sanel commented on a change in pull request #2074: URL: https://github.com/apache/drill/pull/2074#discussion_r431070162
########## File path: common/src/main/java/org/apache/drill/extn/ExtensionsRegistryImpl.java ########## @@ -0,0 +1,235 @@ +/* + * 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.drill.extn; + +import java.io.BufferedReader; +import java.io.File; +import java.io.IOException; +import java.io.InputStreamReader; +import java.net.MalformedURLException; +import java.net.URL; +import java.net.URLClassLoader; +import java.util.ArrayList; +import java.util.IdentityHashMap; +import java.util.List; +import java.util.Map; +import java.util.jar.JarEntry; +import java.util.jar.JarFile; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Implementation of the extensions registry. Provides extensive logging + * to help debug the inevitable problems that will occur in the field. + */ +public class ExtensionsRegistryImpl implements ExtensionsRegistry { + + // Attribute logging to the interface for easier debugging. + private static final Logger logger = LoggerFactory.getLogger(ExtensionsRegistry.class); + + @SuppressWarnings("serial") + private static class ExtException extends Exception { + + public ExtException(String msg, Exception e) { + super(msg, e); + } + } + + private final File extDir; + private final Map<Class<?>, ExtensionsRegistryImpl.ServiceProviderRegistryImpl<?>> services = new IdentityHashMap<>(); + + public ExtensionsRegistryImpl(File extDir, List<Class<?>> services) { + this.extDir = extDir; + defineServices(services); + loadProviders(); + } + + private void defineServices(List<Class<?>> serviceClasses) { + for (Class<?> serviceClass : serviceClasses) { + services.put(serviceClass, new ExtensionsRegistryImpl.ServiceProviderRegistryImpl<>(serviceClass)); + logger.info("Defined extension point: {}", serviceClass.getCanonicalName()); + } + } + + private void loadProviders() { + for (File extFile : extDir.listFiles()) { + if (extFile.isDirectory()) { + loadExtDir(extFile); + } else if (extFile.getName().endsWith(".jar")) { + loadExtJar(null, extFile); + } + } + } + + private void loadExtDir(File providerDir) { + String jarName = providerDir.getName() + ".jar"; + File providerJar = new File(providerDir, jarName); + if (providerDir.exists()) { + loadExtJar(providerDir, providerJar); + } + } + + private void loadExtJar(File providerDir, File providerJar) { + try (JarFile jarFile = new JarFile(providerJar)) { + for (ExtensionsRegistryImpl.ServiceProviderRegistryImpl<?> serviceReg : services.values()) { + if (loadService(providerDir, providerJar, jarFile, serviceReg)) { + return; + } + } + logError(providerDir, providerJar, + "Did not find a provider config file in META_INF/services/, ignoring jar", null); + } catch (IOException e) { + logError(providerDir, providerJar, + "Could not open extension jar", e); + } catch (ExtException e) { + logError(providerDir, providerJar, + e.getMessage(), e.getCause()); + } + } + + private void logError(File providerDir, File providerJar, String msg, Throwable e) { + String path = providerDir == null ? "" : providerDir.getName() + "/"; + path += providerJar.getName(); + logger.error(String.format("%s - Jar: %s", msg, path), e); + } + + private boolean loadService(File providerDir, File providerJar, JarFile jarFile, + ExtensionsRegistryImpl.ServiceProviderRegistryImpl<?> serviceReg) + throws ExtException { + String implClassName = readMappingFile(jarFile, serviceReg.serviceClass()); + if (implClassName == null) { + return false; + } + ExtensionsRegistryImpl.ProviderHost providerHost = new ProviderHost(providerDir, providerJar, implClassName); + serviceReg.addProvider(providerHost); + logger.info("Successfully loaded extension jar {} with class {} implementing {}", + providerJar.getName(), implClassName, + serviceReg.serviceClass().getCanonicalName()); + return true; + } + + private String readMappingFile(JarFile jarFile, Class<?> serviceClass) throws ExtException { + String className = serviceClass.getCanonicalName(); + String mapFilePath = "META-INF/services/" + className; + JarEntry jarEntry = jarFile.getJarEntry(mapFilePath); + if (jarEntry == null) { + // Should never occur: we got here because the entry exists. + return null; + } + try (BufferedReader br = new BufferedReader(new InputStreamReader(jarFile.getInputStream(jarEntry)))) { + return br.readLine(); + } catch (IOException e) { + throw new ExtException(String.format( + "Failed to read the provider configuration file %s", + className), e); + } + } + + @SuppressWarnings("unchecked") + @Override + public <T> ExtensionsRegistry.ServiceProviderRegistry<T> registryFor(Class<T> serviceClass) { + return (ExtensionsRegistry.ServiceProviderRegistry<T>) services.get(serviceClass); + } + + public static class ServiceProviderRegistryImpl<T> implements ExtensionsRegistry.ServiceProviderRegistry<T> { + + private final Class<T> serviceClass; + private final List<ExtensionsRegistryImpl.ProviderHost> providerHosts = new ArrayList<>(); + private final List<T> serviceImpls = new ArrayList<>(); + + public ServiceProviderRegistryImpl(Class<T> serviceClass) { + this.serviceClass = serviceClass; + } + + protected Class<T> serviceClass() { return serviceClass; } + + protected void addProvider(ExtensionsRegistryImpl.ProviderHost provider) { + providerHosts.add(provider); + serviceImpls.add(provider.serviceImpl()); + } + + @Override + public List<T> providers() { + return serviceImpls; + } + } + + protected static class ProviderHost { + + private final File providerDir; + private final File providerJar; + private final ClassLoader classLoader; + private final Class<?> serviceImplClass; + private final Object serviceImpl; + + protected ProviderHost(File providerDir, File providerJar, String implClassName) + throws ExtException { + this.providerDir = providerDir; + this.providerJar = providerJar; + try { + this.classLoader = buildClassLoader(); + } catch (MalformedURLException e) { + throw new ExtException( + "Failed to create a class loader for the extension. Malformed jar names?", e); + } + try { + this.serviceImplClass = classLoader.loadClass(implClassName); + } catch (ClassNotFoundException e) { + throw new ExtException(String.format( + "Extension jar has a provider config file " + + "in META_INF/services/, but the named class %s not found.", + implClassName), e); + } + try { + this.serviceImpl = serviceImplClass.newInstance(); + } catch (InstantiationException | IllegalAccessException e) { + throw new ExtException(String.format( + "Could not create an instance of provider class %s " + + "using the no-argument constructor", implClassName), e); + } + } + + @SuppressWarnings("unchecked") + public <T> T serviceImpl() { + return (T) serviceImpl; + } + + private ClassLoader buildClassLoader() throws MalformedURLException { + List<URL> jars = new ArrayList<>(); + if (providerDir != null) { + expandJars(jars); + } else { + jars.add(providerJar.toURI().toURL()); + } + URL[] urls = new URL[jars.size()]; + jars.toArray(urls); + + // TODO: Replace this with a custom, Tomcat-like class loader. + return new URLClassLoader(urls, getClass().getClassLoader()); + } + + private void expandJars(List<URL> jars) throws MalformedURLException { + for (File file : providerDir.listFiles()) { + if (file.getName().endsWith(".jar")) { + jars.add(file.toURI().toURL()); Review comment: How symbolic links will be handled? E.g. ``` |- ext |- megaDbPlugin-0.7.0 |- metadbplugin-0.7.0.jar |- dependency1.jar |- dependency2.jar |- common.jar (symlink) -> ../coolPlugin-0.1.0/common.jar |- README.md |- coolPlugin-0.1.0 |- common.jar ``` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
