[GLUTEN-12621][CORE] Fix NoSuchElementException in untracked memory mode without off-heap size

gluten-core/src/main/scala/org/apache/gluten/GlutenPlugin.scala

@@ -103,7 +103,8 @@ private object GlutenDriverPlugin extends Logging {
     }
   }
 
-  private def setPredefinedConfigs(conf: SparkConf): Unit = {
+  // Visible for testing.
+  private[gluten] def setPredefinedConfigs(conf: SparkConf): Unit = {
     // check memory off-heap enabled and size.
     checkOffHeapSettings(conf)
 
@@ -134,6 +135,15 @@ private object GlutenDriverPlugin extends Logging {
         ((onHeapSize - (300 * 1024 * 1024)) *
           conf.getDouble(GlutenCoreConfig.DYNAMIC_OFFHEAP_SIZING_MEMORY_FRACTION.key, 0.6d)).toLong
       } else {
+        // Untracked memory mode skips the off-heap size requirement in checkOffHeapSettings, so
+        // the key may be absent here. Normalize it to 0 (mirroring the dynamic-sizing branch
+        // above) so downstream readers that read spark.memory.offHeap.size directly, e.g.
+        // VeloxListenerApi.onDriverStart, don't hit NoSuchElementException. Normal mode always has
+        // the key set because checkOffHeapSettings enforced it, so this only affects untracked
+        // mode without an explicit off-heap size.
+        if (!conf.contains(GlutenCoreConfig.SPARK_OFFHEAP_SIZE_KEY)) {
+          conf.set(GlutenCoreConfig.SPARK_OFFHEAP_SIZE_KEY, "0")
+        }
         conf.getSizeAsBytes(GlutenCoreConfig.SPARK_OFFHEAP_SIZE_KEY)
       }
 

gluten-core/src/test/scala/org/apache/gluten/GlutenDriverPluginSuite.scala

@@ -0,0 +1,50 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.gluten
+
+import org.apache.gluten.config.GlutenCoreConfig
+
+import org.apache.spark.SparkConf
+
+import org.scalatest.funsuite.AnyFunSuite
+
+class GlutenDriverPluginSuite extends AnyFunSuite {
+
+  test("setPredefinedConfigs does not throw in untracked mode without an off-heap size") {
+    // Untracked memory mode skips the off-heap size requirement in checkOffHeapSettings, so
+    // spark.memory.offHeap.size may be absent. setPredefinedConfigs must not read it with the
+    // single-arg getSizeAsBytes, which throws NoSuchElementException on a missing key.
+    val conf = new SparkConf(false)
+      .set("spark.master", "local[1]")
+      .set(GlutenCoreConfig.COLUMNAR_MEMORY_UNTRACKED.key, "true")
+    GlutenDriverPlugin.setPredefinedConfigs(conf)
+    assert(conf.getLong(GlutenCoreConfig.COLUMNAR_OFFHEAP_SIZE_IN_BYTES.key, -1L) == 0L)
+    // The raw key is normalized to 0 so downstream readers (e.g. VeloxListenerApi.onDriverStart)
+    // that call the single-arg getSizeAsBytes don't hit NoSuchElementException later.
+    assert(conf.getSizeAsBytes(GlutenCoreConfig.SPARK_OFFHEAP_SIZE_KEY) == 0L)
+  }
+
+  test("setPredefinedConfigs reads the configured off-heap size in the normal path") {
+    val conf = new SparkConf(false)
+      .set("spark.master", "local[1]")
+      .set(GlutenCoreConfig.SPARK_OFFHEAP_ENABLED_KEY, "true")
+      .set(GlutenCoreConfig.SPARK_OFFHEAP_SIZE_KEY, "512m")
+    GlutenDriverPlugin.setPredefinedConfigs(conf)
+    assert(
+      conf.getLong(GlutenCoreConfig.COLUMNAR_OFFHEAP_SIZE_IN_BYTES.key, -1L) == 512L * 1024 * 1024)
+  }
+}