jvz commented on code in PR #1136: URL: https://github.com/apache/logging-log4j2/pull/1136#discussion_r1017466356
########## log4j-api/src/main/java/org/apache/logging/log4j/spi/LoggingSystem.java: ########## @@ -0,0 +1,349 @@ +/* + * 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.logging.log4j.spi; + +import org.apache.logging.log4j.LogManager; +import org.apache.logging.log4j.ThreadContext; +import org.apache.logging.log4j.simple.SimpleLoggerContextFactory; +import org.apache.logging.log4j.util.Constants; +import org.apache.logging.log4j.util.Lazy; +import org.apache.logging.log4j.util.LoaderUtil; +import org.apache.logging.log4j.util.LowLevelLogUtil; +import org.apache.logging.log4j.util.PropertiesUtil; +import org.apache.logging.log4j.util.PropertyEnvironment; +import org.apache.logging.log4j.util.ServiceRegistry; + +import java.io.IOException; +import java.io.InputStream; +import java.lang.invoke.MethodHandles; +import java.lang.reflect.Constructor; +import java.lang.reflect.InvocationTargetException; +import java.net.URL; +import java.util.List; +import java.util.Objects; +import java.util.Properties; +import java.util.SortedMap; +import java.util.TreeMap; +import java.util.concurrent.locks.Lock; +import java.util.concurrent.locks.ReentrantLock; +import java.util.function.Supplier; +import java.util.stream.Collectors; + +/** + * Handles initializing the Log4j API through {@link Provider} discovery. This keeps track of which + * {@link LoggerContextFactory} to use in {@link LogManager} along with factories for {@link ThreadContextMap} + * and {@link ThreadContextStack} to use in {@link ThreadContext}. + */ +public class LoggingSystem { + /** + * Resource name for a Log4j 2 provider properties file. + */ + private static final String PROVIDER_RESOURCE = "META-INF/log4j-provider.properties"; + private static final String API_VERSION = "Log4jAPIVersion"; + private static final String[] COMPATIBLE_API_VERSIONS = {"3.0.0"}; + private static final String DISABLE_MAP = "disableThreadContextMap"; + private static final String DISABLE_STACK = "disableThreadContextStack"; + private static final String DISABLE_ALL = "disableThreadContext"; + private static final String THREAD_CONTEXT_MAP = "log4j2.threadContextMap"; + private static final String GARBAGEFREE_THREAD_CONTEXT_MAP = "log4j2.garbagefree.threadContextMap"; + private static final Lazy<LoggingSystem> SYSTEM = Lazy.relaxed(LoggingSystem::new); + + private final Lock initializationLock = new ReentrantLock(); + private volatile LoggingProvider provider; + private final Lazy<LoggerContextFactory> loggerContextFactorySupplier = Lazy.lazy(() -> getProvider().createLoggerContextFactory()); + private Supplier<ThreadContextMap> threadContextMapSupplier = () -> getProvider().createContextMap(); + private Supplier<ThreadContextStack> threadContextStackSupplier = () -> getProvider().createContextStack(); + + /** + * Acquires a lock on the initialization of locating a logging system provider. This lock should be + * {@linkplain #releaseInitializationLock() released} once the logging system provider is loaded. This lock is + * provided to allow for lazy initialization via frameworks like OSGi to wait for a provider to be installed + * before allowing initialization to continue. + * + * @see <a href="https://issues.apache.org/jira/browse/LOG4J2-373";>LOG4J2-373</a> + */ + public void acquireInitializationLock() { + initializationLock.lock(); + } + + /** + * Releases a lock on the initialization phase of this logging system. + */ + public void releaseInitializationLock() { + initializationLock.unlock(); + } + + private LoggingProvider getProvider() { + var provider = this.provider; + if (provider == null) { + try { + initializationLock.lockInterruptibly(); + provider = this.provider; + if (provider == null) { + this.provider = provider = findProvider(); + } + } catch (InterruptedException e) { + LowLevelLogUtil.logException("Interrupted before Log4j Providers could be loaded", e); + provider = new LoggingProvider(); + Thread.currentThread().interrupt(); + } finally { + releaseInitializationLock(); + } + } + return provider; + } + + private LoggingProvider findProvider() { + final SortedMap<Integer, Provider> providers = new TreeMap<>(); + loadDefaultProviders().forEach(p -> providers.put(p.getPriority(), p)); + loadLegacyProviders().forEach(p -> providers.put(p.getPriority(), p)); + if (providers.isEmpty()) { + return new LoggingProvider(); + } + final Provider provider = providers.get(providers.lastKey()); + if (providers.size() > 1) { + final StringBuilder sb = new StringBuilder("Multiple logging implementations found: \n"); + providers.forEach((i, p) -> sb.append(p).append('\n')); + sb.append("Using ").append(provider); + LowLevelLogUtil.log(sb.toString()); + } + return new LoggingProvider(provider); + } + + public void setLoggerContextFactory(final LoggerContextFactory loggerContextFactory) { + loggerContextFactorySupplier.set(loggerContextFactory); + } + + public void setThreadContextMapSupplier(final Supplier<ThreadContextMap> threadContextMapSupplier) { + this.threadContextMapSupplier = threadContextMapSupplier; + } + + public void setThreadContextStackSupplier(final Supplier<ThreadContextStack> threadContextStackSupplier) { + this.threadContextStackSupplier = threadContextStackSupplier; + } + + /** + * Gets the LoggingSystem instance. + */ + public static LoggingSystem getInstance() { + return SYSTEM.value(); + } + + /** + * Gets the current LoggerContextFactory. This may initialize the instance if this is the first time it was + * requested. + */ + public static LoggerContextFactory getLoggerContextFactory() { + return getInstance().loggerContextFactorySupplier.get(); + } + + /** + * Creates a new ThreadContextMap. + */ + public static ThreadContextMap createContextMap() { + return getInstance().threadContextMapSupplier.get(); + } + + /** + * Creates a new ThreadContextStack. + */ + public static ThreadContextStack createContextStack() { + return getInstance().threadContextStackSupplier.get(); + } + + private static List<Provider> loadDefaultProviders() { + return ServiceRegistry.getInstance() + .getServices(Provider.class, MethodHandles.lookup(), provider -> validVersion(provider.getVersions())); + } + + private static List<Provider> loadLegacyProviders() { + return LoaderUtil.findUrlResources(PROVIDER_RESOURCE, false) + .stream() + .map(urlResource -> loadLegacyProvider(urlResource.getUrl(), urlResource.getClassLoader())) + .filter(Objects::nonNull) + .collect(Collectors.toList()); + } + + private static Provider loadLegacyProvider(final URL url, final ClassLoader classLoader) { + final Properties properties = new Properties(); + try (final InputStream in = url.openStream()) { + properties.load(in); + } catch (IOException e) { + LowLevelLogUtil.logException("Unable to load file " + url, e); + return null; + } + if (validVersion(properties.getProperty(API_VERSION))) { + return new Provider(properties, url, classLoader); + } + return null; + } + + private static boolean validVersion(final String version) { + for (final String v : COMPATIBLE_API_VERSIONS) { + if (version.startsWith(v)) { + return true; + } + } + return false; + } + + private static <T> T tryInstantiate(final Class<T> clazz) { + Constructor<T> constructor; + try { + constructor = clazz.getConstructor(); + } catch (final NoSuchMethodException ignored) { + try { + constructor = clazz.getDeclaredConstructor(); + if (!(constructor.canAccess(null) || constructor.trySetAccessible())) { + LowLevelLogUtil.log("Unable to access constructor for " + clazz); + return null; + } + } catch (final NoSuchMethodException e) { + LowLevelLogUtil.logException("Unable to find a default constructor for " + clazz, e); + return null; + } + } + try { + return constructor.newInstance(); + } catch (final InvocationTargetException e) { + LowLevelLogUtil.logException("Exception thrown by constructor for " + clazz, e.getCause()); + } catch (final InstantiationException | LinkageError e) { + LowLevelLogUtil.logException("Unable to create instance of " + clazz, e); + } catch (final IllegalAccessException e) { + LowLevelLogUtil.logException("Unable to access constructor for " + clazz, e); + } + return null; + } + + private static ThreadContextMap createCustomContextMap(final String className) { + try { + final Class<?> customClass = LoaderUtil.loadClass(className); + final Class<? extends ThreadContextMap> contextMapClass = customClass.asSubclass(ThreadContextMap.class); + return tryInstantiate(contextMapClass); + } catch (final ClassNotFoundException | ClassCastException e) { + LowLevelLogUtil.logException(String.format("Unable to load custom ThreadContextMap class '%s'", className), e); + return null; + } + } + + private static LoggerContextFactory createCustomFactory(final String className) { + try { + final Class<?> customClass = LoaderUtil.loadClass(className); + final Class<? extends LoggerContextFactory> factoryClass = customClass.asSubclass(LoggerContextFactory.class); + return tryInstantiate(factoryClass); + } catch (final ClassNotFoundException | ClassCastException e) { + LowLevelLogUtil.logException(String.format("Unable to load custom LoggerContextFactory class '%s'", className), e); + return null; + } + } + + private static class LoggingProvider { + private final Provider provider; + + private LoggingProvider() { + this(null); + } + + private LoggingProvider(final Provider provider) { + this.provider = provider; + } + + public LoggerContextFactory createLoggerContextFactory() { + final PropertyEnvironment environment = PropertiesUtil.getProperties(); + final String customFactoryClass = environment.getStringProperty(LogManager.FACTORY_PROPERTY_NAME); + if (customFactoryClass != null) { + final LoggerContextFactory customFactory = createCustomFactory(customFactoryClass); + if (customFactory != null) { + return customFactory; + } + } + if (provider != null) { + final Class<? extends LoggerContextFactory> factoryClass = provider.loadLoggerContextFactory(); + if (factoryClass != null) { + final LoggerContextFactory factory = tryInstantiate(factoryClass); + if (factory != null) { + return factory; + } + } + } + LowLevelLogUtil.log("Log4j could not find a logging implementation. " + + "Please add log4j-core dependencies to classpath or module path. " + + "Using SimpleLogger to log to the console."); + return SimpleLoggerContextFactory.INSTANCE; + } + + /** + * Creates the ThreadContextMap instance used by the ThreadContext. + * <p> + * If {@linkplain Constants#isThreadLocalsEnabled() Log4j can use ThreadLocals}, a garbage-free StringMap-based context map can + * be installed by setting system property {@code log4j2.garbagefree.threadContextMap} to {@code true}. + * </p><p> + * Furthermore, any custom {@code ThreadContextMap} can be installed by setting system property + * {@code log4j2.threadContextMap} to the fully qualified class name of the class implementing the + * {@code ThreadContextMap} interface. (Also implement the {@code ReadOnlyThreadContextMap} interface if your custom + * {@code ThreadContextMap} implementation should be accessible to applications via the + * {@link ThreadContext#getThreadContextMap()} method.) + * </p><p> + * Instead of system properties, the above can also be specified in a properties file named + * {@code log4j2.component.properties} in the classpath. + * </p> + * + * @see ThreadContextMap + * @see ReadOnlyThreadContextMap + * @see org.apache.logging.log4j.ThreadContext + */ + public ThreadContextMap createContextMap() { + final PropertyEnvironment environment = PropertiesUtil.getProperties(); + // TODO(ms): make property lookup lazier here to avoid eager init + GarbageFreeSortedArrayThreadContextMap.init(environment); + CopyOnWriteSortedArrayThreadContextMap.init(environment); + DefaultThreadContextMap.init(environment); Review Comment: Fixing this issue in a subsequent commit. -- This is an automated message from the Apache Git Service. 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