Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/3916#discussion_r22906384
--- Diff: launcher/src/main/java/org/apache/spark/launcher/Main.java ---
@@ -0,0 +1,106 @@
+/*
+ * 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.launcher;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Command line interface for the Spark launcher. Used internally by Spark
scripts.
+ */
+public class Main extends LauncherCommon {
+
+ /**
+ * Usage: Main [class] [class args]
+ * <p/>
+ * This CLI works in two different modes:
+ * <ul>
+ * <li>"spark-submit": if <i>class</i> is
"org.apache.spark.deploy.SparkSubmit", the
+ * {@link SparkLauncher} class is used to launch a Spark
application.</li>
+ * <li>"spark-class": if another class is provided, an internal Spark
class is run.</li>
+ * </ul>
+ *
+ * The ultimate command will not be run in the same process. Instead,
the command to be executed
+ * will be printed to stdout. On Unix systems, this will be one argument
per line. On Windows
+ * systems, this will be a single line containing the command to be
executed.
+ */
+ public static void main(String[] argsArray) throws Exception {
+ checkArgument(argsArray.length > 0, "Not enough arguments: missing
class name.");
+
+ List<String> args = new ArrayList<String>(Arrays.asList(argsArray));
+ String className = args.remove(0);
+
+ boolean printLaunchCommand = false;
+ AbstractLauncher<?> launcher;
+ try {
+ if (className.equals("org.apache.spark.deploy.SparkSubmit")) {
+ launcher = new SparkSubmitCliLauncher(args);
+ printLaunchCommand =
!isEmpty(System.getenv("SPARK_PRINT_LAUNCH_COMMAND"));
+ } else if (className.equals("pyspark")) {
+ launcher = new PySparkLauncher(args);
+ } else {
+ launcher = new SparkClassLauncher(className, args);
+ printLaunchCommand =
!isEmpty(System.getenv("SPARK_PRINT_LAUNCH_COMMAND"));
+ }
+ } catch (IllegalArgumentException e) {
+ launcher = new UsageLauncher();
+ }
+
+ List<String> cmd = launcher.buildLauncherCommand();
+ if (printLaunchCommand) {
+ System.err.println("Spark Command: " + join(" ", cmd));
+ System.err.println("========================================");
+ }
+
+ for (String c : cmd) {
+ System.out.println(c);
+ }
+ }
+
+ /**
+ * Internal launcher used when command line parsing fails. This will
behave differently depending
+ * on the platform:
+ *
+ * - On Unix-like systems, it will print a call to the "usage" function
with argument "1". The
+ * function is expected to print the command's usage and exit with the
provided exit code.
+ * The script should use "export -f usage" after declaring a function
called "usage", so that
+ * the function is available to downstream scripts.
+ *
+ * - On Windows it will set the variable "SPARK_LAUNCHER_USAGE_ERROR" to
"1". The batch script
+ * should check for this variable and print its usage, since batch
scripts don't really support
+ * the "export -f" functionality used in bash.
+ */
+ private static class UsageLauncher extends
AbstractLauncher<UsageLauncher> {
+
+ @Override
+ protected List<String> buildLauncherCommand() {
+ if (isWindows()) {
+ return Arrays.asList("set SPARK_LAUNCHER_USAGE_ERROR=1");
--- End diff --
`spark-shell2.cmd` is the only script that did this before, so I'm not
making anything worse.
Pushing this to `spark-class2.cmd` is not as trivial because you'll want to
customize the message (e.g. to print "spark-submit" instead of "spark-class" in
the usage string), and that's moving beyond the scope of this change (which is
already pretty large as is).
There may be a better way to handle usage messages in general, but I don't
want to solve that problem here. I'm just maintaining the current functionality.
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