log4j-kafka/src/main/java/org/apache/logging/log4j/kafka/appender/KafkaAppender.java

/*
 * 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.kafka.appender;

import org.apache.logging.log4j.core.AbstractLifeCycle;
import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
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.plugins.Node;
import org.apache.logging.log4j.plugins.Plugin;
import org.apache.logging.log4j.plugins.PluginAttribute;
import org.apache.logging.log4j.plugins.PluginFactory;

import java.io.Serializable;
import java.util.Objects;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * Sends log events to an Apache Kafka topic.
 */
@Plugin(name = "Kafka", category = Node.CATEGORY, elementType = Appender.ELEMENT_TYPE, printObject = true)
public final class KafkaAppender extends AbstractAppender {

    /**
     * Builds KafkaAppender instances.
     * 
     * @param <B>
     *            The type to build
     */
    public static class Builder<B extends Builder<B>> extends AbstractAppender.Builder<B>
            implements org.apache.logging.log4j.plugins.util.Builder<KafkaAppender> {

        @PluginAttribute
        private String topic;

        @PluginAttribute
        private String key;

        @PluginAttribute(defaultBoolean = true)
        private boolean syncSend;

        @SuppressWarnings("resource")
        @Override
        public KafkaAppender build() {
            final Layout<? extends Serializable> layout = getLayout();
            if (layout == null) {
                AbstractLifeCycle.LOGGER.error("No layout provided for KafkaAppender");
                return null;
            }
            final KafkaManager kafkaManager = KafkaManager.getManager(getConfiguration().getLoggerContext(),
                    getName(), topic, syncSend, getPropertyArray(), key);
            return new KafkaAppender(getName(), layout, getFilter(), isIgnoreExceptions(), getPropertyArray(), kafkaManager);
        }

        public String getTopic() {
            return topic;
        }

        public boolean isSyncSend() {
            return syncSend;
        }

        public B setTopic(final String topic) {
            this.topic = topic;
            return asBuilder();
        }

        public B setKey(final String key) {
            this.key = key;
            return asBuilder();
        }

        public B setSyncSend(final boolean syncSend) {
            this.syncSend = syncSend;
            return asBuilder();
        }
    }

    /**
     * Creates a builder for a KafkaAppender.
     * 
     * @return a builder for a KafkaAppender.
     */
    @PluginFactory
    public static <B extends Builder<B>> B newBuilder() {
        return new Builder<B>().asBuilder();
    }

    private final KafkaManager manager;

    private KafkaAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter,
            final boolean ignoreExceptions, Property[] properties, final KafkaManager manager) {
        super(name, filter, layout, ignoreExceptions, properties);
        this.manager = Objects.requireNonNull(manager, "manager");
    }

    @Override
    public void append(final LogEvent event) {
        if (event.getLoggerName() != null && event.getLoggerName().startsWith("org.apache.kafka")) {
            LOGGER.warn("Recursive logging from [{}] for appender [{}].", event.getLoggerName(), getName());
        } else {
            try {
                tryAppend(event);
            } catch (final Exception e) {
                error("Unable to write to Kafka in appender [" + getName() + "]", event, e);
            }
        }
    }

    private void tryAppend(final LogEvent event) throws ExecutionException, InterruptedException, TimeoutException {
        final Layout<? extends Serializable> layout = getLayout();
        byte[] data;
        data = layout.toByteArray(event);
        manager.send(data);
    }

    @Override
    public void start() {
        super.start();
        manager.startup();
    }

    @Override
    public boolean stop(final long timeout, final TimeUnit timeUnit) {
        setStopping();
        boolean stopped = super.stop(timeout, timeUnit, false);
        stopped &= manager.stop(timeout, timeUnit);
        setStopped();
        return stopped;
    }

    @Override
    public String toString() {
        return "KafkaAppender{" + "name=" + getName() + ", state=" + getState() + ", topic=" + manager.getTopic() + '}';
    }
}