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 gobblin.hive; import java.io.IOException; import java.util.Map; import java.util.Properties; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.TimeUnit; import org.apache.commons.pool2.impl.GenericObjectPool; import org.apache.commons.pool2.impl.GenericObjectPoolConfig; import org.apache.hadoop.hive.conf.HiveConf; import org.apache.hadoop.hive.metastore.IMetaStoreClient; import com.google.common.base.Optional; import com.google.common.cache.Cache; import com.google.common.cache.CacheBuilder; import com.google.common.cache.RemovalListener; import com.google.common.cache.RemovalNotification; import com.google.common.collect.Maps; import com.google.common.io.Closer; import gobblin.configuration.State; import gobblin.util.AutoReturnableObject; import lombok.Getter; /** * A pool of {@link IMetaStoreClient} for querying the Hive metastore. */ public class HiveMetastoreClientPool { private final GenericObjectPool<IMetaStoreClient> pool; private final HiveMetaStoreClientFactory factory; @Getter private final HiveConf hiveConf; @Getter private final HiveRegProps hiveRegProps; private static final long DEFAULT_POOL_CACHE_TTL_MINUTES = 30; private static final Cache<Optional<String>, HiveMetastoreClientPool> poolCache = CacheBuilder.newBuilder() .expireAfterAccess(DEFAULT_POOL_CACHE_TTL_MINUTES, TimeUnit.MINUTES) .removalListener(new RemovalListener<Optional<String>, HiveMetastoreClientPool>() { @Override public void onRemoval(RemovalNotification<Optional<String>, HiveMetastoreClientPool> notification) { if (notification.getValue() != null) { notification.getValue().close(); } } }).build(); /** * Get a {@link HiveMetastoreClientPool} for the requested metastore URI. Useful for using the same pools across * different classes in the code base. Note that if a pool already exists for that metastore, the max number of * objects available will be unchanged, and it might be lower than requested by this method. * * @param properties {@link Properties} used to generate the pool. * @param metastoreURI URI of the Hive metastore. If absent, use default metastore. * @return a {@link HiveMetastoreClientPool}. * @throws IOException */ public static HiveMetastoreClientPool get(final Properties properties, final Optional<String> metastoreURI) throws IOException { try { return poolCache.get(metastoreURI, new Callable<HiveMetastoreClientPool>() { @Override public HiveMetastoreClientPool call() throws Exception { return new HiveMetastoreClientPool(properties, metastoreURI); } }); } catch (ExecutionException ee) { throw new IOException("Failed to get " + HiveMetastoreClientPool.class.getSimpleName(), ee.getCause()); } } /** * Constructor for {@link HiveMetastoreClientPool}. * @deprecated It is recommended to use the static {@link #get} method instead. Use this constructor only if you * different pool configurations are required. */ @Deprecated public HiveMetastoreClientPool(Properties properties, Optional<String> metastoreURI) { this.hiveRegProps = new HiveRegProps(new State(properties)); GenericObjectPoolConfig config = new GenericObjectPoolConfig(); config.setMaxTotal(this.hiveRegProps.getNumThreads()); config.setMaxIdle(this.hiveRegProps.getNumThreads()); this.factory = new HiveMetaStoreClientFactory(metastoreURI); this.pool = new GenericObjectPool<>(this.factory, config); this.hiveConf = this.factory.getHiveConf(); } public void close() { this.pool.close(); } /** * @return an auto returnable wrapper around a {@link IMetaStoreClient}. * @throws IOException * Note: if you must acquire multiple locks, please use {@link #safeGetClients} instead, as this call may deadlock. */ public AutoReturnableObject<IMetaStoreClient> getClient() throws IOException { return new AutoReturnableObject<>(this.pool); } /** * A class wrapping multiple named {@link IMetaStoreClient}s. */ public static class MultiClient implements AutoCloseable { private final Map<String, AutoReturnableObject<IMetaStoreClient>> clients; private final Closer closer; private MultiClient(Map<String, HiveMetastoreClientPool> namedPools) throws IOException { this.clients = Maps.newHashMap(); this.closer = Closer.create(); Map<HiveMetastoreClientPool, Integer> requiredClientsPerPool = Maps.newHashMap(); for (Map.Entry<String, HiveMetastoreClientPool> entry : namedPools.entrySet()) { if (requiredClientsPerPool.containsKey(entry.getValue())) { requiredClientsPerPool.put(entry.getValue(), requiredClientsPerPool.get(entry.getValue()) + 1); } else { requiredClientsPerPool.put(entry.getValue(), 1); } } for (Map.Entry<HiveMetastoreClientPool, Integer> entry : requiredClientsPerPool.entrySet()) { if (entry.getKey().pool.getMaxTotal() < entry.getValue()) { throw new IOException(String.format( "Not enough clients available in the pool. Required %d, max available %d.", entry.getValue(), entry.getKey().pool.getMaxTotal())); } } for (Map.Entry<String, HiveMetastoreClientPool> entry : namedPools.entrySet()) { this.clients.put(entry.getKey(), this.closer.register(entry.getValue().getClient())); } } /** * Get the {@link IMetaStoreClient} with the provided name. * @throws IOException */ public IMetaStoreClient getClient(String name) throws IOException { if (!this.clients.containsKey(name)) { throw new IOException("There is no client with name " + name); } return this.clients.get(name).get(); } @Override public void close() throws IOException { this.closer.close(); } } /** * A method to get multiple {@link IMetaStoreClient}s while preventing deadlocks. * @param namedPools A map from String to {@link HiveMetastoreClientPool}. * @return a {@link MultiClient} with a {@link IMetaStoreClient} for each entry in the input map. The client can * be retrieved by its name in the input map. * @throws IOException */ public static synchronized MultiClient safeGetClients(Map<String, HiveMetastoreClientPool> namedPools) throws IOException { return new MultiClient(namedPools); } }