Github user jiangxb1987 commented on a diff in the pull request:
https://github.com/apache/spark/pull/21758#discussion_r205096607
--- Diff: core/src/main/scala/org/apache/spark/rdd/RDDBarrier.scala ---
@@ -0,0 +1,52 @@
+/*
+ * 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.spark.rdd
+
+import scala.reflect.ClassTag
+
+import org.apache.spark.BarrierTaskContext
+import org.apache.spark.TaskContext
+import org.apache.spark.annotation.{Experimental, Since}
+
+/** Represents an RDD barrier, which forces Spark to launch tasks of this
stage together. */
+class RDDBarrier[T: ClassTag](rdd: RDD[T]) {
+
+ /**
+ * :: Experimental ::
+ * Maps partitions together with a provided BarrierTaskContext.
+ *
+ * `preservesPartitioning` indicates whether the input function
preserves the partitioner, which
+ * should be `false` unless `rdd` is a pair RDD and the input function
doesn't modify the keys.
+ */
+ @Experimental
+ @Since("2.4.0")
+ def mapPartitions[S: ClassTag](
--- End diff --
`RDDBarrier` is actually expected to be used like a builder, we shall
provide more options for the barrier stage in the future, eg. config a timeout
of a barrier stage.
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