Establishing a Connection

The objects available within our connector are accessible from the "cdata.googledatacatalog" module. To use the module's objects directly:

Import the module as follows:
```
import cdata.googledatacatalog as mod
```
To establish a connection string, call the connect() method from the connector object using an appropriate connection string, such as:
```
mod.connect("InitiateOAuth=GETANDREFRESH;ProjectId=YourProjectId;")
```

Connecting to Google Data Catalog

Provide the following connection properties before adding the authentication properties.

OrganizationId: The ID associated with the Google Cloud Platform organization resource you would like to connect to. Find this by navigating to the cloud console.
Open the Project drop-down menu and click the link to your organization from the list. The organization ID is displayed on this page.
ProjectId: The ID associated with the Google Cloud Platform project resource you would like to connect to.
Find this by navigating to the cloud console dashboard and selecting your project from the Select from drop-down menu. The project ID is displayed in the Project info card.

Authenticating to Google Data Catalog

The connector supports using user accounts, service accounts and GCP instance accounts for authentication.

The following sections discuss the available authentication schemes for Google Data Catalog:

User Accounts (OAuth)
Service Account (OAuthJWT)
GCP Instance Account

User Accounts (OAuth)

AuthScheme must be set to OAuth in all user account flows.

Desktop Applications

CData provides an embedded OAuth application that simplifies OAuth desktop Authentication. Alternatively, you can create a custom OAuth application. See Creating a Custom OAuth App for information about creating custom applications and reasons for doing so.

For authentication, the only difference between the two methods is that you must set two additional connection properties when using custom OAuth applications.

After setting the following connection properties, you are ready to connect:

InitiateOAuth: Set this to GETANDREFRESH, which instructs the connector to automatically attempt to get and refresh the OAuth access token.
OAuthClientId: (custom applications only) Set this to the Client Id in your custom OAuth application settings.
OAuthClientSecret: (custom applications only) Set this to the Client Secret in the custom OAuth application settings.

When you connect the connector opens the OAuth endpoint in your default browser. Log in and grant permissions to the application. The connector then completes the OAuth process as follows:

Extracts the access token from the callback URL.
Obtains a new access token when the old one expires.
Saves OAuth values in OAuthSettingsLocation that persist across connections.

Web Applications

When connecting via a Web application, you need to create and register a custom OAuth application with Google Data Catalog. You can then use the connector to acquire and manage the OAuth token values. See Creating a Custom OAuth App for more information about custom applications.

Get an OAuth Access Token

Set the following connection properties to obtain the OAuthAccessToken:

OAuthClientId: Set this to the Client Id in your application settings.
OAuthClientSecret: Set this to the Client Secret in your application settings.

Then call stored procedures to complete the OAuth exchange:

Call the GetOAuthAuthorizationURL stored procedure. Set the CallbackURL input to the Callback URL you specified in your application settings. The stored procedure returns the URL to the OAuth endpoint.
Navigate to the URL that the stored procedure returned in Step 1. Log in to the custom OAuth application and authorize the web application. Once authenticated, the browser redirects you to the callback URL.
Call the GetOAuthAccessToken stored procedure. Set AuthMode to WEB and the Verifier input to the "code" parameter in the query string of the callback URL.

After you have obtained the access and refresh tokens, you can connect to data and refresh the OAuth access token either automatically or manually.

Automatic Refresh of the OAuth Access Token

To have the driver automatically refresh the OAuth access token, set the following on the first data connection:

InitiateOAuth: Set this to REFRESH.
OAuthClientId: Set this to the Client Id in your application settings.
OAuthClientSecret: Set this to the Client Secret in your application settings.
OAuthAccessToken: Set this to the access token returned by GetOAuthAccessToken.
OAuthRefreshToken: Set this to the refresh token returned by GetOAuthAccessToken.
OAuthSettingsLocation: Set this to the location where the connector saves the OAuth token values, which persist across connections.

On subsequent data connections, the values for OAuthAccessToken and OAuthRefreshToken are taken from OAuthSettingsLocation.

Manual Refresh of the OAuth Access Token

The OAuth refresh token is the only value you need to manually refresh the OAuth access token.

Use the RefreshOAuthAccessToken stored procedure to manually refresh the OAuthAccessToken after the ExpiresIn parameter value returned by GetOAuthAccessToken has elapsed, then set the following connection properties:

OAuthClientId: Set this to the Client Id in your application settings.
OAuthClientSecret: Set this to the Client Secret in your application settings.

Then call RefreshOAuthAccessToken with OAuthRefreshToken set to the OAuth refresh token returned by GetOAuthAccessToken. After the new tokens have been retrieved, open a new connection by setting the OAuthAccessToken property to the value returned by RefreshOAuthAccessToken.

Finally, store the OAuth refresh token so that you can use it to manually refresh the OAuth access token after it has expired.

Headless Machines

To configure the driver to use OAuth with a user account on a headless machine, you need to authenticate on another device that has an internet browser.

Choose one of two options:
- Option 1: Obtain the OAuthVerifier value as described in "Obtain and Exchange a Verifier Code" below.
- Option 2: Install the connector on a machine with an Internet browser and transfer the OAuth authentication values after you authenticate through the usual browser-based flow, as described in "Transfer OAuth Settings" below.
Then configure the connector to automatically refresh the access token on the headless machine.

Option 1: Obtain and Exchange a Verifier Code

To obtain a verifier code, you must authenticate at the OAuth authorization URL.

Follow the steps below to authenticate from the machine with an Internet browser and obtain the OAuthVerifier connection property.

Choose one of these options:
- If you are using the Embedded OAuth Application click Google Data Catalog OAuth endpoint to open the endpoint in your browser.
- If you are using a custom OAuth application, create the Authorization URL by setting the following properties:
  - InitiateOAuth: Set to OFF.
  - OAuthClientId: Set to the client Id assigned when you registered your application.
  - OAuthClientSecret: Set to the client secret assigned when you registered your application.
  Then call the GetOAuthAuthorizationURL stored procedure with the appropriate CallbackURL. Open the URL returned by the stored procedure in a browser.
Log in and grant permissions to the connector. You are then redirected to the callback URL, which contains the verifier code.
Save the value of the verifier code. Later you will set this in the OAuthVerifier connection property.

Next, you need to exchange the OAuth verifier code for OAuth refresh and access tokens. Set the following properties:

On the headless machine, set the following connection properties to obtain the OAuth authentication values:

InitiateOAuth: Set this to REFRESH.
OAuthVerifier: Set this to the verifier code.
OAuthClientId: (custom applications only) Set this to the Client Id in your custom OAuth application settings.
OAuthClientSecret: (custom applications only) Set this to the Client Secret in the custom OAuth application settings.
OAuthSettingsLocation: Set this to persist the encrypted OAuth authentication values to the specified location.

After the OAuth settings file is generated, you need to re-set the following properties to connect:

InitiateOAuth: Set this to REFRESH.
OAuthClientId: (custom applications only) Set this to the client Id assigned when you registered your application.
OAuthClientSecret: (custom applications only) Set this to the client secret assigned when you registered your application.
OAuthSettingsLocation: Set this to the location containing the encrypted OAuth authentication values. Make sure this location gives read and write permissions to the connector to enable the automatic refreshing of the access token.

Option 2: Transfer OAuth Settings

Prior to connecting on a headless machine, you need to create and install a connection with the driver on a device that supports an Internet browser. Set the connection properties as described in "Desktop Applications" above.

After completing the instructions in "Desktop Applications", the resulting authentication values are encrypted and written to the location specified by OAuthSettingsLocation. The default filename is OAuthSettings.txt.

Once you have successfully tested the connection, copy the OAuth settings file to your headless machine.

On the headless machine, set the following connection properties to connect to data:

InitiateOAuth: Set this to REFRESH.
OAuthClientId: (custom applications only) Set this to the client Id assigned when you registered your application.
OAuthClientSecret: (custom applications only) Set this to the client secret assigned when you registered your application.
OAuthSettingsLocation: Set this to the location of your OAuth settings file. Make sure this location gives read and write permissions to the connector to enable the automatic refreshing of the access token.

Service Accounts (OAuthJWT)

To authenticate using a service account, you must create a new service account and have a copy of the accounts certificate. If you do not already have a service account, you can create one by following the procedure in Creating a Custom OAuth App.

For a JSON file, set these properties:

AuthScheme: Set this to OAuthJWT.
InitiateOAuth: Set this to GETANDREFRESH.
OAuthJWTCertType: Set this to GOOGLEJSON.
OAuthJWTCert: Set this to the path to the .json file provided by Google.
OAuthJWTSubject: (optional) Only set this value if the service account is part of a GSuite domain and you want to enable delegation. The value of this property should be the email address of the user whose data you want to access.

For a PFX file, set these properties instead:

AuthScheme: Set this to OAuthJWT.
InitiateOAuth: Set this to GETANDREFRESH.
OAuthJWTCertType: Set this to PFXFILE.
OAuthJWTCert: Set this to the path to the .pfx file provided by Google.
OAuthJWTCertPassword: (optional) Set this to the .pfx file password. In most cases you must provide this since Google encrypts PFX certificates.
OAuthJWTCertSubject: (optional) Set this only if you are using a OAuthJWTCertType, which stores multiple certificates. This should not be set for PFX certificates generated by Google.
OAuthJWTIssuer: Set this to the email address of the service account. This address usually includes the domain iam.gserviceaccount.com.
OAuthJWTSubject: (optional) Only set this value if the service account is part of a GSuite domain and you want to enable delegation. The value of this property is the email address of the user whose data you want to access.

GCP Instance Accounts

When running on a GCP virtual machine, the connector can authenticate using a service account tied to the virtual machine. To use this mode, set AuthScheme to GCPInstanceAccount.

CData Python Connector for Google Data Catalog