Add null check for writer (#5550)

Signed-off-by: Hai Yan <[email protected]>

Author: oeyh

data-prepper-plugins/s3-sink/src/main/java/org/opensearch/dataprepper/plugins/codec/parquet/ParquetOutputCodec.java

@@ -116,7 +116,9 @@ public void writeEvent(final Event event, final OutputStream outputStream) throw
     @Override
     public synchronized void complete(final OutputStream outputStream) throws IOException {
         isClosed = true;
-        writer.close();
+        if (writer != null) {
+            writer.close();
+        }
     }
 
     @Override

data-prepper-plugins/s3-sink/src/test/java/org/opensearch/dataprepper/plugins/codec/parquet/ParquetOutputCodecTest.java

@@ -243,6 +243,18 @@ void writeEvent_throws_exception_when_field_does_not_exist_in_auto_schema() thro
         assertThat(actualException.getMessage(), containsString(invalidFieldName));
     }
 
+    @Test
+    void exception_in_start_should_not_cause_null_pointer_exception_when_complete() throws IOException {
+        final ParquetOutputCodec objectUnderTest = createObjectUnderTest();
+
+        final File tempFile = new File(tempDirectory, FILE_NAME);
+        LocalFilePositionOutputStream outputStream = LocalFilePositionOutputStream.create(tempFile);
+        assertThrows(RuntimeException.class, () -> objectUnderTest.start(null, createEventRecord(generateRecords(1).get(0)), codecContext));
+
+        // Calling complete now should not throw
+        objectUnderTest.complete(outputStream);
+    }
+
     @Test
     void getSize_returns_0_after_construction() {
         config.setSchema(createStandardSchema().toString());