Flask

The Flask helpers create a client, optionally run a read-only startup guard, and register one explicit migration command. Nothing in the wiring applies migrations — invoking the command does.

extra · dblift[flask]

Install

pip install "dblift[flask]"

App factory

app.py

python

from flask import Flask
from sqlalchemy import create_engine

from dblift.integrations.flask import init_dblift, register_cli

engine = create_engine("postgresql+psycopg://user:password@localhost/app")

def create_app() -> Flask:
    app = Flask(__name__)

    client = init_dblift(
        app,
        engine,
        "migrations",
        guard=True,
    )
    register_cli(app, client)

    return app

init_dblift builds the client with DBLiftClient.from_sqlalchemy, stores it at app.extensions["dblift"] and returns it. With guard=True the startup check calls migration_guard(), which reads client.info() and raises if migrations are pending (on_pending="raise" by default). If the check itself errors, the client is closed before the error propagates.

Migration command

flask --app your_app:create_app dblift-migrate

register_cli adds this command to the Flask CLI. Running it is the explicit action that calls client.migrate().

Guard options

Use guard=False when your deploy applies migrations before the web app is created, or when the Flask CLI has to load the app while migrations are still pending.

app.py

python

client = init_dblift(app, engine, "migrations", guard=False)

Reading status in a route

app.py

python

@app.get("/health")
def health():
    client = app.extensions["dblift"]
    info = client.info()
    return {
        "pending_count": len(getattr(info, "pending_migrations", []) or []),
    }

The engine stays yours

You own the Engine lifecycle. Closing the client releases DBLift resources and leaves your engine undisposed.

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