Java tutorial
/* * Copyright 2010-2013 10gen Inc. * * Licensed 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 com.zjy.mongo.splitter; import com.mongodb.CommandResult; import com.mongodb.DBCollection; import com.mongodb.MongoClientURI; import com.zjy.mongo.util.MongoConfigUtil; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.util.ReflectionUtils; /** * Examines a collection and dynamically chooses which implementation of MongoSplitter to use, based on our configuration and the * collection's properties. */ public final class MongoSplitterFactory { private static final Log LOG = LogFactory.getLog(MongoSplitterFactory.class); private MongoSplitterFactory() { } public static MongoSplitter getSplitterByClass(final Configuration conf, final String className) { /* If user has specified a class to use for the splitter, use it */ Class<? extends MongoSplitter> splitterClass = MongoConfigUtil.getClassByName(conf, className, MongoSplitter.class); if (splitterClass != null) { MongoSplitter splitter = ReflectionUtils.newInstance(splitterClass, conf); splitter.setConfiguration(conf); return splitter; } else { return null; } } public static MongoCollectionSplitter getSplitterByStats(final MongoClientURI uri, final Configuration config) { /* Looks at the collection in mongo.input.uri * and choose an implementation based on what's in there. */ MongoCollectionSplitter returnVal; // If the split calculation is totally disabled, just make one // big split for the whole collection. if (!MongoConfigUtil.createInputSplits(config)) { returnVal = new SingleMongoSplitter(config); } else { MongoClientURI authURI = MongoConfigUtil.getAuthURI(config); CommandResult stats; DBCollection coll = null; try { if (authURI != null) { coll = MongoConfigUtil.getCollectionWithAuth(uri, authURI); stats = coll.getStats(); LOG.info("Retrieved Collection stats:" + stats); } else { coll = MongoConfigUtil.getCollection(uri); stats = coll.getStats(); } } finally { if (coll != null) { MongoConfigUtil.close(coll.getDB().getMongo()); } } if (!stats.getBoolean("ok", false)) { throw new RuntimeException( "Unable to calculate input splits from collection stats: " + stats.getString("errmsg")); } if (!stats.getBoolean("sharded", false)) { returnVal = new StandaloneMongoSplitter(config); } else { // Collection is sharded if (MongoConfigUtil.isShardChunkedSplittingEnabled(config)) { // Creates one split per chunk. returnVal = new ShardChunkMongoSplitter(config); } else if (MongoConfigUtil.canReadSplitsFromShards(config)) { // Creates one split per shard, but ignores chunk bounds. // Reads from shards directly (bypassing mongos). // Not usually recommended. returnVal = new ShardMongoSplitter(config); } else { //Not configured to use chunks or shards - //so treat this the same as if it was an unsharded collection returnVal = new StandaloneMongoSplitter(config); } } } return returnVal; } public static MongoSplitter getSplitter(final Configuration config) { String splitterClassName = config.get(MongoConfigUtil.MONGO_SPLITTER_CLASS); MongoSplitter customSplitter = getSplitterByClass(config, splitterClassName); if (customSplitter != null) { return customSplitter; } else { return getSplitterByStats(MongoConfigUtil.getInputURI(config), config); } } }