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.hadoop.hive.ql.exec.mr; import java.io.IOException; import java.lang.management.ManagementFactory; import java.lang.management.MemoryMXBean; import java.net.URLClassLoader; import java.util.ArrayList; import java.util.Arrays; import java.util.Iterator; import java.util.List; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.hive.ql.exec.MapredContext; import org.apache.hadoop.hive.ql.exec.Operator; import org.apache.hadoop.hive.ql.exec.Utilities; import org.apache.hadoop.hive.ql.exec.mr.ExecMapper.ReportStats; import org.apache.hadoop.hive.ql.metadata.HiveException; import org.apache.hadoop.hive.ql.plan.ReduceWork; import org.apache.hadoop.hive.ql.plan.TableDesc; import org.apache.hadoop.hive.serde2.Deserializer; import org.apache.hadoop.hive.serde2.SerDeException; import org.apache.hadoop.hive.serde2.SerDeUtils; import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector; import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorFactory; import org.apache.hadoop.io.BytesWritable; import org.apache.hadoop.mapred.JobConf; import org.apache.hadoop.mapred.MapReduceBase; import org.apache.hadoop.mapred.OutputCollector; import org.apache.hadoop.mapred.Reducer; import org.apache.hadoop.mapred.Reporter; import org.apache.hadoop.util.ReflectionUtils; import org.apache.hadoop.util.StringUtils; /** * ExecReducer is the generic Reducer class for Hive. Together with ExecMapper it is * the bridge between the map-reduce framework and the Hive operator pipeline at * execution time. It's main responsibilities are: * * - Load and setup the operator pipeline from XML * - Run the pipeline by transforming key, value pairs to records and forwarding them to the operators * - Sending start and end group messages to separate records with same key from one another * - Catch and handle errors during execution of the operators. * */ public class ExecReducer extends MapReduceBase implements Reducer { private static final Log LOG = LogFactory.getLog("ExecReducer"); private static final boolean isInfoEnabled = LOG.isInfoEnabled(); private static final boolean isTraceEnabled = LOG.isTraceEnabled(); private static final String PLAN_KEY = "__REDUCE_PLAN__"; // Input value serde needs to be an array to support different SerDe // for different tags private final Deserializer[] inputValueDeserializer = new Deserializer[Byte.MAX_VALUE]; private final Object[] valueObject = new Object[Byte.MAX_VALUE]; private final List<Object> row = new ArrayList<Object>(Utilities.reduceFieldNameList.size()); // TODO: move to DynamicSerDe when it's ready private Deserializer inputKeyDeserializer; private JobConf jc; private OutputCollector<?, ?> oc; private Operator<?> reducer; private Reporter rp; private boolean abort = false; private boolean isTagged = false; private TableDesc keyTableDesc; private TableDesc[] valueTableDesc; private ObjectInspector[] rowObjectInspector; // runtime objects private transient Object keyObject; private transient BytesWritable groupKey; @Override public void configure(JobConf job) { rowObjectInspector = new ObjectInspector[Byte.MAX_VALUE]; ObjectInspector[] valueObjectInspector = new ObjectInspector[Byte.MAX_VALUE]; ObjectInspector keyObjectInspector; if (isInfoEnabled) { try { LOG.info("conf classpath = " + Arrays.asList(((URLClassLoader) job.getClassLoader()).getURLs())); LOG.info("thread classpath = " + Arrays .asList(((URLClassLoader) Thread.currentThread().getContextClassLoader()).getURLs())); } catch (Exception e) { LOG.info("cannot get classpath: " + e.getMessage()); } } jc = job; ReduceWork gWork = Utilities.getReduceWork(job); reducer = gWork.getReducer(); reducer.setParentOperators(null); // clear out any parents as reducer is the // root isTagged = gWork.getNeedsTagging(); try { keyTableDesc = gWork.getKeyDesc(); inputKeyDeserializer = ReflectionUtils.newInstance(keyTableDesc.getDeserializerClass(), null); SerDeUtils.initializeSerDe(inputKeyDeserializer, null, keyTableDesc.getProperties(), null); keyObjectInspector = inputKeyDeserializer.getObjectInspector(); valueTableDesc = new TableDesc[gWork.getTagToValueDesc().size()]; for (int tag = 0; tag < gWork.getTagToValueDesc().size(); tag++) { // We should initialize the SerDe with the TypeInfo when available. valueTableDesc[tag] = gWork.getTagToValueDesc().get(tag); inputValueDeserializer[tag] = ReflectionUtils .newInstance(valueTableDesc[tag].getDeserializerClass(), null); SerDeUtils.initializeSerDe(inputValueDeserializer[tag], null, valueTableDesc[tag].getProperties(), null); valueObjectInspector[tag] = inputValueDeserializer[tag].getObjectInspector(); ArrayList<ObjectInspector> ois = new ArrayList<ObjectInspector>(); ois.add(keyObjectInspector); ois.add(valueObjectInspector[tag]); rowObjectInspector[tag] = ObjectInspectorFactory .getStandardStructObjectInspector(Utilities.reduceFieldNameList, ois); } } catch (Exception e) { throw new RuntimeException(e); } MapredContext.init(false, new JobConf(jc)); // initialize reduce operator tree try { LOG.info(reducer.dump(0)); reducer.initialize(jc, rowObjectInspector); } catch (Throwable e) { abort = true; if (e instanceof OutOfMemoryError) { // Don't create a new object if we are already out of memory throw (OutOfMemoryError) e; } else { throw new RuntimeException("Reduce operator initialization failed", e); } } } public void reduce(Object key, Iterator values, OutputCollector output, Reporter reporter) throws IOException { if (reducer.getDone()) { return; } if (oc == null) { // propagate reporter and output collector to all operators oc = output; rp = reporter; reducer.setReporter(rp); MapredContext.get().setReporter(reporter); } try { BytesWritable keyWritable = (BytesWritable) key; byte tag = 0; if (isTagged) { // remove the tag from key coming out of reducer // and store it in separate variable. int size = keyWritable.getSize() - 1; tag = keyWritable.get()[size]; keyWritable.setSize(size); } if (!keyWritable.equals(groupKey)) { // If a operator wants to do some work at the beginning of a group if (groupKey == null) { // the first group groupKey = new BytesWritable(); } else { // If a operator wants to do some work at the end of a group if (isTraceEnabled) { LOG.trace("End Group"); } reducer.endGroup(); } try { keyObject = inputKeyDeserializer.deserialize(keyWritable); } catch (Exception e) { throw new HiveException("Hive Runtime Error: Unable to deserialize reduce input key from " + Utilities.formatBinaryString(keyWritable.get(), 0, keyWritable.getSize()) + " with properties " + keyTableDesc.getProperties(), e); } groupKey.set(keyWritable.get(), 0, keyWritable.getSize()); if (isTraceEnabled) { LOG.trace("Start Group"); } reducer.startGroup(); reducer.setGroupKeyObject(keyObject); } // System.err.print(keyObject.toString()); while (values.hasNext()) { BytesWritable valueWritable = (BytesWritable) values.next(); // System.err.print(who.getHo().toString()); try { valueObject[tag] = inputValueDeserializer[tag].deserialize(valueWritable); } catch (SerDeException e) { throw new HiveException( "Hive Runtime Error: Unable to deserialize reduce input value (tag=" + tag + ") from " + Utilities.formatBinaryString(valueWritable.get(), 0, valueWritable.getSize()) + " with properties " + valueTableDesc[tag].getProperties(), e); } row.clear(); row.add(keyObject); row.add(valueObject[tag]); try { reducer.process(row, tag); } catch (Exception e) { String rowString = null; try { rowString = SerDeUtils.getJSONString(row, rowObjectInspector[tag]); } catch (Exception e2) { rowString = "[Error getting row data with exception " + StringUtils.stringifyException(e2) + " ]"; } throw new HiveException( "Hive Runtime Error while processing row (tag=" + tag + ") " + rowString, e); } } } catch (Throwable e) { abort = true; if (e instanceof OutOfMemoryError) { // Don't create a new object if we are already out of memory throw (OutOfMemoryError) e; } else { LOG.fatal(StringUtils.stringifyException(e)); throw new RuntimeException(e); } } } @Override public void close() { // No row was processed if (oc == null && isTraceEnabled) { LOG.trace("Close called without any rows processed"); } try { if (groupKey != null) { // If a operator wants to do some work at the end of a group if (isTraceEnabled) { LOG.trace("End Group"); } reducer.endGroup(); } reducer.close(abort); ReportStats rps = new ReportStats(rp, jc); reducer.preorderMap(rps); } catch (Exception e) { if (!abort) { // signal new failure to map-reduce LOG.error("Hit error while closing operators - failing tree"); throw new RuntimeException("Hive Runtime Error while closing operators: " + e.getMessage(), e); } } finally { MapredContext.close(); Utilities.clearWorkMap(); } } }