datasette-scale-to-zero

Quit Datasette if it has not received traffic for a specified time period

Some hosting providers such as Fly offer a scale to zero mechanism, where servers can shut down and will be automatically started when new traffic arrives.

This plugin can be used to configure Datasette to quit X minutes (or seconds, or hours) after the last request it received. It can also cause the Datasette server to exit after a configured maximum time whether or not it is receiving traffic.

Installation

Install this plugin in the same environment as Datasette.

datasette install datasette-scale-to-zero

Configuration

This plugin will only take effect if it has been configured with a duration or max_age value. Without at least one of these settings the plugin will do nothing.

Add the following to your metadata.json or metadata.yml configuration file:

{
    "plugins": {
        "datasette-scale-to-zero": {
            "duration": "10m"
        }
    }
}

This will cause Datasette to quit if it has not received any HTTP traffic for 10 minutes.

You can set this value using a suffix of m for minutes, h for hours or s for seconds.

To cause Datasette to exit if the server has been running for longer than a specific time, use "max_age":

{
    "plugins": {
        "datasette-scale-to-zero": {
            "max_age": "10h"
        }
    }
}

This example will exit the Datasette server if it has been running for more than ten hours.

You can use "duration" and "max_age" together in the same configuration file:

{
    "plugins": {
        "datasette-scale-to-zero": {
            "max_age": "10h",
            "duration": "5m"
        }
    }
}

This example will quit if no traffic has been received in five minutes, or if the server has been running for ten hours.

Configuring a shutdown HTTP message

You can also configure the plugin to send an HTTP request somewhere right before it quits, using the "shutdown_url" option:

{
    "plugins": {
        "datasette-scale-to-zero": {
            "duration": "10m",
            "shutdown_url": "https://example.com/shutdown"
        }
    }
}

You can add additional headers to the GET request - for example to send Authorization headers - using "shutdown_headers":

{
    "plugins": {
        "datasette-scale-to-zero": {
            "duration": "10m",
            "shutdown_url": "https://example.com/shutdown",
            "shutdown_headers": {
                "Authorization": "Bearer secret"
            }
        }
    }
}

Use "shutdown_method" to set a different HTTP method, e.g. for POST. You can also set shutdown_body to specify the body that should be sent with the request:

{
    "plugins": {
        "datasette-scale-to-zero": {
            "duration": "10m",
            "shutdown_url": "https://example.com/shutdown",
            "shutdown_method": "POST",
            "shutdown_headers": {
                "Authorization": "Bearer secret",
                "Content-Type": "application/json"
            },
            "shutdown_body": "{\"message\": \"shutting down\"}"
        }
    }
}

Development

To set up this plugin locally, first checkout the code. Then create a new virtual environment:

cd datasette-scale-to-zero
python3 -m venv venv
source venv/bin/activate

Now install the dependencies and test dependencies:

pip install -e '.[test]'

To run the tests:

pytest