dlmarion commented on code in PR #6156: URL: https://github.com/apache/accumulo/pull/6156#discussion_r2874189385
########## core/src/main/java/org/apache/accumulo/core/clientImpl/OfflineTabletLocatorImpl.java: ########## @@ -0,0 +1,365 @@ +/* + * 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 + * + * https://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.accumulo.core.clientImpl; + +import java.time.Duration; +import java.util.ArrayList; +import java.util.Collection; +import java.util.HashSet; +import java.util.Iterator; +import java.util.List; +import java.util.Map; +import java.util.Properties; +import java.util.Set; +import java.util.TreeSet; +import java.util.concurrent.LinkedBlockingQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.concurrent.locks.ReentrantReadWriteLock; + +import org.apache.accumulo.core.client.AccumuloException; +import org.apache.accumulo.core.client.AccumuloSecurityException; +import org.apache.accumulo.core.client.TableNotFoundException; +import org.apache.accumulo.core.conf.ClientProperty; +import org.apache.accumulo.core.data.Key; +import org.apache.accumulo.core.data.Mutation; +import org.apache.accumulo.core.data.PartialKey; +import org.apache.accumulo.core.data.Range; +import org.apache.accumulo.core.data.TableId; +import org.apache.accumulo.core.dataImpl.KeyExtent; +import org.apache.accumulo.core.manager.state.tables.TableState; +import org.apache.accumulo.core.metadata.schema.TabletMetadata; +import org.apache.accumulo.core.metadata.schema.TabletMetadata.ColumnType; +import org.apache.accumulo.core.metadata.schema.TabletsMetadata; +import org.apache.accumulo.core.util.Timer; +import org.apache.hadoop.io.Text; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import com.github.benmanes.caffeine.cache.Cache; +import com.github.benmanes.caffeine.cache.Caffeine; +import com.github.benmanes.caffeine.cache.Policy.Eviction; +import com.github.benmanes.caffeine.cache.RemovalCause; +import com.github.benmanes.caffeine.cache.RemovalListener; +import com.github.benmanes.caffeine.cache.Ticker; +import com.google.common.base.Preconditions; + +import io.micrometer.core.instrument.Metrics; +import io.micrometer.core.instrument.binder.cache.CaffeineStatsCounter; + +public class OfflineTabletLocatorImpl extends TabletLocator { + + private static final Logger LOG = LoggerFactory.getLogger(OfflineTabletLocatorImpl.class); + + public static class OfflineTabletLocation extends TabletLocation { + + public static final String SERVER = "offline_table_marker"; + + public OfflineTabletLocation(KeyExtent tablet_extent) { + super(tablet_extent, SERVER, SERVER); + } + + } + + private class OfflineTabletsCache implements RemovalListener<KeyExtent,KeyExtent> { + + // This object uses a Caffeine cache to manage the duration of the extents + // cached in the TreeSet. The TreeSet is necessary for expedient operations. + + private final ClientContext context; + private final int maxCacheSize; + private final int prefetch; + private final Cache<KeyExtent,KeyExtent> cache; + private final LinkedBlockingQueue<KeyExtent> evictions = new LinkedBlockingQueue<>(); + private final TreeSet<KeyExtent> extents = new TreeSet<>(); + private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(); + private final Timer scanTimer = Timer.startNew(); + private final AtomicInteger cacheCount = new AtomicInteger(0); + private final Eviction<KeyExtent,KeyExtent> evictionPolicy; + + private OfflineTabletsCache(ClientContext context) { + this.context = context; + Properties clientProperties = context.getProperties(); + Duration cacheDuration = Duration.ofMillis( + ClientProperty.OFFLINE_LOCATOR_CACHE_DURATION.getTimeInMillis(clientProperties)); + maxCacheSize = + Integer.parseInt(ClientProperty.OFFLINE_LOCATOR_CACHE_SIZE.getValue(clientProperties)); + prefetch = Integer + .parseInt(ClientProperty.OFFLINE_LOCATOR_CACHE_PREFETCH.getValue(clientProperties)); + + // This cache is used to evict KeyExtents from the extents TreeSet when + // they have not been accessed in cacheDuration. We are targeting to have + // maxCacheSize objects in the cache, but are not using the Cache's maximumSize + // to achieve this as the Cache will remove things from the Cache that were + // newly inserted and not yet used. This negates the pre-fetching feature + // that we have added into this TabletLocator for offline tables. Here we + // set the maximum size much larger that the property and use the cacheCount + // variable to manage the max size manually. + cache = Caffeine.newBuilder().expireAfterAccess(cacheDuration).initialCapacity(maxCacheSize) + .maximumSize(maxCacheSize * 2).removalListener(this).ticker(Ticker.systemTicker()) + .recordStats(() -> new CaffeineStatsCounter(Metrics.globalRegistry, + OfflineTabletsCache.class.getSimpleName())) + .build(); + evictionPolicy = cache.policy().eviction().orElseThrow(); + } + + @Override + public void onRemoval(KeyExtent key, KeyExtent value, RemovalCause cause) { + if (cause == RemovalCause.REPLACED) { + return; + } + LOG.trace("Extent {} was evicted from cache for {} ", key, cause); + cacheCount.decrementAndGet(); + evictions.add(key); + try { + if (lock.writeLock().tryLock(1, TimeUnit.MILLISECONDS)) { + try { + processRecentCacheEvictions(); + } finally { + lock.writeLock().unlock(); + } + } + } catch (InterruptedException e) { + Thread.currentThread().interrupt(); + throw new RuntimeException("Interrupted while waiting to acquire write lock", e); + } + } + + private void processRecentCacheEvictions() { + Preconditions.checkArgument(lock.writeLock().isHeldByCurrentThread()); + Set<KeyExtent> copy = new HashSet<>(); + evictions.drainTo(copy); + int numEvictions = copy.size(); + if (numEvictions > 0) { + LOG.trace("Processing {} prior evictions", numEvictions); + extents.removeAll(copy); + } + } + + private KeyExtent findOrLoadExtent(KeyExtent searchKey) { + lock.readLock().lock(); + try { + KeyExtent match = extents.ceiling(searchKey); + if (match != null && match.contains(searchKey.endRow())) { + // update access time in cache + @SuppressWarnings("unused") + var unused = cache.getIfPresent(match); + LOG.trace("Extent {} found in cache for start row {}", match, searchKey); + return match; + } + } finally { + lock.readLock().unlock(); + } + lock.writeLock().lock(); + // process prior evictions since we have the write lock + processRecentCacheEvictions(); + // The following block of code fixes an issue with + // the cache where recently pre-fetched extents + // will be evicted from the cache when it reaches + // the maxCacheSize. This is because from the cache's + // perspective they are the coldest objects. The code + // below manually removes the coldest extents that are + // before the searchKey.endRow to make room for the next + // batch of extents that we are going to load into the + // cache so that they are not immediately evicted. + if (cacheCount.get() + prefetch + 1 >= maxCacheSize) { + int evictionSize = prefetch * 2; + Set<KeyExtent> candidates = new HashSet<>(evictionPolicy.coldest(evictionSize).keySet()); Review Comment: `evictionPolicy.coldest()` works when setting the Caffeine `maximumSize` option. Another approach would be to *not* set the `maximumSize` on the Cache at all, and use `cache.policy().expireAfterAccess().orElseThrow().youngest(int)` instead. I'm not sure, but this may be functionally equivalent but might allow us to remove some code trying to deal with Caffeine removing objects prematurely based on size. -- This is an automated message from the Apache Git Service. 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