Typical Scenario: Exporting Data from HDFS/OBS to an SFTP Server

Scenario

This section describes how to use Loader to export data from HDFS/OBS to an SFTP server.

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 SFTP server and the user has the write permission of the data export directory on the SFTP server.
No disk space alarm is reported, and the available disk space is sufficient for importing and exporting data.
When using Loader to export data from HDFS/OBS, the input paths and input path subdirectories of HDFS/OBS data source and the name of the files in these directories do not contain any of the following special characters: /\"':;,.
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.

Procedure

Setting Basic Job Information

Access the Loader web UI.
1. Log in to FusionInsight Manager. For details, see Accessing FusionInsight Manager.
2. Choose Cluster > Name of the desired cluster > Services > Loader.
3. Click LoaderServer(Node name, Active). The Loader web UI is displayed.
  Figure 1 Loader web UI
Click New Job to go to the Basic Information page and set basic job information.

Figure 2 Basic Information
1. Set Name to the name of the job.
2. Set Type to Export.
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.

In the Connection area, click Add to create a connection, set Connector to sftp-connector, click Add, set connection parameters, and click Test to verify whether the connection is available. When "Test Success" is displayed, click OK. Loader allows multiple SFTP servers to be configured. Click Add to add the configuration information of multiple SFTP servers.

**Table 1** Connection parameters
Parameter	Description	Example Value
Name	Specifies the name of the SFTP server connection.	sftpName
SFTP Server IP	Specifies the IP address of the SFTP server.	10.16.0.1
SFTP Server Port	Specifies the port number of the SFTP server.	22
SFTP Username	Specifies the user name for accessing the SFTP server.	root
SFTP Password	Specifies the password for accessing the SFTP server.	xxxx
SFTP Public Key	Specifies public key of the SFTP server.	OdDt/yn...etM

When multiple SFTP servers are configured, the data of HDFS/OBS will be divided into multiple parts and exported to the SFTP servers randomly.

Setting Data Source Information

Click Next. On the displayed From page, set Source type to HDFS.

**Table 2** Data source parameters
Parameter	Description	Example Value
Input directory	Specifies the input path when data is exported from HDFS/OBS. NOTE: You can use macros to define path parameters. For details, see Using Macro Definitions in Configuration Items.	/user/test
Path filter	Specifies the wildcard for filtering the directories in the input paths of the source files. Input directory is not used in filtering. If there are multiple filter conditions, use commas (,) to separate them. If the parameter is empty, the directory is not filtered. The regular expression filtering is not supported. ? matches a single character. * indicates multiple characters. Adding ^ before the condition indicates negated filtering, that is, file filtering.	*
File filter	Specifies the wildcard for filtering the file names of the source files. If there are multiple filter conditions, use commas (,) to separate them. The value cannot be left blank. The regular expression filtering is not supported. ? matches a single character. * indicates multiple characters. Adding ^ before the condition indicates negated filtering, that is, file filtering.	*
File Type	Specifies the file import type. TEXT_FILE: imports a text file and stores it as a text file. SEQUENCE_FILE: imports a text file and stores it as a sequence file. BINARY_FILE: imports files of any format by using binary streams but not to process the files. NOTE: When the file import type to TEXT_FILE or SEQUENCE_FILE, Loader automatically selects a decompression method based on the file name extension to decompress a file.	TEXT_FILE
File Split Type	Indicates whether to split source files by file name or size. The files obtained after the splitting are used as the input files of each map in the MapReduce task for data export. FILE: indicates that the source file is split by file. That is, each map processes one or multiple complete files, the same source file cannot be allocated to different maps, and the source file directory structure is retained after data import. SIZE: indicates that the source file is split by size. That is, each map processes input files of a certain size, and a source file can be divided and processed by multiple maps. After data is stored in the output directory, the number of saved files is the same as the number of maps. The file name format is import_part_xxxx, where xxxx is a unique random number generated by the system.	FILE
Extractors	Specifies the number of maps that are started at the same time in a MapReduce job 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. You are advised to set the parameter to the number of CPU cores on the SFTP server. NOTE: To improve the data import speed, ensure that the following conditions are met: Each map connection is equivalent to a client connection. Therefore, you must ensure that the maximum number of connections of the SFTP server is greater than the number of maps. Ensure that the disk I/O or network bandwidth on the SFTP server does not reach the upper limit.	20
Extractor size	Specifies the size of data processed by maps that are started in a MapReduce job 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.	-

Setting Data Transformation

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** Setting the input and output parameters of the operator
Input Type	Export Type
CSV file input	File output
HTML input	File output
Fixed-width file input	File output

Figure 3 Operator operation procedure
Click to enlarge

Setting Data Storage Information and Executing the Job

Click Next. On the displayed To page, set the data storage mode.

**Table 4** Parameter description
Parameter	Description	Example Value
Output path	Specifies the path or file name of the exported file on an SFTP server. If multiple SFTP server IP addresses are configured for the connector, you can set this parameter to multiple paths or file names separated with semicolons (;). Ensure that the number of paths or file names is the same as the number of SFTP servers configured for the connector. NOTE: You can use macros to define path parameters. For details, see Using Macro Definitions in Configuration Items.	/opt/tempfile
Operation	Specifies the action during data import. When all data is to be 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 the data is imported successfully, the data is deleted from the temporary directory. One of the following actions can be taken when duplicate file names exist during data transfer: OVERRIDE: overrides the old file. RENAME: renames as new file. For a file without an extension, a string is added to the file name as the extension; for a file with an 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 operation, 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 duplicate file names exist. Transferred files are imported successfully, while files that have duplicate names and files that are not transferred fail to be imported.	OVERRIDE
Encode type	Specifies the exported file encoding format, for example, UTF-8. This parameter can be set only in text file export.	UTF-8
Compression	Indicates whether to enable the compressed transmission function when SFTP is used to export data. The value true indicates that compression is enabled. The value false indicates that compression is disabled.	true

Click Save and run to save and run the job.
Checking the Job Execution Result
Go to the Loader WebUI. When Status is Succeeded, the job is complete.

Figure 4 Viewing a job