Apply Database Schema Changes for Flask

Summary

Apply database schema changes for a Flask app on Ample with a release command. python3 migrate.py runs against the injected DATABASE_URL before the new release goes live, and the release fails instead of activating if the migration fails.

Resource Requirements

• Compute
• Postgres

Prerequisites

• A migration command that reads DATABASE_URL and exits non-zero on failure
• A PostgreSQL database (supplied or managed)
• An Ample account token with servers:write and databases:read

Workflow Steps

1. Write an idempotent migration
   Create tables and markers with IF NOT EXISTS or a migration framework so a re-run is safe.
2. Deploy with the release command
   Ample runs the command before activation; a non-zero exit fails the release.

   ample deploy . --name <app_name> --public --start "python3 run.py" --release-command "python3 migrate.py"
   

3. Verify the marker through the app
   Serve a route (/migrated) that reads something only the migration creates.
4. Verify
   Fetch the live URL and run the success checks below. On failure read the build log, then the runtime log, fix the cause and deploy again; do not blind-retry.

   ample logs <app_name> --kind build
   

Example

Flask release-command canary
python3 migrate.py runs before activation against the auto-provisioned managed database.

Success Checks

• Migration marker is readable
  • Kind: http_get
  • Path: /migrated
  • Expect: migrated=release-ok

Limitations

• Verified on the node-22 template at s-1vcpu-1gb; other templates and sizes are not verified by this recipe.
• Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
• The release command runs once per release on the app VM; there is no separate migration runner or rollback of a partially applied migration.

Cost Estimate

• Monthly Amount: $10.00 (USD)
  • App Server
    • Size: s-1vcpu-1gb
    • Monthly Amount: $5.00
  • Managed PostgreSQL Database
    • Size: s-1vcpu-1gb
    • Monthly Amount: $5.00

Next Actions

• Browse the catalog index
  • Method: GET
  • Relative Path: /v1/catalog
• Search published recipes by intent, stack and constraints
  • Method: POST
  • Relative Path: /v1/catalog/search
• Prepare a side-effect-free deployment plan for an authorized project
  • Method: POST
  • Relative Path: /v1/catalog/plan