diff --git a/sql/catalyst/src/main/java/org/apache/spark/sql/connector/metric/CustomMetric.java b/sql/catalyst/src/main/java/org/apache/spark/sql/connector/metric/CustomMetric.java
index 4c4151ad9697..0b24cc601326 100644
--- a/sql/catalyst/src/main/java/org/apache/spark/sql/connector/metric/CustomMetric.java
+++ b/sql/catalyst/src/main/java/org/apache/spark/sql/connector/metric/CustomMetric.java
@@ -25,6 +25,10 @@
  * and combine the metrics at the driver side. How to combine task metrics is defined by the
  * metric class with the same metric name.
  *
+ * When Spark needs to aggregate task metrics, it will internally construct the instance of
+ * custom metric class defined in data source by using reflection. Spark requires the class
+ * implementing this interface to have a 0-arg constructor.
+ *
  * @since 3.2.0
  */
 @Evolving
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/ui/SQLAppStatusListener.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/ui/SQLAppStatusListener.scala
index d892dbdc2316..9988df025b6a 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/ui/SQLAppStatusListener.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/ui/SQLAppStatusListener.scala
@@ -220,7 +220,10 @@ class SQLAppStatusListener(
             metricAggregationMap.put(className, method)
             method
           } catch {
-            case NonFatal(_) =>
+            case NonFatal(e) =>
+              logWarning(s"Unable to load custom metric object for class `$className`. " +
+                "Please make sure that the custom metric class is in the classpath and " +
+                "it has 0-arg constructor.", e)
               // Cannot initialize custom metric object, we might be in history server that does
               // not have the custom metric class.
               val defaultMethod = (_: Array[Long], _: Array[Long]) => "N/A"