Java tutorial
/** * 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.bookkeeper.mledger.offload; import java.io.File; import java.io.IOException; import java.nio.file.DirectoryStream; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; import java.util.Collections; import java.util.concurrent.CompletableFuture; import lombok.extern.slf4j.Slf4j; import org.apache.bookkeeper.mledger.LedgerOffloaderFactory; import org.apache.commons.lang3.StringUtils; import org.apache.commons.lang3.tuple.Pair; import org.apache.pulsar.common.nar.NarClassLoader; import org.apache.pulsar.common.util.ObjectMapperFactory; /** * Utils to load offloaders */ @Slf4j public class OffloaderUtils { private static final String PULSAR_OFFLOADER_SERVICE_NAME = "pulsar-offloader.yaml"; /** * Extract the Pulsar offloader class from a offloader archive. * * @param narPath nar package path * @return the offloader class name * @throws IOException when fail to retrieve the pulsar offloader class */ static Pair<NarClassLoader, LedgerOffloaderFactory> getOffloaderFactory(String narPath) throws IOException { NarClassLoader ncl = NarClassLoader.getFromArchive(new File(narPath), Collections.emptySet()); String configStr = ncl.getServiceDefinition(PULSAR_OFFLOADER_SERVICE_NAME); OffloaderDefinition conf = ObjectMapperFactory.getThreadLocalYaml().readValue(configStr, OffloaderDefinition.class); if (StringUtils.isEmpty(conf.getOffloaderFactoryClass())) { throw new IOException(String.format( "The '%s' offloader does not provide an offloader factory implementation", conf.getName())); } try { // Try to load offloader factory class and check it implements Offloader interface Class factoryClass = ncl.loadClass(conf.getOffloaderFactoryClass()); CompletableFuture<LedgerOffloaderFactory> loadFuture = new CompletableFuture<>(); Thread loadingThread = new Thread(() -> { Thread.currentThread().setContextClassLoader(ncl); log.info("Loading offloader factory {} using class loader {}", factoryClass, ncl); try { Object offloader = factoryClass.newInstance(); if (!(offloader instanceof LedgerOffloaderFactory)) { throw new IOException("Class " + conf.getOffloaderFactoryClass() + " does not implement interface " + LedgerOffloaderFactory.class.getName()); } loadFuture.complete((LedgerOffloaderFactory) offloader); } catch (Throwable t) { loadFuture.completeExceptionally(t); } }, "load-factory-" + factoryClass); try { loadingThread.start(); return Pair.of(ncl, loadFuture.get()); } finally { loadingThread.join(); } } catch (Throwable t) { rethrowIOException(t); } return null; } private static void rethrowIOException(Throwable cause) throws IOException { if (cause instanceof IOException) { throw (IOException) cause; } else if (cause instanceof RuntimeException) { throw (RuntimeException) cause; } else if (cause instanceof Error) { throw (Error) cause; } else { throw new IOException(cause.getMessage(), cause); } } public static OffloaderDefinition getOffloaderDefinition(String narPath) throws IOException { try (NarClassLoader ncl = NarClassLoader.getFromArchive(new File(narPath), Collections.emptySet())) { String configStr = ncl.getServiceDefinition(PULSAR_OFFLOADER_SERVICE_NAME); return ObjectMapperFactory.getThreadLocalYaml().readValue(configStr, OffloaderDefinition.class); } } public static Offloaders searchForOffloaders(String connectorsDirectory) throws IOException { Path path = Paths.get(connectorsDirectory).toAbsolutePath(); log.info("Searching for offloaders in {}", path); Offloaders offloaders = new Offloaders(); if (!path.toFile().exists()) { log.warn("Offloaders archive directory not found"); return offloaders; } try (DirectoryStream<Path> stream = Files.newDirectoryStream(path, "*.nar")) { stream.forEach(archive -> { try { OffloaderDefinition definition = getOffloaderDefinition(archive.toString()); log.info("Found offloader {} from {}", definition, archive); if (!StringUtils.isEmpty(definition.getOffloaderFactoryClass())) { // Validate offloader factory class to be present and of the right type Pair<NarClassLoader, LedgerOffloaderFactory> offloaderFactoryPair = getOffloaderFactory( archive.toString()); if (null != offloaderFactoryPair) { offloaders.getOffloaders().add(offloaderFactoryPair); } } } catch (Throwable t) { log.warn("Failed to load offloader from {}", archive, t); } }); } log.info("Found and loaded {} offloaders", offloaders.getOffloaders().size()); return offloaders; } }