Prevent race condition while calculating unack-msg offset stats (apac…

…he#3015) * Prevent race condition while calculating unack-msg offset stats * local var
larslevie · Nov 20, 2018 · 5fde6f3 · 5fde6f3
1 parent 31345de
commit 5fde6f3
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedCursorImpl.java b/managed-ledger/src/main/java/org/apache/bookkeeper/mledger/impl/ManagedCursorImpl.java
@@ -665,7 +665,13 @@ public long getNumberOfEntries() {
 
     @Override
     public long getNumberOfEntriesSinceFirstNotAckedMessage() {
-        return ledger.getNumberOfEntries(Range.openClosed(markDeletePosition, readPosition));
+        // sometimes for already caught up consumer: due to race condition markDeletePosition > readPosition. so,
+        // validate it before preparing range
+        PositionImpl markDeletePosition = this.markDeletePosition;
+        PositionImpl readPosition = this.readPosition;
+        return (markDeletePosition.compareTo(readPosition) < 0)
+                ? ledger.getNumberOfEntries(Range.openClosed(markDeletePosition, readPosition))
+                : 0;
     }
 
     @Override