neils-dev commented on code in PR #3658: URL: https://github.com/apache/ozone/pull/3658#discussion_r1001093228
########## hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/SnapshotChainManager.java: ########## @@ -0,0 +1,440 @@ +/* + * 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; + private Map<String, LinkedHashMap<String, SnapshotChainInfo>> + snapshotChainPath; + private Map<String, String> latestPathSnapshotID; + private String latestGlobalSnapshotID; + private static final Logger LOG = + LoggerFactory.getLogger(SnapshotChainManager.class); + + public SnapshotChainManager(OMMetadataManager metadataManager) + throws IOException { + snapshotChainGlobal = new LinkedHashMap<>(); + snapshotChainPath = new HashMap<>(); + latestPathSnapshotID = new HashMap<>(); + latestGlobalSnapshotID = null; + loadFromSnapshotInfoTable(metadataManager); + } + + private void addSnapshotGlobal(String snapshotID, + String prevGlobalID) throws IOException { + // set previous snapshotID to null if it is "" for + // internal in-mem structure + if (prevGlobalID != null && prevGlobalID.equals("")) { + prevGlobalID = null; + } + // on add snapshot; set previous snapshot entry nextSnapshotID = + // snapshotID + if (prevGlobalID != null && + snapshotChainGlobal.containsKey(prevGlobalID)) { + snapshotChainGlobal + .get(prevGlobalID) + .setNextSnapshotID(snapshotID); + } + if (prevGlobalID != null && + !snapshotChainGlobal.containsKey(prevGlobalID)) { + throw new IOException("Snapshot Chain corruption: " + + " previous snapshotID given but no associated snapshot " + + "found in snapshot chain: SnapshotID " + + prevGlobalID); + } + snapshotChainGlobal.put(snapshotID, + new SnapshotChainInfo(snapshotID, prevGlobalID, null)); + + // set state variable latestGlobal snapshot entry to this snapshotID + latestGlobalSnapshotID = snapshotID; + }; + + private void addSnapshotPath(String snapshotPath, + String snapshotID, + String prevPathID) throws IOException { + // set previous snapshotID to null if it is "" for + // internal in-mem structure + if (prevPathID != null && prevPathID.equals("")) { + prevPathID = null; + } + + // on add snapshot; set previous snapshot entry nextSnapshotID = + // snapshotID + if (prevPathID != null && + ((!snapshotChainPath + .containsKey(snapshotPath)) || + (!snapshotChainPath + .get(snapshotPath) + .containsKey(prevPathID)))) { + throw new IOException("Snapshot Chain corruption: " + + "previous snapshotID given but no associated snapshot " + + "found in snapshot chain: SnapshotID " + + prevPathID); + } + + if (prevPathID != null && + snapshotChainPath.containsKey(snapshotPath)) { + snapshotChainPath + .get(snapshotPath) + .get(prevPathID) + .setNextSnapshotID(snapshotID); + } + + if (!snapshotChainPath.containsKey(snapshotPath)) { + snapshotChainPath.put(snapshotPath, new LinkedHashMap<>()); + } + + snapshotChainPath + .get(snapshotPath) + .put(snapshotID, + new SnapshotChainInfo(snapshotID, prevPathID, null)); + + // set state variable latestPath snapshot entry to this snapshotID + latestPathSnapshotID.put(snapshotPath, snapshotID); + }; + + private boolean deleteSnapshotGlobal(String snapshotID) throws IOException { + boolean status = true; + if (snapshotChainGlobal.containsKey(snapshotID)) { + // reset prev and next snapshot entries in chain ordered list + // for node removal + String next = snapshotChainGlobal.get(snapshotID).getNextSnapshotID(); + String prev = snapshotChainGlobal.get(snapshotID).getPreviousSnapshotID(); + + if (prev != null && !snapshotChainGlobal.containsKey(prev)) { + throw new IOException("Snapshot chain corruption: snapshot node to be " + + "deleted has prev node element not found in snapshot chain: " + + "SnapshotID " + prev); + } + if (next != null && !snapshotChainGlobal.containsKey(next)) { + throw new IOException("Snapshot chain corruption: snapshot node to be " + + "deleted has next node element not found in snapshot chain: " + + "SnapshotID " + next); + } + snapshotChainGlobal.remove(snapshotID); + if (next != null) { + snapshotChainGlobal.get(next).setPreviousSnapshotID(prev); + } + if (prev != null) { + snapshotChainGlobal.get(prev).setNextSnapshotID(next); + } + // remove from latest list if necessary + if (latestGlobalSnapshotID.equals(snapshotID)) { + latestGlobalSnapshotID = prev; + } + } else { + // snapshotID not found in snapshot chain, log warning and return + LOG.warn("Snapshot chain: snapshotID not found: SnapshotID {}", + snapshotID); + status = false; + } + + return status; + } + + private boolean deleteSnapshotPath(String snapshotPath, + String snapshotID) throws IOException { + boolean status = true; + if (snapshotChainPath.containsKey(snapshotPath) && + snapshotChainPath + .get(snapshotPath) + .containsKey(snapshotID)) { + // reset prev and next snapshot entries in chain ordered list + // for node removal + String next = snapshotChainPath + .get(snapshotPath) + .get(snapshotID) + .getNextSnapshotID(); + String prev = snapshotChainPath + .get(snapshotPath) + .get(snapshotID) + .getPreviousSnapshotID(); + + if (prev != null && + !snapshotChainPath + .get(snapshotPath) + .containsKey(prev)) { + throw new IOException("Snapshot chain corruption: snapshot node to " + + "be deleted has prev node element not found in snapshot " + + "chain: Snapshot path " + snapshotPath + ", SnapshotID " + + prev); + } + if (next != null && !snapshotChainPath + .get(snapshotPath) + .containsKey(next)) { + throw new IOException("Snapshot chain corruption: snapshot node to " + + "be deleted has next node element not found in snapshot " + + "chain: Snapshot path " + snapshotPath + ", SnapshotID " + + next); + } + snapshotChainPath + .get(snapshotPath) + .remove(snapshotID); + if (next != null) { + snapshotChainPath + .get(snapshotPath) + .get(next) + .setPreviousSnapshotID(prev); + } + if (prev != null) { + snapshotChainPath + .get(snapshotPath) + .get(prev) + .setNextSnapshotID(next); + } + // remove path if no entries + if (snapshotChainPath.get(snapshotPath).isEmpty()) { + snapshotChainPath.remove(snapshotPath); + } + // remove from latest list if necessary + if (latestPathSnapshotID.get(snapshotPath).equals(snapshotID)) { + latestPathSnapshotID.remove(snapshotPath); + if (prev != null) { + latestPathSnapshotID.put(snapshotPath, prev); + } + } + + } else { + // snapshotID not found in snapshot chain, log warning and return + LOG.warn("Snapshot chain: snapshotID not found: Snapshot path {}," + + " SnapshotID {}", + snapshotPath, snapshotID); + status = false; + } + + return status; + } + + private void loadFromSnapshotInfoTable(OMMetadataManager metadataManager) + throws IOException { + // read from snapshotInfo table to populate + // snapshot chains - both global and local path + TableIterator<String, ? extends Table.KeyValue<String, SnapshotInfo>> + keyIter = metadataManager.getSnapshotInfoTable().iterator(); + Map<Long, SnapshotInfo> snaps = new TreeMap<>(); + Table.KeyValue< String, SnapshotInfo > kv; + snapshotChainGlobal.clear(); + snapshotChainPath.clear(); + + while (keyIter.hasNext()) { + kv = keyIter.next(); + snaps.put(kv.getValue().getCreationTime(), kv.getValue()); + } + for (SnapshotInfo sinfo : snaps.values()) { + addSnapshot(sinfo); + } + } + + public void addSnapshot(SnapshotInfo sinfo) throws IOException { Review Comment: updated public methods with javadoc descriptions as suggested. 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