Migrating ClickHouse® clusters

With Data Transfer, you can transfer your database from a third-party ClickHouse® source cluster to a Managed Service for ClickHouse® target cluster.

This method allows you to:

• Copy the database without interrupting user service.
• Go without creating an intermediate VM or granting online access to your Managed Service for ClickHouse® target cluster.

For more information, see What tasks Yandex Data Transfer is used for.

Getting startedGetting started

Allow connecting to the source cluster from the internet.

Transferring dataTransferring data

1. Prepare the source cluster.

2. Prepare the infrastructure:

   Manually

   Using Terraform

   1. Create a security group and configure it.

   2. Create a Managed Service for ClickHouse® target cluster with the computing capacity and storage size appropriate for the environment where the copied database is deployed.

      When creating a cluster, specify the security group prepared earlier.

      The database name in the target cluster must be the same as the source database name.

   3. Create a source endpoint:

      • Database type: ClickHouse

      • Endpoint parameters → Connection settings: On-premise

        Specify the parameters for connecting to the source cluster.

   4. Create a target endpoint:

      • Database type: ClickHouse

      • Endpoint parameters → Connection settings: Managed cluster

        Select a target cluster from the list and specify its connection settings.

   5. Create a transfer of the Snapshot type that will use the created endpoints.

   6. Activate your transfer.

   1. If you do not have Terraform yet, install it.

   2. Get the authentication credentials. You can add them to environment variables or specify them later in the provider configuration file.

   3. Configure and initialize a provider. There is no need to create a provider configuration file manually, you can download it.

   4. Place the configuration file in a separate working directory and specify the parameter values. If you did not add the authentication credentials to environment variables, specify them in the configuration file.

   5. Download the data-transfer-ch-mch.tf configuration file to the same working directory.

      This file describes:

      • Network.
      • Subnet.
      • Security group and the rule required to connect to a cluster.
      • Managed Service for ClickHouse® target cluster.
      • Source endpoint.
      • Target endpoint.
      • Transfer.

   6. In the data-transfer-ch-mch.tf file, specify:

      • Source endpoint parameters:

        • source_user and source_pwd: Username and password to access the source.
        • source_db_name: Database name.
        • source_host: FQDN or IP address of the ClickHouse® server.
        • source_shard: Shard name.
        • source_http_port and source_native_port: HTTP and ClickHouse® native interface connection ports.

      • Target cluster parameters also used as target endpoint parameters:

        • target_clickhouse_version: ClickHouse® version.
        • target_user and target_password: Database owner username and password.

   7. Make sure the Terraform configuration files are correct using this command:

      terraform validate
      

      If there are any errors in the configuration files, Terraform will point them out.

   8. Create the required infrastructure:

      1. Run the command to view planned changes:

         terraform plan
         

         If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.

      2. If you are happy with the planned changes, apply them:

         1. Run the command:

            terraform apply
            

         2. Confirm the update of resources.

         3. Wait for the operation to complete.

      All the required resources will be created in the specified folder. You can check resource availability and their settings in the management console.

      Once created, your transfer will be activated automatically.

3. Wait for the transfer status to change to Completed.

   For more information about transfer statuses, see Transfer lifecycle.

4. Some resources are not free of charge. To avoid paying for them, delete the resources you no longer need:

   Manually

   Using Terraform

   • Delete the Managed Service for ClickHouse® cluster.
   • Delete the completed transfer.
   • Delete endpoints for both the source and target.

   1. In the terminal window, go to the directory containing the infrastructure plan.

   2. Delete the data-transfer-ch-mch.tf configuration file.

   3. Make sure the Terraform configuration files are correct using this command:

      terraform validate
      

      If there are any errors in the configuration files, Terraform will point them out.

   4. Confirm updating the resources.

      1. Run the command to view planned changes:

         terraform plan
         

         If the resource configuration descriptions are correct, the terminal will display a list of the resources to modify and their parameters. This is a test step. No resources are updated.

      2. If you are happy with the planned changes, apply them:

         1. Run the command:

            terraform apply
            

         2. Confirm the update of resources.

         3. Wait for the operation to complete.

      All the resources described in the data-transfer-ch-mch.tf configuration file will be deleted.

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