【技术解析】Dolphinscheduler实现MapReduce任务的高效管理
MapReduce是一种编程模型，用于处理和生成大数据集，主要用于大规模数据集（TB级数据规模）的并行运算。本文详细介绍了Dolphinscheduler在MapReduce任务中的应用，包括GenericOptionsParser与args的区别、hadoop jar命令参数的完整解释、MapReduce实例代码，以及如何在Dolphinscheduler中配置和运行MapReduce任务。
GenericOptionsParser vs args区别
GenericOptionsParser 如下:
GenericOptionsParser optionParser = new GenericOptionsParser(conf, args);
String[] remainingArgs = optionParser.getRemainingArgs();
查看 GenericOptionsParser 源码做了什么？
1、构造方法
public GenericOptionsParser(Configuration conf, String[] args)
throws IOException {
this(conf, new Options(), args);
}
2、点击 this
public GenericOptionsParser(Configuration conf,
Options options, String[] args) throws IOException {
this.conf = conf;
parseSuccessful = parseGeneralOptions(options, args);
}
3、查看 parseGeneralOptions
private boolean parseGeneralOptions(Options opts, String[] args)
throws IOException {
opts = buildGeneralOptions(opts);
CommandLineParser parser = new GnuParser();
boolean parsed = false;
try {
commandLine = parser.parse(opts, preProcessForWindows(args), true);
processGeneralOptions(commandLine);
parsed = true;
} catch(ParseException e) {
LOG.warn("options parsing failed: "+e.getMessage());
HelpFormatter formatter = new HelpFormatter();
formatter.printHelp("general options are: ", opts);
}
return parsed;
}
4、看 GnuParser
package org.apache.commons.cli;
import java.util.ArrayList;
import java.util.List;
[@Deprecated](https://my.oschina.net/jianhuaw)
public class GnuParser extends Parser {
.......
}
org.apache.commons.cli Parser，是不是有点熟悉？对，请参考 https://segmentfault.com/a/1190000045394541 这篇文章吧
5、看 processGeneralOptions 方法
private void processGeneralOptions(CommandLine line) throws IOException {
if (line.hasOption("fs")) {
FileSystem.setDefaultUri(conf, line.getOptionValue("fs"));
}
if (line.hasOption("jt")) {
String optionValue = line.getOptionValue("jt");
if (optionValue.equalsIgnoreCase("local")) {
conf.set("mapreduce.framework.name", optionValue);
}
conf.set("yarn.resourcemanager.address", optionValue,
"from -jt command line option");
}
if (line.hasOption("conf")) {
String[] values = line.getOptionValues("conf");
for(String value : values) {
conf.addResource(new Path(value));
}
}
if (line.hasOption('D')) {
String[] property = line.getOptionValues('D');
for(String prop : property) {
String[] keyval = prop.split("=", 2);
if (keyval.length == 2) {
conf.set(keyval[0], keyval[1], "from command line");
}
}
}
if (line.hasOption("libjars")) {
// for libjars, we allow expansion of wildcards
conf.set("tmpjars",
validateFiles(line.getOptionValue("libjars"), true),
"from -libjars command line option");
//setting libjars in client classpath
URL[] libjars = getLibJars(conf);
if(libjars!=null && libjars.length>0) {
conf.setClassLoader(new URLClassLoader(libjars, conf.getClassLoader()));
Thread.currentThread().setContextClassLoader(
new URLClassLoader(libjars,
Thread.currentThread().getContextClassLoader()));
}
}
if (line.hasOption("files")) {
conf.set("tmpfiles",
validateFiles(line.getOptionValue("files")),
"from -files command line option");
}
if (line.hasOption("archives")) {
conf.set("tmparchives",
validateFiles(line.getOptionValue("archives")),
"from -archives command line option");
}
conf.setBoolean("mapreduce.client.genericoptionsparser.used", true);
// tokensFile
if(line.hasOption("tokenCacheFile")) {
String fileName = line.getOptionValue("tokenCacheFile");
// check if the local file exists
FileSystem localFs = FileSystem.getLocal(conf);
Path p = localFs.makeQualified(new Path(fileName));
localFs.getFileStatus(p);
if(LOG.isDebugEnabled()) {
LOG.debug("setting conf tokensFile: " + fileName);
}
UserGroupInformation.getCurrentUser().addCredentials(
Credentials.readTokenStorageFile(p, conf));
conf.set("mapreduce.job.credentials.binary", p.toString(),
"from -tokenCacheFile command line option");
}
}
原理是把 fs、jt、D、libjars、files、archives、tokenCacheFile 相关参数放入到 Hadoop的 Configuration中了，终于清楚 GenericOptionsParser是干什么的了
args呢？如果要使用args，以上这种 fs、jt、D、libjars、files、archives、tokenCacheFile 是需要自己解析的。
Hadoop jar完整参数解释
hadoop jar wordcount.jar org.myorg.WordCount \
-fs hdfs://namenode.example.com:8020 \
-jt resourcemanager.example.com:8032 \
-D mapreduce.job.queuename=default \
-libjars /path/to/dependency1.jar,/path/to/dependency2.jar \
-files /path/to/file1.txt,/path/to/file2.txt \
-archives /path/to/archive1.zip,/path/to/archive2.tar.gz \
-tokenCacheFile /path/to/credential.file \
/input /output
这条命令会：
- 将作业提交到 hdfs://namenode.example.com:8020 文件系统
- 使用 resourcemanager.example.com:8032 作为 YARN ResourceManager
- 提交到 default 队列
- 使用 /path/to/dependency1.jar 和 /path/to/dependency2.jar 作为依赖
- 分发本地文件 /path/to/file1.txt 和 /path/to/file2.txt，注意 : 是本地文件哦
- 解压并分发 /path/to/archive1.zip 和 /path/to/archive2.tar.gz
- 分发凭证文件 /path/to/credential.file
MR实例
WordCount经典示例
public class WCMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
private IntWritable one = new IntWritable(1);
private Text word = new Text();
[@Override](https://my.oschina.net/u/1162528)
protected void map(LongWritable key,
Text value,
Mapper<LongWritable, Text, Text, IntWritable>.Context context) throws IOException, InterruptedException {
String[] fields = value.toString().split("\\s+");
for (String field : fields) {
word.set(field);
context.write(word, one);
}
}
}
public class WCReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
private IntWritable result = new IntWritable();
[@Override](https://my.oschina.net/u/1162528)
protected void reduce(Text key,
Iterable<IntWritable> values,
Reducer<Text, IntWritable, Text, IntWritable>.Context context) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
public class WCJob {
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
// TODO 如果要是本地访问远程的hdfs，需要指定hdfs的根路径，否则只能访问本地的文件系统
// conf.set("fs.defaultFS", "hdfs://xx.xx.xx.xx:8020");
GenericOptionsParser optionParser = new GenericOptionsParser(conf, args);
String[] remainingArgs = optionParser.getRemainingArgs();
for (String arg : args) {
System.out.println("arg :" + arg);
}
for (String remainingArg : remainingArgs) {
System.out.println("remainingArg :" + remainingArg);
}
if (remainingArgs.length < 2) {
throw new RuntimeException("input and output path must set.");
}
Path outputPath = new Path(remainingArgs[1]);
FileSystem fileSystem = FileSystem.get(conf);
boolean exists = fileSystem.exists(outputPath);
// 如果目标目录存在，则删除
if (exists) {
fileSystem.delete(outputPath, true);
}
Job job = Job.getInstance(conf, "MRWordCount");
job.setJarByClass(WCJob.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
job.setMapperClass(WCMapper.class);
job.setReducerClass(WCReducer.class);
FileInputFormat.addInputPath(job, new Path(remainingArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(remainingArgs[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
文件分发
public class ConfigMapper extends Mapper<LongWritable, Text, Text, NullWritable> {
private List<String> whiteList = new ArrayList<>();
private Text text = new Text();
[@Override](https://my.oschina.net/u/1162528)
protected void setup(Mapper<LongWritable, Text, Text, NullWritable>.Context context) throws IOException, InterruptedException {
// 获取作业提交时传递的文件
URI[] files = context.getCacheFiles();
if (files != null && files.length > 0) {
// 读取文件内容
File configFile = new File("white.txt"); // 文件名要与传递的文件名保持一致
try (BufferedReader reader = new BufferedReader(new FileReader(configFile))){
String line = null;
while ((line = reader.readLine()) != null) {
whiteList.add(line);
}
}
}
}
[@Override](https://my.oschina.net/u/1162528)
protected void map(LongWritable key,
Text value,
Mapper<LongWritable, Text, Text, NullWritable>.Context context) throws IOException, InterruptedException {
String line = value.toString();
String[] datas = line.split("\\s+");
List<String> whiteDatas = Arrays.stream(datas).filter(data -> whiteList.contains(data)).collect(Collectors.toList());
for (String data : whiteDatas) {
text.set(data);
context.write(text , NullWritable.get());
}
}
}
public class ConfigJob {
public static void main(String[] args) throws Exception {
// 设置用户名
System.setProperty("HADOOP_USER_NAME", "root");
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://xx.xx.xx.xx:8020");
GenericOptionsParser optionParser = new GenericOptionsParser(conf, args);
String[] remainingArgs = optionParser.getRemainingArgs();
if (remainingArgs.length < 2) {
throw new RuntimeException("input and output path must set.");
}
Path outputPath = new Path(remainingArgs[1]);
FileSystem fileSystem = FileSystem.get(conf);
boolean exists = fileSystem.exists(outputPath);
// 如果目标目录存在，则删除
if (exists) {
fileSystem.delete(outputPath, true);
}
Job job = Job.getInstance(conf, "MRConfig");
job.setJarByClass(ConfigJob.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(NullWritable.class);
job.setMapperClass(ConfigMapper.class);
FileInputFormat.addInputPath(job, new Path(remainingArgs[0]));
FileOutputFormat.setOutputPath(job, new Path(remainingArgs[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
Dolphinscheduler MR使用
Yarn test队列设置
YARN 的配置目录中找到 capacity-scheduler.xml 文件。通常位于 $HADOOP_HOME/etc/hadoop/ 目录下。
修改 capacity-scheduler.xml
<property>
<name>yarn.scheduler.capacity.root.queues</name>
<value>default, test</value>
</property>
<property>
<name>yarn.scheduler.capacity.root.test.capacity</name>
<value>30</value>
</property>
<property>
<name>yarn.scheduler.capacity.root.test.maximum-capacity</name>
<value>50</value>
</property>
<property>
<name>yarn.scheduler.capacity.root.test.user-limit-factor</name>
<value>1</value>
</property>
刷新队列配置 yarn rmadmin -refreshQueues
流程定义设置
执行结果
离线任务实例
YARN作业展示
源码分析
org.apache.dolphinscheduler.plugin.task.mr.MapReduceArgsUtils#buildArgs
String others = param.getOthers();
// TODO 这里其实就是想说，没有通过 -D mapreduce.job.queuename 形式指定队列，是用页面上直接指定队列名称的，页面上 Yarn队列 输入框
if (StringUtils.isEmpty(others) || !others.contains(MR_YARN_QUEUE)) {
String yarnQueue = param.getYarnQueue();
if (StringUtils.isNotEmpty(yarnQueue)) {
args.add(String.format("%s%s=%s", D, MR_YARN_QUEUE, yarnQueue));
}
}
// TODO 这里就是页面上，选项参数 输入框
// -conf -archives -files -libjars -D
if (StringUtils.isNotEmpty(others)) {
args.add(others);
}
转载自Journey 原文链接：https://segmentfault.com/a/1190000045403915
本文由 白鲸开源科技 提供发布支持！
