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.Objects; import java.util.concurrent.ExecutionException; import java.util.concurrent.TimeUnit; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.hbase.TableNotFoundException; import org.apache.hadoop.hbase.client.HTableInterface; import org.apache.hadoop.hbase.util.Bytes; import org.apache.phoenix.hbase.index.util.ImmutableBytesPtr; import org.apache.phoenix.jdbc.PhoenixDatabaseMetaData; import org.apache.phoenix.schema.stats.PTableStats; 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 PTableStats} for Phoenix tables. Intended to decouple * Phoenix from a specific version of Guava's cache. */ public class TableStatsCache { private static final Logger logger = LoggerFactory.getLogger(TableStatsCache.class); private final ConnectionQueryServices queryServices; private final LoadingCache<ImmutableBytesPtr, PTableStats> cache; public TableStatsCache(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<ImmutableBytesPtr, PTableStats>() { @Override public int weigh(ImmutableBytesPtr key, PTableStats stats) { return stats.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<ImmutableBytesPtr, PTableStats> { @Override public PTableStats load(ImmutableBytesPtr tableName) throws Exception { @SuppressWarnings("deprecation") HTableInterface statsHTable = queryServices.getTable(SchemaUtil .getPhysicalName(PhoenixDatabaseMetaData.SYSTEM_STATS_NAME_BYTES, queryServices.getProps()) .getName()); final byte[] tableNameBytes = tableName.copyBytesIfNecessary(); try { PTableStats stats = StatisticsUtil.readStatistics(statsHTable, tableNameBytes, Long.MAX_VALUE); traceStatsUpdate(tableNameBytes, stats); return stats; } 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 PTableStats.EMPTY_STATS; } 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 PTableStats.EMPTY_STATS; } 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(byte[] tableName, PTableStats stats) { logger.trace("Updating local TableStats cache (id={}) for {}, size={}bytes", new Object[] { Objects.hashCode(TableStatsCache.this), Bytes.toString(tableName), stats.getEstimatedSize() }); } } /** * Returns the underlying cache. Try to use the provided methods instead of accessing the cache * directly. */ LoadingCache<ImmutableBytesPtr, PTableStats> 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 PTableStats get(ImmutableBytesPtr tableName) throws ExecutionException { return getCache().get(tableName); } /** * 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(ImmutableBytesPtr tableName, PTableStats stats) { getCache().put(Objects.requireNonNull(tableName), Objects.requireNonNull(stats)); } /** * Removes the mapping for <code>tableName</code> if it exists. * * @see com.google.common.cache.Cache#invalidate(Object) */ public void invalidate(ImmutableBytesPtr tableName) { getCache().invalidate(Objects.requireNonNull(tableName)); } /** * Removes all mappings from the cache. * * @see com.google.common.cache.Cache#invalidateAll() */ public void invalidateAll() { getCache().invalidateAll(); } /** * A {@link RemovalListener} implementation to track evictions from the table stats cache. */ static class PhoenixStatsCacheRemovalListener implements RemovalListener<ImmutableBytesPtr, PTableStats> { @Override public void onRemoval(RemovalNotification<ImmutableBytesPtr, PTableStats> notification) { final RemovalCause cause = notification.getCause(); if (wasEvicted(cause)) { ImmutableBytesPtr ptr = notification.getKey(); String tableName = new String(ptr.get(), ptr.getOffset(), ptr.getLength()); logger.trace("Cached stats for {} with size={}bytes was evicted due to cause={}", new Object[] { tableName, 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; } } }