[jvm-packages] fix the persistence of XGBoostEstimator (#2265)

* add back train method but mark as deprecated

* fix scalastyle error

* fix the persistence of XGBoostEstimator

* test persistence of a complete pipeline

* fix compilation issue

* do not allow persist custom_eval and custom_obj

* fix the failed tesl

.gitignore

@@ -88,4 +88,7 @@ build_tests
 /tests/cpp/xgboost_test
 
 .DS_Store
-lib/
+lib/
+
+# spark
+metastore_db

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoost.scala

@@ -18,21 +18,22 @@ package ml.dmlc.xgboost4j.scala.spark
 
 import scala.collection.mutable
 import scala.collection.mutable.ListBuffer
+
 import ml.dmlc.xgboost4j.java.{IRabitTracker, Rabit, XGBoostError, DMatrix => JDMatrix, RabitTracker => PyRabitTracker}
 import ml.dmlc.xgboost4j.scala.rabit.RabitTracker
 import ml.dmlc.xgboost4j.scala.{XGBoost => SXGBoost, _}
 import org.apache.commons.logging.LogFactory
 import org.apache.hadoop.fs.{FSDataInputStream, Path}
+
 import org.apache.spark.ml.feature.{LabeledPoint => MLLabeledPoint}
 import org.apache.spark.ml.linalg.SparseVector
 import org.apache.spark.rdd.RDD
 import org.apache.spark.sql.Dataset
 import org.apache.spark.{SparkContext, TaskContext}
-
+import scala.concurrent.duration.{Duration, FiniteDuration, MILLISECONDS}
-import scala.concurrent.duration.{Duration, MILLISECONDS}
 
 object TrackerConf {
-  def apply(): TrackerConf = TrackerConf(Duration.apply(0L, MILLISECONDS), "python")
+  def apply(): TrackerConf = TrackerConf(0L, "python")
 }
 
 /**
@@ -40,13 +41,14 @@ object TrackerConf {
   * @param workerConnectionTimeout The timeout for all workers to connect to the tracker.
   *                                Set timeout length to zero to disable timeout.
   *                                Use a finite, non-zero timeout value to prevent tracker from
-  *                                hanging indefinitely (supported by "scala" implementation only.)
+  *                                hanging indefinitely (in milliseconds)
+ *                                (supported by "scala" implementation only.)
   * @param trackerImpl Choice between "python" or "scala". The former utilizes the Java wrapper of
   *                    the Python Rabit tracker (in dmlc_core), whereas the latter is implemented
   *                    in Scala without Python components, and with full support of timeouts.
   *                    The Scala implementation is currently experimental, use at your own risk.
   */
-case class TrackerConf(workerConnectionTimeout: Duration, trackerImpl: String)
+case class TrackerConf(workerConnectionTimeout: Long, trackerImpl: String)
 
 object XGBoost extends Serializable {
   private val logger = LogFactory.getLog("XGBoostSpark")
@@ -240,14 +242,7 @@ object XGBoost extends Serializable {
       case _ => new PyRabitTracker(nWorkers)
     }
 
-    val connectionTimeout = if (trackerConf.workerConnectionTimeout.isFinite()) {
+    require(tracker.start(trackerConf.workerConnectionTimeout), "FAULT: Failed to start tracker")
-      trackerConf.workerConnectionTimeout.toMillis
-    } else {
-      // 0 == Duration.Inf
-      0L
-    }
-
-    require(tracker.start(connectionTimeout), "FAULT: Failed to start tracker")
     tracker
   }
 

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostEstimator.scala

@@ -18,12 +18,14 @@ package ml.dmlc.xgboost4j.scala.spark
 
 import scala.collection.mutable
 
-import ml.dmlc.xgboost4j.scala.spark.params.{BoosterParams, GeneralParams, LearningTaskParams}
+import ml.dmlc.xgboost4j.scala.spark.params._
+import org.json4s.DefaultFormats
+
 import org.apache.spark.ml.Predictor
 import org.apache.spark.ml.feature.LabeledPoint
 import org.apache.spark.ml.linalg.{Vector => MLVector}
 import org.apache.spark.ml.param._
-import org.apache.spark.ml.util.Identifiable
+import org.apache.spark.ml.util._
 import org.apache.spark.sql.functions._
 import org.apache.spark.sql.types.DoubleType
 import org.apache.spark.sql.{Dataset, Row}
@@ -34,7 +36,7 @@ import org.apache.spark.sql.{Dataset, Row}
 class XGBoostEstimator private[spark](
   override val uid: String, xgboostParams: Map[String, Any])
   extends Predictor[MLVector, XGBoostEstimator, XGBoostModel]
-  with LearningTaskParams with GeneralParams with BoosterParams {
+  with LearningTaskParams with GeneralParams with BoosterParams with MLWritable {
 
   def this(xgboostParams: Map[String, Any]) =
     this(Identifiable.randomUID("XGBoostEstimator"), xgboostParams: Map[String, Any])
@@ -129,4 +131,38 @@ class XGBoostEstimator private[spark](
   override def copy(extra: ParamMap): XGBoostEstimator = {
     defaultCopy(extra).asInstanceOf[XGBoostEstimator]
   }
+
+  override def write: MLWriter = new XGBoostEstimator.XGBoostEstimatorWriter(this)
+}
+
+object XGBoostEstimator extends MLReadable[XGBoostEstimator] {
+
+  override def read: MLReader[XGBoostEstimator] = new XGBoostEstimatorReader
+
+  override def load(path: String): XGBoostEstimator = super.load(path)
+
+  private[XGBoostEstimator] class XGBoostEstimatorWriter(instance: XGBoostEstimator)
+    extends MLWriter {
+    override protected def saveImpl(path: String): Unit = {
+      require(instance.fromParamsToXGBParamMap("custom_eval") == null &&
+        instance.fromParamsToXGBParamMap("custom_obj") == null,
+        "we do not support persist XGBoostEstimator with customized evaluator and objective" +
+          " function for now")
+      implicit val format = DefaultFormats
+      implicit val sc = super.sparkSession.sparkContext
+      DefaultXGBoostParamsWriter.saveMetadata(instance, path, sc)
+    }
+  }
+
+  private class XGBoostEstimatorReader extends MLReader[XGBoostEstimator] {
+
+    override def load(path: String): XGBoostEstimator = {
+      val metadata = DefaultXGBoostParamsReader.loadMetadata(path, sc)
+      val cls = Utils.classForName(metadata.className)
+      val instance =
+        cls.getConstructor(classOf[String]).newInstance(metadata.uid).asInstanceOf[Params]
+      DefaultXGBoostParamsReader.getAndSetParams(instance, metadata)
+      instance.asInstanceOf[XGBoostEstimator]
+    }
+  }
 }

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostModel.scala

@@ -324,14 +324,13 @@ object XGBoostModel extends MLReadable[XGBoostModel] {
       implicit val format = DefaultFormats
       implicit val sc = super.sparkSession.sparkContext
       DefaultXGBoostParamsWriter.saveMetadata(instance, path, sc)
-
       val dataPath = new Path(path, "data").toString
       instance.saveModelAsHadoopFile(dataPath)
     }
   }
 
   private class XGBoostModelModelReader extends MLReader[XGBoostModel] {
-    private val className = classOf[XGBoostModel].getName
+
     override def load(path: String): XGBoostModel = {
       implicit val sc = super.sparkSession.sparkContext
       val dataPath = new Path(path, "data").toString
@@ -340,5 +339,4 @@ object XGBoostModel extends MLReadable[XGBoostModel] {
       XGBoost.loadModelFromHadoopFile(dataPath)
     }
   }
-
 }

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/params/CustomParams.scala

@@ -0,0 +1,106 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.spark.params
+
+import ml.dmlc.xgboost4j.scala.{EvalTrait, ObjectiveTrait}
+import ml.dmlc.xgboost4j.scala.spark.TrackerConf
+import org.json4s.{DefaultFormats, Extraction, NoTypeHints}
+import org.json4s.jackson.JsonMethods.{compact, parse, render}
+
+import org.apache.spark.ml.param.{Param, ParamPair, Params}
+
+class GroupDataParam(
+    parent: Params,
+    name: String,
+    doc: String) extends Param[Seq[Seq[Int]]](parent, name, doc) {
+
+  /** Creates a param pair with the given value (for Java). */
+  override def w(value: Seq[Seq[Int]]): ParamPair[Seq[Seq[Int]]] = super.w(value)
+
+  override def jsonEncode(value: Seq[Seq[Int]]): String = {
+    import org.json4s.jackson.Serialization
+    implicit val formats = Serialization.formats(NoTypeHints)
+    compact(render(Extraction.decompose(value)))
+  }
+
+  override def jsonDecode(json: String): Seq[Seq[Int]] = {
+    implicit val formats = DefaultFormats
+    parse(json).extract[Seq[Seq[Int]]]
+  }
+}
+
+class CustomEvalParam(
+    parent: Params,
+    name: String,
+    doc: String) extends Param[EvalTrait](parent, name, doc) {
+
+  /** Creates a param pair with the given value (for Java). */
+  override def w(value: EvalTrait): ParamPair[EvalTrait] = super.w(value)
+
+  override def jsonEncode(value: EvalTrait): String = {
+    import org.json4s.jackson.Serialization
+    implicit val formats = Serialization.formats(NoTypeHints)
+    compact(render(Extraction.decompose(value)))
+  }
+
+  override def jsonDecode(json: String): EvalTrait = {
+    implicit val formats = DefaultFormats
+    parse(json).extract[EvalTrait]
+  }
+}
+
+class CustomObjParam(
+    parent: Params,
+    name: String,
+    doc: String) extends Param[ObjectiveTrait](parent, name, doc) {
+
+  /** Creates a param pair with the given value (for Java). */
+  override def w(value: ObjectiveTrait): ParamPair[ObjectiveTrait] = super.w(value)
+
+  override def jsonEncode(value: ObjectiveTrait): String = {
+    import org.json4s.jackson.Serialization
+    implicit val formats = Serialization.formats(NoTypeHints)
+    compact(render(Extraction.decompose(value)))
+  }
+
+  override def jsonDecode(json: String): ObjectiveTrait = {
+    implicit val formats = DefaultFormats
+    parse(json).extract[ObjectiveTrait]
+  }
+}
+
+class TrackerConfParam(
+    parent: Params,
+    name: String,
+    doc: String) extends Param[TrackerConf](parent, name, doc) {
+
+  /** Creates a param pair with the given value (for Java). */
+  override def w(value: TrackerConf): ParamPair[TrackerConf] = super.w(value)
+
+  override def jsonEncode(value: TrackerConf): String = {
+    import org.json4s.jackson.Serialization
+    implicit val formats = Serialization.formats(NoTypeHints)
+    compact(render(Extraction.decompose(value)))
+  }
+
+  override def jsonDecode(json: String): TrackerConf = {
+    implicit val formats = DefaultFormats
+    val parsedValue = parse(json)
+    println(parsedValue.children)
+    parsedValue.extract[TrackerConf]
+  }
+}

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/params/DefaultXGBoostParamsReader.scala

@@ -0,0 +1,136 @@
+/*
+ Copyright (c) 2014 by Contributors
+
+ Licensed 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 ml.dmlc.xgboost4j.scala.spark.params
+
+import org.apache.hadoop.fs.Path
+import org.json4s.{DefaultFormats, JValue}
+import org.json4s.JsonAST.JObject
+import org.json4s.jackson.JsonMethods.{compact, parse, render}
+
+import org.apache.spark.SparkContext
+import org.apache.spark.ml.param.Params
+import org.apache.spark.ml.util.MLReader
+
+// This originates from apache-spark DefaultPramsReader copy paste
+private[spark] object DefaultXGBoostParamsReader {
+
+  /**
+   * All info from metadata file.
+   *
+   * @param params       paramMap, as a `JValue`
+   * @param metadata     All metadata, including the other fields
+   * @param metadataJson Full metadata file String (for debugging)
+   */
+  case class Metadata(
+      className: String,
+      uid: String,
+      timestamp: Long,
+      sparkVersion: String,
+      params: JValue,
+      metadata: JValue,
+      metadataJson: String) {
+
+    /**
+     * Get the JSON value of the [[org.apache.spark.ml.param.Param]] of the given name.
+     * This can be useful for getting a Param value before an instance of `Params`
+     * is available.
+     */
+    def getParamValue(paramName: String): JValue = {
+      implicit val format = DefaultFormats
+      params match {
+        case JObject(pairs) =>
+          val values = pairs.filter { case (pName, jsonValue) =>
+            pName == paramName
+          }.map(_._2)
+          assert(values.length == 1, s"Expected one instance of Param '$paramName' but found" +
+            s" ${values.length} in JSON Params: " + pairs.map(_.toString).mkString(", "))
+          values.head
+        case _ =>
+          throw new IllegalArgumentException(
+            s"Cannot recognize JSON metadata: $metadataJson.")
+      }
+    }
+  }
+
+  /**
+   * Load metadata saved using [[DefaultXGBoostParamsWriter.saveMetadata()]]
+   *
+   * @param expectedClassName If non empty, this is checked against the loaded metadata.
+   * @throws IllegalArgumentException if expectedClassName is specified and does not match metadata
+   */
+  def loadMetadata(path: String, sc: SparkContext, expectedClassName: String = ""): Metadata = {
+    val metadataPath = new Path(path, "metadata").toString
+    val metadataStr = sc.textFile(metadataPath, 1).first()
+    parseMetadata(metadataStr, expectedClassName)
+  }
+
+  /**
+   * Parse metadata JSON string produced by [[DefaultXGBoostParamsWriter.getMetadataToSave()]].
+   * This is a helper function for [[loadMetadata()]].
+   *
+   * @param metadataStr       JSON string of metadata
+   * @param expectedClassName If non empty, this is checked against the loaded metadata.
+   * @throws IllegalArgumentException if expectedClassName is specified and does not match metadata
+   */
+  def parseMetadata(metadataStr: String, expectedClassName: String = ""): Metadata = {
+    val metadata = parse(metadataStr)
+
+    implicit val format = DefaultFormats
+    val className = (metadata \ "class").extract[String]
+    val uid = (metadata \ "uid").extract[String]
+    val timestamp = (metadata \ "timestamp").extract[Long]
+    val sparkVersion = (metadata \ "sparkVersion").extract[String]
+    val params = metadata \ "paramMap"
+    if (expectedClassName.nonEmpty) {
+      require(className == expectedClassName, s"Error loading metadata: Expected class name" +
+        s" $expectedClassName but found class name $className")
+    }
+
+    Metadata(className, uid, timestamp, sparkVersion, params, metadata, metadataStr)
+  }
+
+  /**
+   * Extract Params from metadata, and set them in the instance.
+   * This works if all Params implement [[org.apache.spark.ml.param.Param.jsonDecode()]].
+   * TODO: Move to [[Metadata]] method
+   */
+  def getAndSetParams(instance: Params, metadata: Metadata): Unit = {
+    implicit val format = DefaultFormats
+    metadata.params match {
+      case JObject(pairs) =>
+        pairs.foreach { case (paramName, jsonValue) =>
+          val param = instance.getParam(paramName)
+          val value = param.jsonDecode(compact(render(jsonValue)))
+          instance.set(param, value)
+        }
+      case _ =>
+        throw new IllegalArgumentException(
+          s"Cannot recognize JSON metadata: ${metadata.metadataJson}.")
+    }
+  }
+
+  /**
+   * Load a `Params` instance from the given path, and return it.
+   * This assumes the instance implements [[org.apache.spark.ml.util.MLReadable]].
+   */
+  def loadParamsInstance[T](path: String, sc: SparkContext): T = {
+    val metadata = DefaultXGBoostParamsReader.loadMetadata(path, sc)
+    val cls = Utils.classForName(metadata.className)
+    cls.getMethod("read").invoke(null).asInstanceOf[MLReader[T]].load(path)
+  }
+}
+

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/params/DefaultXGBoostParamsWriter.scala

@@ -46,6 +46,7 @@ private[spark] object DefaultXGBoostParamsWriter {
     sc: SparkContext,
     extraMetadata: Option[JObject] = None,
     paramMap: Option[JValue] = None): Unit = {
+
     val metadataPath = new Path(path, "metadata").toString
     val metadataJson = getMetadataToSave(instance, sc, extraMetadata, paramMap)
     sc.parallelize(Seq(metadataJson), 1).saveAsTextFile(metadataPath)
@@ -65,7 +66,9 @@ private[spark] object DefaultXGBoostParamsWriter {
     val uid = instance.uid
     val cls = instance.getClass.getName
     val params = instance.extractParamMap().toSeq.asInstanceOf[Seq[ParamPair[Any]]]
-    val jsonParams = paramMap.getOrElse(render(params.map {
+    val jsonParams = paramMap.getOrElse(render(params.filter{
+      case ParamPair(p, _) => p != null
+    }.map {
       case ParamPair(p, v) =>
         p.name -> parse(p.jsonEncode(v))
     }.toList))

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/params/GeneralParams.scala

@@ -20,8 +20,6 @@ import ml.dmlc.xgboost4j.scala.spark.TrackerConf
 import ml.dmlc.xgboost4j.scala.{EvalTrait, ObjectiveTrait}
 import org.apache.spark.ml.param._
 
-import scala.concurrent.duration.{Duration, NANOSECONDS}
-
 trait GeneralParams extends Params {
 
   /**
@@ -58,13 +56,13 @@ trait GeneralParams extends Params {
   /**
    * customized objective function provided by user. default: null
    */
-  val customObj = new Param[ObjectiveTrait](this, "custom_obj", "customized objective function " +
+  val customObj = new CustomObjParam(this, "custom_obj", "customized objective function " +
     "provided by user")
 
   /**
    * customized evaluation function provided by user. default: null
    */
-  val customEval = new Param[EvalTrait](this, "custom_eval", "customized evaluation function " +
+  val customEval = new CustomEvalParam(this, "custom_eval", "customized evaluation function " +
     "provided by user")
 
   /**
@@ -99,7 +97,7 @@ trait GeneralParams extends Params {
     *        Note that zero timeout value means to wait indefinitely (equivalent to Duration.Inf).
     *        Ignored if the tracker implementation is "python".
     */
-  val trackerConf = new Param[TrackerConf](this, "tracker_conf", "Rabit tracker configurations")
+  val trackerConf = new TrackerConfParam(this, "tracker_conf", "Rabit tracker configurations")
 
   setDefault(round -> 1, nWorkers -> 1, numThreadPerTask -> 1,
     useExternalMemory -> false, silent -> 0,

jvm-packages/xgboost4j-spark/src/main/scala/ml/dmlc/xgboost4j/scala/spark/params/LearningTaskParams.scala

@@ -57,7 +57,7 @@ trait LearningTaskParams extends Params {
     * group data specify each group sizes for ranking task. To correspond to partition of
     * training data, it is nested.
     */
-  val groupData = new Param[Seq[Seq[Int]]](this, "groupData", "group data specify each group size" +
+  val groupData = new GroupDataParam(this, "groupData", "group data specify each group size" +
     " for ranking task. To correspond to partition of training data, it is nested.")
 
   setDefault(objective -> "reg:linear", baseScore -> 0.5, numClasses -> 2, groupData -> null)

jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostDFSuite.scala

@@ -18,17 +18,21 @@ package ml.dmlc.xgboost4j.scala.spark
 
 import java.io.File
 
+import scala.collection.mutable
 import scala.collection.mutable.ListBuffer
 import scala.io.Source
+import scala.util.Random
 
 import ml.dmlc.xgboost4j.java.{DMatrix => JDMatrix}
 import ml.dmlc.xgboost4j.scala.{DMatrix, XGBoost => ScalaXGBoost}
 
 import org.apache.spark.SparkContext
 import org.apache.spark.ml.Pipeline
-import org.apache.spark.ml.feature.LabeledPoint
+import org.apache.spark.ml.evaluation.RegressionEvaluator
+import org.apache.spark.ml.feature.{LabeledPoint, VectorAssembler}
 import org.apache.spark.ml.linalg.DenseVector
 import org.apache.spark.ml.param.ParamMap
+import org.apache.spark.ml.tuning.{CrossValidator, ParamGridBuilder}
 import org.apache.spark.sql._
 
 class XGBoostDFSuite extends SharedSparkContext with Utils {

jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostGeneralSuite.scala

@@ -110,7 +110,7 @@ class XGBoostGeneralSuite extends SharedSparkContext with Utils {
     val testSetDMatrix = new DMatrix(new JDMatrix(testSet, null))
     val paramMap = List("eta" -> "1", "max_depth" -> "6", "silent" -> "1",
       "objective" -> "binary:logistic",
-      "tracker_conf" -> TrackerConf(1 minute, "scala")).toMap
+      "tracker_conf" -> TrackerConf(60 * 60 * 1000, "scala")).toMap
     val xgBoostModel = XGBoost.trainWithRDD(trainingRDD, paramMap, round = 5,
       nWorkers = numWorkers)
     assert(eval.eval(xgBoostModel.booster.predict(testSetDMatrix, outPutMargin = true),

jvm-packages/xgboost4j-spark/src/test/scala/ml/dmlc/xgboost4j/scala/spark/XGBoostSparkPipelinePersistence.scala

@@ -18,67 +18,84 @@ package ml.dmlc.xgboost4j.scala.spark
 
 import java.io.{File, FileNotFoundException}
 
+import scala.util.Random
+
 import org.apache.spark.SparkConf
 import org.apache.spark.ml.feature._
 import org.apache.spark.ml.{Pipeline, PipelineModel}
 import org.apache.spark.sql.SparkSession
-import scala.concurrent.duration._
-
-case class Foobar(TARGET: Int, bar: Double, baz: Double)
 
 class XGBoostSparkPipelinePersistence extends SharedSparkContext with Utils {
 
   override def afterAll(): Unit = {
     super.afterAll()
     delete(new File("./testxgbPipe"))
-    delete(new File("./test2xgbPipe"))
+    delete(new File("./testxgbEst"))
+    delete(new File("./testxgbModel"))
+    delete(new File("./test2xgbModel"))
   }
 
   private def delete(f: File) {
-    if (f.isDirectory()) {
+    if (f.exists()) {
-      for (c <- f.listFiles()) {
+      if (f.isDirectory()) {
-        delete(c)
+        for (c <- f.listFiles()) {
+          delete(c)
+        }
+      }
+      if (!f.delete()) {
+        throw new FileNotFoundException("Failed to delete file: " + f)
       }
-    }
-    if (!f.delete()) {
-      throw new FileNotFoundException("Failed to delete file: " + f)
     }
   }
 
-  test("test sparks pipeline persistence of dataframe-based model") {
+  test("test persistence of XGBoostEstimator") {
-    //  maybe move to shared context, but requires session to import implicits.
+    val paramMap = Map("eta" -> "0.1", "max_depth" -> "6", "silent" -> "1",
-    // what about introducing https://github.com/holdenk/spark-testing-base ?
+      "objective" -> "multi:softmax", "num_class" -> "6")
-    val conf: SparkConf = new SparkConf()
+    val xgbEstimator = new XGBoostEstimator(paramMap)
-      .setAppName("foo")
+    xgbEstimator.write.overwrite().save("./testxgbEst")
-      .setMaster("local[*]")
+    val loadedxgbEstimator = XGBoostEstimator.read.load("./testxgbEst")
+    val loadedParamMap = loadedxgbEstimator.fromParamsToXGBParamMap
+    paramMap.foreach {
+      case (k, v) => assert(v == loadedParamMap(k).toString)
+    }
+  }
 
-    val spark: SparkSession = SparkSession
+  test("test persistence of a complete pipeline") {
-      .builder()
+    val conf = new SparkConf().setAppName("foo").setMaster("local[*]")
-      .config(conf)
+    val spark = SparkSession.builder().config(conf).getOrCreate()
-      .getOrCreate()
+    val paramMap = Map("eta" -> "0.1", "max_depth" -> "6", "silent" -> "1",
+      "objective" -> "multi:softmax", "num_class" -> "6")
+    val r = new Random(0)
+    val assembler = new VectorAssembler().setInputCols(Array("feature")).setOutputCol("features")
+    val xgbEstimator = new XGBoostEstimator(paramMap)
+    val pipeline = new Pipeline().setStages(Array(assembler, xgbEstimator))
+    pipeline.write.overwrite().save("testxgbPipe")
+    val loadedPipeline = Pipeline.read.load("testxgbPipe")
+    val loadedEstimator = loadedPipeline.getStages(1).asInstanceOf[XGBoostEstimator]
+    val loadedParamMap = loadedEstimator.fromParamsToXGBParamMap
+    paramMap.foreach {
+      case (k, v) => assert(v == loadedParamMap(k).toString)
+    }
+  }
 
-    import spark.implicits._
+  test("test persistence of XGBoostModel") {
+    val conf = new SparkConf().setAppName("foo").setMaster("local[*]")
+    val spark = SparkSession.builder().config(conf).getOrCreate()
+    val r = new Random(0)
     // maybe move to shared context, but requires session to import implicits
-
+    val df = spark.createDataFrame(Seq.fill(10000)(r.nextInt(2)).map(i => (i, i))).
-    val df = Seq(Foobar(0, 0.5, 1), Foobar(1, 0.01, 0.8),
+      toDF("feature", "label")
-      Foobar(0, 0.8, 0.5), Foobar(1, 8.4, 0.04))
-      .toDS
-
     val vectorAssembler = new VectorAssembler()
       .setInputCols(df.columns
-        .filter(!_.contains("TARGET")))
+        .filter(!_.contains("label")))
       .setOutputCol("features")
-
     val xgbEstimator = new XGBoostEstimator(Map("num_rounds" -> 10,
-      "tracker_conf" -> TrackerConf(1 minute, "scala")
+      "tracker_conf" -> TrackerConf(60 * 60 * 1000, "scala")
-    ))
+    )).setFeaturesCol("features").setLabelCol("label")
-      .setFeaturesCol("features")
-      .setLabelCol("TARGET")
-
     // separate
     val predModel = xgbEstimator.fit(vectorAssembler.transform(df))
-    predModel.write.overwrite.save("test2xgbPipe")
+    predModel.write.overwrite.save("test2xgbModel")
-    val same2Model = XGBoostModel.load("test2xgbPipe")
+    val same2Model = XGBoostModel.load("test2xgbModel")
 
     assert(java.util.Arrays.equals(predModel.booster.toByteArray, same2Model.booster.toByteArray))
     val predParamMap = predModel.extractParamMap()
@@ -93,8 +110,8 @@ class XGBoostSparkPipelinePersistence extends SharedSparkContext with Utils {
 
     // chained
     val predictionModel = new Pipeline().setStages(Array(vectorAssembler, xgbEstimator)).fit(df)
-    predictionModel.write.overwrite.save("testxgbPipe")
+    predictionModel.write.overwrite.save("testxgbModel")
-    val sameModel = PipelineModel.load("testxgbPipe")
+    val sameModel = PipelineModel.load("testxgbModel")
 
     val predictionModelXGB = predictionModel.stages.collect { case xgb: XGBoostModel => xgb } head
     val sameModelXGB = sameModel.stages.collect { case xgb: XGBoostModel => xgb } head