/*
 * 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.core.appender.mom.kafka;

import java.io.Serializable;
import java.nio.charset.StandardCharsets;

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.appender.AppenderLoggingException;
import org.apache.logging.log4j.core.config.Node;
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.core.config.plugins.validation.constraints.Required;
import org.apache.logging.log4j.core.layout.SerializedLayout;
import org.apache.logging.log4j.core.util.StringEncoder;

/**
 * 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 {

    @PluginFactory
    public static KafkaAppender createAppender(
            @PluginElement("Layout") final Layout<? extends Serializable> layout,
            @PluginElement("Filter") final Filter filter,
            @Required(message = "No name provided for KafkaAppender") @PluginAttribute("name") final String name,
            @PluginAttribute(value = "ignoreExceptions", defaultBoolean = true) final boolean ignoreExceptions,
            @Required(message = "No topic provided for KafkaAppender") @PluginAttribute("topic") final String topic,
            @PluginElement("Properties") final Property[] properties) {
        final KafkaManager kafkaManager = new KafkaManager(name, topic, properties);
        return new KafkaAppender(name, layout, filter, ignoreExceptions, kafkaManager);
    }

    private final KafkaManager manager;

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

    @Override
    public void append(final LogEvent event) {
        if (event.getLoggerName().startsWith("org.apache.kafka")) {
            LOGGER.warn("Recursive logging from [{}] for appender [{}].", event.getLoggerName(), getName());
        } else {
            try {
                Layout<? extends Serializable> layout = getLayout();
                byte[] data;
                if (layout != null) {
                    if (layout instanceof SerializedLayout) {
                        byte[] header = layout.getHeader();
                        byte[] body = layout.toByteArray(event);
                        data = new byte[header.length + body.length];
                        System.arraycopy(header, 0, data, 0, header.length);
                        System.arraycopy(body, 0, data, header.length, body.length);
                    } else {
                        data = layout.toByteArray(event);
                    }
                } else {
                    data = StringEncoder.toBytes(event.getMessage().getFormattedMessage(), StandardCharsets.UTF_8);
                }
                manager.send(data);
            } catch (final Exception e) {
                LOGGER.error("Unable to write to Kafka [{}] for appender [{}].", manager.getName(), getName(), e);
                throw new AppenderLoggingException("Unable to write to Kafka in appender: " + e.getMessage(), e);
            }
        }
    }

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

    @Override
    public void stop() {
        super.stop();
        manager.release();
    }

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

@@ -4993,24 +4993,63 @@
 etName() +%0D%0A
+            %22, state=%22 + getState() +%0D%0A
             

Add state to toString() output.