How to set up on-premises Looker access

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πŸ€“ Who can do this? You will need access to a machine that can run Docker on-premises. You will also need your Looker access details, including credentials.

In some cases you won't be able to expose your Looker instance for Atlan to crawl and ingest metadata. For example, this may happen when security requirements restrict access to sensitive, mission critical data.

In such cases you may want to decouple the extraction of metadata from its ingestion in Atlan. This approach gives you full control over your resources and metadata transfer to Atlan.

Prerequisites

To extract metadata from your on-premises Looker instance you will need to use Atlan's looker-extractor tool.

πŸ’ͺ Did you know? Atlan uses exactly the same looker-extractor behind the scenes when it connects to Looker in the cloud.

Install Docker Compose

Docker Compose is a tool for defining and running applications composed of many Docker containers. (Any guesses where the name came from? πŸ˜‰)

To install Docker Compose:

  1. Install Docker
  2. Install Docker Compose
πŸ’ͺ Did you know? Instructions provided in this documentation should be enough even if you are completely new to Docker and Docker Compose. But you can also walk through the Get started with Docker Compose tutorial if you want to learn Docker Compose basics first.

Get the looker-extractor tool

To get the looker-extractor tool:

  1. Raise a support ticket to get a link to the latest version.
  2. Downloaded the image using the link provided by support.
  3. Load the image to the server you'll use to crawl Looker:
    sudo docker load -i /path/to/looker-extractor-master.tar

Get the compose file

Atlan provides you a configuration file for the looker-extractor tool. This is a Docker compose file.

To get the compose file:

  1. Download the latest compose file.
  2. Save the file to an empty directory on the server you'll use to access your on-premises databases.
  3. The file is docker-compose.yaml.

Define Looker connections

The structure of the compose file includes three main sections:

  • x-templates contains configuration fragments. You should ignore this section β€” do not make any changes to it.
  • services is where you will define your Looker connections.
  • volumes contains mount information. You should ignore this section as well β€” do not make any changes to it.

Define services

For each on-premises Looker instance, define an entry under services in the compose file.

Each entry will have the following structure:

services:
  CONNECTION-NAME:
    <<: *extract
    environment:
      <<: *looker-defaults
      INCLUDE_PROJECTS: "project1,project2"
      USE_FIELD_LEVEL_LINEAGE: "true"
    volumes:
      - ./output/looker-example:/output/process
  • Replace CONNECTION-NAME with the name of your connection.
  • <<: *extract tells the looker-extractor tool to run.
  • environment contains all parameters for the tool. Replaces the values given for INCLUDE_PROJECTS with the names of your own Looker projects you want to extract. Separate each project name by a comma.
  • volumes specifies where to store results. In this example, the extractor will store results in the ./output/looker-example folder on the local file system.

You can add as many Looker connections as you want.

πŸ’ͺ Did you know? Docker's documentation describes the services format in more detail.

Provide credentials

To define the credentials for your Looker connections you will need to provide:

  • A Looker SDK configuration file
  • A private key to access your git repository via ssh (to extract field-level lineage)
  • A passphrase to decipher the private key (to extract field-level lineage)

The Looker SDK configuration is a .ini file with the following format:

[Looker]
# Base URL for your looker instance API. Do not include /api/* in the URL.
base_url=https://<host>:<port>
# API 3 client id
client_id=YourClientID
# API 3 client secret
client_secret=YourClientSecret
verify_ssl=True

Secure credentials

Using local files

🚨 Careful! If you decide to keep Looker credentials in plaintext files, we recommend you restrict access to the directory and the compose file. For extra security, we recommend you use Docker secrets to store the sensitive passwords.

To specify the local files in your compose file:

secrets:
  looker_config:
    file: ./looker.ini
  looker_git_private_key:
    file: ./id_ed25519
  looker_git_private_key_passphrase:
    file: ./passphrase.txt
🚨 Careful! This secrets section is at the same top-level as the services section described earlier. It is not a sub-section of the services section.

Using Docker secrets

To create and use Docker secrets:

  1. Store the Looker SDK configuration file:
    sudo docker secret create looker_config path/to/looker.ini
  2. At the top of your compose file, add a secrets element to access your secret:
    secrets:
      looker_config:
        external: true
        name: looker_config
    • The name should be the same one you used in the docker secret create command above.
    • Once stored as a Docker secret, you can remove the local Looker SDK configuration file.
    πŸ’ͺ Did you know? You can use the same steps to create Docker secrets for your git details, as well. Replace the name (looker_config) and path to the file, but otherwise run the same command.
  3. Within the service section of the compose file, add a new secrets element and specify the name of the secret within your service to use it.

Example

Let's explain in detail with an example:

secrets:
  looker_config:
    external: true
    name: looker_config
  looker_git_private_key:
    file: ./id_ed25519
  looker_git_private_key_passphrase:
    external: true
    name: looker_git_private_key_passphrase

x-templates:
  # ...

services:
  my-looker:
    <<: *extract
    environment:
      <<: *looker-defaults
      INCLUDE_PROJECTS: "project1,project2"
      USE_FIELD_LEVEL_LINEAGE: "true"
    volumes:
      - ./output/looker-example:/output/process
    secrets:
      - looker_config
      - looker_git_private_key
      - looker_git_private_key_passphrase

volumes:
  jars:
  1. In this example we've defined the secrets at the top of the file (you could also define them at the bottom):
    • looker_config refers to an external Docker secret created using the docker secret create command.
    • looker_git_private_key refers to a local file.
    • looker_git_private_key_passphrase refers to an external Docker secret created using the docker secret create command.
  2. The name of this service is my-looker. You can use any meaningful name you want.
  3. The <<: *looker-defaults sets the connection type to Looker.
  4. INCLUDE_PROJECTS tells the extractor to only extract project1 and project2 from Looker.
  5. USE_FIELD_LEVEL_LINEAGE tells the extractor to extract field-level lineage. This means the git private key information is also required.
  6. The ./output/looker-example:/output/process line tells the extractor where to store results. In this example, the extractor will store results in the ./output/looker-example directory on the local file system. We recommend you output metadata for different connections in separate directories.
  7. The secrets section within services tells the extractor which secrets to use for this service. Each of these refers to the name of a secret listed at the beginning of the compose file.

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