Speed up the rebuildinding of RocksDB index (#3458)

* Speed up the rebuildinding of RocksDB index

* fix check style

Co-authored-by: chenhang <chenhang@apache.org>

bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/storage/ldb/LocationsIndexRebuildOp.java

@@ -31,6 +31,8 @@
 import java.util.Date;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicReference;
 import org.apache.bookkeeper.bookie.BookieImpl;
 import org.apache.bookkeeper.bookie.DefaultEntryLogger;
 import org.apache.bookkeeper.bookie.LedgerDirsManager;
@@ -53,6 +55,8 @@ public LocationsIndexRebuildOp(ServerConfiguration conf) {
         this.conf = conf;
     }
 
+    private static final int BATCH_COMMIT_SIZE = 10_000;
+
     public void initiate() throws IOException {
         LOG.info("Starting locations index rebuilding");
         File[] indexDirs = conf.getIndexDirs();
@@ -90,6 +94,8 @@ public void initiate() throws IOException {
             int totalEntryLogs = entryLogs.size();
             int completedEntryLogs = 0;
             LOG.info("Scanning {} entry logs", totalEntryLogs);
+            AtomicReference<KeyValueStorage.Batch> batch = new AtomicReference<>(newIndex.newBatch());
+            AtomicInteger count = new AtomicInteger();
 
             for (long entryLogId : entryLogs) {
                 entryLogger.scanEntryLog(entryLogId, new EntryLogScanner() {
@@ -108,7 +114,15 @@ public void process(long ledgerId, long offset, ByteBuf entry) throws IOExceptio
                         // Update the ledger index page
                         LongPairWrapper key = LongPairWrapper.get(ledgerId, entryId);
                         LongWrapper value = LongWrapper.get(location);
-                        newIndex.put(key.array, value.array);
+                        batch.get().put(key.array, value.array);
+
+                        if (count.incrementAndGet() > BATCH_COMMIT_SIZE) {
+                            batch.get().flush();
+                            batch.get().close();
+
+                            batch.set(newIndex.newBatch());
+                            count.set(0);
+                        }
                     }
 
                     @Override
@@ -122,6 +136,9 @@ public boolean accept(long ledgerId) {
                         completedEntryLogs, totalEntryLogs);
             }
 
+            batch.get().flush();
+            batch.get().close();
+
             newIndex.sync();
             newIndex.close();
         }