diff --git a/core/src/main/scala/org/apache/spark/BarrierTaskContext.scala b/core/src/main/scala/org/apache/spark/BarrierTaskContext.scala
index 2263538a11676..0c2ceb1a02c7b 100644
--- a/core/src/main/scala/org/apache/spark/BarrierTaskContext.scala
+++ b/core/src/main/scala/org/apache/spark/BarrierTaskContext.scala
@@ -217,11 +217,11 @@ class BarrierTaskContext private[spark] (
    */
   @Experimental
   @Since("3.0.0")
-  def allGather(message: String): ArrayBuffer[String] = {
+  def allGather(message: String): Array[String] = {
     val json = runBarrier(RequestMethod.ALL_GATHER, message)
     val jsonArray = parse(json)
     implicit val formats = DefaultFormats
-    ArrayBuffer(jsonArray.extract[Array[String]]: _*)
+    jsonArray.extract[Array[String]]
   }
 
   /**
diff --git a/core/src/main/scala/org/apache/spark/api/python/PythonRunner.scala b/core/src/main/scala/org/apache/spark/api/python/PythonRunner.scala
index fa8bf0fc06358..06c9446c7534e 100644
--- a/core/src/main/scala/org/apache/spark/api/python/PythonRunner.scala
+++ b/core/src/main/scala/org/apache/spark/api/python/PythonRunner.scala
@@ -420,7 +420,7 @@ private[spark] abstract class BasePythonRunner[IN, OUT](
             context.asInstanceOf[BarrierTaskContext].barrier()
             result = BarrierTaskContextMessageProtocol.BARRIER_RESULT_SUCCESS
           case BarrierTaskContextMessageProtocol.ALL_GATHER_FUNCTION =>
-            val messages: ArrayBuffer[String] = context.asInstanceOf[BarrierTaskContext].allGather(
+            val messages: Array[String] = context.asInstanceOf[BarrierTaskContext].allGather(
               message
             )
             result = compact(render(JArray(
diff --git a/core/src/test/scala/org/apache/spark/scheduler/BarrierTaskContextSuite.scala b/core/src/test/scala/org/apache/spark/scheduler/BarrierTaskContextSuite.scala
index 33594c0a50d14..0dd8be72dc904 100644
--- a/core/src/test/scala/org/apache/spark/scheduler/BarrierTaskContextSuite.scala
+++ b/core/src/test/scala/org/apache/spark/scheduler/BarrierTaskContextSuite.scala
@@ -65,7 +65,7 @@ class BarrierTaskContextSuite extends SparkFunSuite with LocalSparkContext {
       Thread.sleep(Random.nextInt(1000))
       // Pass partitionId message in
       val message: String = context.partitionId().toString
-      val messages: ArrayBuffer[String] = context.allGather(message)
+      val messages: Array[String] = context.allGather(message)
       messages.toList.iterator
     }
     // Take a sorted list of all the partitionId messages