[backport] #7808 #7810 (#7811)

* [jvm-packages] add hostIp and python exec for rabit tracker (#7808)

* Fix training continuation with categorical model. (#7810)

* Make sure the task is initialized before construction of tree updater.

This is a quick fix meant to be backported to 1.6, for a full fix we should pass the model
param into tree updater by reference instead.

Co-authored-by: Bobby Wang <wbo4958@gmail.com>

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

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014,2021 by Contributors
+ Copyright (c) 2014-2022 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -46,8 +46,14 @@ import org.apache.spark.sql.SparkSession
  *                    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.
+ *
+ * @param hostIp The Rabit Tracker host IP address which is only used for python implementation.
+ *               This is only needed if the host IP cannot be automatically guessed.
+ * @param pythonExec The python executed path for Rabit Tracker,
+ *                   which is only used for python implementation.
  */
-case class TrackerConf(workerConnectionTimeout: Long, trackerImpl: String )
+case class TrackerConf(workerConnectionTimeout: Long, trackerImpl: String,
+  hostIp: String = "", pythonExec: String = "")
 
 object TrackerConf {
   def apply(): TrackerConf = TrackerConf(0L, "python")
@@ -336,13 +342,18 @@ object XGBoost extends Serializable {
     }
   }
 
-  private def startTracker(nWorkers: Int, trackerConf: TrackerConf): IRabitTracker = {
+  /** visiable for testing */
+  private[scala] def getTracker(nWorkers: Int, trackerConf: TrackerConf): IRabitTracker = {
     val tracker: IRabitTracker = trackerConf.trackerImpl match {
       case "scala" => new RabitTracker(nWorkers)
-      case "python" => new PyRabitTracker(nWorkers)
+      case "python" => new PyRabitTracker(nWorkers, trackerConf.hostIp, trackerConf.pythonExec)
       case _ => new PyRabitTracker(nWorkers)
     }
+    tracker
+  }
 
+  private def startTracker(nWorkers: Int, trackerConf: TrackerConf): IRabitTracker = {
+    val tracker = getTracker(nWorkers, trackerConf)
     require(tracker.start(trackerConf.workerConnectionTimeout), "FAULT: Failed to start tracker")
     tracker
   }

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

@@ -1,5 +1,5 @@
 /*
- Copyright (c) 2014 by Contributors
+ Copyright (c) 2014-2022 by Contributors
 
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
@@ -24,11 +24,61 @@ import ml.dmlc.xgboost4j.java.{Rabit, RabitTracker => PyRabitTracker}
 import ml.dmlc.xgboost4j.scala.rabit.{RabitTracker => ScalaRabitTracker}
 import ml.dmlc.xgboost4j.java.IRabitTracker.TrackerStatus
 import ml.dmlc.xgboost4j.scala.DMatrix
-
-import org.scalatest.{FunSuite, Ignore}
+import org.scalatest.{FunSuite}
 
 class RabitRobustnessSuite extends FunSuite with PerTest {
 
+  private def getXGBoostExecutionParams(paramMap: Map[String, Any]): XGBoostExecutionParams = {
+    val classifier = new XGBoostClassifier(paramMap)
+    val xgbParamsFactory = new XGBoostExecutionParamsFactory(classifier.MLlib2XGBoostParams, sc)
+    xgbParamsFactory.buildXGBRuntimeParams
+  }
+
+
+  test("Customize host ip and python exec for Rabit tracker") {
+    val hostIp = "192.168.22.111"
+    val pythonExec = "/usr/bin/python3"
+
+    val paramMap = Map(
+      "num_workers" -> numWorkers,
+      "tracker_conf" -> TrackerConf(0L, "python", hostIp))
+    val xgbExecParams = getXGBoostExecutionParams(paramMap)
+    val tracker = XGBoost.getTracker(xgbExecParams.numWorkers, xgbExecParams.trackerConf)
+    tracker match {
+      case pyTracker: PyRabitTracker =>
+        val cmd = pyTracker.getRabitTrackerCommand
+        assert(cmd.contains(hostIp))
+        assert(cmd.startsWith("python"))
+      case _ => assert(false, "expected python tracker implementation")
+    }
+
+    val paramMap1 = Map(
+      "num_workers" -> numWorkers,
+      "tracker_conf" -> TrackerConf(0L, "python", "", pythonExec))
+    val xgbExecParams1 = getXGBoostExecutionParams(paramMap1)
+    val tracker1 = XGBoost.getTracker(xgbExecParams1.numWorkers, xgbExecParams1.trackerConf)
+    tracker1 match {
+      case pyTracker: PyRabitTracker =>
+        val cmd = pyTracker.getRabitTrackerCommand
+        assert(cmd.startsWith(pythonExec))
+        assert(!cmd.contains(hostIp))
+      case _ => assert(false, "expected python tracker implementation")
+    }
+
+    val paramMap2 = Map(
+      "num_workers" -> numWorkers,
+      "tracker_conf" -> TrackerConf(0L, "python", hostIp, pythonExec))
+    val xgbExecParams2 = getXGBoostExecutionParams(paramMap2)
+    val tracker2 = XGBoost.getTracker(xgbExecParams2.numWorkers, xgbExecParams2.trackerConf)
+    tracker2 match {
+      case pyTracker: PyRabitTracker =>
+        val cmd = pyTracker.getRabitTrackerCommand
+        assert(cmd.startsWith(pythonExec))
+        assert(cmd.contains(s" --host-ip=${hostIp}"))
+      case _ => assert(false, "expected python tracker implementation")
+    }
+  }
+
   test("training with Scala-implemented Rabit tracker") {
     val eval = new EvalError()
     val training = buildDataFrame(Classification.train)

jvm-packages/xgboost4j/src/main/java/ml/dmlc/xgboost4j/java/RabitTracker.java

@@ -30,6 +30,8 @@ public class RabitTracker implements IRabitTracker {
   private Map<String, String> envs = new HashMap<String, String>();
   // number of workers to be submitted.
   private int numWorkers;
+  private String hostIp = "";
+  private String pythonExec = "";
   private AtomicReference<Process> trackerProcess = new AtomicReference<Process>();
 
   static {
@@ -85,6 +87,13 @@ public class RabitTracker implements IRabitTracker {
     this.numWorkers = numWorkers;
   }
 
+  public RabitTracker(int numWorkers, String hostIp, String pythonExec)
+      throws XGBoostError {
+    this(numWorkers);
+    this.hostIp = hostIp;
+    this.pythonExec = pythonExec;
+  }
+
   public void uncaughtException(Thread t, Throwable e) {
     logger.error("Uncaught exception thrown by worker:", e);
     try {
@@ -126,12 +135,34 @@ public class RabitTracker implements IRabitTracker {
     }
   }
 
+  /** visible for testing */
+  public String getRabitTrackerCommand() {
+    StringBuilder sb = new StringBuilder();
+    if (pythonExec == null || pythonExec.isEmpty()) {
+      sb.append("python ");
+    } else {
+      sb.append(pythonExec + " ");
+    }
+    sb.append(" " + tracker_py + " ");
+    sb.append(" --log-level=DEBUG" + " ");
+    sb.append(" --num-workers=" + numWorkers + " ");
+
+    // we first check the property then check the parameter
+    String hostIpFromProperties = trackerProperties.getHostIp();
+    if(hostIpFromProperties != null && !hostIpFromProperties.isEmpty()) {
+      logger.debug("Using provided host-ip: " + hostIpFromProperties + " from properties");
+      sb.append(" --host-ip=" + hostIpFromProperties + " ");
+    } else if (hostIp != null & !hostIp.isEmpty()) {
+      logger.debug("Using the parametr host-ip: " + hostIp);
+      sb.append(" --host-ip=" + hostIp + " ");
+    }
+    return sb.toString();
+  }
+
   private boolean startTrackerProcess() {
     try {
-      String trackerExecString = this.addTrackerProperties("python " + tracker_py +
-          " --log-level=DEBUG --num-workers=" + String.valueOf(numWorkers));
-
-      trackerProcess.set(Runtime.getRuntime().exec(trackerExecString));
+      String cmd = getRabitTrackerCommand();
+      trackerProcess.set(Runtime.getRuntime().exec(cmd));
       loadEnvs(trackerProcess.get().getInputStream());
       return true;
     } catch (IOException ioe) {
@@ -140,18 +171,6 @@ public class RabitTracker implements IRabitTracker {
     }
   }
 
-  private String addTrackerProperties(String trackerExecString) {
-    StringBuilder sb = new StringBuilder(trackerExecString);
-    String hostIp = trackerProperties.getHostIp();
-
-    if(hostIp != null && !hostIp.isEmpty()){
-      logger.debug("Using provided host-ip: " + hostIp);
-      sb.append(" --host-ip=").append(hostIp);
-    }
-
-    return sb.toString();
-  }
-
   public void stop() {
     if (trackerProcess.get() != null) {
       trackerProcess.get().destroy();

src/learner.cc

@@ -419,6 +419,7 @@ class LearnerConfiguration : public Learner {
       obj_.reset(ObjFunction::Create(tparam_.objective, &generic_parameters_));
     }
     obj_->LoadConfig(objective_fn);
+    learner_model_param_.task = obj_->Task();
 
     tparam_.booster = get<String>(gradient_booster["name"]);
     if (!gbm_) {