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Dynamic Dependency Injection with different ways to manage the resolver-strategy
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/*
 * 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.async;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.util.Integers;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.PropertiesUtil;

import com.lmax.disruptor.BlockingWaitStrategy;
import com.lmax.disruptor.ExceptionHandler;
import com.lmax.disruptor.SleepingWaitStrategy;
import com.lmax.disruptor.WaitStrategy;
import com.lmax.disruptor.YieldingWaitStrategy;

/**
 * Utility methods for getting Disruptor related configuration.
 */
final class DisruptorUtil {
    private static final Logger LOGGER = StatusLogger.getLogger();
    private static final int RINGBUFFER_MIN_SIZE = 128;
    private static final int RINGBUFFER_DEFAULT_SIZE = 256 * 1024;

    private DisruptorUtil() {
    }

    static WaitStrategy createWaitStrategy(final String propertyName) {
        final String strategy = PropertiesUtil.getProperties().getStringProperty(propertyName);
        if (strategy != null) {
            LOGGER.trace("property {}={}", propertyName, strategy);
            if ("Sleep".equalsIgnoreCase(strategy)) {
                return new SleepingWaitStrategy();
            } else if ("Yield".equalsIgnoreCase(strategy)) {
                return new YieldingWaitStrategy();
            } else if ("Block".equalsIgnoreCase(strategy)) {
                return new BlockingWaitStrategy();
            }
        }
        return new BlockingWaitStrategy();
    }

    static int calculateRingBufferSize(final String propertyName) {
        int ringBufferSize = RINGBUFFER_DEFAULT_SIZE;
        final String userPreferredRBSize = PropertiesUtil.getProperties().getStringProperty(propertyName,
                String.valueOf(ringBufferSize));
        try {
            int size = Integer.parseInt(userPreferredRBSize);
            if (size < RINGBUFFER_MIN_SIZE) {
                size = RINGBUFFER_MIN_SIZE;
                LOGGER.warn("Invalid RingBufferSize {}, using minimum size {}.", userPreferredRBSize,
                        RINGBUFFER_MIN_SIZE);
            }
            ringBufferSize = size;
        } catch (final Exception ex) {
            LOGGER.warn("Invalid RingBufferSize {}, using default size {}.", userPreferredRBSize, ringBufferSize);
        }
        return Integers.ceilingNextPowerOfTwo(ringBufferSize);
    }

    static  ExceptionHandler getExceptionHandler(final String propertyName, Class type) {
        final String cls = PropertiesUtil.getProperties().getStringProperty(propertyName);
        if (cls == null) {
            return null;
        }
        try {
            @SuppressWarnings("unchecked")
            final Class> klass = (Class>) Class
                    .forName(cls);
            return klass.newInstance();
        } catch (final Exception ignored) {
            LOGGER.debug("Invalid {} value: error creating {}: ", propertyName, cls, ignored);
            return null;
        }
    }

    /**
     * Returns the thread ID of the background appender thread. This allows us to detect Logger.log() calls initiated
     * from the appender thread, which may cause deadlock when the RingBuffer is full. (LOG4J2-471)
     * 
     * @param executor runs the appender thread
     * @return the thread ID of the background appender thread
     */
    public static long getExecutorThreadId(final ExecutorService executor) {
        Future result = executor.submit(new Callable() {
            @Override
            public Long call() {
                return Thread.currentThread().getId();
            }
        });
        try {
            return result.get();
        } catch (final Exception ex) {
            final String msg = "Could not obtain executor thread Id. "
                    + "Giving up to avoid the risk of application deadlock.";
            throw new IllegalStateException(msg, ex);
        }
    }

}