## Crawl ClickHouse

URL: https://docs.atlan.com/apps/connectors/database/clickhouse/how-tos/crawl-clickhouse

> Create a ClickHouse crawler workflow in Atlan to extract metadata from your database.

Create a ClickHouse crawler workflow in Atlan to extract metadata from your database. The workflow configures the connection, extraction method, and crawl scope.

## Prerequisites

Before you begin:

* Complete [Set up ClickHouse](https://docs.atlan.com/llms/connectors/clickhouse/set-up-clickhouse/llms.txt) so user permissions and credentials are configured in ClickHouse.
* Review the [order of operations](https://docs.atlan.com/llms/catalog/connector-capabilities/order-workflows/llms.txt) for connection workflows.

## Create crawler workflow

1. In your Atlan workspace, click **Connectors** in the left sidebar.
 * If you are using the **Old UI (Classic)**, click **New Workflow** in the top navigation.

2. Click **Marketplace**.

3. Search for **ClickHouse Assets** and select it.

4. Click **Install**.

5. Once installation completes, click **Setup Workflow** on the same tile.

### Configure extraction

Select your extraction method and provide the connection details.

### Direct

In **Direct** extraction, Atlan connects to your database and crawls metadata directly.

1. Enter your ClickHouse connection details:
 - **Host Name**: Enter the host for your ClickHouse instance.
 - **Port**: Enter the port number of your ClickHouse HTTPS interface (default is `8443`).

2. Choose **Basic** authentication and enter the credentials you configured when [setting up the ClickHouse user](https://docs.atlan.com/llms/connectors/clickhouse/set-up-clickhouse/llms.txt):
 - **Username**: Enter the username you configured in ClickHouse.
 - **Password**: Enter the password for the specified user.

3. Click **Test Authentication** to confirm connectivity to ClickHouse using these details.

4. When successful, at the bottom of the screen click **Next**.

### Agent

In **Agent** extraction, Self-Deployed Runtime executes metadata extraction within your organization's environment.

1. Install Self-Deployed Runtime if you haven't already:
 - [Install via Docker Compose](https://docs.atlan.com/llms/platform/self-deployed-runtime/install-on-docker-compose/llms.txt)
 - [Install on Kubernetes](https://docs.atlan.com/llms/platform/self-deployed-runtime/install-on-kubernetes/llms.txt)
2. Select the **Agent** tab.

3. Enter the ClickHouse connection details:
 - **Host Name**: Enter the host for your ClickHouse instance as reachable from within your network.
 - **Port**: Enter the port number of your ClickHouse HTTPS interface (default is `8443`).
4. Store sensitive information in the secret store configured with the Self-Deployed Runtime and reference the secrets in the corresponding fields. For more information, see [Secret management](https://docs.atlan.com/llms/platform/self-deployed-runtime/secret-management/llms.txt).

5. Click **Next** after completing the configuration.

### Configure connection

Complete the ClickHouse connection configuration:

1. Enter a **Connection Name** that represents your source environment (for example, `production`, `development`, `gold`, or `analytics`).

2. Under **Connection Admins**, add the users or groups that can manage this connection. If you leave this empty, no one can manage the connection, including admins.

3. At the bottom of the screen, click **Next**.

### Configure crawler

Configure crawl scope before running the crawler:

* Click **Include Metadata** to choose which assets to include (default is all if none are specified).
* Click **Exclude Metadata** to choose which assets to exclude (default is none). If an asset matches both include and exclude, the exclude filter takes precedence.
* In **Exclude regex for tables**, enter a regular expression to ignore tables and views by naming convention.

### Run crawler

Configure the frequency of crawler runs: choose to run the crawler immediately or schedule it to run at an interval.

1. In Direct mode only, click **Preflight checks** to validate [permissions and configuration](https://docs.atlan.com/llms/connectors/clickhouse/preflight-checks-for-clickhouse/llms.txt) before running.

2. At the bottom of the screen, click **Run** to run once, or **Schedule Run** to run hourly, daily, weekly, or monthly.

After the crawler completes, assets appear in the asset page.

## See also

* [What does Atlan crawl from ClickHouse](https://docs.atlan.com/llms/connectors/clickhouse/what-does-atlan-crawl-from-clickhouse/llms.txt): Assets and metadata discovered
* [Preflight checks for ClickHouse](https://docs.atlan.com/llms/connectors/clickhouse/preflight-checks-for-clickhouse/llms.txt): Prerequisites and validation

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