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/*
* Copyright (c) 2021 MarkLogic Corporation
*
* 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.marklogic.contentpump;
import java.io.IOException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.atomic.AtomicBoolean;
import com.marklogic.mapreduce.utilities.InternalUtilities;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Counter;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.OutputFormat;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.StatusReporter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.util.ReflectionUtils;
import com.marklogic.contentpump.utilities.ReflectionUtil;
/**
* Multithreaded implementation for @link org.apache.hadoop.mapreduce.Mapper,
* currently used by import operations when applicable to leverage concurrent
* updates to MarkLogic.
*/
public class MultithreadedMapper extends
Mapper {
private static final Log LOG = LogFactory
.getLog(MultithreadedMapper.class);
private Class> mapClass;
private Context outer;
private List runnerList = new ArrayList<>();
private List> runnerFutureList = new ArrayList<>();
private int threadCount = 0;
private ThreadPoolExecutor threadPool;
/**
* Get thread count set for this mapper.
* @return thread count set for this mapper.
*/
public int getThreadCount(Context context) {
if (threadCount > 0) {
return threadCount;
} else {
return getNumberOfThreads(context);
}
}
/**
* Set thread count for this mapper.
* @param threadCount Thread count for this mapper.
*/
public void setThreadCount(int threadCount) {
this.threadCount = threadCount;
}
/**
* Set the thread pool for this mapper.
* @param pool thread pool to be used for this mapper.
*/
public void setThreadPool(ThreadPoolExecutor pool) {
this.threadPool = pool;
}
/**
* The number of threads in the thread pool that will run the map function.
*
* @param job
* the job
* @return the number of threads
*/
public static int getNumberOfThreads(JobContext job) {
return job.getConfiguration().getInt(
ConfigConstants.CONF_THREADS_PER_SPLIT,
ConfigConstants.DEFAULT_THREAD_COUNT);
}
/**
* Set the number of threads in the pool for running maps.
*
* @param job
* the job to modify
* @param threads
* the new number of threads
*/
public static void setNumberOfThreads(Job job, int threads) {
job.getConfiguration().setInt(ConfigConstants.CONF_THREADS_PER_SPLIT,
threads);
}
public static void setNumberOfThreads(Configuration conf, int threads) {
conf.setInt(ConfigConstants.CONF_THREADS_PER_SPLIT, threads);
}
/**
* Get the application's mapper class.
*
* @param
* the map's input key type
* @param
* the map's input value type
* @param
* the map's output key type
* @param
* the map's output value type
* @param job
* the job
* @return the mapper class to run
*/
@SuppressWarnings("unchecked")
public static Class> getMapperClass(
JobContext job) {
Configuration conf = job.getConfiguration();
return (Class>)conf.getClass(
ConfigConstants.CONF_MULTITHREADEDMAPPER_CLASS, BaseMapper.class);
}
/**
* Set the application's mapper class.
* @param conf
* @param internalMapperClass the class to use as the mapper
* @param the map input key type
* @param the map input value type
* @param the map output key type
* @param the map output value type
*/
public static void setMapperClass(Configuration conf,
Class> internalMapperClass) {
if (MultithreadedMapper.class.isAssignableFrom(internalMapperClass)) {
throw new IllegalArgumentException("Can't have recursive "
+ "MultithreadedMapper instances.");
}
conf.setClass(ConfigConstants.CONF_MULTITHREADEDMAPPER_CLASS, internalMapperClass,
Mapper.class);
}
public void createRunners(int numRunners) throws IOException,
InterruptedException, ClassNotFoundException {
synchronized (threadPool) {
for (int i = 0; i < numRunners; i++) {
MapRunner runner = new MapRunner();
synchronized (runnerFutureList) {
runnerList.add(runner);
if (!threadPool.isShutdown()) {
Future future = threadPool.submit(runner);
runnerFutureList.add(future);
} else {
throw new InterruptedException(
"Thread Pool has been shut down");
}
}
}
threadPool.notify();
}
}
public void stopRunners(int numRunners) {
for (int i = 0; i < numRunners; i++) {
// Stop the last numThreads of runners
runnerList.get(runnerList.size()-i-1).setShutdown(true);
}
// Wait until every runner is shutdown
while(true) {
boolean allDone = true;
synchronized (runnerList) {
for (int i = 0; i < numRunners; i++) {
allDone &= runnerList.get(runnerList.size()-i-1).
getIsShutdownDone();
}
}
if (allDone) break;
// Speculative fix for Bug 55693: Sleep for 0.5s between every check
try {
InternalUtilities.sleep(500);
} catch (Exception e) {}
}
synchronized (runnerFutureList) {
for (int i = 0; i < numRunners; i++) {
runnerList.remove(runnerList.size()-1);
runnerFutureList.remove(runnerFutureList.size()-1);
}
}
}
/**
* Run the application's maps using a thread pool.
*/
@Override
public void run(Context context) throws IOException, InterruptedException {
outer = context;
int numberOfThreads = getThreadCount(context);
mapClass = getMapperClass(context);
// current mapper takes 1 thread
numberOfThreads--;
// submit runners
try {
if (threadPool != null) {
createRunners(numberOfThreads);
// MapRunner that runs in current thread
MapRunner r = new MapRunner();
r.run();
// Wait until all runners are done (non-blocking)
while (true) {
boolean allDone = true;
synchronized (runnerFutureList) {
for (Future f : runnerFutureList) {
allDone &= f.isDone();
}
}
if (allDone) break;
}
synchronized (runnerFutureList) {
for (Future f : runnerFutureList) {
f.get();
}
}
} else {
for (int i = 0; i < numberOfThreads; ++i) {
MapRunner thread;
thread = new MapRunner();
thread.start();
runnerList.add(i, thread);
}
// MapRunner runs in current thread
MapRunner r = new MapRunner();
r.run();
for (int i = 0; i < numberOfThreads; ++i) {
MapRunner thread = runnerList.get(i);
thread.join();
Throwable th = thread.throwable;
if (th != null) {
if (th instanceof IOException) {
throw (IOException) th;
} else if (th instanceof InterruptedException) {
throw (InterruptedException) th;
} else {
throw new RuntimeException(th);
}
}
}
}
} catch (ClassNotFoundException e) {
LOG.error("MapRunner class not found", e);
} catch (ExecutionException e) {
LOG.error("Error waiting for MapRunner threads to complete", e);
}
}
private class SubMapRecordReader extends RecordReader {
private K1 key;
private V1 value;
@Override
public void close() throws IOException {
}
@Override
public float getProgress() throws IOException, InterruptedException {
return 0;
}
@Override
public void initialize(InputSplit split, TaskAttemptContext context)
throws IOException, InterruptedException {
}
@SuppressWarnings("unchecked")
@Override
public boolean nextKeyValue() throws IOException, InterruptedException {
if (!outer.nextKeyValue()) {
return false;
}
if (outer.getCurrentKey() == null) {
return true;
}
key = (K1) ReflectionUtils.newInstance(outer.getCurrentKey()
.getClass(), outer.getConfiguration());
key = ReflectionUtils.copy(outer.getConfiguration(),
outer.getCurrentKey(), key);
V1 outerVal = outer.getCurrentValue();
if (outerVal != null) {
value = (V1) ReflectionUtils.newInstance(outerVal.getClass(),
outer.getConfiguration());
value = ReflectionUtils.copy(outer.getConfiguration(),
outer.getCurrentValue(), value);
}
return true;
}
public K1 getCurrentKey() {
return key;
}
@Override
public V1 getCurrentValue() {
return value;
}
}
private class SubMapStatusReporter extends StatusReporter {
@Override
public Counter getCounter(Enum name) {
return outer.getCounter(name);
}
@Override
public Counter getCounter(String group, String name) {
return outer.getCounter(group, name);
}
@Override
public void progress() {
outer.progress();
}
@Override
public void setStatus(String status) {
outer.setStatus(status);
}
public float getProgress() {
Method getProgressMethod;
try {
getProgressMethod = outer.getClass().getMethod(
"getProgress", new Class[0]);
if (getProgressMethod != null) {
return (Float) getProgressMethod.invoke(outer,
new Object[0]);
}
} catch (Exception e) {
LOG.error("Error getting progress", e);
}
return 0;
}
}
protected class MapRunner extends Thread {
private BaseMapper mapper;
private Context subcontext;
private Throwable throwable;
private RecordWriter writer;
// Whether the polling thread has notified the runner to shutdown in a
// scaling-in event
AtomicBoolean shutdown = new AtomicBoolean(false);
// Whether the runner itself has finished shutting-down in a scaling-in
// event
AtomicBoolean isShutdownDone = new AtomicBoolean(false);
MapRunner() throws IOException, ClassNotFoundException {
// initiate the real mapper that does the work
mapper = ReflectionUtils.newInstance(mapClass,
outer.getConfiguration());
@SuppressWarnings("unchecked")
OutputFormat outputFormat = (OutputFormat)
ReflectionUtils.newInstance(outer.getOutputFormatClass(),
outer.getConfiguration());
try {
// outputFormat is not initialized. Relying on everything it
// needs can be obtained from the AssignmentManager singleton.
writer = outputFormat.getRecordWriter(outer);
subcontext = (Context)ReflectionUtil.createMapperContext(
mapper, outer.getConfiguration(), outer.getTaskAttemptID(),
new SubMapRecordReader(), writer,
outer.getOutputCommitter(), new SubMapStatusReporter(),
outer.getInputSplit());
} catch (Exception e) {
throw new IOException("Error creating mapper context", e);
}
}
public BaseMapper getMapper() {
return mapper;
}
@Override
public void run() {
try {
mapper.runThreadSafe(outer, subcontext, this);
} catch (Throwable ie) {
if (LOG.isDebugEnabled()) {
LOG.debug("Error running task:" + ie);
ie.printStackTrace();
}
}
try {
writer.close(subcontext);
} catch (Throwable t) {
LOG.error("Error closing writer: " + t.getMessage());
if (LOG.isDebugEnabled()) {
LOG.debug(t);
}
}
isShutdownDone.set(true);
}
public void setShutdown(boolean shutdown) {
this.shutdown.set(shutdown);
}
public boolean getShutdown() {
return shutdown.get();
}
public boolean getIsShutdownDone() {
return isShutdownDone.get();
}
}
}
