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Description
Prerequisites
Overall Process
Step 1: Create a Queue
Step 2: Create an RDS MySQL Database and Table
Step 3: Create a GaussDB(DWS) Database and Table
Step 4: Create an Enhanced Datasource Connection
Step 5: Run a Job
Step 6: Send Data and Query Results

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Help Center/ Data Lake Insight/ Developer Guide/ Flink Jobs/ Flink OpenSource SQL Jobs/ Reading Data from MySQL CDC and Writing Data to GaussDB(DWS)

Reading Data from MySQL CDC and Writing Data to GaussDB(DWS)

Updated on 2025-01-10 GMT+08:00

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NOTICE:

This guide provides reference for Flink 1.12 only.

Description

Change Data Capture (CDC) can synchronize incremental changes from the source database to one or more destinations. During data synchronization, CDC processes data, for example, grouping (GROUP BY) and joining multiple tables (JOIN).

This example creates a MySQL CDC source table to monitor MySQL data changes and insert the changed data into a GaussDB(DWS) database.

Prerequisites

You have created an RDS for MySQL DB instance. In this example, the RDS for MySQL database version is 8.0.
For details, see Buying an RDS for MySQL DB Instance.
You have created a GaussDB(DWS) instance.
For how to create a GaussDB(DWS) cluster, see Creating a GaussDB(DWS) Cluster.

Overall Process

Figure 1 shows the overall development process.

Figure 1 Job development process

Step 1: Create a Queue

Step 2: Create an RDS MySQL Database and Table

Step 3: Create a GaussDB(DWS) Database and Table

Step 4: Create an Enhanced Datasource Connection

Step 5: Run a Job

Step 6: Send Data and Query Results

Step 1: Create a Queue

Log in to the DLI console. In the navigation pane on the left, choose Resources > Queue Management.
On the displayed page, click Buy Queue in the upper right corner.
On the Buy Queue page, set queue parameters as follows:
- Billing Mode: .
- Region and Project: Retain the default values.
- Name: Enter a queue name.
  NOTE:
  
  The queue name can contain only digits, letters, and underscores (_), but cannot contain only digits or start with an underscore (_). The name must contain 1 to 128 characters.
  
  The queue name is case-insensitive. Uppercase letters will be automatically converted to lowercase letters.
- Type: Select For general purpose. Select the Dedicated Resource Mode.
- AZ Mode and Specifications: Retain the default values.
- Enterprise Project: Select default.
- Advanced Settings: Select Custom.
- CIDR Block: Specify the queue network segment. For example, 10.0.0.0/16.
  CAUTION:
  
  The CIDR block of a queue cannot overlap with the CIDR blocks of DMS Kafka and RDS for MySQL DB instances. Otherwise, datasource connections will fail to be created.
- Set other parameters as required.
Click Buy. Confirm the configuration and click Submit.

Step 2: Create an RDS MySQL Database and Table

Log in to the RDS console. On the displayed page, locate the target MySQL DB instance and choose More > Log In in the Operation column.
On the displayed login dialog box, enter the username and password and click Log In.
On the Databases page, click Create Database. In the displayed dialog box, enter testrdsdb as the database name and retain default values of rest parameters. Then, click OK.

In the Operation column of row where the created database locates, click SQL Window and enter the following statement to create a table:

CREATE TABLE mysqlcdc (
	`order_id` VARCHAR(64) NOT NULL,
	`order_channel` VARCHAR(32) NOT NULL,
	`order_time` VARCHAR(32),
	`pay_amount` DOUBLE,
	`real_pay` DOUBLE,
	`pay_time` VARCHAR(32),
	`user_id` VARCHAR(32),
	`user_name` VARCHAR(32),
	`area_id` VARCHAR(32)

)	ENGINE = InnoDB
	DEFAULT CHARACTER SET = utf8mb4;

Step 3: Create a GaussDB(DWS) Database and Table

Connect to the created GaussDB(DWS) cluster.
For details, see Using the gsql CLI Client to Connect to a Cluster.
Connect to the default database gaussdb of a GaussDB(DWS) cluster.
```
gsql -d gaussdb -h Connection address of the GaussDB(DWS) cluster -U dbadmin -p 8000 -W password -r
```
- gaussdb: Default database of the GaussDB(DWS) cluster
- Connection address of the DWS cluster: If a public network address is used for connection, set this parameter to the public network IP address or domain name. If a private network address is used for connection, set this parameter to the private network IP address or domain name. For details, see section Obtaining the Cluster Connection Address. If an ELB is used for connection, set this parameter to the ELB address.
- dbadmin: Default administrator username used during cluster creation
- -W: Default password of the administrator
Run the following command to create the testdwsdb database:
```
CREATE DATABASE testdwsdb;
```

Run the following command to exit the gaussdb database and connect to testdwsdb:

\q
gsql -d testdwsdb -h Connection address of the GaussDB(DWS) cluster -U dbadmin -p 8000 -W password -r

Run the following commands to create a table:

create schema test;
set current_schema= test;
drop table if exists dwsresult;
CREATE TABLE dwsresult
(
    car_id VARCHAR, 
    car_owner VARCHAR,
    car_age INTEGER ,
    average_speed FLOAT8,
    total_miles FLOAT8
);

Step 4: Create an Enhanced Datasource Connection

Connecting DLI to RDS
1. Go to the RDS console, click the name of the target RDS DB instance on the Instances page. Basic information of the instance is displayed.
2. In the Connection Information pane, obtain the floating IP address, database port, VPC, and subnet.
3. Click the security group name. On the displayed page, click the Inbound Rules tab and add a rule to allow access from DLI queues. For example, if the CIDR block of the queue is 10.0.0.0/16, set Priority to 1, Action to Allow, Protocol to TCP, Type to IPv4, Source to 10.0.0.0/16, and click OK.
4. Log in to the DLI management console. In the navigation pane on the left, choose Datasource Connections. On the displayed page, click Create in the Enhanced tab.
5. In the displayed dialog box, set the following parameters: For details, see the following section:
  - Connection Name: Enter a name for the enhanced datasource connection. For this example, enter dli_rds.
  - Resource Pool: Select the name of the queue created in Step 1: Create a Queue.
  - VPC: Select the VPC of the RDS DB instance.
  - Subnet: Select the subnet of RDS DB instance.
  - Set other parameters as you need.
  Click OK. Click the name of the created datasource connection to view its status. You can perform subsequent steps only after the connection status changes to Active.
6. Choose Resources > Queue Management from the navigation pane, locate the queue you created in Step 1: Create a Queue. In the Operation column, click More > Test Address Connectivity.
7. In the displayed dialog box, enter floating IP address:database port of the RDS DB instance you have obtained in 2 in the Address box and click Test to check whether the database is reachable.
Connecting DLI to GaussDB(DWS)
1. On the GaussDB(DWS) management console, choose Clusters. On the displayed page, click the name of the created GaussDB(DWS) cluster to view basic information.
2. In the Basic Information tab, locate the Database Attributes pane and obtain the private IP address and port number of the DB instance. In the Network pane, obtain VPC, and subnet information.
3. Click the security group name. On the displayed page, click the Inbound Rules tab and add a rule to allow access from DLI queues. For example, if the CIDR block of the queue is 10.0.0.0/16, set Priority to 1, Action to Allow, Protocol to TCP, Type to IPv4, Source to 10.0.0.0/16, and click OK.
4. Check whether the RDS instance and GaussDB(DWS) instance are in the same VPC and subnet.
  1. If they are, go to 7. You do not need to create an enhanced datasource connection again.
  2. If they are not, go to 5. Create an enhanced datasource connection to connect RDS to the subnet where the GaussDB(DWS) instance locates.
5. Log in to the DLI management console. In the navigation pane on the left, choose Datasource Connections. On the displayed page, click Create in the Enhanced tab.
6. In the displayed dialog box, set the following parameters: For details, see the following section:
  - Connection Name: Enter a name for the enhanced datasource connection. For this example, enter dli_dws.
  - Resource Pool: Select the name of the queue created in Step 1: Create a Queue.
  - VPC: Select the VPC of the GaussDB(DWS) instance.
  - Subnet: Select the subnet of GaussDB(DWS) instance.
  - Set other parameters as you need.
  Click OK. Click the name of the created datasource connection to view its status. You can perform subsequent steps only after the connection status changes to Active.
7. Choose Resources > Queue Management from the navigation pane, locate the queue you created in Step 1: Create a Queue. In the Operation column, click More > Test Address Connectivity.
8. In the displayed dialog box, enter floating IP address:database port of the GaussDB(DWS) instance you have obtained in 2 in the Address box and click Test to check whether the database is reachable.

Step 5: Run a Job

On the DLI management console, choose Job Management > Flink Jobs. On the Flink Jobs page, click Create Job.
In the Create Job dialog box, set Type to Flink OpenSource SQL and Name to FlinkCDCMySQLDWS. Click OK.

On the job editing page, set the following parameters and retain the default values of other parameters.

Queue: Select the queue created in Step 1: Create a Queue.
Flink Version: Select 1.12.
Save Job Log: Enable this function.
OBS Bucket: Select an OBS bucket for storing job logs and grant access permissions of the OBS bucket as prompted.
Enable Checkpointing: Enable this function.

Enter a SQL statement in the editing pane. The following is an example. Modify the parameters in bold as you need.

NOTE:

In this example, the syntax version of Flink OpenSource SQL is 1.12. In this example, the data source is Kafka and the result data is written to Elasticsearch.

For details, see MySQL CDC Source Table and GaussDB(DWS) Result Table.

create table mysqlCdcSource(
  order_id string,
  order_channel string,
  order_time string,
  pay_amount double,
  real_pay double,
  pay_time string,
  user_id string,
  user_name string,
  area_id STRING
) with (
  'connector' = 'mysql-cdc',
  'hostname' = ' 192.168.12.148',--IP address of the RDS MySQL instance
  'port'= ' 3306',--Port number of the RDS MySQL instance
  'pwd_auth_name'= 'xxxxx', -- Name of the datasource authentication of the password type created on DLI. If datasource authentication is used, you do not need to set the username and password for the job.
  'database-name' = ' testrdsdb',--Database name of the RDS MySQL instance
  'table-name' = ' mysqlcdc'--Name of the target table in the database
);

create table dwsSink(
  order_channel string,
  pay_amount double,
  real_pay double,
  primary key(order_channel) not enforced
) with (
  'connector' = 'gaussdb',
  'driver' = 'com.huawei.gauss200.jdbc.Driver',
  'url'='jdbc:gaussdb://192.168.168.16:8000/testdwsdb ', ---192.168.168.16:8000 indicates the internal IP address and port of the GaussDB(DWS) instance. testdwsdb indicates the name of the created GaussDB(DWS) database.
  'table-name' = ' test\".\"dwsresult', ---test indicates the schema of the created GaussDB(DWS) table, and dwsresult indicates the GaussDB(DWS) table name.
  'pwd_auth_name'= 'xxxxx', -- Name of the datasource authentication of the password type created on DLI. If datasource authentication is used, you do not need to set the username and password for the job.
  'write.mode' = 'insert'
);

insert into dwsSink select order_channel, sum(pay_amount),sum(real_pay) from mysqlCdcSource group by order_channel;

Click Check Semantic and ensure that the SQL statement passes the check. Click Save. Click Start, confirm the job parameters, and click Start Now to execute the job. Wait until the job status changes to Running.

Step 6: Send Data and Query Results

Log in to the RDS console. On the displayed page, locate the target MySQL DB instance and choose More > Log In in the Operation column.
On the displayed login dialog box, enter the username and password and click Log In.

In the Operation column of row where the created database locates, click SQL Window and enter the following statement to create a table and insert data to the table:

insert into mysqlcdc values
('202103241000000001','webShop','2021-03-24 10:00:00','100.00','100.00','2021-03-24 10:02:03','0001','Alice','330106'),
('202103241206060001','appShop','2021-03-24 12:06:06','200.00','180.00','2021-03-24 16:10:06','0002','Jason','330106'),
('202103241403000001','webShop','2021-03-24 14:03:00','300.00','100.00','2021-03-24 10:02:03','0003','Lily','330106'),
('202103241636060001','appShop','2021-03-24 16:36:06','200.00','150.00','2021-03-24 16:10:06','0001','Henry','330106');

Connect to the created GaussDB(DWS) cluster by referring to Using the gsql CLI Client to Connect to a Cluster.

Connect to the default database testdwsdb of a GaussDB(DWS) cluster.

gsql -d testdwsdb -h Connection address of the GaussDB(DWS) cluster -U dbadmin -p 8000 -W password -r

Run the following statements to query table data:

select * from test.dwsresult;

The query result is as follows:

order_channel  pay_amount  real_pay 
appShop         400.0       330.0
webShop         400.0       200.0

Parent topic: Flink OpenSource SQL Jobs

Previous topic: Reading Data from Kafka and Writing Data to Elasticsearch

Next topic: Reading Data from PostgreSQL CDC and Writing Data to GaussDB(DWS)

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