Alembic on custom tables

If you want to manage custom tables (GMF tables; not in the main nor the static schema) with alembic you must setup a custom alembic process. Here’s an example. Others solutions are possible, but do not try to reuse the existing alembic.ini (because you will not be able to specify a schema through the configuration levels).

The following example uses docker cp. You can achieve the same with a volume, but you will have to set the owner (root) of copied files.

Init alembic

In your project, add a geoportal/alembic_<project_name> folder.

Build and run your project.

In the running container initialize alembic in a folder that have not already an alembic.ini file, like the /tmp folder. Create also directly the first revision file:

docker compose exec geoportal mkdir /tmp/new_alembic
docker compose exec geoportal bash -c "cd /tmp/new_alembic; alembic init alembic"
# Ignore the warning message about setting the alembic.ini file for now.
docker compose exec geoportal bash -c "cd /tmp/new_alembic; alembic revision -m 'Inital revision'"

Run docker compose ps geoportal to know the name of the running geoportal container.

Then copy the generated alembic folder in the geoportal folder of your project:

docker cp <geoportal_container_name>:/tmp/new_alembic geoportal/alembic_${PROJECT}

You can now customize the alembic.ini and the

Configure alembic.ini

The main change to apply is to use environment variables to run alembic on the right database. To do so, use a tmpl file:

mv geoportal/alembic_${PROJECT}/alembic.ini{,.tmpl}
rm geoportal/alembic_${PROJECT}/alembic.ini
echo "/geoportal/alembic_${PROJECT}/alembic.ini" >> .gitignore

And inside the alembic.ini.tmpl set the sqlalchemy.url to postgresql://${PGUSER}:${PGPASSWORD}@${PGHOST}:${PGPORT}/${PGDATABASE}.

In this file, you may also directly set a new variable version_table_schema to set the name of the schema inside which alembic must create its revision table. See: The Environment Context.

You must now set permissions on this tmpl file to authorize evaluation of this tmpl file. Add the following lines in the geoportal/Dockerfile just before the command ENTRYPOINT [ "/usr/bin/eval-templates" ], in the FROM camptocamp/geomapfish section.

# Custom - To be able to run tmpl on alembic.ini.tmpl file
RUN rm -f /app/alembic_<project>/alembic.ini && \
    chmod g+w /app/alembic_<project> && \
    chown www-data /app/alembic_<project>/alembic.ini.tmpl


Edit the file geoportal/alembic_${PROJECT}/alembic/

In there, update the run_migrations_offline function by adding version_table_schema = config.get_main_option("version_table_schema") to get the schema name from the alembic.ini file. Add this value as parameter of the context.configure() function.

Do the same in the run_migrations_online function.

At this point, you should be able to run your (currently empty) first revision file.

Run an alembic upgrade

Once your revision file completed, build and run docker compose up on your project. Your alembic files should be in the running container. You can now run manually an upgrade with:

docker compose exec geoportal bash -c "cd /app/alembic_${PROJECT}; alembic upgrade head"

Create a new revision file

With a running instance, execute:

docker compose exec geoportal bash -c "cd /app/alembic_${PROJECT}; alembic revision -m '<msg>'"
docker cp <geoportal_container_name>:/app/alembic_${PROJECT}/alembic/versions/<the_new_file> geoportal/alembic_${PROJECT}/alembic/versions/.