fix: coverity reported null returns in Log4j2 agent

[lttng-ust.git] / src / lib / lttng-ust-java-agent / java / lttng-ust-agent-log4j2 / org / lttng / ust / agent / log4j2 / LttngLogAppender.java

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2015-2022 EfficiOS Inc.
 * Copyright (C) 2015 Alexandre Montplaisir <alexmonthy@efficios.com>
 * Copyright (C) 2014 Christian Babeux <christian.babeux@efficios.com>
 */

package org.lttng.ust.agent.log4j2;

import java.io.IOException;
import java.util.Collection;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Core;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.config.Property;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.message.Message;
import org.lttng.ust.agent.ILttngHandler;
import org.lttng.ust.agent.context.ContextInfoSerializer;

/**
 * LTTng-UST Log4j 2.x log handler.
 *
 * Applications can attach this appender to their
 * {@link org.apache.log4j.Logger} to have it generate UST events from logging
 * events received through the logger.
 *
 * It sends its events to UST via the JNI library "liblttng-ust-log4j-jni.so".
 * Make sure this library is available before using this appender.
 *
 */
@Plugin(name = LttngLogAppender.PLUGIN_NAME, category = Core.CATEGORY_NAME, elementType = Appender.ELEMENT_TYPE, printObject = false)
public final class LttngLogAppender extends AbstractAppender implements ILttngHandler {

	/**
	 * The name of the appender in the configuration.
	 */
	public static final String PLUGIN_NAME = "Lttng";

	private static final String SHARED_OBJECT_NAME = "lttng-ust-log4j-jni";

	/**
	 * Number of events logged (really sent through JNI) by this handler
	 */
	private final AtomicLong eventCount = new AtomicLong(0);

	private final LttngLog4j2Agent agent;

	/**
	 * Constructor
	 *
	 * @param name             The name of the Appender.
	 * @param filter           The Filter or null.
	 * @param ignoreExceptions If {@code "true"} (default) exceptions encountered
	 *                         when appending events are logged; otherwise they are
	 *                         propagated to the caller.
	 *
	 * @throws IOException       This handler requires the lttng-ust-log4j-jni.so
	 *                           native library, through which it will send the
	 *                           trace events. This exception is thrown if this
	 *                           library cannot be found.
	 * @throws SecurityException We will forward any SecurityExcepion that may be
	 *                           thrown when trying to load the JNI library.
	 */
	protected LttngLogAppender(String name, Filter filter, boolean ignoreExceptions)
			throws IOException, SecurityException {

		super(name, filter, null, ignoreExceptions, Property.EMPTY_ARRAY);

		/* Initialize LTTng UST tracer. */
		try {
			System.loadLibrary(SHARED_OBJECT_NAME); // $NON-NLS-1$
		} catch (UnsatisfiedLinkError e) {
			throw new IOException(e);
		}

		/* Register to the relevant agent. */
		agent = LttngLog4j2Agent.getInstance();
		agent.registerHandler(this);
	}

	/**
	 * Create an LttngLogAppender.
	 *
	 * @param name             The name of the Appender, null returns null.
	 * @param ignoreExceptions If {@code "true"} (default) exceptions encountered
	 *                         when appending events are logged; otherwise they are
	 *                         propagated to the caller.
	 * @param filter           The Filter or null.
	 *
	 * @return A new LttngLogAppender, null if the name was null.
	 *
	 * @throws IOException       This handler requires the lttng-ust-log4j-jni.so
	 *                           native library, through which it will send the
	 *                           trace events. This exception is thrown if this
	 *                           library cannot be found.
	 * @throws SecurityException We will forward any SecurityExcepion that may be
	 *                           thrown when trying to load the JNI library.
	 */
	@PluginFactory
	public static LttngLogAppender createAppender(@PluginAttribute("name") String name,
			@PluginAttribute("ignoreExceptions") Boolean ignoreExceptions, @PluginElement("Filters") Filter filter)
			throws IOException, SecurityException {

		if (name == null) {
			LOGGER.error("No name provided for LttngLogAppender");
			return null;
		}

		if (ignoreExceptions == null) {
			ignoreExceptions = true;
		}

		return new LttngLogAppender(name, filter, ignoreExceptions);
	}

	@Override
	public synchronized void close() {
		agent.unregisterHandler(this);
	}

	@Override
	public void stop() {
		close();
		super.stop();

		getStatusLogger().debug("Appender Lttng stopped");
	}

	@Override
	public boolean stop(final long timeout, final TimeUnit timeUnit) {
		close();
		boolean status = super.stop(timeout, timeUnit);

		getStatusLogger().debug("Appender Lttng stopped with status " + status);

		return status;
	}

	/**
	 * Get the number of events logged by this handler so far. This means the number
	 * of events actually sent through JNI to UST.
	 *
	 * @return The number of events logged so far
	 */
	@Override
	public long getEventCount() {
		return eventCount.get();
	}

	@Override
	public void append(LogEvent event) {
		/*
		 * Check if the current message should be logged, according to the UST session
		 * settings.
		 */
		String loggername = event.getLoggerName();
		if (loggername == null || !agent.isEventEnabled(loggername)) {
			return;
		}

		/*
		 * Default value if the Message is null.
		 */
		String message = "";

		Message eventMessage = event.getMessage();
		if (eventMessage != null) {
			message = eventMessage.getFormattedMessage();
		}

		/*
		 * Default values if the StackTraceElement is null.
		 */
		String classname = "";
		String methodname = "";
		String filename = "";
		int line = -1;

		StackTraceElement ste = event.getSource();
		if (ste != null) {
			classname = ste.getClassName();
			methodname = ste.getMethodName();
			filename = ste.getFileName();
			line = ste.getLineNumber();
		}

		/* Retrieve all the requested context information we can find. */
		Collection<Entry<String, Map<String, Integer>>> enabledContexts = agent.getEnabledAppContexts();
		ContextInfoSerializer.SerializedContexts contextInfo = ContextInfoSerializer
				.queryAndSerializeRequestedContexts(enabledContexts);

		eventCount.incrementAndGet();

		LttngLog4j2Api.tracepointWithContext(message, loggername, classname, methodname, filename, line,
				event.getTimeMillis(), event.getLevel().intLevel(), event.getThreadName(),
				contextInfo.getEntriesArray(), contextInfo.getStringsArray());
	}
}