billingMode

billingMode is a custom policy check that ensures the billing mode for new tables is PROVISIONED.

Learn how to create and customize the billingMode Liquibase Custom Policy Check using a Python script.

This example utilizes DynamoDB. You can use this check as it is or customize it further to fit your needs in your NoSQL database.

For a conceptual overview of this feature, see What are policy checks?

Scope	Database
`changelog`	DynamoDB

Before you begin

Confirm that you have the following:

Linux, macOS, or Windows operating system
Create a Check Settings file
Ensure the Liquibase Checks extension is installed. In Liquibase 4.31.0+, it is already installed in the /liquibase/internal/lib directory, so no action is needed.
If the checks JAR is not installed, download liquibase-checks-<version>.jar and put it in the liquibase/lib directory.
(Maven users only) Add the liquibase-checks dependency to your pom.xml file. See Add extensions with Maven for more information.

Tip: Downloading Python itself is not required to create custom checks in the Liquibase checks framework, but it may be useful to test checks against Python 3.10.14+.

Procedure

These steps describe how to create the Custom Policy Check. It does not exist by default in Liquibase Secure.

Add this code to your Checks Settings file:

billingMode Python Script

    billingMode Python Script

    # # #
    # # # This script ensures the billing mode
    for new tables is PROVISIONED.
    # # #
    # # # Notes:

        # # #
    # # # Helpers come from Liquibase
    # # #
    import sys
    import liquibase_utilities

    # # #
    # # # Retrieve log handler
    # # # Ex.liquibase_logger.info(message)
    # # #
    liquibase_logger = liquibase_utilities.get_logger()

    # # #
    # # # Retrieve status handler
    # # #
    liquibase_status = liquibase_utilities.get_status()

    # # #
    # # # Retrive billing mode from check definition
    # # #
    billing_mode = liquibase_utilities.get_arg("BILLING_MODE")
    if len(billing_mode) == 0:
        liquibase_logger.error(f "Missing billing mode from check definition.")
    sys.exit(1)

    # # #
    # # # Retrieve all changes in changeset
    # # #
    changes = liquibase_utilities.get_changeset().getChanges()

    # # #
    # # # Loop through all changes
    # # #
    for change in changes:
        change_type = change.getClass().getSimpleName()
    if change_type.casefold() != "DynamoCreateTableChange".casefold():
        liquibase_logger.info(f "{change_type} changetype skipped.")
    continue
    new_billing_mode = change.getBillingMode()
    if new_billing_mode.casefold() != billing_mode.casefold():
        liquibase_status.fired = True
    liquibase_status.message = str(liquibase_utilities.get_script_message()).replace("__BILLING_MODE__", f "'{billing_mode}'")
    sys.exit(1)

    # # #
    # # # Default
    return code
    # # #
    False

Initiate the customization process

liquibase checks customize --check-name=CustomCheckTemplate

The CLI prompts you to finish configuring your file. A message displays:

This check cannot be customized directly because one or more fields does not have a default value.

Liquibase will then create a copy ofCustomCheckTemplateand initiate the customization workflow.

Give your check a short name so you can easily identify what Python script it is associated with

You may use up to 64 alpha-numeric characters only.

In this example we will name the check: billingMode

Set the Severity to return a code of 0-4 when triggered.

These severity codes allow you to determine if the job moves forward or stops when this check triggers. Learn more here: Use Policy Checks in Automation: Severity and Exit Code options: 'INFO'=0, 'MINOR'=1, 'MAJOR'=2, 'CRITICAL'=3, 'BLOCKER'=4

Set SCRIPT_DESCRIPTION

In this example, we will set the description to:

This script checks that the Buffer Pool specified in the tablespace matches the default Buffer Pool for the database.

Set the SCRIPT_SCOPE

In this example, we will set the scope to:

changelog: for example, if your check looks for syntax patterns or attributes in your Liquibase Changelog (the changes you author in your repository). With this value, the check runs once per changeset.

Set the SCRIPT_MESSAGE.

This message will display when the check is triggered. In this example, we will use:

This script identified new tables that need a PROVISIONED billing mode. Specify __BILLING_MODE__ mode for all new tables.

Set the SCRIPT_PATH

This is the relative path where your script is stored in relation to the changelog specified in --changelog-file, whether it is stored locally or in a repository.

In this example, we will set the path to: scripts/billing-mode.py

Set the SCRIPT_ARGUMENT

This allows you to pass dynamic information into the custom policy check without modifying the Python code.

In this example, specify BILLING_MODE=PROVISIONED to retrieve it in your code with a variable billing_mode = liquibase_utilities.get_arg("BILLING_MODE") If you customize your check later, you can specify a new value in the CLI. If you don't need dynamic arguments, leave this field blank.

Set the REQUIRES_SNAPSHOT

If your script scope is changelog, set whether the check requires a database snapshot. Specify true if your check needs to inspect database objects.

If your script scope is database, Liquibase always takes a snapshot, so this prompt does not appear.

Note: The larger your database, the more performance impact a snapshot causes. If you cannot run a snapshot due to memory limitations, see Memory Limits of Inspecting Large Schemas.