Typical Scenario: Importing Data from a Relational Database to HDFS or OBS

Scenario

Use Loader to import data from a relational database to HDFS or OBS.

Prerequisites

• You have obtained the service username and password for creating a Loader job.
• You have had the permission to access the HDFS or OBS directories and data involved in job execution.
• You have obtained the username and password of the relational database.
• No disk space alarm is reported, and the available disk space is sufficient for importing and exporting data.
• If a configured task requires the Yarn queue function, the user must be authorized with related Yarn queue permission.
• The user who configures a task must obtain execution permission on the task and obtain usage permission on the related connection of the task.
• Before the operation, perform the following steps:
  1. Obtain the JAR file of the relational database driver and save it to the following directory on the active and standby Loader nodes: ${BIGDATA_HOME}/FusionInsight_Porter_*/install/FusionInsight-Sqoop-1.99.3/FusionInsight-Sqoop-1.99.3/server/webapps/loader/WEB-INF/ext-lib.
  2. Run the following command on the active and standby nodes as user root to modify the permission:

     cd ${BIGDATA_HOME}/FusionInsight_Porter_*/install/FusionInsight-Sqoop-1.99.3/FusionInsight-Sqoop-1.99.3/server/webapps/loader/WEB-INF/ext-lib

     chown omm:wheel JAR file name

     chmod 600 JAR file name

  3. Log in to FusionInsight Manager and choose Cluster > Services > Loader. On the Dashboard tab page that is displayed, click More and select Restart Service. In the displayed dialog box, enter the administrator password to restart the Loader service.

Procedure

Configure basic job information.

1. Access the Loader web UI.
   1. Log in to FusionInsight Manager.
   2. Choose Cluster > Services > Loader.
   3. Click LoaderServer(Node name, Active). The Loader web UI is displayed.
      Figure 1 Loader web UI
      

2. Click New Job to go to the Basic Information page and set basic job information.
   Figure 2 Basic Information page
   
   1. Set Name to the name of the job.
   2. Set Type to Import.
   3. Set Group to the group to which the job belongs. No group is created by default. You need to click Add to create a group and click OK to save the created group.
   4. Set Queue to the Yarn queue that executes the job. The default value is root.default.
   5. Set Priority to the priority of the Yarn queue that executes the job. The default value is NORMAL. The options are VERY_LOW, LOW, NORMAL, HIGH, and VERY_HIGH.

3. In the Connection area, click Add to create a connection, set Connector to generic-jdbc-connector or a dedicated database connector (oracle-connector, oracle-partition-connector, or mysql-fastpath-connector), set connection parameters, and click Test to verify whether the connection is available. When "Test Success" is displayed, click OK.
   

   • For connection to relational databases, general database connectors (generic-jdbc-connector) or dedicated database connectors (oracle-connector, oracle-partition-connector, and mysql-fastpath-connector) are available. However, compared with general database connectors, dedicated database connectors perform better in data import and export because they are optimized for specific database types.
   • When mysql-fastpath-connector is used, the mysqldump and mysqlimport commands of MySQL must be available on NodeManager nodes, and the MySQL client version to which the two commands belong must be compatible with the MySQL server version. If the two commands are unavailable or the versions are incompatible, install the MySQL client applications and tools following the instructions at http://dev.mysql.com/doc/refman/5.7/en/linux-installation-rpm.html.

   Table 1 generic-jdbc-connector connection parameters

   Parameter	Description	Example Value
   Name	Name of a relational database connection	dbName
   JDBC Driver Class	Name of a Java database connectivity (JDBC) driver class	oracle.jdbc.driver.OracleDriver
   JDBC Connection String	JDBC connection string, in the format of jdbc:oracle:thin:@Database IP address:Database port number:Database name	jdbc:oracle:thin:@10.16.0.1:1521:oradb
   Username	Username for connecting to the database	omm
   Password	Password for connecting to the database	xxxx
   JDBC Connection Properties	JDBC connection attribute. Click Add to manually add the attribute. Name: connection attribute name Value: connection attribute value	Name: socketTimeout Value: 20

   Configure data source information.

4. Click Next. On the displayed From page, set the data source information.

   Table 2 Parameter description

   Parameter	Description	Example Value
   Schema name	Database schema name. This parameter exists in the Table name schema.	public
   Table name	Database table name. This parameter exists in the Table name schema.	test
   Table SQL statement	SQL statement for Loader to query data to be imported in Table SQL statement mode. The SQL statement requires the query condition WHERE ${CONDITIONS}. Without this condition, the SQL statement cannot be run properly. An example SQL statement is as follows: select * from TABLE WHERE A>B and ${CONDITIONS}. If Table column names is set, the column specified by Table column names will replace the column queried in the SQL statement. This parameter cannot be set when Schema name or Table name is set. NOTE: You can use macros to define SQL Where statements. For details, see Using Macro Definitions in Configuration Items.	select * from TABLE WHERE A>B and ${CONDITIONS}
   Table column names	Table columns whose content is to be imported by Loader. Use commas (,) to separate multiple fields. If the parameter is not set, all the columns are imported and the Select * order is used as the column location.	id,name
   Partition column name	Database table column based on which to-be-imported data is determined. This parameter is used for partitioning in a Map job. You are advised to configure the primary key field. NOTE: A partition column must have an index. If no index exists, do not specify a partition column. If a partition column without an index is specified, the database server disk I/O will be busy, the access of other services to the database will be affected, and the import will take a long period. In multiple fields with indexes, select the field that has the most discrete value as the partition column. A partition column that is not discrete may result in load imbalance when multiple MapReduce jobs are imported. The sorting rules of partition columns must be case-sensitive. Otherwise, data may be lost during data import. You are not advised to select fields of the float or double type for the partition column. Otherwise, the records containing the minimum and maximum values of the partition column may fail to be imported due to precision issues.	id
   Nulls in partition column	Indicates whether to process records whose values are null in database table columns. true: Records whose values are null are processed. false: Records whose values are not null are processed.	true
   Need partition column	Indicates whether to specify a partition column.	true

   Configure data transformation.

5. Click Next. On the displayed Transform page, set the transformation operations in the data transformation process. For details about how to select operators and set parameters, see Operator Help and Table 3.

   Table 3 Input and output parameters of the operator

   Input Type	Output Type
   Table Input	File Output

   In input, drag Table Input to the grid. In output, drag File Output to the grid. Use an arrow to connect Table Input to File Output.

   Set data storage information and execute the job.

6. Click Next. On the displayed To page, set Storage type to HDFS.

   Table 4 Parameter description

   Parameter	Description	Example Value
   File Type	Type of the file to be saved after being imported. The options are as follows: TEXT_FILE: imports a text file and saves it as a text file. SEQUENCE_FILE: imports a text file and saves it as a sequence file. BINARY_FILE: imports files of any format using binary streams.	TEXT_FILE
   Compression Format	Compression format of files imported to HDFS or OBS. Select a format from the drop-down list. If you select NONE or leave this parameter blank, data is not compressed.	NONE
   Output Directory	Directory for storing data imported to HDFS or OBS. NOTE: You can use macros to define path parameters. For details, see Using Macro Definitions in Configuration Items.	/user/test
   Operation	Action during data import. When all data is imported from the input path to the destination path, the data is stored in a temporary directory and then copied from the temporary directory to the destination path. After data import is complete, the data in the temporary directory is deleted. One of the following actions can be taken when there are duplicate file names during data transfer: OVERRIDE: overrides the old file. RENAME: renames the new file. For a file without a file name extension, a string is added to the file name as the extension; for a file with a file name extension, a string is added to the extension. The string is unique. APPEND: adds the content of the new file to the end of the old file. This action only adds content regardless of whether the file can be used. For example, a text file can be used after this action, while a compressed file cannot. IGNORE: reserves the old file and does not copy the new file. ERROR: stops the task and reports an error if there are duplicate file names. Transferred files are imported successfully, while files that have duplicate names and files that are not transferred fail to import.	OVERRIDE
   Extractors	Number of Maps that are started at the same time in a MapReduce task of a data configuration operation. This parameter cannot be set when Extractor Size is set. The value must be less than or equal to 3000.	-
   Extractor Size	Size of data processed by Maps that are started in a MapReduce task of a data configuration operation. The unit is MB. The value must be greater than or equal to 100. The recommended value is 1000. This parameter cannot be set when Extractors is set. When a relational database connector is used, Extractor Size is unavailable. You need to set Extractors.	1000

7. Click Save and Run to save and run the job.

   View the job execution result.

8. Go to the Loader web UI. When Status is Succeeded, the job is complete.
   Figure 3 Viewing job details