Streaming ELT from MySQL to StarRocks #

This tutorial is to show how to quickly build a Streaming ELT job from MySQL to StarRocks using Flink CDC, including the feature of sync all table of one database, schema change evolution and sync sharding tables into one table.
All exercises in this tutorial are performed in the Flink CDC CLI, and the entire process uses standard SQL syntax, without a single line of Java/Scala code or IDE installation.

Preparation #

Prepare a Linux or MacOS computer with Docker installed.

Prepare Flink Standalone cluster #

Download Flink 1.18.0 ，unzip and get flink-1.18.0 directory.
Use the following command to navigate to the Flink directory and set FLINK_HOME to the directory where flink-1.18.0 is located.
```
cd flink-1.18.0
```
Enable checkpointing by appending the following parameters to the conf/flink-conf.yaml configuration file to perform a checkpoint every 3 seconds.
```
execution.checkpointing.interval: 3000
```
Start the Flink cluster using the following command.
```
./bin/start-cluster.sh
```

If successfully started, you can access the Flink Web UI at http://localhost:8081/, as shown below.

Executing start-cluster.sh multiple times can start multiple TaskManagers.

Prepare docker compose #

The following tutorial will prepare the required components using docker-compose. Create a docker-compose.yml file using the content provided below:

version: '2.1'
services:
   StarRocks:
      image: starrocks/allin1-ubuntu:3.2.6
      ports:
         - "8080:8080"
         - "9030:9030"
   MySQL:
      image: debezium/example-mysql:1.1
      ports:
         - "3306:3306"
      environment:
         - MYSQL_ROOT_PASSWORD=123456
         - MYSQL_USER=mysqluser
         - MYSQL_PASSWORD=mysqlpw

The Docker Compose should include the following services (containers):

MySQL: include a database named app_db
StarRocks: to store tables from MySQL

To start all containers, run the following command in the directory that contains the docker-compose.yml file.

docker-compose up -d

This command automatically starts all the containers defined in the Docker Compose configuration in a detached mode. Run docker ps to check whether these containers are running properly. You can also visit http://localhost:8030/ to check whether StarRocks is running.

Prepare records for MySQL #

Enter MySQL container

docker-compose exec MySQL mysql -uroot -p123456

create app_db database and orders,products,shipments tables, then insert records

-- create database
CREATE DATABASE app_db;

USE app_db;

-- create orders table
CREATE TABLE `orders` (
`id` INT NOT NULL,
`price` DECIMAL(10,2) NOT NULL,
PRIMARY KEY (`id`)
);

-- insert records
INSERT INTO `orders` (`id`, `price`) VALUES (1, 4.00);
INSERT INTO `orders` (`id`, `price`) VALUES (2, 100.00);

-- create shipments table
CREATE TABLE `shipments` (
`id` INT NOT NULL,
`city` VARCHAR(255) NOT NULL,
PRIMARY KEY (`id`)
);

-- insert records
INSERT INTO `shipments` (`id`, `city`) VALUES (1, 'beijing');
INSERT INTO `shipments` (`id`, `city`) VALUES (2, 'xian');

-- create products table
CREATE TABLE `products` (
`id` INT NOT NULL,
`product` VARCHAR(255) NOT NULL,
PRIMARY KEY (`id`)
);

-- insert records
INSERT INTO `products` (`id`, `product`) VALUES (1, 'Beer');
INSERT INTO `products` (`id`, `product`) VALUES (2, 'Cap');
INSERT INTO `products` (`id`, `product`) VALUES (3, 'Peanut');

Submit job with Flink CDC CLI #

Download the binary compressed packages listed below and extract them to the directory flink cdc-3.2.1'：
flink-cdc-3.2.1-bin.tar.gz flink-cdc-3.2.1 directory will contain four directory: bin, lib, log, and conf.
Download the connector package listed below and move it to the lib directory
Download links are available only for stable releases, SNAPSHOT dependencies need to be built based on master or release branches by yourself. Please note that you need to move the jar to the lib directory of Flink CDC Home, not to the lib directory of Flink Home.
- MySQL pipeline connector 3.2.1
- StarRocks pipeline connector 3.2.1
You also need to place MySQL connector into Flink lib folder or pass it with --jar argument, since they’re no longer packaged with CDC connectors:
- MySQL Connector Java

Write task configuration yaml file. Here is an example file for synchronizing the entire database mysql-to-starrocks.yaml：

################################################################################
# Description: Sync MySQL all tables to StarRocks
################################################################################
source:
  type: mysql
  hostname: localhost
  port: 3306
  username: root
  password: 123456
  tables: app_db.\.*
  server-id: 5400-5404
  server-time-zone: UTC

sink:
  type: starrocks
  name: StarRocks Sink
  jdbc-url: jdbc:mysql://127.0.0.1:9030
  load-url: 127.0.0.1:8080
  username: root
  password: ""
  table.create.properties.replication_num: 1

pipeline:
  name: Sync MySQL Database to StarRocks
  parallelism: 2

Notice that:

tables: app_db.\.* in source synchronize all tables in app_db through Regular Matching.
table.create.properties.replication_num in sink is because there is only one StarRocks BE node in the Docker image.

Finally, submit job to Flink Standalone cluster using Cli.
```
bash bin/flink-cdc.sh mysql-to-starrocks.yaml
```

After successful submission, the return information is as follows：

Pipeline has been submitted to cluster.
Job ID: 02a31c92f0e7bc9a1f4c0051980088a0
Job Description: Sync MySQL Database to StarRocks

We can find a job named Sync MySQL Database to StarRocks is running through Flink Web UI.

Connect to jdbc through database connection tools such as Dbeaver using mysql://127.0.0.1:9030. You can view the data written to three tables in StarRocks.

Synchronize Schema and Data changes #

Enter MySQL container

docker-compose exec mysql mysql -uroot -p123456

Then, modify schema and record in MySQL, and the tables of StarRocks will change the same in real time：

insert one record in orders from MySQL:

INSERT INTO app_db.orders (id, price) VALUES (3, 100.00);

add one column in orders from MySQL:

ALTER TABLE app_db.orders ADD amount varchar(100) NULL;

update one record in orders from MySQL:

UPDATE app_db.orders SET price=100.00, amount=100.00 WHERE id=1;

delete one record in orders from MySQL:
```
DELETE FROM app_db.orders WHERE id=2;
```

Refresh the Dbeaver every time you execute a step, and you can see that the orders table displayed in StarRocks will be updated in real-time, like the following：

Similarly, by modifying the shipments and products tables, you can also see the results of synchronized changes in real-time in StarRocks.

Route the changes #

Flink CDC provides the configuration to route the table structure/data of the source table to other table names.
With this ability, we can achieve functions such as table name, database name replacement, and whole database synchronization. Here is an example file for using route feature:

################################################################################
# Description: Sync MySQL all tables to StarRocks
################################################################################
source:
   type: mysql
   hostname: localhost
   port: 3306
   username: root
   password: 123456
   tables: app_db.\.*
   server-id: 5400-5404
   server-time-zone: UTC

sink:
   type: starrocks
   jdbc-url: jdbc:mysql://127.0.0.1:9030
   load-url: 127.0.0.1:8030
   username: root
   password: ""
   table.create.properties.replication_num: 1

route:
   - source-table: app_db.orders
     sink-table: ods_db.ods_orders
   - source-table: app_db.shipments
     sink-table: ods_db.ods_shipments
   - source-table: app_db.products
     sink-table: ods_db.ods_products

pipeline:
   name: Sync MySQL Database to StarRocks
   parallelism: 2

Using the upper route configuration, we can synchronize the table schema and data of app_db.orders to ods_db.ods_orders, thus achieving the function of database migration.
Specifically, source-table support regular expression matching with multiple tables to synchronize sharding databases and tables. like the following：

route:
  - source-table: app_db.order\.*
    sink-table: ods_db.ods_orders

In this way, we can synchronize sharding tables like app_db.order01、app_db.order02、app_db.order03 into one ods_db.ods_orders tables.
Warning that there is currently no support for scenarios where the same primary key data exists in multiple tables, which will be supported in future versions.

Clean up #

After finishing the tutorial, run the following command to stop all containers in the directory of docker-compose.yml:

docker-compose down

Run the following command to stop the Flink cluster in the directory of Flink flink-1.18.0:

./bin/stop-cluster.sh