScanSourceSplit; +import org.apache.flink.connector.mongodb.source.split.MongoSourceSplitSerializer; +import org.apache.flink.core.io.SimpleVersionedSerializer; + +import java.io.ByteArrayInputStream; +import java.io.ByteArrayOutputStream; +import java.io.DataInput; +import java.io.DataInputStream; +import java.io.DataOutputStream; +import java.io.IOException; +import java.util.List; +import java.util.Map; + +import static org.apache.flink.connector.mongodb.common.utils.MongoSerdeUtils.deserializeList; +import static org.apache.flink.connector.mongodb.common.utils.MongoSerdeUtils.deserializeMap; +import static org.apache.flink.connector.mongodb.common.utils.MongoSerdeUtils.serializeList; +import static org.apache.flink.connector.mongodb.common.utils.MongoSerdeUtils.serializeMap; + +/** The {@link SimpleVersionedSerializer Serializer} for the enumerator state of Mongo source. */ +@Internal +public class MongoSourceEnumStateSerializer + implements SimpleVersionedSerializer<MongoSourceEnumState> { + + public static final MongoSourceEnumStateSerializer INSTANCE = + new MongoSourceEnumStateSerializer(); + + private MongoSourceEnumStateSerializer() { + // Singleton instance. + } + + @Override + public int getVersion() { + // We use MongoSourceSplitSerializer's version because we use reuse this class. + return MongoSourceSplitSerializer.CURRENT_VERSION; + } + + @Override + public byte[] serialize(MongoSourceEnumState state) throws IOException { + try (ByteArrayOutputStream baos = new ByteArrayOutputStream(); + DataOutputStream out = new DataOutputStream(baos)) { + serializeList(out, state.getRemainingCollections(), DataOutputStream::writeUTF); + + serializeList(out, state.getAlreadyProcessedCollections(), DataOutputStream::writeUTF); + + serializeList( + out, + state.getRemainingScanSplits(), + MongoSourceSplitSerializer.INSTANCE::serializeMongoSplit); + + serializeMap( + out, + state.getAssignedScanSplits(), + DataOutputStream::writeUTF, + MongoSourceSplitSerializer.INSTANCE::serializeMongoSplit); + + out.writeBoolean(state.isInitialized()); + + out.flush(); + return baos.toByteArray(); + } + } + + @Override + public MongoSourceEnumState deserialize(int version, byte[] serialized) throws IOException { + try (ByteArrayInputStream bais = new ByteArrayInputStream(serialized); + DataInputStream in = new DataInputStream(bais)) { + List<String> remainingCollections = deserializeList(in, DataInput::readUTF); + List<String> alreadyProcessedCollections = deserializeList(in, DataInput::readUTF); + List<MongoScanSourceSplit> remainingScanSplits = + deserializeList(in, i -> deserializeMongoScanSourceSplit(version, i)); + + Map<String, MongoScanSourceSplit> assignedScanSplits = + deserializeMap( + in, + DataInput::readUTF, + i -> deserializeMongoScanSourceSplit(version, i)); + + boolean initialized = in.readBoolean(); + + return new MongoSourceEnumState( + remainingCollections, + alreadyProcessedCollections, + remainingScanSplits, + assignedScanSplits, + initialized); + } + } + + private MongoScanSourceSplit deserializeMongoScanSourceSplit(int version, DataInputStream in) + throws IOException { + return (MongoScanSourceSplit) Review Comment: MongoDB can support not only batch reads, but also streaming reads. We can use MongoDB [change streams](https://www.mongodb.com/docs/manual/changeStreams/#change-streams) feature to read operation changes, and then convert them into flink's upsert mode changelog. Batch read is currently implemented in this PR, some abstractions are also left for streaming reading: MongoSourceSplit -> MongoScanSourceSplit MongoSourceSplit -> MongoStreamSourceSplit Here I made some adjustments in recent commit, check the split type to avoid type casting. Whether we need to left some abstractions for this now, I would like to hear your opinion. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
