Accessing RDS MySQL Using ClickHouse

Prerequisites

• You have prepared the RDS database instance to be interconnected with and the username and password of the database. Step 1: Set Up for RDS.
• A ClickHouse cluster has been created and is running properly.

Constraints

• The RDS database instance and ClickHouse cluster are in the same VPC and subnet.
• Before synchronizing data, you need to evaluate the impact on the performance of the source and destination databases. You are advised to synchronize data during off-peak hours.
• Currently, ClickHouse can interconnect with MySQL and PostgreSQL instances of RDS, but cannot interconnect with SQL Server instances.

Interconnecting ClickHouse with RDS Using the MySQL Engine

The MySQL engine is used to map tables on the remote MySQL server to ClickHouse and allows you to run INSERT and SELECT statements on tables to facilitate data exchange between ClickHouse and MySQL.

• Syntax for using the MySQL engine:

  CREATE DATABASE [IF NOT EXISTS] db_name [ON CLUSTER cluster]
  ENGINE = MySQL('host:port', ['database' | database], 'user', 'password')

  Table 1 Parameters of the MySQL database

  Parameter	Description
  hostport	IP address and port number of the RDS MySQL database instance.
  database	RDS MySQL database
  user	Username of the RDS MySQL database.
  password	Password of the RDS MySQL database user.

  Example of using the MySQL engine:

  1. Connect to the MySQL database of RDS. For details, see Connect to a DB Instance.
  2. Create a table in the MySQL database and insert data into the table.
  3. Run the client command to connect to ClickHouse.
     Use the following command to connect to a normal cluster.

     ./clickhouse client --host Private IP address of the cluster   --port Port --user admin --password Password

     Use the following command to connect to a secure cluster. For details, see Configuring Secure Channel Encryption for ClickHouse Clusters.

     ./clickhouse client --host Private IP address of the cluster --port port --user admin --password Password --secure --config-file /root/config.xml
     NOTE:

     Private IP Address: cluster access address on the cluster details page. Replace it with the access address of the cluster you purchased.

  4. Create a MySQL database in ClickHouse. After the database is created, it automatically exchanges data with a MySQL server.

     CREATE DATABASE mysql_db ENGINE = MySQL('IP address of the RDS MySQL database instance:Port number of the MySQL database instance', 'MySQL database name', 'MySQL database username', 'Password of the MySQL database user');
  5. Switch to the created database mysql_db.

     USE mysql_db;

     Query the table data in the MySQL database in ClickHouse.

     SELECT * FROM mysql_table;
     ┌─int_id─┬─float─┐
     │      1   │     2   │
     └─────┴──── ┘

     Data can be properly queried after being inserted.

     INSERT INTO mysql_table VALUES (3,4);

     SELECT * FROM mysql_table;
     ┌─int_id─┬─float─┐
     │      1   │       2 │
     │      3   │       4 │
     └─────┴──── ┘