Step 2: Creating Links

Scenario

Before migrating the local MySQL database to DWS, create two links:

1. MySQL link: used to connect to the on-premises MySQL database.
2. DWS link: used to connect to the DWS database.

CDM needs to access the on-premises data source. Therefore, before creating links, bind an EIP to the CDM cluster.

Prerequisites

• Your on-premises MySQL database can be accessed using the public IP address.
• You have obtained the IP address, port, database name, username, and password for connecting to the MySQL database. In addition, the user has the read, write, and delete permissions on the MySQL database.
• You have a DWS instance and have obtained the IP address, port number, database name, username, and password for accessing DWS. In addition, the user has the read, write, and delete permissions for the DWS database.
• You have uploaded the MySQL database driver by referring to Managing Drivers.

Binding an EIP to a CDM Cluster

1. Log in to the CDM management console.
2. Locate a CDM cluster and click Bind EIP in the Operation column. In the displayed dialog box, select an EIP.

   If no EIP is available, create one as prompted.

3. Click OK.

Creating a MySQL Link

1. In the left navigation pane, choose Cluster Management. Locate the cdm-aff1 cluster created in Step 1: Creating a Cluster.
2. In the Operation column, click Bind EIP, and select and bind an EIP to the cluster.
   

   If SSL encryption is configured for the access channel of a local data source, CDM cannot connect to the data source using the EIP.

3. Click Job Management in the Operation column of the CDM cluster. On the displayed page, click the Links tab and then Create Link. The Select Connector page is displayed.
   Figure 1 Selecting a connector
   

4. Select MySQL and click Next. On the page that is displayed, configure MySQL link parameters.
   Figure 2 Creating a MySQL link
   

   Click Show Advanced Attributes and set optional parameters. For details, see Link to Relational Databases. Retain the default values of the optional parameters and configure the mandatory parameters according to Table 1.

   Table 1 MySQL link parameters

   Parameter	Description	Example Value
   Name	Unique link name	mysqllink
   Database Server	IP address or domain name of the MySQL database server	192.168.1.110
   Port	MySQL database port	3306
   Database Name	Name of the MySQL database	sqoop
   Username	User who has the read, write, and delete permissions on the MySQL database	admin
   Password	Password of the user	-
   Use Local API	Whether to use the local API of the database for acceleration. (The system attempts to enable the local_infile system variable of the MySQL database.)	Yes
   Use Agent	Whether to extract data from the data source through an agent	Yes
   local_infile Character Set	When using local_infile to import data to MySQL, you can configure the encoding format.	utf8
   Driver Version	A driver version that adapts to MySQL	-
   Agent	Click Select to select the agent created in Connecting to an Agent.	-
   Fetch Size	(Optional) Displayed when you click Show Advanced Attributes. Number of rows obtained by each request. Set this parameter based on the data source and the job's data size. If the value is either too large or too small, the job may run for a long time.	1000
   Commit Size	(Optional) Displayed when you click Show Advanced Attributes. Number of records submitted each time. Set this parameter based on the data destination and the job's data size. If the value is either too large or too small, the job may run for a long time.	1000
   Link Attributes	Custom attributes of the link	useCompression=true
   Reference Sign	Delimiter used to separate referenced table names or column names This parameter is left blank by default.	'
   Batch Size	Number of rows written each time. It should be less than Commit Size. When the number of rows written reaches the value of Commit Size, the rows will be committed to the database.	100

5. Click Save. The Link Management page is displayed.
   

   If an error occurs during the saving, the security settings of the MySQL database are incorrect. In this case, you need to enable the EIP of the CDM cluster to access the MySQL database.

Creating a DWS Link

1. Click Job Management in the Operation column of the CDM cluster. On the displayed page, click the Links tab and then Create Link. The Select Connector page is displayed.
   Figure 3 Selecting a connector
   

2. Select Data Warehouse Service and click Next to configure the DWS link parameters. Set the mandatory parameters listed in Table 2 and retain the default values for the optional parameters.

   Table 2 DWS link parameters

   Parameter	Description	Example Value
   Name	Unique link name	dwslink
   Database Server	IP address or domain name of the DWS database server	192.168.0.3
   Port	DWS database port	8000
   Database Name	Name of the DWS database	db_demo
   Username	User who has the read, write, and delete permissions on the DWS database	dbadmin
   Password	Password of the user	-
   Use Agent	Whether to extract data from the data source through an agent	Yes
   Agent	Click Select to select the agent created in Connecting to an Agent.	-

3. Click Save.