[SPARK-24243][CORE] Expose exceptions from InProcessAppHandle

Adds a new method to `SparkAppHandle` called `getError` which returns
the exception (if present) that caused the underlying Spark app to
fail.

New tests added to `SparkLauncherSuite` for the new method.

Author: Sahil Takiar

core/src/test/java/org/apache/spark/launcher/SparkLauncherSuite.java

@@ -41,6 +41,8 @@
 public class SparkLauncherSuite extends BaseSuite {
 
   private static final NamedThreadFactory TF = new NamedThreadFactory("SparkLauncherSuite-%d");
+  private static final String EXCEPTION_MESSAGE = "dummy-exception";
+  private static final RuntimeException DUMMY_EXCEPTION = new RuntimeException(EXCEPTION_MESSAGE);
 
   private final SparkLauncher launcher = new SparkLauncher();
 
@@ -130,17 +132,8 @@ public void testInProcessLauncher() throws Exception {
     try {
       inProcessLauncherTestImpl();
     } finally {
-      Properties p = new Properties();
-      for (Map.Entry<Object, Object> e : properties.entrySet()) {
-        p.put(e.getKey(), e.getValue());
-      }
-      System.setProperties(p);
-      // Here DAGScheduler is stopped, while SparkContext.clearActiveContext may not be called yet.
-      // Wait for a reasonable amount of time to avoid creating two active SparkContext in JVM.
-      // See SPARK-23019 and SparkContext.stop() for details.
-      eventually(Duration.ofSeconds(5), Duration.ofMillis(10), () -> {
-        assertTrue("SparkContext is still alive.", SparkContext$.MODULE$.getActive().isEmpty());
-      });
+      restoreSystemProperties(properties);
+      waitForSparkContextShutdown();
     }
   }
 
@@ -227,6 +220,82 @@ public void testInProcessLauncherDoesNotKillJvm() throws Exception {
     assertEquals(SparkAppHandle.State.LOST, handle.getState());
   }
 
+  @Test
+  public void testInProcessLauncherGetError() throws Exception {
+    // Because this test runs SparkLauncher in process and in client mode, it pollutes the system
+    // properties, and that can cause test failures down the test pipeline. So restore the original
+    // system properties after this test runs.
+    Map<Object, Object> properties = new HashMap<>(System.getProperties());
+
+    SparkAppHandle handle = null;
+    try {
+      handle = new InProcessLauncher()
+        .setMaster("local")
+        .setAppResource(SparkLauncher.NO_RESOURCE)
+        .setMainClass(ErrorInProcessTestApp.class.getName())
+        .addAppArgs("hello")
+        .startApplication();
+
+      final SparkAppHandle _handle = handle;
+      eventually(Duration.ofSeconds(60), Duration.ofMillis(1000), () -> {
+        assertEquals(SparkAppHandle.State.FAILED, _handle.getState());
+      });
+
+      assertNotNull(handle.getError());
+      assertTrue(handle.getError().isPresent());
+      assertSame(handle.getError().get(), DUMMY_EXCEPTION);
+    } finally {
+      if (handle != null) {
+        handle.kill();
+      }
+      restoreSystemProperties(properties);
+      waitForSparkContextShutdown();
+    }
+  }
+
+  @Test
+  public void testSparkLauncherGetError() throws Exception {
+    SparkAppHandle handle = null;
+    try {
+      handle = new SparkLauncher()
+        .setMaster("local")
+        .setAppResource(SparkLauncher.NO_RESOURCE)
+        .setMainClass(ErrorInProcessTestApp.class.getName())
+        .addAppArgs("hello")
+        .startApplication();
+
+      final SparkAppHandle _handle = handle;
+      eventually(Duration.ofSeconds(60), Duration.ofMillis(1000), () -> {
+        assertEquals(SparkAppHandle.State.FAILED, _handle.getState());
+      });
+
+      assertNotNull(handle.getError());
+      assertTrue(handle.getError().isPresent());
+      assertTrue(handle.getError().get().getMessage().contains(EXCEPTION_MESSAGE));
+    } finally {
+      if (handle != null) {
+        handle.kill();
+      }
+    }
+  }
+
+  private void restoreSystemProperties(Map<Object, Object> properties) {
+    Properties p = new Properties();
+    for (Map.Entry<Object, Object> e : properties.entrySet()) {
+      p.put(e.getKey(), e.getValue());
+    }
+    System.setProperties(p);
+  }
+
+  private void waitForSparkContextShutdown() throws Exception {
+    // Here DAGScheduler is stopped, while SparkContext.clearActiveContext may not be called yet.
+    // Wait for a reasonable amount of time to avoid creating two active SparkContext in JVM.
+    // See SPARK-23019 and SparkContext.stop() for details.
+    eventually(Duration.ofSeconds(5), Duration.ofMillis(10), () -> {
+      assertTrue("SparkContext is still alive.", SparkContext$.MODULE$.getActive().isEmpty());
+    });
+  }
+
   public static class SparkLauncherTestApp {
 
     public static void main(String[] args) throws Exception {
@@ -264,4 +333,15 @@ public static void main(String[] args) throws Exception {
 
   }
 
+  /**
+   * Similar to {@link InProcessTestApp} except it throws an exception
+   */
+  public static class ErrorInProcessTestApp {
+
+    public static void main(String[] args) {
+      assertNotEquals(0, args.length);
+      assertEquals(args[0], "hello");
+      throw DUMMY_EXCEPTION;
+    }
+  }
 }

launcher/src/main/java/org/apache/spark/launcher/ChildProcAppHandle.java

@@ -18,6 +18,7 @@
 package org.apache.spark.launcher;
 
 import java.io.InputStream;
+import java.util.Optional;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -29,7 +30,7 @@ class ChildProcAppHandle extends AbstractAppHandle {
   private static final Logger LOG = Logger.getLogger(ChildProcAppHandle.class.getName());
 
   private volatile Process childProc;
-  private OutputRedirector redirector;
+  private volatile OutputRedirector redirector;
 
   ChildProcAppHandle(LauncherServer server) {
     super(server);
@@ -46,6 +47,25 @@ public synchronized void disconnect() {
     }
   }
 
+  /**
+   * Parses the logs of {@code spark-submit} and returns the last exception thrown.
+   *
+   * <p>
+   *   Since {@link SparkLauncher} runs {@code spark-submit} in a sub-process, its difficult to
+   *   accurately retrieve the full {@link Throwable} from the {@code spark-submit} process.
+   *   This method parses the logs of the sub-process and provides a best-effort attempt at
+   *   returning the last exception thrown by the {@code spark-submit} process. Only the exception
+   *   message is parsed, the associated stacktrace is meaningless.
+   * </p>
+   *
+   * @return an {@link Optional} containing a {@link RuntimeException} with the parsed
+   * exception, otherwise returns a {@link Optional#EMPTY}
+   */
+  @Override
+  public Optional<Throwable> getError() {
+    return redirector != null ? Optional.ofNullable(redirector.getError()) : Optional.empty();
+  }
+
   @Override
   public synchronized void kill() {
     if (!isDisposed()) {

launcher/src/main/java/org/apache/spark/launcher/InProcessAppHandle.java

@@ -17,7 +17,9 @@
 
 package org.apache.spark.launcher;
 
+import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -31,6 +33,8 @@ class InProcessAppHandle extends AbstractAppHandle {
   // Avoid really long thread names.
   private static final int MAX_APP_NAME_LEN = 16;
 
+  private volatile Throwable error;
+
   private Thread app;
 
   InProcessAppHandle(LauncherServer server) {
@@ -51,6 +55,11 @@ public synchronized void kill() {
     }
   }
 
+  @Override
+  public Optional<Throwable> getError() {
+    return Optional.ofNullable(error);
+  }
+
   synchronized void start(String appName, Method main, String[] args) {
     CommandBuilderUtils.checkState(app == null, "Handle already started.");
 
@@ -62,7 +71,11 @@ synchronized void start(String appName, Method main, String[] args) {
       try {
         main.invoke(null, (Object) args);
       } catch (Throwable t) {
+        if (t instanceof InvocationTargetException) {
+          t = t.getCause();
+        }
         LOG.log(Level.WARNING, "Application failed with exception.", t);
+        error = t;
         setState(State.FAILED);
       }
 

launcher/src/main/java/org/apache/spark/launcher/OutputRedirector.java

@@ -37,6 +37,7 @@ class OutputRedirector {
   private final ChildProcAppHandle callback;
 
   private volatile boolean active;
+  private volatile Throwable error;
 
   OutputRedirector(InputStream in, String loggerName, ThreadFactory tf) {
     this(in, loggerName, tf, null);
@@ -61,6 +62,10 @@ private void redirect() {
       while ((line = reader.readLine()) != null) {
         if (active) {
           sink.info(line.replaceFirst("\\s*$", ""));
+          if (error == null && containsIgnoreCase(line, "Error") || containsIgnoreCase(line,
+                  "Exception")) {
+            error = new RuntimeException(line);
+          }
         }
       }
     } catch (IOException e) {
@@ -85,4 +90,24 @@ boolean isAlive() {
     return thread.isAlive();
   }
 
+  Throwable getError() {
+    return error;
+  }
+
+  /**
+   * Copied from Apache Commons Lang {@code StringUtils#containsIgnoreCase(String, String)}
+   */
+  private static boolean containsIgnoreCase(String str, String searchStr) {
+    if (str == null || searchStr == null) {
+      return false;
+    }
+    int len = searchStr.length();
+    int max = str.length() - len;
+    for (int i = 0; i <= max; i++) {
+      if (str.regionMatches(true, i, searchStr, 0, len)) {
+        return true;
+      }
+    }
+    return false;
+  }
 }

launcher/src/main/java/org/apache/spark/launcher/SparkAppHandle.java

@@ -17,6 +17,8 @@
 
 package org.apache.spark.launcher;
 
+import java.util.Optional;
+
 /**
  * A handle to a running Spark application.
  * <p>
@@ -100,6 +102,12 @@ public boolean isFinal() {
    */
   void disconnect();
 
+  /**
+   * If the application failed due to an error, return the underlying error. If the app
+   * succeeded, this method returns an empty {@link Optional}.
+   */
+  Optional<Throwable> getError();
+
   /**
    * Listener for updates to a handle's state. The callbacks do not receive information about
    * what exactly has changed, just that an update has occurred.

project/MimaExcludes.scala

@@ -106,7 +106,10 @@ object MimaExcludes {
     ProblemFilters.exclude[InheritedNewAbstractMethodProblem]("org.apache.spark.ml.param.shared.HasValidationIndicatorCol.validationIndicatorCol"),
 
     // [SPARK-23042] Use OneHotEncoderModel to encode labels in MultilayerPerceptronClassifier
-    ProblemFilters.exclude[MissingClassProblem]("org.apache.spark.ml.classification.LabelConverter")
+    ProblemFilters.exclude[MissingClassProblem]("org.apache.spark.ml.classification.LabelConverter"),
+
+    // [SPARK-24243][CORE] Expose exceptions from InProcessAppHandle
+    ProblemFilters.exclude[ReversedMissingMethodProblem]("org.apache.spark.launcher.SparkAppHandle.getError")
   )
 
   // Exclude rules for 2.3.x