[GitHub] [spark] mridulm commented on a diff in pull request #36200: [SPARK-38909][CORE][YARN] Encapsulate `LevelDB` used to store remote/external shuffle state as `DB`

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

mridulm commented on code in PR #36200:
URL: https://github.com/apache/spark/pull/36200#discussion_r940910008


##########
common/network-common/src/main/java/org/apache/spark/network/util/DBProvider.java:
##########
@@ -0,0 +1,60 @@
+/*
+ * 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.spark.network.util;
+
+import java.io.File;
+import java.io.IOException;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.common.annotations.VisibleForTesting;
+
+import org.apache.spark.network.shuffledb.DBBackend;
+import org.apache.spark.network.shuffledb.LevelDB;
+import org.apache.spark.network.shuffledb.DB;
+import org.apache.spark.network.shuffledb.StoreVersion;
+
+public class DBProvider {
+    public static DB initDB(
+        DBBackend dbBackend,
+        File dbFile,
+        StoreVersion version,
+        ObjectMapper mapper) throws IOException {
+      if (dbFile != null) {
+        // TODO: SPARK-38888, add rocksdb implementation.
+        switch (dbBackend) {
+          case LEVELDB:
+            org.iq80.leveldb.DB levelDB = LevelDBProvider.initLevelDB(dbFile, version, mapper);
+            return levelDB != null ? new LevelDB(levelDB) : null;
+          default:
+            return null;
+        }
+      }
+      return null;
+    }
+
+    @VisibleForTesting
+    public static DB initDB(DBBackend dbBackend, File file) throws IOException {
+      if (file != null) {
+        // TODO: SPARK-38888, add rocksdb implementation.
+        switch (dbBackend) {
+          case LEVELDB: return new LevelDB(LevelDBProvider.initLevelDB(file));
+        default: return null;

Review Comment:
   Discuss: Should we throw exception instead ?



##########
common/network-yarn/src/main/java/org/apache/spark/network/yarn/YarnShuffleService.java:
##########
@@ -331,13 +344,13 @@ static MergedShuffleFileManager newMergedShuffleFileManagerInstance(
   }
 
   private void loadSecretsFromDb() throws IOException {
-    secretsFile = initRecoveryDb(SECRETS_RECOVERY_FILE_NAME);
+    secretsFile = initRecoveryDb(SECRETS_RECOVERY_FILE_NAME + dbBackend.suffix());

Review Comment:
   minor nit: perhaps we can add `dbBackend.fileName(prefix: String)` or some such instead  (and remove suffix as well) ?



##########
common/network-common/src/main/java/org/apache/spark/network/shuffledb/LevelDBIterator.java:
##########
@@ -0,0 +1,92 @@
+/*
+ * 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.spark.network.shuffledb;
+
+import com.google.common.base.Throwables;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.NoSuchElementException;
+
+public class LevelDBIterator implements DBIterator {
+
+    private final org.iq80.leveldb.DBIterator it;
+
+    private boolean checkedNext;
+
+    private boolean closed;
+
+    private Map.Entry<byte[], byte[]> next;
+
+    public LevelDBIterator(org.iq80.leveldb.DBIterator it) {
+        this.it = it;
+    }
+
+    @Override
+    public boolean hasNext() {
+      if (!checkedNext && !closed) {
+        next = loadNext();
+        checkedNext = true;
+      }
+      if (!closed && next == null) {
+        try {
+          close();
+        } catch (IOException ioe) {
+          throw Throwables.propagate(ioe);
+        }
+      }
+      return next != null;
+    }
+
+    @Override
+    public Map.Entry<byte[], byte[]> next() {
+        if (!hasNext()) {
+          throw new NoSuchElementException();
+        }
+        checkedNext = false;
+        Map.Entry<byte[], byte[]> ret = next;
+        next = null;
+        return ret;
+    }
+
+    @Override
+    public void close() throws IOException {
+      if (!closed) {
+       it.close();
+       closed = true;
+      }

Review Comment:
   set `next` to `null` (for ex, `hasNext`, `close`, `hasNext` -> `true`, should be `false`)



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