Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/19519#discussion_r146734568
--- Diff:
core/src/main/scala/org/apache/spark/deploy/SparkApplication.scala ---
@@ -0,0 +1,55 @@
+/*
+ * 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.deploy
+
+import java.lang.reflect.Modifier
+
+import org.apache.spark.SparkConf
+
+/**
+ * Entry point for a Spark application. Implementations must provide a
no-argument constructor.
+ */
+private[spark] trait SparkApplication {
+
+ def start(args: Array[String], conf: SparkConf): Unit
+
+}
+
+/**
+ * Implementation of SparkApplication that wraps a standard Java class
with a "main" method.
+ *
+ * Configuration is propagated to the application via system properties,
so running multiple
+ * of these in the same JVM may lead to undefined behavior due to
configuration leaks.
+ */
+private[deploy] class JavaMainApplication(klass: Class[_]) extends
SparkApplication {
+
+ override def start(args: Array[String], conf: SparkConf): Unit = {
+ val mainMethod = klass.getMethod("main", new Array[String](0).getClass)
+ if (!Modifier.isStatic(mainMethod.getModifiers)) {
+ throw new IllegalStateException("The main method in the given main
class must be static")
+ }
+
+ val sysProps = conf.getAll.toMap
+ sysProps.foreach { case (k, v) =>
+ sys.props(k) = v
+ }
+
+ mainMethod.invoke(null, args)
+ }
--- End diff --
Yes, and there's not much we can do in that case. The main use case will be
to make cluster mode applications do the right thing first, and warn about
starting in-process client mode applications through the launcher API.
If you have a better solution I'm all ears.
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