Github user mattf-horton commented on a diff in the pull request: https://github.com/apache/metron/pull/530#discussion_r131831288 --- Diff: bundles-lib/src/main/java/org/apache/metron/bundles/BundleClassLoaders.java --- @@ -0,0 +1,353 @@ +/* + * 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.metron.bundles; + +import java.net.URISyntaxException; +import java.util.*; + +import org.apache.commons.collections.CollectionUtils; +import org.apache.commons.vfs2.FileObject; +import org.apache.commons.vfs2.FileSystemException; +import org.apache.commons.vfs2.FileSystemManager; +import org.apache.metron.bundles.bundle.Bundle; +import org.apache.metron.bundles.bundle.BundleCoordinate; +import org.apache.metron.bundles.bundle.BundleDetails; +import org.apache.metron.bundles.util.BundleProperties; +import org.apache.metron.bundles.util.BundleSelector; +import org.apache.metron.bundles.util.FileUtils; +import org.apache.metron.bundles.util.BundleUtil; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * A singleton class used to initialize the extension and framework classloaders. + */ +public final class BundleClassLoaders { + + private static volatile BundleClassLoaders bundleClassLoaders; + private volatile InitContext initContext; + private static final Logger logger = LoggerFactory.getLogger(BundleClassLoaders.class); + + private final static class InitContext { + + private final List<FileObject> extensionDirs; + private final Map<String, Bundle> bundles; + + private InitContext( + final List<FileObject> extensionDirs, + final Map<String, Bundle> bundles) { + this.extensionDirs = extensionDirs; + this.bundles = bundles; + } + } + + private BundleClassLoaders() { + } + + /** + * @return The singleton instance of the BundleClassLoaders + */ + public static BundleClassLoaders getInstance() { + BundleClassLoaders result = bundleClassLoaders; + if (result == null) { + synchronized (BundleClassLoaders.class) { + result = bundleClassLoaders; + if (result == null) { + bundleClassLoaders = result = new BundleClassLoaders(); + } + } + } + return result; + } + + public static void reset() { + getInstance().unInit(); + } + + private void unInit() { + synchronized (this) { + initContext = null; + } + } + + /** + * Initializes and loads the BundleClassLoaders. This method must be called before the rest of the + * methods to access the classloaders are called and it can be safely called any number of times + * provided the same framework and extension working dirs are used. + * + * @param fileSystemManager the FileSystemManager + * @param extensionsDirs where to find extension artifacts + * @param props BundleProperties + * @throws FileSystemException if any issue occurs while exploding bundle working directories. + * @throws java.lang.ClassNotFoundException if unable to load class definition + * @throws IllegalStateException already initialized with a given pair of directories cannot + * reinitialize or use a different pair of directories. + */ + public void init(final FileSystemManager fileSystemManager, final List<FileObject> extensionsDirs, + BundleProperties props) + throws FileSystemException, ClassNotFoundException, URISyntaxException { + if (extensionsDirs == null || fileSystemManager == null) { + throw new NullPointerException("cannot have empty arguments"); + } + InitContext ic = initContext; + if (ic == null) { + synchronized (this) { + ic = initContext; + if (ic == null) { + initContext = ic = load(fileSystemManager, extensionsDirs, props); + } + } + } else { + boolean matching = CollectionUtils + .isEqualCollection(initContext.extensionDirs, extensionsDirs); + if (!matching) { + throw new IllegalStateException( + "Cannot reinitialize and extension/framework directories cannot change"); + } + } + } + + /** + * Should be called at most once. + */ + private InitContext load(final FileSystemManager fileSystemManager, + final List<FileObject> extensionsDirs, BundleProperties props) + throws FileSystemException, ClassNotFoundException, URISyntaxException { + // get the system classloader + final ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader(); + + // find all bundle files and create class loaders for them. + final Map<String, Bundle> directoryBundleLookup = new LinkedHashMap<>(); + final Map<String, ClassLoader> coordinateClassLoaderLookup = new HashMap<>(); + final Map<String, Set<BundleCoordinate>> idBundleLookup = new HashMap<>(); + + for (FileObject extensionsDir : extensionsDirs) { + // make sure the bundle directory is there and accessible + FileUtils.ensureDirectoryExistAndCanRead(extensionsDir); + + final List<FileObject> bundleDirContents = new ArrayList<>(); + FileObject[] dirFiles = extensionsDir.findFiles(new BundleSelector(props.getArchiveExtension())); + if (dirFiles != null) { + List<FileObject> fileList = Arrays.asList(dirFiles); + bundleDirContents.addAll(fileList); + } + + if (!bundleDirContents.isEmpty()) { + final List<BundleDetails> bundleDetails = new ArrayList<>(); + final Map<String, String> bundleCoordinatesToBundleFile = new HashMap<>(); + + // load the bundle details which includes bundle dependencies + for (final FileObject bundleFile : bundleDirContents) { + if(!bundleFile.exists() || !bundleFile.isFile()) { + continue; + } + BundleDetails bundleDetail = null; + try { + bundleDetail = getBundleDetails(bundleFile, props); + } catch (IllegalStateException e) { + logger.warn("Unable to load BUNDLE {} due to {}, skipping...", + new Object[]{bundleFile.getURL(), e.getMessage()}); + } + + // prevent the application from starting when there are two BUNDLEs with same group, id, and version + final String bundleCoordinate = bundleDetail.getCoordinate().getCoordinate(); + if (bundleCoordinatesToBundleFile.containsKey(bundleCoordinate)) { + final String existingBundleWorkingDir = bundleCoordinatesToBundleFile + .get(bundleCoordinate); + throw new IllegalStateException( + "Unable to load BUNDLE with coordinates " + bundleCoordinate + + " and working directory " + bundleDetail.getBundleFile() + + " because another BUNDLE with the same coordinates already exists at " + + existingBundleWorkingDir); + } + + bundleDetails.add(bundleDetail); + bundleCoordinatesToBundleFile.put(bundleCoordinate, + bundleDetail.getBundleFile().getURL().toURI().toString()); + } + + // attempt to locate the jetty bundle + ClassLoader jettyClassLoader = null; + for (final Iterator<BundleDetails> bundleDetailsIter = bundleDetails.iterator(); + bundleDetailsIter.hasNext(); ) { + final BundleDetails bundleDetail = bundleDetailsIter.next(); + // populate bundle lookup + idBundleLookup.computeIfAbsent(bundleDetail.getCoordinate().getId(), + id -> new HashSet<>()).add(bundleDetail.getCoordinate()); + } + + int bundleCount; + do { + // record the number of bundles to be loaded + bundleCount = bundleDetails.size(); + + // attempt to create each bundle class loader + for (final Iterator<BundleDetails> bundleDetailsIter = bundleDetails.iterator(); + bundleDetailsIter.hasNext(); ) { + final BundleDetails bundleDetail = bundleDetailsIter.next(); + final BundleCoordinate bundleDependencyCoordinate = bundleDetail + .getDependencyCoordinate(); + + // see if this class loader is eligible for loading + ClassLoader potentialBundleClassLoader = null; + if (bundleDependencyCoordinate == null) { + potentialBundleClassLoader = createBundleClassLoader(fileSystemManager, + bundleDetail.getBundleFile(), ClassLoader.getSystemClassLoader()); + } else { + final String dependencyCoordinateStr = bundleDependencyCoordinate + .getCoordinate(); + + // if the declared dependency has already been loaded + if (coordinateClassLoaderLookup.containsKey(dependencyCoordinateStr)) { + final ClassLoader bundleDependencyClassLoader = coordinateClassLoaderLookup + .get(dependencyCoordinateStr); + potentialBundleClassLoader = createBundleClassLoader( + fileSystemManager, bundleDetail.getBundleFile(), + bundleDependencyClassLoader); + } else { + // get all bundles that match the declared dependency id + final Set<BundleCoordinate> coordinates = idBundleLookup + .get(bundleDependencyCoordinate.getId()); + + // ensure there are known bundles that match the declared dependency id + if (coordinates != null && !coordinates + .contains(bundleDependencyCoordinate)) { + // ensure the declared dependency only has one possible bundle + if (coordinates.size() == 1) { + // get the bundle with the matching id + final BundleCoordinate coordinate = coordinates.stream() + .findFirst().get(); + + // if that bundle is loaded, use it + if (coordinateClassLoaderLookup + .containsKey(coordinate.getCoordinate())) { + logger.warn(String.format( + "While loading '%s' unable to locate exact BUNDLE dependency '%s'. Only found one possible match '%s'. Continuing...", + bundleDetail.getCoordinate().getCoordinate(), + dependencyCoordinateStr, + coordinate.getCoordinate())); + + final ClassLoader bundleDependencyClassLoader = coordinateClassLoaderLookup + .get(coordinate.getCoordinate()); + potentialBundleClassLoader = createBundleClassLoader( + fileSystemManager, bundleDetail.getBundleFile(), + bundleDependencyClassLoader); + } + } + } + } + } + + // if we were able to create the bundle class loader, store it and remove the details + final ClassLoader bundleClassLoader = potentialBundleClassLoader; + if (bundleClassLoader != null) { + directoryBundleLookup + .put(bundleDetail.getBundleFile().getURL().toURI().toString(), + new Bundle(bundleDetail, bundleClassLoader)); + coordinateClassLoaderLookup + .put(bundleDetail.getCoordinate().getCoordinate(), + bundleClassLoader); + bundleDetailsIter.remove(); + } + } + + // attempt to load more if some were successfully loaded this iteration + } while (bundleCount != bundleDetails.size()); + + // see if any bundle couldn't be loaded + for (final BundleDetails bundleDetail : bundleDetails) { + logger.warn(String + .format("Unable to resolve required dependency '%s'. Skipping BUNDLE '%s'", + bundleDetail.getDependencyCoordinate().getId(), + bundleDetail.getBundleFile().getURL().toURI().toString())); + } + } + } + return new InitContext(extensionsDirs, new LinkedHashMap<>(directoryBundleLookup)); + } + + /** + * Creates a new BundleClassLoader. The parentClassLoader may be null. + * + * @param bundleFile the Bundle File + * @param parentClassLoader parent classloader of bundle + * @return the bundle classloader + * @throws FileSystemException ioe + * @throws ClassNotFoundException cfne + */ + private static ClassLoader createBundleClassLoader(final FileSystemManager fileSystemManager, + final FileObject bundleFile, final ClassLoader parentClassLoader) + throws FileSystemException, ClassNotFoundException { + logger.debug("Loading Bundle file: " + bundleFile.getURL()); + VFSBundleClassLoader.Builder builder = new VFSBundleClassLoader.Builder() + .withFileSystemManager(fileSystemManager) + .withBundleFile(bundleFile) + .withParentClassloader(parentClassLoader); + final ClassLoader bundleClassLoader = builder.build(); --- End diff -- Nit: this is okay, but it is a little more elegant (at least in my opinion) to do the build and assignment in one stroke, leaving the ephemeral `builder` anonymous: ```java final ClassLoader bundleClassLoader = new VFSBundleClassLoader.Builder() .withFileSystemManager(fileSystemManager) .withBundleFile(bundleFile) .withParentClassloader(parentClassLoader) .build(); ```
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