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Clickhouse Source Connector Documentation

ClickHouse

Overview​

The ClickHouse source supports both Full Refresh and Incremental syncs. You can choose if this connector will copy only the new or updated data, or all rows in the tables and columns you set up for replication, every time a sync is run.

This Clickhouse source connector is built on top of the source-jdbc code base and is configured to rely on JDBC v0.3.1 standard drivers provided by ClickHouse here as described in ClickHouse documentation here.

Resulting schema​

The ClickHouse source does not alter the schema present in your warehouse. Depending on the destination connected to this source, however, the schema may be altered. See the destination's documentation for more details.

Features​

Feature Supported Notes
Full Refresh Sync Yes  
Incremental Sync Yes Coming soon
Replicate Incremental Deletes Coming soon  
Logical Replication (WAL) Coming soon  
SSL Support Yes  
SSH Tunnel Connection Yes  
Namespaces Yes Enabled by default

Getting started​

Requirements​

  1. ClickHouse Server 21.3.10.1 or later.
  2. Create a dedicated read-only Connect user with access to all tables needed for replication

Setup guide​

1. Make sure your database is accessible from the machine running Seek Connect​

This is dependent on your networking setup. The easiest way to verify if Seek Connect is able to connect to your ClickHouse instance via the check connection tool in the UI.

2. Create a dedicated read-only user with access to the relevant tables (Recommended but optional)​

This step is optional but highly recommended to allow for better permission control and auditing. Alternatively, you can use Connect with an existing user in your database.

To create a dedicated database user, run the following commands against your database:

CREATE USER 'connect'@'%' IDENTIFIED BY 'your_password_here';

Then give it access to the relevant schema:

GRANT SELECT ON <database name>.* TO 'connect'@'%';

You can limit this grant down to specific tables instead of the whole database. Note that to replicate data from multiple ClickHouse databases, you can re-run the command above to grant access to all the relevant schemas, but you'll need to set up multiple sources connecting to the same db on multiple schemas.

Your database user should now be ready for use with Seek Connect.

Connection via SSH Tunnel​

Seek Connect has the ability to connect to a Clickhouse instance via an SSH Tunnel. The reason you might want to do this because it is not possible (or against security policy) to connect to the database directly (e.g. it does not have a public IP address).

When using an SSH tunnel, you are configuring Seek Connect to connect to an intermediate server (a.k.a. a bastion sever) that does have direct access to the database. Seek connects to the bastion and then asks the bastion to connect directly to the server.

Using this feature requires additional configuration, when creating the source. We will talk through what each piece of configuration means.

  1. Configure all fields for the source as you normally would, except SSH Tunnel Method.
  2. SSH Tunnel Method defaults to No Tunnel (meaning a direct connection). If you want to use an SSH Tunnel choose SSH Key Authentication or Password Authentication.
    1. Choose Key Authentication if you will be using an RSA private key as your secret for establishing the SSH Tunnel (see below for more information on generating this key).
    2. Choose Password Authentication if you will be using a password as your secret for establishing the SSH Tunnel.
  3. SSH Tunnel Jump Server Host refers to the intermediate (bastion) server that Seek will connect to. This should be a hostname or an IP Address.
  4. SSH Connection Port is the port on the bastion server with which to make the SSH connection. The default port for SSH connections is 22, so unless you have explicitly changed something, go with the default.
  5. SSH Login Username is the username that Seek Connect should use when connecting to the bastion server. This is NOT the Clickhouse username.
  6. If you are using Password Authentication, then SSH Login Username should be set to the password of the User from the previous step. If you are using SSH Key Authentication leave this blank. Again, this is not the Clickhouse password, but the password for the OS-user that Seek Connect is using to perform commands on the bastion.
  7. If you are using SSH Key Authentication, then SSH Private Key should be set to the RSA Private Key that you are using to create the SSH connection. This should be the full contents of the key file starting with -----BEGIN RSA PRIVATE KEY----- and ending with -----END RSA PRIVATE KEY-----.