Using the URL shortener feature for better rickrolls

By default, RickRoll stores the original URL to rickroll directly in the URL. For example, when rickrolling https://dev.to, the rickrolled page is available at:

https://localhost:8080/t/https%253A%252F%252Fdev.to

When sharing such URLs, your coworkers or friends may get very suspicious and never actually click on the link.

To avoid such suspicion, the idea is to make the service behave like an URL shortener, so the rickrolled URL would look like:

https://localhost:8080/t/52f5bD768bCCAbe

The part after the /t/ is called the slug.

This shortener feature, however, requires a kind of persistence. Supported databases are:

SQLite
PostgreSQL
MongoDB

Enabling URL shortening
Configuration options
- Database cleanup
- Max URL per user

Enabling URL shortening

To enable the URL shortening feature, all you need is a database, and to instruct rickroller to use it by setting the environment variable DATABASE_URL:

export DATABASE_URL=scheme://username:password@host:port/path?query#fragment

Supported schemes are: postgresql, sqlite, mongo, mongo+srv.

Using an in-memory database

For local development only, it is possible to use an in-memory SQLite database, by setting:

DATABASE_URL=sqlite://

Note that this won't work from within a Docker container, as gunicorn uses multiple workers in different processes!

Using an SQLite database

SQLite databases are stored inside files. To use a file in the local directory:

# notice the triple slash for relative path!
DATABASE_URL=sqlite:///rickroll.db poetry run python -m rickroll

When running in Docker, you need to mount a volume first, then use four slashes (sqlite:////) to pass an absolute path to sqlite. For example:

# Use the file /tmp/rickroll.db, mounted as /db/rickroll.db inside the container
docker run \
    -p 8080:8080 \
    -v /tmp:/db \
    -e DATABASE_URL=sqlite:////db/rickroll.db \
    derlin/rickroller:latest

Using a PostgreSQL database

To get a PostgreSQL database running locally, you can use the following docker-compose.yaml:

services:
  postgres:
    image: postgres
    ports:
      - 5432:5432
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: password
      POSTGRES_DB: rickroll
      PGDATA: /var/lib/postgresql/data/pgdata
    # Uncomment the following lines to persist the data
    #volumes:
    #  - ./data/db:/var/lib/postgresql/data

Once running (using docker compose up -d), you can start RickRoller using:

DATABASE_URL=postgresql://user:password@localhost/rickroll poetry run python -m rickroll

Using a MongoDB database

To get a MongoDB database running locally, you can use the following docker-compose.yaml:

services:
  mongo:
    image: mongo
    restart: always
    ports:
      - 27017:27017
    environment:
      MONGO_INITDB_ROOT_USERNAME: user
      MONGO_INITDB_ROOT_PASSWORD: password
      MONGO_INITDB_DATABASE: rickroll

# mongodb://root:example@localhost:27017/urls?authSource=admin
# mongodb+srv://derrollin-Wfg45cZU39:Zh_ke7fvjFNv-G7Q74q9-ReWM4P-z_GV5svKq-h6u_LG3Nc5yWdtJ@cluster0.noly4wt.mongodb.net/rickroll?retryWrites=true&w=majority

Once running (using docker compose up -d), you can start RickRoller using:

DATABASE_URL=mongodb://user:password@localhost:27017/rickroll?authSource=admin poetry run python -m rickroll

You can also use a free Mongo instance on e.g. https://mongodb.com (Mongo ATLAS). In this case, ensure you create a database user with a strong password and add the IP 0.0.0.0/0 to the access list. You can then click on the "connect" button in the main view, choose "connect your application" and copy the connection string starting with mongodb+srv. For example:

DATABASE_URL=mongodb+srv://super-secret-user:<password>@cluster0.some-subdomain.mongodb.net/?retryWrites=true&w=majority

Configuration options

Database cleanup

Without any proper handling, the database could grow indefinitely.

RickRoller comes by default with a cleanup policy: that ensures any idle slug is discarded after a while.

More precisely, the application runs a cron job every X units, that discards any entry in the database that hasn't been used in the last Y units.

X and Y are integers, and units should be one of hours, minutes or seconds. Those are configurable with environment variables. Here are the defaults:

# X => interval at which to run the cleanup job
CLEANUP_INTERVAL=15
CLEANUP_INTERVAL_UNITS="minutes"
# Y => a slug should have been accessed in the given
# interval to be kept in the database (default: the last hour)
SLUG_RETENTION=60
SLUG_RETENTION_UNITS="minutes"

Max URL per user

To avoid people flooding the service, RickRoll sets a limit on the number of slugs created by the same user. Since there is no login required, here "user" means IP address.

RickRoll sets the limit to 40 by default, but you can change it using the following environment variable:

MAX_URLS_PER_USER=40

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