add stats for rocksdb getLastEntryInLedger

Author: fanjianye

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

@@ -117,8 +117,16 @@ public long getLastEntryInLedger(long ledgerId) throws IOException {
     private long getLastEntryInLedgerInternal(long ledgerId) throws IOException {
         LongPairWrapper maxEntryId = LongPairWrapper.get(ledgerId, Long.MAX_VALUE);
 
+        long startTimeNanos = MathUtils.nowInNano();
         // Search the last entry in storage
         Entry<byte[], byte[]> entry = locationsDb.getFloor(maxEntryId.array);
+        if (entry != null) {
+            stats.getGetLastEntryInLedgerStats()
+                    .registerSuccessfulEvent(MathUtils.elapsedNanos(startTimeNanos), TimeUnit.NANOSECONDS);
+        } else {
+            stats.getGetLastEntryInLedgerStats()
+                    .registerFailedEvent(MathUtils.elapsedNanos(startTimeNanos), TimeUnit.NANOSECONDS);
+        }
         maxEntryId.recycle();
 
         if (entry == null) {

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

@@ -42,6 +42,7 @@ class EntryLocationIndexStats {
 
     private static final String ENTRIES_COUNT = "entries-count";
     private static final String LOOKUP_ENTRY_LOCATION = "lookup-entry-location";
+    private static final String GET_LAST_ENTRY_IN_LEDGER = "get-last-entry-in-ledger";
 
     @StatsDoc(
         name = ENTRIES_COUNT,
@@ -55,6 +56,12 @@ class EntryLocationIndexStats {
     )
     private final OpStatsLogger lookupEntryLocationStats;
 
+    @StatsDoc(
+            name = GET_LAST_ENTRY_IN_LEDGER,
+            help = "operation stats of get last entry in ledger"
+    )
+    private final OpStatsLogger getLastEntryInLedgerStats;
+
     EntryLocationIndexStats(StatsLogger statsLogger,
                             Supplier<Long> entriesCountSupplier) {
         entriesCountGauge = new Gauge<Long>() {
@@ -70,6 +77,7 @@ public Long getSample() {
         };
         statsLogger.registerGauge(ENTRIES_COUNT, entriesCountGauge);
         lookupEntryLocationStats = statsLogger.getOpStatsLogger(LOOKUP_ENTRY_LOCATION);
+        getLastEntryInLedgerStats = statsLogger.getOpStatsLogger(GET_LAST_ENTRY_IN_LEDGER);
     }
 
 }