[GitHub] [ozone] aswinshakil commented on a diff in pull request #4244: HDDS-7740. Implement SnapshotDeletingService

["aswinshakil (via GitHub)" <gi...@apache.org>]

aswinshakil commented on code in PR #4244:
URL: https://github.com/apache/ozone/pull/4244#discussion_r1117575219


##########
hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/service/SnapshotDeletingService.java:
##########
@@ -0,0 +1,378 @@
+/*
+ * 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.hadoop.ozone.om.service;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.protobuf.ServiceException;
+import org.apache.hadoop.hdds.conf.OzoneConfiguration;
+import org.apache.hadoop.hdds.utils.BackgroundService;
+import org.apache.hadoop.hdds.utils.BackgroundTask;
+import org.apache.hadoop.hdds.utils.BackgroundTaskQueue;
+import org.apache.hadoop.hdds.utils.BackgroundTaskResult;
+import org.apache.hadoop.hdds.utils.db.Table;
+import org.apache.hadoop.hdds.utils.db.TableIterator;
+import org.apache.hadoop.ozone.ClientVersion;
+import org.apache.hadoop.ozone.om.OmSnapshot;
+import org.apache.hadoop.ozone.om.OmSnapshotManager;
+import org.apache.hadoop.ozone.om.OzoneManager;
+import org.apache.hadoop.ozone.om.SnapshotChainManager;
+import org.apache.hadoop.ozone.om.helpers.OMRatisHelper;
+import org.apache.hadoop.ozone.om.helpers.OmBucketInfo;
+import org.apache.hadoop.ozone.om.helpers.OmKeyInfo;
+import org.apache.hadoop.ozone.om.helpers.RepeatedOmKeyInfo;
+import org.apache.hadoop.ozone.om.helpers.SnapshotInfo;
+import org.apache.hadoop.ozone.om.ratis.OzoneManagerRatisServer;
+import org.apache.hadoop.ozone.protocol.proto.OzoneManagerProtocolProtos.KeyValuePair;
+import org.apache.hadoop.ozone.protocol.proto.OzoneManagerProtocolProtos.OMRequest;
+import org.apache.hadoop.ozone.protocol.proto.OzoneManagerProtocolProtos.SnapshotMoveDeletedKeysRequest;
+import org.apache.hadoop.ozone.protocol.proto.OzoneManagerProtocolProtos.Type;
+import org.apache.ratis.protocol.ClientId;
+import org.apache.ratis.protocol.Message;
+import org.apache.ratis.protocol.RaftClientRequest;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicLong;
+
+import static org.apache.hadoop.ozone.om.OMConfigKeys.SNAPSHOT_DELETING_LIMIT_PER_TASK;
+import static org.apache.hadoop.ozone.om.OMConfigKeys.SNAPSHOT_DELETING_LIMIT_PER_TASK_DEFAULT;
+import static org.apache.hadoop.ozone.om.OmSnapshotManager.getSnapshotPrefix;
+
+/**
+ * Background Service to clean-up deleted snapshot and reclaim space.
+ */
+public class SnapshotDeletingService extends BackgroundService {
+  private static final Logger LOG =
+      LoggerFactory.getLogger(SnapshotDeletingService.class);
+
+  // Use only a single thread for Snapshot Deletion. Multiple threads would read
+  // from the same table and can send deletion requests for same snapshot
+  // multiple times.
+  private static final int SNAPSHOT_DELETING_CORE_POOL_SIZE = 1;
+  private final ClientId clientId = ClientId.randomId();
+  private final AtomicLong runCount;
+
+  private final OzoneManager ozoneManager;
+  private final OmSnapshotManager omSnapshotManager;
+  private final SnapshotChainManager chainManager;
+  private final AtomicBoolean suspended;
+  private final OzoneConfiguration conf;
+  private final AtomicLong successRunCount;
+  private final long snapshotDeletionPerTask;
+
+  public SnapshotDeletingService(long interval, long serviceTimeout,
+      OzoneManager ozoneManager) throws IOException {
+    super("SnapshotDeletingService", interval, TimeUnit.MILLISECONDS,
+        SNAPSHOT_DELETING_CORE_POOL_SIZE, serviceTimeout);
+    this.ozoneManager = ozoneManager;
+    this.omSnapshotManager = ozoneManager.getOmSnapshotManager();
+    this.chainManager = ozoneManager.getSnapshotChainManager();
+    this.runCount = new AtomicLong(0);
+    this.successRunCount = new AtomicLong(0);
+    this.suspended = new AtomicBoolean(false);
+    this.conf = ozoneManager.getConfiguration();
+    this.snapshotDeletionPerTask = conf
+        .getLong(SNAPSHOT_DELETING_LIMIT_PER_TASK,
+        SNAPSHOT_DELETING_LIMIT_PER_TASK_DEFAULT);
+  }
+
+  private class SnapshotDeletingTask implements BackgroundTask {
+
+    @Override
+    public BackgroundTaskResult call() throws Exception {
+      if (!shouldRun()) {
+        return BackgroundTaskResult.EmptyTaskResult.newResult();
+      }
+
+      runCount.incrementAndGet();
+
+      Table<String, SnapshotInfo> snapshotInfoTable =
+          ozoneManager.getMetadataManager().getSnapshotInfoTable();
+      try (TableIterator<String, ? extends Table.KeyValue
+          <String, SnapshotInfo>> iterator = snapshotInfoTable.iterator()) {
+        iterator.seekToFirst();
+
+        long snapshotLimit = snapshotDeletionPerTask;
+
+        while (iterator.hasNext() && snapshotLimit > 0) {
+          SnapshotInfo snapInfo = iterator.next().getValue();
+          SnapshotInfo.SnapshotStatus snapshotStatus =
+              snapInfo.getSnapshotStatus();
+
+          // Only Iterate in deleted snapshot
+          if (!snapshotStatus.equals(
+              SnapshotInfo.SnapshotStatus.SNAPSHOT_DELETED)) {
+            continue;
+          }
+
+          OmSnapshot omSnapshot = (OmSnapshot) omSnapshotManager
+              .checkForSnapshot(snapInfo.getVolumeName(),
+                  snapInfo.getBucketName(),
+                  getSnapshotPrefix(snapInfo.getName()));
+
+          Table<String, RepeatedOmKeyInfo> snapshotDeletedTable =
+              omSnapshot.getMetadataManager().getDeletedTable();
+
+          if (snapshotDeletedTable.getEstimatedKeyCount() == 0) {
+            continue;
+          }
+
+          // Get bucketInfo for the snapshot bucket to get bucket layout.
+          String dbBucketKey = ozoneManager.getMetadataManager().getBucketKey(
+              snapInfo.getVolumeName(), snapInfo.getBucketName());
+          OmBucketInfo bucketInfo = ozoneManager.getMetadataManager()
+              .getBucketTable().get(dbBucketKey);
+
+
+          chainManager.loadFromSnapshotInfoTable(
+              ozoneManager.getMetadataManager());
+          SnapshotInfo nextSnapshot = getNextNonDeletedSnapshot(snapInfo);
+
+          SnapshotInfo previousSnapshot = getPreviousSnapshot(snapInfo);
+          Table<String, OmKeyInfo> previousKeyTable = null;
+          OmSnapshot omPreviousSnapshot = null;
+
+          // Handle case when the deleted snapshot is the first snapshot.
+          // Move deleted keys to activeDB's deletedKeyTable
+          if (previousSnapshot != null) {
+            omPreviousSnapshot = (OmSnapshot) omSnapshotManager
+                .checkForSnapshot(previousSnapshot.getVolumeName(),
+                    previousSnapshot.getBucketName(),
+                    getSnapshotPrefix(previousSnapshot.getName()));
+
+            previousKeyTable = omPreviousSnapshot
+                .getMetadataManager().getKeyTable(bucketInfo.getBucketLayout());
+          }
+
+          // Move key to either next non deleted snapshot's snapshotDeletedTable
+          // or move to active object store deleted table
+
+          List<KeyValuePair> toActiveDBList = new ArrayList<>();
+          List<KeyValuePair> toNextDBList = new ArrayList<>();
+
+          try (TableIterator<String, ? extends Table.KeyValue<String,
+              RepeatedOmKeyInfo>> deletedIterator = snapshotDeletedTable
+              .iterator()) {
+
+            iterator.seekToFirst();
+
+            while (deletedIterator.hasNext()) {
+              Table.KeyValue<String, RepeatedOmKeyInfo>

Review Comment:
   Yes we can do that. 



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