[lttng-ust.git] /

/*
 * 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.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.
                 */
                if (!agent.isEventEnabled(event.getLoggerName())) {
                        return;
                }

                /*
                 * 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(event.getMessage().getFormattedMessage(), event.getLoggerName(), classname,
                                methodname, filename, line, event.getTimeMillis(), event.getLevel().intLevel(), event.getThreadName(),
                                contextInfo.getEntriesArray(), contextInfo.getStringsArray());
        }
}