From 5b8bc664a8dca97789c2472d633868fb8f553652 Mon Sep 17 00:00:00 2001
From: Danny Chan <yuzhao.cyz@gmail.com>
Date: Mon, 11 Oct 2021 16:22:22 +0800
Subject: [PATCH] [HUDI-2542] AppendWriteFunction throws NPE when checkpointing
 without written data (#3777)

---
 .../java/org/apache/hudi/sink/append/AppendWriteFunction.java | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hudi-flink/src/main/java/org/apache/hudi/sink/append/AppendWriteFunction.java b/hudi-flink/src/main/java/org/apache/hudi/sink/append/AppendWriteFunction.java
index 0279313ff..0c295781f 100644
--- a/hudi-flink/src/main/java/org/apache/hudi/sink/append/AppendWriteFunction.java
+++ b/hudi-flink/src/main/java/org/apache/hudi/sink/append/AppendWriteFunction.java
@@ -122,6 +122,10 @@ public class AppendWriteFunction<I> extends AbstractStreamWriteFunction<I> {
   }
 
   private void flushData(boolean endInput) {
+    if (this.writerHelper == null) {
+      // does not process any inputs, returns early.
+      return;
+    }
     final List<WriteStatus> writeStatus = this.writerHelper.getWriteStatuses(this.taskID);
     final WriteMetadataEvent event = WriteMetadataEvent.builder()
         .taskID(taskID)