capsul-flask/README.md
2020-05-10 13:51:54 -05:00

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# capsulflask
Python Flask web application for capsul.org
## how to run locally
Ensure you have the pre-requisites for the psycopg2 Postgres database adapter package
```
sudo apt-get install python3-dev libpq-dev
pg_config --version
```
Create python virtual environment and install packages
```
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
```
Run an instance of Postgres (I used docker for this, you can use whatever you want, point is its listening on localhost:5432)
```
docker run --rm -it -e POSTGRES_PASSWORD=dev -p 5432:5432 postgres
```
Run the app
```
FLASK_APP=capsulflask flask run
```
## postgres database schema management
capsulflask has a concept of a schema version. When the application starts, it will query the database for a table named
`schemaversion` that has one row and one column (`version`). If the `version` it finds is not equal to the `desiredSchemaVersion` variable set in `db.py`, it will run migration scripts from the `schema_migrations` folder one by one until the `schemaversion` table shows the correct version.
For example, the script named `02_up_xyz.sql` should contain code that migrates the database from schema version 1 to schema version 2. Likewise, the script `02_down_xyz.sql` should contain code that migrates from schema version 2 back to schema version 1.
**IMPORTANT: if you need to make changes to the schema, make a NEW schema version. DO NOT EDIT the existing schema versions.**
In general, for safety, schema version upgrades should not delete data. Schema version downgrades will simply throw an error and exit for now.