diff --git a/R/pkg/R/mllib_tree.R b/R/pkg/R/mllib_tree.R
index 40a806c41bad0..82279be6fbe77 100644
--- a/R/pkg/R/mllib_tree.R
+++ b/R/pkg/R/mllib_tree.R
@@ -52,12 +52,14 @@ summary.treeEnsemble <- function(model) {
   numFeatures <- callJMethod(jobj, "numFeatures")
   features <-  callJMethod(jobj, "features")
   featureImportances <- callJMethod(callJMethod(jobj, "featureImportances"), "toString")
+  maxDepth <- callJMethod(jobj, "maxDepth")
   numTrees <- callJMethod(jobj, "numTrees")
   treeWeights <- callJMethod(jobj, "treeWeights")
   list(formula = formula,
        numFeatures = numFeatures,
        features = features,
        featureImportances = featureImportances,
+       maxDepth = maxDepth,
        numTrees = numTrees,
        treeWeights = treeWeights,
        jobj = jobj)
@@ -70,6 +72,7 @@ print.summary.treeEnsemble <- function(x) {
   cat("\nNumber of features: ", x$numFeatures)
   cat("\nFeatures: ", unlist(x$features))
   cat("\nFeature importances: ", x$featureImportances)
+  cat("\nMax Depth: ", x$maxDepth)
   cat("\nNumber of trees: ", x$numTrees)
   cat("\nTree weights: ", unlist(x$treeWeights))
 
@@ -197,8 +200,8 @@ setMethod("spark.gbt", signature(data = "SparkDataFrame", formula = "formula"),
 #' @return \code{summary} returns summary information of the fitted model, which is a list.
 #'         The list of components includes \code{formula} (formula),
 #'         \code{numFeatures} (number of features), \code{features} (list of features),
-#'         \code{featureImportances} (feature importances), \code{numTrees} (number of trees),
-#'         and \code{treeWeights} (tree weights).
+#'         \code{featureImportances} (feature importances), \code{maxDepth} (max depth of trees),
+#'         \code{numTrees} (number of trees), and \code{treeWeights} (tree weights).
 #' @rdname spark.gbt
 #' @aliases summary,GBTRegressionModel-method
 #' @export
@@ -403,8 +406,8 @@ setMethod("spark.randomForest", signature(data = "SparkDataFrame", formula = "fo
 #' @return \code{summary} returns summary information of the fitted model, which is a list.
 #'         The list of components includes \code{formula} (formula),
 #'         \code{numFeatures} (number of features), \code{features} (list of features),
-#'         \code{featureImportances} (feature importances), \code{numTrees} (number of trees),
-#'         and \code{treeWeights} (tree weights).
+#'         \code{featureImportances} (feature importances), \code{maxDepth} (max depth of trees),
+#'         \code{numTrees} (number of trees), and \code{treeWeights} (tree weights).
 #' @rdname spark.randomForest
 #' @aliases summary,RandomForestRegressionModel-method
 #' @export
diff --git a/R/pkg/inst/tests/testthat/test_mllib_tree.R b/R/pkg/inst/tests/testthat/test_mllib_tree.R
index e6fda251ebea2..e0802a9b02d13 100644
--- a/R/pkg/inst/tests/testthat/test_mllib_tree.R
+++ b/R/pkg/inst/tests/testthat/test_mllib_tree.R
@@ -39,6 +39,7 @@ test_that("spark.gbt", {
                tolerance = 1e-4)
   stats <- summary(model)
   expect_equal(stats$numTrees, 20)
+  expect_equal(stats$maxDepth, 5)
   expect_equal(stats$formula, "Employed ~ .")
   expect_equal(stats$numFeatures, 6)
   expect_equal(length(stats$treeWeights), 20)
@@ -53,6 +54,7 @@ test_that("spark.gbt", {
   expect_equal(stats$numFeatures, stats2$numFeatures)
   expect_equal(stats$features, stats2$features)
   expect_equal(stats$featureImportances, stats2$featureImportances)
+  expect_equal(stats$maxDepth, stats2$maxDepth)
   expect_equal(stats$numTrees, stats2$numTrees)
   expect_equal(stats$treeWeights, stats2$treeWeights)
 
@@ -66,6 +68,7 @@ test_that("spark.gbt", {
   stats <- summary(model)
   expect_equal(stats$numFeatures, 2)
   expect_equal(stats$numTrees, 20)
+  expect_equal(stats$maxDepth, 5)
   expect_error(capture.output(stats), NA)
   expect_true(length(capture.output(stats)) > 6)
   predictions <- collect(predict(model, data))$prediction
@@ -93,6 +96,7 @@ test_that("spark.gbt", {
   expect_equal(iris2$NumericSpecies, as.double(collect(predict(m, df))$prediction))
   expect_equal(s$numFeatures, 5)
   expect_equal(s$numTrees, 20)
+  expect_equal(stats$maxDepth, 5)
 
   # spark.gbt classification can work on libsvm data
   data <- read.df(absoluteSparkPath("data/mllib/sample_binary_classification_data.txt"),
@@ -116,6 +120,7 @@ test_that("spark.randomForest", {
 
   stats <- summary(model)
   expect_equal(stats$numTrees, 1)
+  expect_equal(stats$maxDepth, 5)
   expect_error(capture.output(stats), NA)
   expect_true(length(capture.output(stats)) > 6)
 
@@ -129,6 +134,7 @@ test_that("spark.randomForest", {
                tolerance = 1e-4)
   stats <- summary(model)
   expect_equal(stats$numTrees, 20)
+  expect_equal(stats$maxDepth, 5)
 
   modelPath <- tempfile(pattern = "spark-randomForestRegression", fileext = ".tmp")
   write.ml(model, modelPath)
@@ -141,6 +147,7 @@ test_that("spark.randomForest", {
   expect_equal(stats$features, stats2$features)
   expect_equal(stats$featureImportances, stats2$featureImportances)
   expect_equal(stats$numTrees, stats2$numTrees)
+  expect_equal(stats$maxDepth, stats2$maxDepth)
   expect_equal(stats$treeWeights, stats2$treeWeights)
 
   unlink(modelPath)
@@ -153,6 +160,7 @@ test_that("spark.randomForest", {
   stats <- summary(model)
   expect_equal(stats$numFeatures, 2)
   expect_equal(stats$numTrees, 20)
+  expect_equal(stats$maxDepth, 5)
   expect_error(capture.output(stats), NA)
   expect_true(length(capture.output(stats)) > 6)
   # Test string prediction values
@@ -187,6 +195,8 @@ test_that("spark.randomForest", {
   stats <- summary(model)
   expect_equal(stats$numFeatures, 2)
   expect_equal(stats$numTrees, 20)
+  expect_equal(stats$maxDepth, 5)
+
   # Test numeric prediction values
   predictions <- collect(predict(model, data))$prediction
   expect_equal(length(grep("1.0", predictions)), 50)
diff --git a/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala b/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
index e48817ebbafdd..00b9d1af373db 100755
--- a/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
+++ b/core/src/main/scala/org/apache/spark/deploy/worker/Worker.scala
@@ -62,8 +62,8 @@ private[deploy] class Worker(
   private val forwordMessageScheduler =
     ThreadUtils.newDaemonSingleThreadScheduledExecutor("worker-forward-message-scheduler")
 
-  // A separated thread to clean up the workDir. Used to provide the implicit parameter of `Future`
-  // methods.
+  // A separated thread to clean up the workDir and the directories of finished applications.
+  // Used to provide the implicit parameter of `Future` methods.
   private val cleanupThreadExecutor = ExecutionContext.fromExecutorService(
     ThreadUtils.newDaemonSingleThreadExecutor("worker-cleanup-thread"))
 
@@ -578,10 +578,15 @@ private[deploy] class Worker(
     if (shouldCleanup) {
       finishedApps -= id
       appDirectories.remove(id).foreach { dirList =>
-        logInfo(s"Cleaning up local directories for application $id")
-        dirList.foreach { dir =>
-          Utils.deleteRecursively(new File(dir))
-        }
+        concurrent.Future {
+          logInfo(s"Cleaning up local directories for application $id")
+          dirList.foreach { dir =>
+            Utils.deleteRecursively(new File(dir))
+          }
+        }(cleanupThreadExecutor).onFailure {
+          case e: Throwable =>
+            logError(s"Clean up app dir $dirList failed: ${e.getMessage}", e)
+        }(cleanupThreadExecutor)
       }
       shuffleService.applicationRemoved(id)
     }
diff --git a/docs/structured-streaming-programming-guide.md b/docs/structured-streaming-programming-guide.md
index 995ac77a4fb3b..798847237866b 100644
--- a/docs/structured-streaming-programming-guide.md
+++ b/docs/structured-streaming-programming-guide.md
@@ -539,7 +539,7 @@ spark = SparkSession. ...
 
 # Read text from socket 
 socketDF = spark \
-    .readStream() \
+    .readStream \
     .format("socket") \
     .option("host", "localhost") \
     .option("port", 9999) \
@@ -552,7 +552,7 @@ socketDF.printSchema()
 # Read all the csv files written atomically in a directory
 userSchema = StructType().add("name", "string").add("age", "integer")
 csvDF = spark \
-    .readStream() \
+    .readStream \
     .option("sep", ";") \
     .schema(userSchema) \
     .csv("/path/to/directory")  # Equivalent to format("csv").load("/path/to/directory")
@@ -971,7 +971,7 @@ Here is the compatibility matrix.
         <br/><br/>
         Update mode uses watermark to drop old aggregation state.
         <br/><br/>
-        Complete mode does drop not old aggregation state since by definition this mode
+        Complete mode does not drop old aggregation state since by definition this mode
         preserves all data in the Result Table.
     </td>    
   </tr>
@@ -1201,13 +1201,13 @@ noAggDF = deviceDataDf.select("device").where("signal > 10")
 
 # Print new data to console
 noAggDF \
-    .writeStream() \
+    .writeStream \
     .format("console") \
     .start()
 
 # Write new data to Parquet files
 noAggDF \
-    .writeStream() \
+    .writeStream \
     .format("parquet") \
     .option("checkpointLocation", "path/to/checkpoint/dir") \
     .option("path", "path/to/destination/dir") \
@@ -1218,14 +1218,14 @@ aggDF = df.groupBy("device").count()
 
 # Print updated aggregations to console
 aggDF \
-    .writeStream() \
+    .writeStream \
     .outputMode("complete") \
     .format("console") \
     .start()
 
 # Have all the aggregates in an in memory table. The query name will be the table name
 aggDF \
-    .writeStream() \
+    .writeStream \
     .queryName("aggregates") \
     .outputMode("complete") \
     .format("memory") \
@@ -1313,7 +1313,7 @@ query.lastProgress();    // the most recent progress update of this streaming qu
 <div data-lang="python"  markdown="1">
 
 {% highlight python %}
-query = df.writeStream().format("console").start()   # get the query object
+query = df.writeStream.format("console").start()   # get the query object
 
 query.id()          # get the unique identifier of the running query that persists across restarts from checkpoint data
 
@@ -1658,7 +1658,7 @@ aggDF
 
 {% highlight python %}
 aggDF \
-    .writeStream() \
+    .writeStream \
     .outputMode("complete") \
     .option("checkpointLocation", "path/to/HDFS/dir") \
     .format("memory") \
diff --git a/mllib/src/main/scala/org/apache/spark/ml/r/GBTClassificationWrapper.scala b/mllib/src/main/scala/org/apache/spark/ml/r/GBTClassificationWrapper.scala
index aacb41ee2659b..c07eadb30a4d2 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/r/GBTClassificationWrapper.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/r/GBTClassificationWrapper.scala
@@ -44,6 +44,7 @@ private[r] class GBTClassifierWrapper private (
   lazy val featureImportances: Vector = gbtcModel.featureImportances
   lazy val numTrees: Int = gbtcModel.getNumTrees
   lazy val treeWeights: Array[Double] = gbtcModel.treeWeights
+  lazy val maxDepth: Int = gbtcModel.getMaxDepth
 
   def summary: String = gbtcModel.toDebugString
 
diff --git a/mllib/src/main/scala/org/apache/spark/ml/r/GBTRegressionWrapper.scala b/mllib/src/main/scala/org/apache/spark/ml/r/GBTRegressionWrapper.scala
index 585077588eb9b..b568d7859221f 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/r/GBTRegressionWrapper.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/r/GBTRegressionWrapper.scala
@@ -42,6 +42,7 @@ private[r] class GBTRegressorWrapper private (
   lazy val featureImportances: Vector = gbtrModel.featureImportances
   lazy val numTrees: Int = gbtrModel.getNumTrees
   lazy val treeWeights: Array[Double] = gbtrModel.treeWeights
+  lazy val maxDepth: Int = gbtrModel.getMaxDepth
 
   def summary: String = gbtrModel.toDebugString
 
diff --git a/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestClassificationWrapper.scala b/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestClassificationWrapper.scala
index 366f375b58582..8a83d4e980f7b 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestClassificationWrapper.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestClassificationWrapper.scala
@@ -44,6 +44,7 @@ private[r] class RandomForestClassifierWrapper private (
   lazy val featureImportances: Vector = rfcModel.featureImportances
   lazy val numTrees: Int = rfcModel.getNumTrees
   lazy val treeWeights: Array[Double] = rfcModel.treeWeights
+  lazy val maxDepth: Int = rfcModel.getMaxDepth
 
   def summary: String = rfcModel.toDebugString
 
diff --git a/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestRegressionWrapper.scala b/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestRegressionWrapper.scala
index 4b9a3a731da9b..038bd79c7022b 100644
--- a/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestRegressionWrapper.scala
+++ b/mllib/src/main/scala/org/apache/spark/ml/r/RandomForestRegressionWrapper.scala
@@ -42,6 +42,7 @@ private[r] class RandomForestRegressorWrapper private (
   lazy val featureImportances: Vector = rfrModel.featureImportances
   lazy val numTrees: Int = rfrModel.getNumTrees
   lazy val treeWeights: Array[Double] = rfrModel.treeWeights
+  lazy val maxDepth: Int = rfrModel.getMaxDepth
 
   def summary: String = rfrModel.toDebugString
 
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala
index 411a15ffceb6a..a9e64c640042a 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala
@@ -97,7 +97,7 @@ class FileStreamSource(
   }
   seenFiles.purge()
 
-  logInfo(s"maxFilesPerBatch = $maxFilesPerBatch, maxFileAge = $maxFileAgeMs")
+  logInfo(s"maxFilesPerBatch = $maxFilesPerBatch, maxFileAgeMs = $maxFileAgeMs")
 
   /**
    * Returns the maximum offset that can be retrieved from the source.
diff --git a/streaming/src/main/scala/org/apache/spark/streaming/dstream/FileInputDStream.scala b/streaming/src/main/scala/org/apache/spark/streaming/dstream/FileInputDStream.scala
index ed9305875cb77..905b1c52afa69 100644
--- a/streaming/src/main/scala/org/apache/spark/streaming/dstream/FileInputDStream.scala
+++ b/streaming/src/main/scala/org/apache/spark/streaming/dstream/FileInputDStream.scala
@@ -230,7 +230,7 @@ class FileInputDStream[K, V, F <: NewInputFormat[K, V]](
    * - It must pass the user-provided file filter.
    * - It must be newer than the ignore threshold. It is assumed that files older than the ignore
    *   threshold have already been considered or are existing files before start
-   *   (when newFileOnly = true).
+   *   (when newFilesOnly = true).
    * - It must not be present in the recently selected files that this class remembers.
    * - It must not be newer than the time of the batch (i.e. `currentTime` for which this
    *   file is being tested. This can occur if the driver was recovered, and the missing batches