Java tutorial
/* * 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.phoenix.query; import java.io.IOException; import java.util.List; import java.util.Objects; import java.util.concurrent.ExecutionException; import java.util.concurrent.TimeUnit; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.HConstants; import org.apache.hadoop.hbase.HTableDescriptor; import org.apache.hadoop.hbase.TableNotFoundException; import org.apache.hadoop.hbase.client.HTableInterface; import org.apache.hadoop.hbase.util.Bytes; import org.apache.phoenix.jdbc.PhoenixDatabaseMetaData; import org.apache.phoenix.schema.PColumnFamily; import org.apache.phoenix.schema.PTable; import org.apache.phoenix.schema.stats.GuidePostsInfo; import org.apache.phoenix.schema.stats.GuidePostsKey; import org.apache.phoenix.schema.stats.StatisticsUtil; import org.apache.phoenix.util.SchemaUtil; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.google.common.cache.CacheBuilder; import com.google.common.cache.CacheLoader; import com.google.common.cache.LoadingCache; import com.google.common.cache.RemovalCause; import com.google.common.cache.RemovalListener; import com.google.common.cache.RemovalNotification; import com.google.common.cache.Weigher; /** * "Client-side" cache for storing {@link GuidePostsInfo} for a column family. Intended to decouple * Phoenix from a specific version of Guava's cache. */ public class GuidePostsCache { private static final Logger logger = LoggerFactory.getLogger(GuidePostsCache.class); private final ConnectionQueryServices queryServices; private final LoadingCache<GuidePostsKey, GuidePostsInfo> cache; public GuidePostsCache(ConnectionQueryServices queryServices, Configuration config) { this.queryServices = Objects.requireNonNull(queryServices); // Number of millis to expire cache values after write final long statsUpdateFrequency = config.getLong(QueryServices.STATS_UPDATE_FREQ_MS_ATTRIB, QueryServicesOptions.DEFAULT_STATS_UPDATE_FREQ_MS); // Maximum number of entries (tables) to store in the cache at one time final long maxTableStatsCacheSize = config.getLong(QueryServices.STATS_MAX_CACHE_SIZE, QueryServicesOptions.DEFAULT_STATS_MAX_CACHE_SIZE); cache = CacheBuilder.newBuilder() // Expire entries a given amount of time after they were written .expireAfterWrite(statsUpdateFrequency, TimeUnit.MILLISECONDS) // Maximum total weight (size in bytes) of stats entries .maximumWeight(maxTableStatsCacheSize) // Defer actual size to the PTableStats.getEstimatedSize() .weigher(new Weigher<GuidePostsKey, GuidePostsInfo>() { @Override public int weigh(GuidePostsKey key, GuidePostsInfo info) { return info.getEstimatedSize(); } }) // Log removals at TRACE for debugging .removalListener(new PhoenixStatsCacheRemovalListener()) // Automatically load the cache when entries are missing .build(new StatsLoader()); } /** * {@link CacheLoader} implementation for the Phoenix Table Stats cache. */ protected class StatsLoader extends CacheLoader<GuidePostsKey, GuidePostsInfo> { @Override public GuidePostsInfo load(GuidePostsKey statsKey) throws Exception { @SuppressWarnings("deprecation") HTableInterface statsHTable = queryServices.getTable(SchemaUtil .getPhysicalName(PhoenixDatabaseMetaData.SYSTEM_STATS_NAME_BYTES, queryServices.getProps()) .getName()); try { GuidePostsInfo guidePostsInfo = StatisticsUtil.readStatistics(statsHTable, statsKey, HConstants.LATEST_TIMESTAMP); traceStatsUpdate(statsKey, guidePostsInfo); return guidePostsInfo; } catch (TableNotFoundException e) { // On a fresh install, stats might not yet be created, don't warn about this. logger.debug("Unable to locate Phoenix stats table", e); return GuidePostsInfo.NO_GUIDEPOST; } catch (IOException e) { logger.warn("Unable to read from stats table", e); // Just cache empty stats. We'll try again after some time anyway. return GuidePostsInfo.NO_GUIDEPOST; } finally { try { statsHTable.close(); } catch (IOException e) { // Log, but continue. We have our stats anyway now. logger.warn("Unable to close stats table", e); } } } /** * Logs a trace message for newly inserted entries to the stats cache. */ void traceStatsUpdate(GuidePostsKey key, GuidePostsInfo info) { if (logger.isTraceEnabled()) { logger.trace("Updating local TableStats cache (id={}) for {}, size={}bytes", new Object[] { Objects.hashCode(GuidePostsCache.this), key, info.getEstimatedSize() }); } } } /** * Returns the underlying cache. Try to use the provided methods instead of accessing the cache * directly. */ LoadingCache<GuidePostsKey, GuidePostsInfo> getCache() { return cache; } /** * Returns the PTableStats for the given <code>tableName</code, using the provided * <code>valueLoader</code> if no such mapping exists. * * @see com.google.common.cache.LoadingCache#get(Object) */ public GuidePostsInfo get(GuidePostsKey key) throws ExecutionException { return getCache().get(key); } /** * Cache the given <code>stats</code> to the cache for the given <code>tableName</code>. * * @see com.google.common.cache.Cache#put(Object, Object) */ public void put(GuidePostsKey key, GuidePostsInfo info) { getCache().put(Objects.requireNonNull(key), Objects.requireNonNull(info)); } /** * Removes the mapping for <code>tableName</code> if it exists. * * @see com.google.common.cache.Cache#invalidate(Object) */ public void invalidate(GuidePostsKey key) { getCache().invalidate(Objects.requireNonNull(key)); } /** * Removes all mappings from the cache. * * @see com.google.common.cache.Cache#invalidateAll() */ public void invalidateAll() { getCache().invalidateAll(); } /** * Removes all mappings where the {@link org.apache.phoenix.schema.stats.GuidePostsKey#getPhysicalName()} * equals physicalName. Because all keys in the map must be iterated, this method should be avoided. * @param physicalName */ public void invalidateAll(byte[] physicalName) { for (GuidePostsKey key : getCache().asMap().keySet()) { if (Bytes.compareTo(key.getPhysicalName(), physicalName) == 0) { invalidate(key); } } } public void invalidateAll(HTableDescriptor htableDesc) { byte[] tableName = htableDesc.getTableName().getName(); for (byte[] fam : htableDesc.getFamiliesKeys()) { invalidate(new GuidePostsKey(tableName, fam)); } } public void invalidateAll(PTable table) { byte[] physicalName = table.getPhysicalName().getBytes(); List<PColumnFamily> families = table.getColumnFamilies(); if (families.isEmpty()) { invalidate(new GuidePostsKey(physicalName, SchemaUtil.getEmptyColumnFamily(table))); } else { for (PColumnFamily family : families) { invalidate(new GuidePostsKey(physicalName, family.getName().getBytes())); } } } /** * A {@link RemovalListener} implementation to track evictions from the table stats cache. */ static class PhoenixStatsCacheRemovalListener implements RemovalListener<GuidePostsKey, GuidePostsInfo> { @Override public void onRemoval(RemovalNotification<GuidePostsKey, GuidePostsInfo> notification) { if (logger.isTraceEnabled()) { final RemovalCause cause = notification.getCause(); if (wasEvicted(cause)) { GuidePostsKey key = notification.getKey(); logger.trace("Cached stats for {} with size={}bytes was evicted due to cause={}", new Object[] { key, notification.getValue().getEstimatedSize(), cause }); } } } boolean wasEvicted(RemovalCause cause) { // This is actually a method on RemovalCause but isn't exposed return RemovalCause.EXPLICIT != cause && RemovalCause.REPLACED != cause; } } }