[GitHub] [ozone] sadanand48 commented on a diff in pull request #3729: HDDS-6855. [SNAPSHOTS] Path Based Access for Ozone Snapshots.

[GitBox <gi...@apache.org>]

sadanand48 commented on code in PR #3729:
URL: https://github.com/apache/ozone/pull/3729#discussion_r980923601


##########
hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OmSnapshotManager.java:
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@@ -0,0 +1,186 @@
+/*
+ * 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;
+
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
+import org.apache.hadoop.hdds.utils.db.DBCheckpoint;
+import org.apache.hadoop.hdds.utils.db.RDBStore;
+import org.apache.hadoop.ozone.OzoneConfigKeys;
+import org.apache.hadoop.ozone.om.exceptions.OMException;
+import org.apache.hadoop.ozone.om.helpers.SnapshotInfo;
+
+import java.io.IOException;
+
+import org.apache.hadoop.hdds.conf.OzoneConfiguration;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.annotation.Nonnull;
+import java.util.concurrent.ExecutionException;
+
+import static org.apache.hadoop.ozone.OzoneConsts.OM_KEY_PREFIX;
+import static org.apache.hadoop.ozone.OzoneConsts.OM_SNAPSHOT_INDICATOR;
+import static org.apache.hadoop.ozone.om.exceptions.OMException.ResultCodes.INVALID_KEY_NAME;
+import static org.apache.hadoop.ozone.om.exceptions.OMException.ResultCodes.KEY_NOT_FOUND;
+
+
+/**
+ * This class is used to manage/create OM snapshots.
+ */
+public final class OmSnapshotManager {
+  private final OzoneManager ozoneManager;
+  private final LoadingCache<String, OmSnapshot> snapshotCache;
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(OmSnapshotManager.class);
+
+  OmSnapshotManager(OzoneManager ozoneManager) {
+    this.ozoneManager = ozoneManager;
+
+    // size of lru cache
+    int cacheSize = ozoneManager.getConfiguration().getInt(
+        OzoneConfigKeys.OZONE_OM_SNAPSHOT_CACHE_MAX_SIZE,
+        OzoneConfigKeys.OZONE_OM_SNAPSHOT_CACHE_MAX_SIZE_DEFAULT);
+
+    CacheLoader<String, OmSnapshot> loader;
+    loader = new CacheLoader<String, OmSnapshot>() {
+      @Override
+
+      // load the snapshot into the cache if not already there
+      @Nonnull
+      public OmSnapshot load(@Nonnull String snapshotTableKey)
+          throws IOException {
+        SnapshotInfo snapshotInfo;
+        // see if the snapshot exists
+        snapshotInfo = getSnapshotInfo(snapshotTableKey);
+
+        // read in the snapshot
+        OzoneConfiguration conf = ozoneManager.getConfiguration();
+        OMMetadataManager snapshotMetadataManager;
+
+        // Create the snapshot metadata manager by finding the corresponding
+        // RocksDB instance, creating an OmMetadataManagerImpl instance based on
+        // that
+        try {
+          snapshotMetadataManager = OmMetadataManagerImpl
+              .createSnapshotMetadataManager(

Review Comment:
   We should also close the open RocksDB instances during cache eviction.



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