cassandra-trunk/src/java/org/apache/cassandra/utils/logging/LoggingSupportFactory.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.cassandra.utils.logging;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.utils.FBUtilities;

/**
 * Dynamically loads and instantiates an appropriate {@link LoggingSupport} implementation according to the used slf4j binding.
 * For production use, this should always be {@link LogbackLoggingSupport}.
 */
public class LoggingSupportFactory
{
    private static final Logger logger = LoggerFactory.getLogger(LoggingSupportFactory.class);

    private static volatile LoggingSupport loggingSupport;

    private LoggingSupportFactory() {}

    /**
     * @return An appropriate {@link LoggingSupport} implementation according to the used slf4j binding.
     */
    public static LoggingSupport getLoggingSupport()
    {
        if (loggingSupport == null)
        {
            // unfortunately, this is the best way to determine if logback is being used for logger
            String loggerFactoryClass = LoggerFactory.getILoggerFactory().getClass().getName();
            if (loggerFactoryClass.contains("logback"))
            {
                loggingSupport = FBUtilities.instanceOrConstruct("org.apache.cassandra.utils.logging.LogbackLoggingSupport", "LogbackLoggingSupport");
            }
            else
            {
                loggingSupport = new NoOpFallbackLoggingSupport();
                logger.warn("You are using Cassandra with an unsupported deployment. The intended logging implementation library logback is not used by slf4j. Detected slf4j logger factory: {}. "
                            + "You will not be able to dynamically manage log levels via JMX and may have performance or other issues.", loggerFactoryClass);
            }
        }
        return loggingSupport;
    }
}
