/*
    * 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.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.logging.log4j.Level;
  import org.apache.logging.log4j.core.AbstractLifeCycle;
  import org.apache.logging.log4j.core.jmx.RingBufferAdmin;
  import org.apache.logging.log4j.core.util.ExecutorServices;
  import org.apache.logging.log4j.core.util.Log4jThreadFactory;
  
  import com.lmax.disruptor.ExceptionHandler;
  import com.lmax.disruptor.RingBuffer;
  import com.lmax.disruptor.TimeoutException;
  import com.lmax.disruptor.WaitStrategy;
  import com.lmax.disruptor.dsl.Disruptor;
  import com.lmax.disruptor.dsl.ProducerType;
  
  /**
   * Helper class for async loggers: AsyncLoggerDisruptor handles the mechanics of working with the LMAX Disruptor, and
   * works with its associated AsyncLoggerContext to synchronize the life cycle of the Disruptor and its thread with the
   * life cycle of the context. The AsyncLoggerDisruptor of the context is shared by all AsyncLogger objects created by
   * that AsyncLoggerContext.
   */
  class AsyncLoggerDisruptor extends AbstractLifeCycle {
      private static final int SLEEP_MILLIS_BETWEEN_DRAIN_ATTEMPTS = 50;
      private static final int MAX_DRAIN_ATTEMPTS_BEFORE_SHUTDOWN = 200;
  
      private volatile Disruptor<RingBufferLogEvent> disruptor;
      private ExecutorService executor;
      private String contextName;
  
      private boolean useThreadLocalTranslator = true;
      private long backgroundThreadId;
      private AsyncQueueFullPolicy asyncQueueFullPolicy;
      private int ringBufferSize;
  
      AsyncLoggerDisruptor(final String contextName) {
          this.contextName = contextName;
      }
  
      public String getContextName() {
          return contextName;
      }
  
      public void setContextName(final String name) {
          contextName = name;
      }
  
      Disruptor<RingBufferLogEvent> getDisruptor() {
          return disruptor;
      }
  
      /**
       * Creates and starts a new Disruptor and associated thread if none currently exists.
       *
       * @see #stop()
       */
      @Override
      public synchronized void start() {
          if (disruptor != null) {
              LOGGER.trace(
                      "[{}] AsyncLoggerDisruptor not starting new disruptor for this context, using existing object.",
                      contextName);
              return;
          }
          LOGGER.trace("[{}] AsyncLoggerDisruptor creating new disruptor for this context.", contextName);
          ringBufferSize = DisruptorUtil.calculateRingBufferSize("AsyncLogger.RingBufferSize");
          final WaitStrategy waitStrategy = DisruptorUtil.createWaitStrategy("AsyncLogger.WaitStrategy");
          executor = Executors.newSingleThreadExecutor(Log4jThreadFactory.createDaemonThreadFactory("AsyncLogger[" + contextName + "]"));
          backgroundThreadId = DisruptorUtil.getExecutorThreadId(executor);
          asyncQueueFullPolicy = AsyncQueueFullPolicyFactory.create();
  
          disruptor = new Disruptor<>(RingBufferLogEvent.FACTORY, ringBufferSize, executor, ProducerType.MULTI,
                  waitStrategy);
  
          final ExceptionHandler<RingBufferLogEvent> errorHandler = DisruptorUtil.getAsyncLoggerExceptionHandler();
          disruptor.handleExceptionsWith(errorHandler);
  
          final RingBufferLogEventHandler[] handlers = {new RingBufferLogEventHandler()};
          disruptor.handleEventsWith(handlers);
 
         LOGGER.debug("[{}] Starting AsyncLogger disruptor for this context with ringbufferSize={}, waitStrategy={}, "
                 + "exceptionHandler={}...", contextName, disruptor.getRingBuffer().getBufferSize(), waitStrategy
                 .getClass().getSimpleName(), errorHandler);
         disruptor.start();
 
         LOGGER.trace("[{}] AsyncLoggers use a {} translator", contextName, useThreadLocalTranslator ? "threadlocal"
                 : "vararg");
         super.start();
     }
 
     /**
      * Decreases the reference count. If the reference count reached zero, the Disruptor and its associated thread are
      * shut down and their references set to {@code null}.
      */
     @Override
     public boolean stop(final long timeout, final TimeUnit timeUnit) {
         final Disruptor<RingBufferLogEvent> temp = getDisruptor();
         if (temp == null) {
             LOGGER.trace("[{}] AsyncLoggerDisruptor: disruptor for this context already shut down.", contextName);
             return true; // disruptor was already shut down by another thread
         }
         setStopping();
         LOGGER.debug("[{}] AsyncLoggerDisruptor: shutting down disruptor for this context.", contextName);
 
         // We must guarantee that publishing to the RingBuffer has stopped before we call disruptor.shutdown().
         disruptor = null; // client code fails with NPE if log after stop. This is by design.
 
         // Calling Disruptor.shutdown() will wait until all enqueued events are fully processed,
         // but this waiting happens in a busy-spin. To avoid (postpone) wasting CPU,
         // we sleep in short chunks, up to 10 seconds, waiting for the ringbuffer to drain.
         for (int i = 0; hasBacklog(temp) && i < MAX_DRAIN_ATTEMPTS_BEFORE_SHUTDOWN; i++) {
             try {
                 Thread.sleep(SLEEP_MILLIS_BETWEEN_DRAIN_ATTEMPTS); // give up the CPU for a while
             } catch (final InterruptedException e) { // ignored
             }
         }
         try {
             // busy-spins until all events currently in the disruptor have been processed
             temp.shutdown(timeout, timeUnit);
         } catch (final TimeoutException e) {
             temp.shutdown();
         } 
 
         LOGGER.trace("[{}] AsyncLoggerDisruptor: shutting down disruptor executor.", contextName);
         // finally, kill the processor thread
         ExecutorServices.shutdown(executor, timeout, timeUnit, toString());
         executor = null;
 
         if (DiscardingAsyncQueueFullPolicy.getDiscardCount(asyncQueueFullPolicy) > 0) {
             LOGGER.trace("AsyncLoggerDisruptor: {} discarded {} events.", asyncQueueFullPolicy,
                     DiscardingAsyncQueueFullPolicy.getDiscardCount(asyncQueueFullPolicy));
         }
         setStopped();
         return true;
     }
 
     /**
      * Returns {@code true} if the specified disruptor still has unprocessed events.
      */
     private static boolean hasBacklog(final Disruptor<?> theDisruptor) {
         final RingBuffer<?> ringBuffer = theDisruptor.getRingBuffer();
         return !ringBuffer.hasAvailableCapacity(ringBuffer.getBufferSize());
     }
 
     /**
      * Creates and returns a new {@code RingBufferAdmin} that instruments the ringbuffer of the {@code AsyncLogger}.
      *
      * @param jmxContextName name of the {@code AsyncLoggerContext}
      * @return a new {@code RingBufferAdmin} that instruments the ringbuffer
      */
     public RingBufferAdmin createRingBufferAdmin(final String jmxContextName) {
         final RingBuffer<RingBufferLogEvent> ring = disruptor == null ? null : disruptor.getRingBuffer();
         return RingBufferAdmin.forAsyncLogger(ring, jmxContextName);
     }
 
     EventRoute getEventRoute(final Level logLevel) {
         final int remainingCapacity = remainingDisruptorCapacity();
         if (remainingCapacity < 0) {
             return EventRoute.DISCARD;
         }
         return asyncQueueFullPolicy.getRoute(backgroundThreadId, logLevel);
     }
 
     private int remainingDisruptorCapacity() {
         final Disruptor<RingBufferLogEvent> temp = disruptor;
         if (hasLog4jBeenShutDown(temp)) {
             return -1;
         }
         return (int) temp.getRingBuffer().remainingCapacity();
     }
         /**
          * Returns {@code true} if the specified disruptor is null.
          */
     private boolean hasLog4jBeenShutDown(final Disruptor<RingBufferLogEvent> aDisruptor) {
         if (aDisruptor == null) { // LOG4J2-639
             LOGGER.warn("Ignoring log event after log4j was shut down");
             return true;
         }
         return false;
     }
 
     public boolean tryPublish(final RingBufferLogEventTranslator translator) {
         // LOG4J2-639: catch NPE if disruptor field was set to null in stop()
         try {
             return disruptor.getRingBuffer().tryPublishEvent(translator);
         } catch (final NullPointerException npe) {
             LOGGER.warn("[{}] Ignoring log event after log4j was shut down.", contextName);
             return false;
         }
     }
 
     void enqueueLogMessageInfo(final RingBufferLogEventTranslator translator) {
         // LOG4J2-639: catch NPE if disruptor field was set to null in stop()
         try {
             // Note: we deliberately access the volatile disruptor field afresh here.
             // Avoiding this and using an older reference could result in adding a log event to the disruptor after it
             // was shut down, which could cause the publishEvent method to hang and never return.
             disruptor.publishEvent(translator);
         } catch (final NullPointerException npe) {
             LOGGER.warn("[{}] Ignoring log event after log4j was shut down.", contextName);
         }
     }
 
     /**
      * Returns whether it is allowed to store non-JDK classes in ThreadLocal objects for efficiency.
      *
      * @return whether AsyncLoggers are allowed to use ThreadLocal objects
      * @since 2.5
      * @see <a href="https://issues.apache.org/jira/browse/LOG4J2-1172">LOG4J2-1172</a>
      */
     public boolean isUseThreadLocals() {
         return useThreadLocalTranslator;
     }
 
     /**
      * Signals this AsyncLoggerDisruptor whether it is allowed to store non-JDK classes in ThreadLocal objects for
      * efficiency.
      * <p>
      * This property may be modified after the {@link #start()} method has been called.
      * </p>
      *
      * @param allow whether AsyncLoggers are allowed to use ThreadLocal objects
      * @since 2.5
      * @see <a href="https://issues.apache.org/jira/browse/LOG4J2-1172">LOG4J2-1172</a>
      */
     public void setUseThreadLocals(final boolean allow) {
         useThreadLocalTranslator = allow;
         LOGGER.trace("[{}] AsyncLoggers have been modified to use a {} translator", contextName,
                 useThreadLocalTranslator ? "threadlocal" : "vararg");
     }
 }