co.cask.cdap.internal.app.runtime.spark.SparkClassLoader.java Source code

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Here is the source code for co.cask.cdap.internal.app.runtime.spark.SparkClassLoader.java

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/*
 * Copyright  2015 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.internal.app.runtime.spark;

import co.cask.cdap.common.lang.ClassLoaders;
import co.cask.cdap.common.lang.CombineClassLoader;
import co.cask.cdap.common.lang.ProgramClassLoader;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import org.apache.spark.executor.ExecutorURLClassLoader;
import org.apache.spark.util.MutableURLClassLoader;

/**
 * ClassLoader being used in Spark execution context. It is used in driver as well as in executor node.
 * It load classes from {@link ProgramClassLoader} followed by CDAP system ClassLoader.
 */
public class SparkClassLoader extends CombineClassLoader {

    private final ClassLoader programClassLoader;
    private final ExecutionSparkContext context;

    /**
     * Finds the SparkClassLoader from the context ClassLoader hierarchy.
     *
     * @return the SparkClassLoader found
     * @throws IllegalStateException if no SparkClassLoader was found
     */
    public static SparkClassLoader findFromContext() {
        ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();
        SparkClassLoader sparkClassLoader = ClassLoaders.find(contextClassLoader, SparkClassLoader.class);
        // Should found the Spark ClassLoader
        Preconditions.checkState(sparkClassLoader != null,
                "Cannot find SparkClassLoader from context ClassLoader %s", contextClassLoader);
        return sparkClassLoader;
    }

    /**
     * Creates a new SparkClassLoader from the execution context. It should only be called from
     * {@link ExecutorURLClassLoader} or {@link MutableURLClassLoader} when invoked in the executor container only.
     */
    public static SparkClassLoader create() {
        ExecutionSparkContext sparkContext = SparkContextProvider.getSparkContext();
        return new SparkClassLoader(sparkContext);
    }

    /**
     * Creates a new SparkClassLoader with the given {@link ExecutionSparkContext}.
     */
    public SparkClassLoader(ExecutionSparkContext context) {
        super(null, ImmutableList.of(context.getProgramClassLoader(), SparkClassLoader.class.getClassLoader()));
        this.programClassLoader = context.getProgramClassLoader();
        this.context = context;
    }

    /**
     * Returns the program ClassLoader.
     */
    public ClassLoader getProgramClassLoader() {
        return programClassLoader;
    }

    /**
     * Returns the {@link ExecutionSparkContext}.
     */
    public ExecutionSparkContext getContext() {
        return context;
    }
}