[GitHub] [spark] cloud-fan commented on a change in pull request #27983: [SPARK-32105][SQL]Refactor current ScriptTransformationExec code

[GitBox <gi...@apache.org>]

cloud-fan commented on a change in pull request #27983:
URL: https://github.com/apache/spark/pull/27983#discussion_r448816141



##########
File path: sql/core/src/main/scala/org/apache/spark/sql/execution/script/ScriptTransformbase.scala
##########
@@ -0,0 +1,161 @@
+/*
+ * 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.sql.execution.script
+
+import java.io.OutputStream
+import java.util.concurrent.TimeUnit
+
+import scala.util.control.NonFatal
+
+import org.apache.hadoop.conf.Configuration
+
+import org.apache.spark.{SparkException, TaskContext}
+import org.apache.spark.internal.Logging
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions.UnsafeProjection
+import org.apache.spark.sql.execution.UnaryExecNode
+import org.apache.spark.sql.internal.SQLConf
+import org.apache.spark.sql.types.DataType
+import org.apache.spark.util.{CircularBuffer, SerializableConfiguration, Utils}
+
+trait ScriptTransformBase extends UnaryExecNode {
+  override def doExecute(): RDD[InternalRow] = {
+    val broadcastedHadoopConf =
+      new SerializableConfiguration(sqlContext.sessionState.newHadoopConf())
+
+    child.execute().mapPartitions { iter =>
+      if (iter.hasNext) {
+        val proj = UnsafeProjection.create(schema)
+        processIterator(iter, broadcastedHadoopConf.value).map(proj)
+      } else {
+        // If the input iterator has no rows then do not launch the external script.
+        Iterator.empty
+      }
+    }
+  }
+
+  def processIterator(
+      inputIterator: Iterator[InternalRow],
+      hadoopConf: Configuration): Iterator[InternalRow]
+
+  protected def checkFailureAndPropagate(
+      writerThread: ScriptTransformationWriterThreadBase,
+      cause: Throwable = null,
+      proc: Process,
+      stderrBuffer: CircularBuffer): Unit = {
+    if (writerThread.exception.isDefined) {
+      throw writerThread.exception.get
+    }
+
+    // There can be a lag between reader read EOF and the process termination.
+    // If the script fails to startup, this kind of error may be missed.
+    // So explicitly waiting for the process termination.
+    val timeout = conf.getConf(SQLConf.SCRIPT_TRANSFORMATION_EXIT_TIMEOUT)
+    val exitRes = proc.waitFor(timeout, TimeUnit.SECONDS)
+    if (!exitRes) {
+      log.warn(s"Transformation script process exits timeout in $timeout seconds")
+    }
+
+    if (!proc.isAlive) {
+      val exitCode = proc.exitValue()
+      if (exitCode != 0) {
+        logError(stderrBuffer.toString) // log the stderr circular buffer
+        throw new SparkException(s"Subprocess exited with status $exitCode. " +
+          s"Error: ${stderrBuffer.toString}", cause)
+      }
+    }
+  }
+}
+
+abstract class ScriptTransformationWriterThreadBase(
+    iter: Iterator[InternalRow],
+    inputSchema: Seq[DataType],
+    outputStream: OutputStream,
+    proc: Process,
+    stderrBuffer: CircularBuffer,
+    taskContext: TaskContext,
+    conf: Configuration) extends Thread with Logging {
+  @volatile protected var _exception: Throwable = null
+
+  /** Contains the exception thrown while writing the parent iterator to the external process. */
+  def exception: Option[Throwable] = Option(_exception)
+
+  protected def processRows(): Unit
+
+  override def run(): Unit = Utils.logUncaughtExceptions {
+    TaskContext.setTaskContext(taskContext)
+
+    // We can't use Utils.tryWithSafeFinally here because we also need a `catch` block, so
+    // let's use a variable to record whether the `finally` block was hit due to an exception
+    var threwException: Boolean = true
+    try {
+      processRows()
+      threwException = false
+    } catch {
+      // SPARK-25158 Exception should not be thrown again, otherwise it will be captured by
+      // SparkUncaughtExceptionHandler, then Executor will exit because of this Uncaught Exception,
+      // so pass the exception to `ScriptTransformationExec` is enough.
+      case t: Throwable =>
+        // An error occurred while writing input, so kill the child process. According to the
+        // Javadoc this call will not throw an exception:
+        _exception = t
+        proc.destroy()
+        logError("Thread-ScriptTransformation-Feed exit cause by: ", t)
+    } finally {
+      try {
+        Utils.tryLogNonFatalError(outputStream.close())
+        if (proc.waitFor() != 0) {
+          logError(stderrBuffer.toString) // log the stderr circular buffer
+        }
+      } catch {
+        case NonFatal(exceptionFromFinallyBlock) =>
+          if (!threwException) {
+            throw exceptionFromFinallyBlock
+          } else {
+            log.error("Exception in finally block", exceptionFromFinallyBlock)
+          }
+      }
+    }
+  }
+}
+
+/**
+ * The wrapper class of input and output schema properties
+ */
+abstract class ScriptTransformIOSchemaBase(
+    inputRowFormat: Seq[(String, String)],
+    outputRowFormat: Seq[(String, String)],
+    inputSerdeClass: Option[String],
+    outputSerdeClass: Option[String],
+    inputSerdeProps: Seq[(String, String)],
+    outputSerdeProps: Seq[(String, String)],
+    recordReaderClass: Option[String],
+    recordWriterClass: Option[String],
+    schemaLess: Boolean) extends Serializable {
+
+  protected val defaultFormat = Map(
+    ("TOK_TABLEROWFORMATFIELD", "\t"),
+    ("TOK_TABLEROWFORMATLINES", "\n")
+  )
+
+  val inputRowFormatMap = inputRowFormat.toMap.withDefault((k) => defaultFormat(k))
+  val outputRowFormatMap = outputRowFormat.toMap.withDefault((k) => defaultFormat(k))
+
+  def isSchemaLess: Boolean = schemaLess

Review comment:
       nit: you can remove the `schemaLess` parameter and just define a `def schemaLess: Boolean`. Then it's easier for case class to extend this class.




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