stevenzwu commented on code in PR #6299: URL: https://github.com/apache/iceberg/pull/6299#discussion_r1036434639
########## flink/v1.16/flink/src/main/java/org/apache/iceberg/flink/source/enumerator/EnumerationHistory.java: ########## @@ -0,0 +1,58 @@ +/* + * 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.iceberg.flink.source.enumerator; + +import javax.annotation.concurrent.ThreadSafe; +import org.apache.flink.calcite.shaded.com.google.common.collect.EvictingQueue; + +/** + * This enumeration history is used for split discovery throttling. It wraps Guava {@link + * EvictingQueue} to provide thread safety. + */ +@ThreadSafe +class EnumerationHistory { + + // EvictingQueue is not thread safe. + private final EvictingQueue<Integer> enumerationSplitCountHistory; + + EnumerationHistory(int maxHistorySize) { + this.enumerationSplitCountHistory = EvictingQueue.create(maxHistorySize); + } + + /** Add the split count from the last enumeration result. */ + synchronized void add(int splitCount) { + enumerationSplitCountHistory.add(splitCount); + } + + /** @return true if split discovery should pause because assigner has too many splits already. */ + synchronized boolean shouldPauseSplitDiscovery(int pendingSplitCountFromAssigner) { + if (enumerationSplitCountHistory.remainingCapacity() > 0) { + // only check throttling when full history is obtained. Review Comment: @pvary you are correct here. This is the downside of not checkpointing enumeration history. After checkpoint recovery, enumerator can discover more splits because totalSplitCountFromRecentDiscovery is 0 after recovery. There are two scenarios. 1. job was stuck in a failure/restart loop. this is not a concern as there is no successful checkpoint. newly discovered splits aren't saved. the tracked splits won't grow forever. 2. here is a pathological scenario. Job was in a restart loop with successful checkpoints (like 1 or 2) btw restart. This would essentially bypass the throttling check. Potentially the tracked splits can keep growing. That is the small concern I has regarding not checkpointing. The concern is small, because this scenario is very unusual. Hence, I didn't implement the checkpointing of enumeration history (for throttling purpose). On the other hand, it's not too difficult to add the checkpointing of enumeration history for completeness or ability to handle the above edge case. I am open to add it if desired. -- 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: issues-unsubscr...@iceberg.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@iceberg.apache.org For additional commands, e-mail: issues-h...@iceberg.apache.org
