[GitHub] [bookkeeper] eolivelli commented on a diff in pull request #3368: add async or sync for :ledger metadata index's rocksdb write

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

eolivelli commented on code in PR #3368:
URL: https://github.com/apache/bookkeeper/pull/3368#discussion_r949895963


##########
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/storage/ldb/LedgerMetadataIndexAsync.java:
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@@ -0,0 +1,117 @@
+/**
+ *
+ * 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.bookkeeper.bookie.storage.ldb;
+
+import java.io.IOException;
+import java.util.Map.Entry;
+
+import org.apache.bookkeeper.bookie.storage.ldb.DbLedgerStorageDataFormats.LedgerData;
+import org.apache.bookkeeper.conf.ServerConfiguration;
+import org.apache.bookkeeper.stats.StatsLogger;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Maintains an index for the ledgers metadata.
+ *
+ * <p>Asynchronous write mode class,
+ * the key is the ledgerId and the value is the {@link LedgerData} content.
+ */
+public class LedgerMetadataIndexAsync extends LedgerMetadataIndex {
+
+    private static final Logger log = LoggerFactory.getLogger(LedgerMetadataIndexAsync.class);
+
+    public LedgerMetadataIndexAsync(ServerConfiguration conf, KeyValueStorageFactory storageFactory, String basePath,
+                                    StatsLogger stats) throws IOException {
+        super(conf, storageFactory, basePath, stats);
+    }
+
+    /**
+     * Flushes all pending changes.
+     */
+    @Override
+    public void flush() throws IOException {
+        LongWrapper key = LongWrapper.get();
+
+        int updatedLedgers = 0;
+        while (!pendingLedgersUpdates.isEmpty()) {
+            Entry<Long, LedgerData> entry = pendingLedgersUpdates.poll();
+            key.set(entry.getKey());
+            byte[] value = entry.getValue().toByteArray();
+            ledgersDb.put(key.array, value);
+            ++updatedLedgers;
+        }
+
+        if (log.isDebugEnabled()) {
+            log.debug("Persisting updates to {} ledgers", updatedLedgers);
+        }
+
+        ledgersDb.sync();
+        key.recycle();
+    }
+
+    @Override
+    public void removeDeletedLedgers() throws IOException {
+        LongWrapper key = LongWrapper.get();
+
+        int deletedLedgers = 0;
+        while (!pendingDeletedLedgers.isEmpty()) {
+            long ledgerId = pendingDeletedLedgers.poll();
+            key.set(ledgerId);
+            ledgersDb.delete(key.array);
+        }
+
+        if (log.isDebugEnabled()) {
+            log.debug("Persisting deletes of ledgers {}", deletedLedgers);
+        }
+
+        ledgersDb.sync();
+        key.recycle();
+    }
+
+    @Override
+    boolean setStorageStateFlags(int expected, int newFlags) throws IOException {
+        LongWrapper keyWrapper = LongWrapper.get();
+        LongWrapper currentWrapper = LongWrapper.get();
+        LongWrapper newFlagsWrapper = LongWrapper.get();
+
+        try {
+            keyWrapper.set(STORAGE_FLAGS);
+            newFlagsWrapper.set(newFlags);
+            synchronized (ledgersDb) {

Review Comment:
   it seems to be that synchronisation around  `ledgersDb` is not consistent.
   sometimes we don't access the variable that way.
   
   I wonder why spotbugs does not complain



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