Example Code

Updated on 2022-07-11 GMT+08:00

View PDF

Function

The functions of the sample project are as follows:

Collect the name information from HDFS source files, query and combine data of HBase and Hive using the MultiComponentMapper class inherited from the Mapper abstract class.
Obtain the last piece of mapped data and output to HBase and HDFS, using the MultiComponentMapper class inherited from the Reducer abstract class.
The main function creates a MapReduce job and submits the MapReduce job to Hadoop clusters.

Example Code

For details about code, see the class com.huawei.bigdata.mapreduce.examples.MultiComponentExampl.

Example code of the map function used by MultiComponentMapper class to define the Mapper abstract class.

  private static class MultiComponentMapper extends Mapper<Object, Text, Text, Text> {

    Configuration conf;

    @Override protected void map(Object key, Text value, Context context) throws IOException, InterruptedException {

      conf = context.getConfiguration();

      // for components that depend on Zookeeper, need provide the conf of jaas and krb5
      // Notice, no need to login again here, will use the credentials in main function
      String krb5 = "krb5.conf";
      String jaas = "jaas_mr.conf";
      // These files are uploaded at main function
      File jaasFile = new File(jaas);
      File krb5File = new File(krb5);
      System.setProperty("java.security.auth.login.config", jaasFile.getCanonicalPath());
      System.setProperty("java.security.krb5.conf", krb5File.getCanonicalPath());
      System.setProperty("zookeeper.sasl.client", "true");

      LOG.info("UGI :" + UserGroupInformation.getCurrentUser());

      String name = "";
      String line = value.toString();
      if (line.contains("male")) {
        // A character string that has been read
        name = line.substring(0, line.indexOf(","));
      }
      // 1. read from HBase
      String hbaseData = readHBase();

      // 2. read from Hive
      String hiveData = readHive(name);

      // The Map task outputs a key-value pair.
      context.write(new Text(name), new Text("hbase:" + hbaseData + ", hive:" + hiveData));
    }

Example code of the readHBase function.

    private String readHBase() {
      String tableName = "table1";
      String columnFamily = "cf";
      String hbaseKey = "1";
      String hbaseValue;

      Configuration hbaseConfig = HBaseConfiguration.create(conf);
      org.apache.hadoop.hbase.client.Connection conn = null;
      try {
        // Create a HBase connection
        conn = ConnectionFactory.createConnection(hbaseConfig);
        // get table
        Table table = conn.getTable(TableName.valueOf(tableName));
        // Instantiate a Get object.
        Get get = new Get(hbaseKey.getBytes());
        // Submit a get request.
        Result result = table.get(get);
        hbaseValue = Bytes.toString(result.getValue(columnFamily.getBytes(), "cid".getBytes()));

        return hbaseValue;

      } catch (IOException e) {
        LOG.warn("Exception occur ", e);
      } finally {
          if (conn != null) {
                    try {
                        conn.close();
                    } catch (Exception e1) {
                        LOG.error("Failed to close the connection ", e1);
                    }
                  }
       
      }

      return "";
    }

Example of the readHive function.

    private String readHive(String name) throws IOException  {
      //Load the configuration file
      Properties clientInfo = null;
      String userdir = System.getProperty("user.dir") + "/";
      InputStream fileInputStream = null;
      try {
        clientInfo = new Properties();
        String hiveclientProp = userdir + "hiveclient.properties";
        File propertiesFile = new File(hiveclientProp);
        fileInputStream = new FileInputStream(propertiesFile);
        clientInfo.load(fileInputStream);
      } catch (Exception e) {
        throw new IOException(e);
      } finally {
        if (fileInputStream != null) {
          fileInputStream.close();
        }
      }
      String zkQuorum = clientInfo.getProperty("zk.quorum");
      String zooKeeperNamespace = clientInfo.getProperty("zooKeeperNamespace");
      String serviceDiscoveryMode = clientInfo.getProperty("serviceDiscoveryMode");
      // Read this carefully:
      // MapReduce can only use Hive through JDBC.
      // Hive will submit another MapReduce Job to execute query.
      // So we run Hive in MapReduce is not recommended.
      final String driver = "org.apache.hive.jdbc.HiveDriver";

      String sql = "select name,sum(stayTime) as " + "stayTime from person where name = '" + name + "' group by name";

      StringBuilder sBuilder = new StringBuilder("jdbc:hive2://").append(zkQuorum).append("/");
      // in map or reduce, use 'auth=delegationToken'
      sBuilder
         .append(";serviceDiscoveryMode=")

          .append(serviceDiscoveryMode)
          .append(";zooKeeperNamespace=")
          .append(zooKeeperNamespace)
          .append(";auth=delegationToken;");
      String url = sBuilder.toString();
      Connection connection = null;
      PreparedStatement statement = null;
      ResultSet resultSet = null;
      try {
        Class.forName(driver);
        connection = DriverManager.getConnection(url, "", "");
        statement = connection.prepareStatement(sql);
        resultSet = statement.executeQuery();

        if (resultSet.next()) {
          return resultSet.getString(1);
        }
      } catch (ClassNotFoundException e) {
        LOG.warn("Exception occur ", e);
      } catch (SQLException e) {
        LOG.warn("Exception occur ", e);
      } finally {
          if (null != resultSet) {
                    try {
                        resultSet.close();
                    } catch (SQLException e) {
                        // handle exception
                    }
                }
                if (null != statement) {
                    try {
                        statement.close();
                    } catch (SQLException e) {
                        // handle exception
                    }
                }
                if (null != connection) {
                    try {
                        connection.close();
                    } catch (SQLException e) {
                        // handle exception
                    }
                }
        
      }

      return "";
    }

Example code of the reduce function used by MultiComponentReducer class to define the Reducer abstract class.

  private static class MultiComponentReducer extends Reducer<Text, Text, Text, Text> {
    Configuration conf;

    public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
      conf = context.getConfiguration();

      // for components that depend on Zookeeper, need provide the conf of jaas and krb5
      // Notice, no need to login again here, will use the credentials in main function
      String krb5 = "krb5.conf";
      String jaas = "jaas_mr.conf";
      // These files are uploaded at main function
      File jaasFile = new File(jaas);
      File krb5File = new File(krb5);
      System.setProperty("java.security.auth.login.config", jaasFile.getCanonicalPath());
      System.setProperty("java.security.krb5.conf", krb5File.getCanonicalPath());
      System.setProperty("zookeeper.sasl.client", "true");

      Text finalValue = new Text("");
      // just pick the last value as the data to save
      for (Text value : values) {
        finalValue = value;
      }

      // write data to HBase
      writeHBase(key.toString(), finalValue.toString());

      // save result to HDFS
      context.write(key, finalValue);
    }

Example of the writeHBase function.

    private void writeHBase(String rowKey, String data) {
      String tableName = "table1";
      String columnFamily = "cf";

      try {
        LOG.info("UGI read :" + UserGroupInformation.getCurrentUser());
      } catch (IOException e1) {
        // handler exception
      }

      Configuration hbaseConfig = HBaseConfiguration.create(conf);
      org.apache.hadoop.hbase.client.Connection conn = null;
      try {
        // Create a HBase connection
        conn = ConnectionFactory.createConnection(hbaseConfig);
        // get table
        Table table = conn.getTable(TableName.valueOf(tableName));

        // create a Put to HBase
        List<Put> list = new ArrayList<Put>();
        byte[] row = Bytes.toBytes("row" + rowKey);
        Put put = new Put(row);
        byte[] family = Bytes.toBytes(columnFamily);
        byte[] qualifier = Bytes.toBytes("value");
        byte[] value = Bytes.toBytes(data);
        put.addColumn(family, qualifier, value);
        list.add(put);
        // execute Put
        table.put(list);
      } catch (IOException e) {
        LOG.warn("Exception occur ", e);
      } finally {
           if (conn != null) {
                    try {
                        conn.close();
                    } catch (Exception e1) {
                        LOG.error("Failed to close the connection ", e1);
                    }
                }
      }

    }

Example code: the main() function creates a job, configures the dependency and permission, and submits the job to Hadoop clusters.

    public static void main(String[] args) throws Exception {
      //Load the hiveclient.properties configuration file
        Properties clientInfo = null;
        try {
            clientInfo = new Properties();
            clientInfo.load(MultiComponentExample.class.getClassLoader().getResourceAsStream("hiveclient.properties"));
        } catch (Exception e) {
            throw new IOException(e);
        } finally {

        }
      String zkQuorum = clientInfo.getProperty("zk.quorum");
      String zooKeeperNamespace = clientInfo.getProperty("zooKeeperNamespace");
      String serviceDiscoveryMode = clientInfo.getProperty("serviceDiscoveryMode");
      String principal = clientInfo.getProperty("principal");
      String auth = clientInfo.getProperty("auth");
      String sasl_qop = clientInfo.getProperty("sasl.qop");
      String hbaseKeytab = MultiComponentExample.class.getClassLoader().getResource("user.keytab").getPath();
      String hbaseJaas = MultiComponentExample.class.getClassLoader().getResource("jaas_mr.conf").getPath();
      String hiveClientProperties = MultiComponentExample.class.getClassLoader().getResource("hiveclient.properties").getPath();
      // a list of files, separated by comma
      String files = "file://" + KEYTAB + "," + "file://" + KRB + "," + "file://" + JAAS;
      files = files + "," + "file://" + hbaseKeytab;
      files = files + "," + "file://" + hbaseJaas;
      files = files + "," + "file://" + hiveClientProperties;
      // this setting will ask Job upload these files to HDFS
      config.set("tmpfiles", files);

      // clean control files before job submit
      MultiComponentExample.cleanupBeforeRun();

      // Security login
      LoginUtil.setJaasConf(ZOOKEEPER_DEFAULT_LOGIN_CONTEXT_NAME, PRINCIPAL, hbaseKeytab);
      LoginUtil.setZookeeperServerPrincipal(ZOOKEEPER_DEFAULT_SERVER_PRINCIPAL);
      LoginUtil.login(PRINCIPAL, KEYTAB, KRB, config);

      // find dependency jars for hive
      Class hiveDriverClass = Class.forName("org.apache.hive.jdbc.HiveDriver");
      Class thriftClass = Class.forName("org.apache.thrift.TException");
      Class serviceThriftCLIClass = Class.forName("org.apache.hive.service.rpc.thrift.TCLIService");
      Class hiveConfClass = Class.forName("org.apache.hadoop.hive.conf.HiveConf");
      Class hiveTransClass = Class.forName("org.apache.thrift.transport.HiveTSaslServerTransport");
      Class hiveMetaClass = Class.forName("org.apache.hadoop.hive.metastore.api.MetaException");
      Class hiveShimClass = Class.forName("org.apache.hadoop.hive.metastore.security.HadoopThriftAuthBridge23");
      Class thriftCLIClass = Class.forName("org.apache.hive.service.cli.thrift.ThriftCLIService");

      // add dependency jars to Job
      JarFinderUtil.addDependencyJars(config, hiveDriverClass, serviceThriftCLIClass, thriftCLIClass, thriftClass,
                hiveConfClass, hiveTransClass, hiveMetaClass, hiveShimClass);

      // add hive config file
      config.addResource("hive-site.xml");
      // add hbase config file
      Configuration conf = HBaseConfiguration.create(config);

      // Initialize the job object.
      Job job = Job.getInstance(conf);
      job.setJarByClass(MultiComponentExample.class);

      // set mapper&reducer class
      job.setMapperClass(MultiComponentMapper.class);
      job.setReducerClass(MultiComponentReducer.class);

      //set job input&output
      FileInputFormat.addInputPath(job, new Path(baseDir, INPUT_DIR_NAME + File.separator + "data.txt"));
      FileOutputFormat.setOutputPath(job, new Path(baseDir, OUTPUT_DIR_NAME));

      // Set the output type of the job.
      job.setOutputKeyClass(Text.class);
      job.setOutputValueClass(Text.class);

      // HBase use this utility class to add dependecy jars of hbase to MR job
      TableMapReduceUtil.addDependencyJars(job);

      // this is mandatory when access to security HBase cluster
      // HBase add security credentials to Job, and will use in map and reduce
      TableMapReduceUtil.initCredentials(job);

      // create Hive security credentials

      StringBuilder sBuilder = new StringBuilder("jdbc:hive2://").append(zkQuorum).append("/");
      sBuilder.append(";serviceDiscoveryMode=").append(serviceDiscoveryMode).append(";zooKeeperNamespace=")
          .append(zooKeeperNamespace)
          .append(";sasl.qop=")
          .append(sasl_qop)
          .append(";auth=")
          .append(auth)
          .append(";principal=")
          .append(principal)
          .append(";");
      String url = sBuilder.toString();
      Connection connection = DriverManager.getConnection(url, "", "");
      String tokenStr = ((HiveConnection) connection)
          .getDelegationToken(UserGroupInformation.getCurrentUser().getShortUserName(), PRINCIPAL);
      connection.close();
      Token<DelegationTokenIdentifier> hive2Token = new Token<DelegationTokenIdentifier>();
      hive2Token.decodeFromUrlString(tokenStr);
      // add Hive security credentials to Job
      job.getCredentials().addToken(new Text("hive.server2.delegation.token"), hive2Token);
      job.getCredentials().addToken(new Text(HiveAuthConstants.HS2_CLIENT_TOKEN), hive2Token);

      // Submit the job to a remote environment for execution.
      System.exit(job.waitForCompletion(true) ? 0 : 1);

    }

NOTE:

Replace all the zkQuorum objects with the actual information about the ZooKeeper cluster nodes.

Parent topic: MapReduce Accessing Multi-Component Example Project

Previous topic: Instance

Next topic: Commissioning the Application

Feedback

Was this page helpful?

Helpful Not helpful

Provide feedback

Thank you very much for your feedback. We will continue working to improve the documentation.See the reply and handling status in My Cloud VOC.

The system is busy. Please try again later.

Which of the following issues have you encountered?

Content is inconsistent with the product UI

Unclear descriptions

Lack of examples or code

Incorrect steps

Can't find what I need

Lack of best practices

Feedback (optional)

0/500

Select at least one type of issue, and enter your comments or suggestions.

Enter a maximum of 500 characters.

Submit Cancel

For any further questions, feel free to contact us through the chatbot.

Chatbot