neils-dev commented on code in PR #3658: URL: https://github.com/apache/ozone/pull/3658#discussion_r960130103
########## hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/SnapshotChainManager.java: ########## @@ -0,0 +1,446 @@ +/* + * 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 + * <p> + * http://www.apache.org/licenses/LICENSE-2.0 + * <p> + * 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.hadoop.ozone.om; + +import com.google.common.annotations.VisibleForTesting; +import org.apache.hadoop.hdds.utils.db.Table; +import org.apache.hadoop.hdds.utils.db.TableIterator; +import org.apache.hadoop.ozone.om.helpers.SnapshotInfo; + +import java.io.IOException; +import java.util.HashMap; +import java.util.Map; +import java.util.NoSuchElementException; +import java.util.LinkedHashMap; +import java.util.TreeMap; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * This class is used for creating and accessing Snapshot Chains. + * + * The snapshot chain maintains the in-memory sequence of snapshots + * created in chronological order. There are two such snapshots maintained + * i.) Path based snapshot chain, sequence of snapshots created for a + * given /volume/bucket + * ii.) Global snapshot chain, sequence of all snapshots created in order + * + * On start, the snapshot chains are initialized from the on disk + * SnapshotInfoTable from the om RocksDB. + */ +public class SnapshotChainManager { + private LinkedHashMap<String, SnapshotChainInfo> snapshotChainGlobal; Review Comment: The `LinkedHashMap `preserves the order of insertion for little or no cost over the HashMap. In using the LinkedHashMap we can easily access an iterator to iterate through the data structure in-order (order is necessary for the chain), something not preserved with the HashMap. The `LinkedHashMap` also gives us constant time inserts, deletes and lookups. -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
