# Migrate Heroku App: Django

Move Django compute from Heroku app to Ample, one component at a time. Destination verified on Ample: the app built, started and answered on its public HTTPS URL with encrypted configuration delivered.

## Summary
Source procedure: Export config vars with `heroku config -s -a <app_name>` into an env file kept out of the repository. Not migrated automatically: Heroku add-ons other than Postgres, release-phase scheduling, dyno autoscaling and Heroku Scheduler are not migrated; use `--release-command` for release tasks. Cutover: Add the custom domain with `ample domain add`, update DNS from the Heroku DNS target, keep the Heroku app until verified, then scale it down. Rollback: keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

## Prerequisites
- Authorized access to the Heroku app source and its export tooling
- An inventory of every component in scope and out of scope
- A validated backup or copy before any cutover
- An Ample account token with servers:write, databases:read

## Workflow Steps
1. **Inventory the source**  
   List what Heroku app provides beyond the component you are moving. Out of scope here: Heroku add-ons other than Postgres, release-phase scheduling, dyno autoscaling and Heroku Scheduler are not migrated; use `--release-command` for release tasks.

2. **Source step 1**  
   Export config vars with `heroku config -s -a <app_name>` into an env file kept out of the repository.

3. **Source step 2**  
   Translate the `Procfile` web process into the start command (`--start` or the package manifest's start script); worker processes need a separate `--kind worker` service.

4. **Source step 3**  
   Note buildpacks and add-ons in use; managed databases replace Heroku Postgres; other add-ons need their own plan.

5. **Deploy on Ample in parallel**  
   pip install into .ample/python from requirements.txt, then waitress serving project.wsgi from run.py reading PORT on the python-3.12 template. Pass the exported variables with --env; keep the source running.
   `ample deploy . --name <service_name> --public --start "python3 run.py" --env-file .env.production`

6. **Validate before cutover**  
   Run the app's own checks and, for data, compare counts and checksums; the example checks are the pattern self-tests (/p/configuration-secrets, /p/relational-records).

7. **Cut over**  
   Add the custom domain with `ample domain add`, update DNS from the Heroku DNS target, keep the Heroku app until verified, then scale it down.

8. **Rollback**  
   Point DNS or configuration back to the source. The source was never modified; deletion is a separate, user-executed step after validation.

## Resource Requirements
- **Primitive: Compute**  
  Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.  
- **Primitive: Postgres**  
  Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

## Migration Source
Heroku app

## Limitations
- Documentation only: nothing is executed automatically and no execution binding is offered.
- The source-side procedure is documented from Heroku app's standard tooling and was not executed in this catalog's evidence; the destination side was verified with the pattern fixture.
- Verified on the python-3.12 template at s-1vcpu-1gb; region, compliance and request-duration limits are unknown.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures on the managed side are not verified beyond the pattern checks.

## Examples
### Django pattern fixture (destination)
- Verified destination basis: Django compute.
- Source reference: tests/deploy-canaries/django-patterns

## Success Checks
- Destination app responds on its public URL.
- Configuration-secrets check from the destination example.
- Relational-records check from the destination example.
- Data or object counts and checksums match the source.

## Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 10.0

### Components
- App server (size: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0)
- Managed PostgreSQL database (size: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0)

### Note
Destination always-on monthly price of the tested sizes; apps auto-pause when idle. Source costs are unknown to Ample.