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.cassandra.io.sstable.indexsummary;
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ScheduledFuture;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  import java.util.function.Supplier;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.collect.ImmutableSet;
  import com.google.common.collect.Sets;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import com.codahale.metrics.Timer;
  import org.apache.cassandra.concurrent.ScheduledExecutorPlus;
  import org.apache.cassandra.config.DatabaseDescriptor;
  import org.apache.cassandra.db.ColumnFamilyStore;
  import org.apache.cassandra.db.Keyspace;
  import org.apache.cassandra.db.compaction.CompactionInterruptedException;
  import org.apache.cassandra.db.compaction.CompactionManager;
  import org.apache.cassandra.db.compaction.OperationType;
  import org.apache.cassandra.db.lifecycle.LifecycleTransaction;
  import org.apache.cassandra.db.lifecycle.SSTableSet;
  import org.apache.cassandra.db.lifecycle.View;
  import org.apache.cassandra.io.sstable.format.SSTableReader;
  import org.apache.cassandra.schema.TableId;
  import org.apache.cassandra.utils.ExecutorUtils;
  import org.apache.cassandra.utils.FBUtilities;
  import org.apache.cassandra.utils.MBeanWrapper;
  import org.apache.cassandra.utils.Pair;
  import org.apache.cassandra.utils.WrappedRunnable;
  
  import static org.apache.cassandra.concurrent.ExecutorFactory.Global.executorFactory;
  /**
   * Manages the fixed-size memory pool for index summaries, periodically resizing them
   * in order to give more memory to hot sstables and less memory to cold sstables.
   */
  public class IndexSummaryManager<T extends SSTableReader & IndexSummarySupport<T>> implements IndexSummaryManagerMBean
  {
      private static final Logger logger = LoggerFactory.getLogger(IndexSummaryManager.class);
      public static final String MBEAN_NAME = "org.apache.cassandra.db:type=IndexSummaries";
      public static final IndexSummaryManager<?> instance;
  
      private long memoryPoolBytes;
  
      private final ScheduledExecutorPlus executor;
  
      // our next scheduled resizing run
      private ScheduledFuture future;
  
      private final Supplier<List<T>> indexSummariesProvider;
  
      private static <T extends SSTableReader & IndexSummarySupport<T>> List<T> getAllSupportedReaders() {
          List<T> readers = new ArrayList<>();
          for (Keyspace keyspace : Keyspace.all())
              for (ColumnFamilyStore cfs : keyspace.getColumnFamilyStores())
                  for (SSTableReader sstr : cfs.getLiveSSTables())
                      if (sstr instanceof IndexSummarySupport)
                          readers.add(((T) sstr));
          return readers;
      }
  
      static
      {
          instance = newInstance();
          MBeanWrapper.instance.registerMBean(instance, MBEAN_NAME);
      }
  
      private static <T extends SSTableReader & IndexSummarySupport<T>> IndexSummaryManager<T> newInstance()
      {
          return new IndexSummaryManager<>(IndexSummaryManager::getAllSupportedReaders);
      }
  
      private IndexSummaryManager(Supplier<List<T>> indexSummariesProvider)
      {
          this.indexSummariesProvider = indexSummariesProvider;
  
          executor = executorFactory().scheduled(false, "IndexSummaryManager", Thread.MIN_PRIORITY);
  
          long indexSummarySizeInMB = DatabaseDescriptor.getIndexSummaryCapacityInMiB();
          int interval = DatabaseDescriptor.getIndexSummaryResizeIntervalInMinutes();
          logger.info("Initializing index summary manager with a memory pool size of {} MB and a resize interval of {} minutes",
                      indexSummarySizeInMB, interval);
  
          setMemoryPoolCapacityInMB(DatabaseDescriptor.getIndexSummaryCapacityInMiB());
          setResizeIntervalInMinutes(DatabaseDescriptor.getIndexSummaryResizeIntervalInMinutes());
      }
  
      public int getResizeIntervalInMinutes()
      {
          return DatabaseDescriptor.getIndexSummaryResizeIntervalInMinutes();
      }
  
      public void setResizeIntervalInMinutes(int resizeIntervalInMinutes)
      {
          int oldInterval = getResizeIntervalInMinutes();
          DatabaseDescriptor.setIndexSummaryResizeIntervalInMinutes(resizeIntervalInMinutes);
  
          long initialDelay;
          if (future != null)
          {
              initialDelay = oldInterval < 0
                             ? resizeIntervalInMinutes
                             : Math.max(0, resizeIntervalInMinutes - (oldInterval - future.getDelay(TimeUnit.MINUTES)));
              future.cancel(false);
          }
          else
          {
              initialDelay = resizeIntervalInMinutes;
          }
  
          if (resizeIntervalInMinutes < 0)
          {
              future = null;
              return;
          }
  
          future = executor.scheduleWithFixedDelay(new WrappedRunnable()
          {
              protected void runMayThrow() throws Exception
              {
                  redistributeSummaries();
              }
          }, initialDelay, resizeIntervalInMinutes, TimeUnit.MINUTES);
      }
  
      // for testing only
      @VisibleForTesting
      Long getTimeToNextResize(TimeUnit timeUnit)
      {
          if (future == null)
              return null;
  
          return future.getDelay(timeUnit);
      }
  
      public long getMemoryPoolCapacityInMB()
      {
          return memoryPoolBytes / 1024L / 1024L;
      }
  
      public Map<String, Integer> getIndexIntervals()
      {
          List<T> summaryProviders = indexSummariesProvider.get();
          Map<String, Integer> intervals = new HashMap<>(summaryProviders.size());
          for (T summaryProvider : summaryProviders)
              intervals.put(summaryProvider.getFilename(), (int) Math.round(summaryProvider.getIndexSummary().getEffectiveIndexInterval()));
  
          return intervals;
      }
  
      public double getAverageIndexInterval()
      {
          List<T> summaryProviders = indexSummariesProvider.get();
          double total = 0.0;
          for (IndexSummarySupport summaryProvider : summaryProviders)
              total += summaryProvider.getIndexSummary().getEffectiveIndexInterval();
          return total / summaryProviders.size();
      }
  
      public void setMemoryPoolCapacityInMB(long memoryPoolCapacityInMB)
      {
          this.memoryPoolBytes = memoryPoolCapacityInMB * 1024L * 1024L;
      }
  
      /**
       * Returns the actual space consumed by index summaries for all sstables.
       * @return space currently used in MB
       */
      public double getMemoryPoolSizeInMB()
      {
          long total = 0;
          for (IndexSummarySupport summaryProvider : indexSummariesProvider.get())
              total += summaryProvider.getIndexSummary().getOffHeapSize();
          return total / 1024.0 / 1024.0;
      }
  
      /**
       * Marks the non-compacting sstables as compacting for index summary redistribution for all keyspaces/tables.
       *
       * @return Pair containing:
       *          left: total size of the off heap index summaries for the sstables we were unable to mark compacting (they were involved in other compactions)
       *          right: the transactions, keyed by table id.
       */
      private Pair<Long, Map<TableId, LifecycleTransaction>> getRestributionTransactions()
      {
          List<SSTableReader> allCompacting = new ArrayList<>();
          Map<TableId, LifecycleTransaction> allNonCompacting = new HashMap<>();
          for (Keyspace ks : Keyspace.all())
          {
              for (ColumnFamilyStore cfStore: ks.getColumnFamilyStores())
              {
                  Set<SSTableReader> nonCompacting, allSSTables;
                  LifecycleTransaction txn;
                  do
                  {
                      View view = cfStore.getTracker().getView();
                      allSSTables = ImmutableSet.copyOf(view.select(SSTableSet.CANONICAL));
                      nonCompacting = ImmutableSet.copyOf(view.getUncompacting(allSSTables));
                  }
                  while (null == (txn = cfStore.getTracker().tryModify(nonCompacting, OperationType.INDEX_SUMMARY)));
  
                  allNonCompacting.put(cfStore.metadata.id, txn);
                  allCompacting.addAll(Sets.difference(allSSTables, nonCompacting));
              }
          }
          long nonRedistributingOffHeapSize = allCompacting.stream()
                                                           .filter(IndexSummarySupport.class::isInstance)
                                                           .map(IndexSummarySupport.class::cast)
                                                           .map(IndexSummarySupport::getIndexSummary)
                                                           .mapToLong(IndexSummary::getOffHeapSize)
                                                           .sum();
          return Pair.create(nonRedistributingOffHeapSize, allNonCompacting);
      }
  
      public void redistributeSummaries() throws IOException
      {
          if (CompactionManager.instance.isGlobalCompactionPaused())
              return;
          Pair<Long, Map<TableId, LifecycleTransaction>> redistributionTransactionInfo = getRestributionTransactions();
          Map<TableId, LifecycleTransaction> transactions = redistributionTransactionInfo.right;
          long nonRedistributingOffHeapSize = redistributionTransactionInfo.left;
          try (Timer.Context ctx = CompactionManager.instance.getMetrics().indexSummaryRedistributionTime.time())
          {
              redistributeSummaries(new IndexSummaryRedistribution(transactions,
                                                                   nonRedistributingOffHeapSize,
                                                                   this.memoryPoolBytes));
          }
          catch (Exception e)
          {
              if (e instanceof CompactionInterruptedException)
              {
                  logger.info("Index summary interrupted: {}", e.getMessage());
              }
              else
              {
                  logger.error("Got exception during index summary redistribution", e);
                  throw e;
              }
          }
          finally
          {
              try
              {
                  FBUtilities.closeAll(transactions.values());
              }
              catch (Exception e)
              {
                  throw new RuntimeException(e);
              }
          }
      }
  
      /**
       * Attempts to fairly distribute a fixed pool of memory for index summaries across a set of SSTables based on
       * their recent read rates.
       * @param redistribution encapsulating the transactions containing the sstables we are to redistribute the
       *                       memory pool across and a size (in bytes) that the total index summary space usage
       *                       should stay close to or under, if possible
       * @return a list of new SSTableReader instances
       */
      @VisibleForTesting
      public static <T extends SSTableReader & IndexSummarySupport> List<T> redistributeSummaries(IndexSummaryRedistribution redistribution) throws IOException
      {
          return (List<T>) CompactionManager.instance.runAsActiveCompaction(redistribution, redistribution::redistributeSummaries);
      }
  
      @VisibleForTesting
      public void shutdownAndWait(long timeout, TimeUnit unit) throws InterruptedException, TimeoutException
      {
          if (future != null)
          {
              future.cancel(false);
              future = null;
          }
          ExecutorUtils.shutdownAndWait(timeout, unit, executor);
      }
  }
  