content: /*
   * 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.ambari.server.controller.metrics.timeline.cache;
  
  import java.io.IOException;
  import java.net.SocketTimeoutException;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.apache.hadoop.metrics2.sink.timeline.TimelineMetrics;
  import org.ehcache.Cache;
  import org.ehcache.core.internal.statistics.DefaultStatisticsService;
  import org.ehcache.core.statistics.CacheStatistics;
  import org.ehcache.spi.loaderwriter.CacheLoadingException;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class TimelineMetricCache {
    private final Cache<TimelineAppMetricCacheKey, TimelineMetricsCacheValue> cache;
    private final DefaultStatisticsService statisticsService;
    private final TimelineMetricCacheEntryFactory cacheEntryFactory;
    public static final String TIMELINE_METRIC_CACHE_INSTANCE_NAME = "timelineMetricCache";
    private final static Logger LOG = LoggerFactory.getLogger(TimelineMetricCache.class);
    private static AtomicInteger printCacheStatsCounter = new AtomicInteger(0);
  
    /**
     * Creates a TimelineMetricCache.
     *
     * @param cache @Cache
     * @param cacheEntryFactory @CacheEntryFactory
     * @param statisticsService @DefaultStatisticsService
     */
    public TimelineMetricCache(Cache<TimelineAppMetricCacheKey, TimelineMetricsCacheValue> cache, TimelineMetricCacheEntryFactory cacheEntryFactory, DefaultStatisticsService statisticsService) {
      this.cache = cache;
      this.cacheEntryFactory = cacheEntryFactory;
      this.statisticsService = statisticsService;
    }
  
    /**
     * Get metrics for an app grouped by the requested @TemporalInfo which is a
     * part of the @TimelineAppMetricCacheKey
     * @param key @TimelineAppMetricCacheKey
     * @return @org.apache.hadoop.metrics2.sink.timeline.TimelineMetrics
     */
    public TimelineMetrics getAppTimelineMetricsFromCache(TimelineAppMetricCacheKey key) throws IllegalArgumentException, IOException {
      if (LOG.isDebugEnabled()) {
        LOG.debug("Fetching metrics with key: {}", key);
      }
  
      // Make sure key is valid
      validateKey(key);
  
      TimelineMetricsCacheValue value = null;
      try {
        value = cache.get(key);
      } catch (CacheLoadingException cle) {
        Throwable t = cle.getCause();
        if(t instanceof SocketTimeoutException) {
          throw new SocketTimeoutException(t.getMessage());
        }
        if(t instanceof IOException) {
          throw new IOException(t.getMessage());
        }
        throw cle;
      }
  
      TimelineMetrics timelineMetrics = new TimelineMetrics();
      if (value != null) {
        if (LOG.isDebugEnabled()) {
          LOG.debug("Returning value from cache: {}", value);
        }
        timelineMetrics = value.getTimelineMetrics();
      }
  
      if (LOG.isDebugEnabled()) {
        // Print stats every 100 calls - Note: Supported in debug mode only
        if (printCacheStatsCounter.getAndIncrement() == 0) {
          CacheStatistics cacheStatistics = statisticsService.getCacheStatistics(TIMELINE_METRIC_CACHE_INSTANCE_NAME);
          if(cacheStatistics == null) {
            LOG.warn("Cache statistics not available.");
            return timelineMetrics;
          }
          LOG.debug("Metrics cache stats => \n, Evictions = {}, Expired = {}, Hits = {}, Misses = {}, Hit ratio = {}, Puts = {}",
                  cacheStatistics.getCacheEvictions(), cacheStatistics.getCacheExpirations(), cacheStatistics.getCacheHits(), cacheStatistics.getCacheMisses(), cacheStatistics.getCacheHitPercentage(), cacheStatistics.getCachePuts()
          );
        } else {
          printCacheStatsCounter.compareAndSet(100, 0);
        }
      }
      return timelineMetrics;
    }
  
    private void validateKey(TimelineAppMetricCacheKey key) throws IllegalArgumentException {
      StringBuilder msg = new StringBuilder("Invalid metric key requested.");
      boolean throwException = false;
  
      if (key.getTemporalInfo() == null) {
        msg.append(" No temporal info provided.");
        throwException = true;
      }
  
      if (key.getSpec() == null) {
        msg.append(" Missing call spec for metric request.");
      }
  
      if (throwException) {
        throw new IllegalArgumentException(msg.toString());
      }
    }
  }
  