kevinrr888 commented on code in PR #28: URL: https://github.com/apache/accumulo-classloaders/pull/28#discussion_r2456307444
########## modules/classloaders/hdfs-class-loader/src/main/java/org/apache/accumulo/classloader/hdfs/HDFSContextClassLoaderFactory.java: ########## @@ -0,0 +1,186 @@ +/* + * 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 + * + * https://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.accumulo.classloader.vfs; + +import java.io.IOException; +import java.net.URL; +import java.net.URLClassLoader; +import java.nio.file.Files; +import java.util.List; + +import org.apache.accumulo.core.spi.common.ContextClassLoaderFactory; +import org.apache.hadoop.fs.FileSystem; +import org.apache.hadoop.fs.Path; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import com.google.common.annotations.VisibleForTesting; +import com.google.common.cache.Cache; +import com.google.common.cache.CacheBuilder; +import com.google.gson.Gson; + +/** + * A {@link ContextClassLoaderFactory} implementation which uses a {@link URLClassLoader} per + * defined context. To use this class, need to set the Accumulo configuration property + * <b>general.context.class.loader.factory</b> to the fully qualified name of this class. <br> + * <br> + * Configuration of this class is done by having a base directory in HDFS which stores context + * directories (e.g., hdfs://test:1234/contexts could be the base directory) and where the children + * are specific contexts (e.g., contextA, contextB). To set the HDFS file system for this class, use + * {@link HDFSContextClassLoaderFactory#setHDFSFileSystem(FileSystem)}. The "contexts" directory + * should not contain any other files or directories. Each context directory should contain a + * manifest file <b>manifest.json</b> and JAR files. The manifest file defines the context name and + * the JAR info for what JARs should be in the {@link URLClassLoader} for that context. For example: + * + * <pre> + * { + * "context": "contextA", + * "jars": [ + * { + * "name": "Iterators.jar", + * "checksum": "f2ca1bb6c7e907d06dafe4687e579fce76b37e4e93b7605022da52e6ccc26fd2" + * }, + * { + * "name": "IteratorsV2.jar", + * "checksum": "934ee77f70dc82403618c154aa63af6f4ebbe3ac1eaf22df21e7e64f0fb6643d" + * } + * ] + * } + * </pre> + * + * Two system properties need to be set to use this class: <br> + * <b>hdfs.contexts.class.loader.base.dir</b> <br> + * This defines where the context directories exist within HDFS (e.g., hdfs://test:1234/contexts in + * our example) <br> + * <b>local.contexts.class.loader.download.dir</b> <br> + * This defines where the context info will be locally downloaded to. This includes the manifest + * file(s) and JAR(s). For example, if set to "/path/to/contexts" and + * {@link HDFSContextClassLoaderFactory#getClassLoader(String)} is called with the argument + * "contextA", will create the local directory "/path/to/contexts/contextA" (note that all parent + * directories will be created if needed), will download the manifest file from HDFS to the contextA + * directory, and will download the JARs Iterators.jar and IteratorsV2.jar from HDFS to the contextA + * directory. The {@link URLClassLoader} will be constructed from these local JARs, will be + * associated with "contextA", and will be cached. + */ +public class HDFSContextClassLoaderFactory implements ContextClassLoaderFactory { + private static final Logger LOG = LoggerFactory.getLogger(HDFSContextClassLoaderFactory.class); + public static final String MANIFEST_FILE_NAME = "manifest.json"; + public static final String HDFS_CONTEXTS_BASE_DIR = "hdfs.contexts.class.loader.base.dir"; + public static final String LOCAL_CONTEXTS_DOWNLOAD_DIR = + "local.contexts.class.loader.download.dir"; + // Cache the class loaders for re-use + // WeakReferences are used so that the class loaders can be cleaned up when no longer needed + // Classes that are loaded contain a reference to the class loader used to load them + // so the class loader will be garbage collected when no more classes are loaded that reference it + private final Cache<Path,URLClassLoader> classLoaders = + CacheBuilder.newBuilder().weakValues().build(); Review Comment: Added support for cleanup of local context directories: bbc67b6f34a21e20ada727edc7f78cc50d5e3c61 -- This is an automated message from the Apache Git Service. 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