# Connect Postgres for Flask

## Summary
Connect a Flask app to PostgreSQL on Ample. Read DATABASE_URL at runtime with psycopg: when you supply one with --env it is delivered encrypted and takes precedence; when you supply none and the app needs PostgreSQL, Ample auto-provisions a managed PostgreSQL 16 database and injects its connection string.

## Prerequisites
- psycopg reading the DATABASE_URL environment variable at runtime
- Either a production DATABASE_URL to pass with --env, or nothing (auto-provision)
- An Ample account token with servers:write and databases:read

## Workflow Steps
1. **Read the URL at runtime**  
   Open connections from the DATABASE_URL environment variable inside the app; never commit credentials and never connect at build time.
2. **Choose the source of the database**  
   Pass --env DATABASE_URL=... for an existing database, or omit it to let Ample provision a managed one on first deploy and reuse it on redeploys.  
   Command: `ample deploy . --name  --public --start "python3 run.py"`
3. **Test the connection through the app**  
   Expose a route (/items) that runs a trivial query and returns postgres=ok.
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.  
   Command: `ample logs  --kind build`

## Examples
- **Flask + PostgreSQL canary**: Auto-provisioned managed database with a real query.  
  Source Ref: `tests/deploy-canaries/flask-postgres-app`

## Success Checks
- Database route reports a live connection  
  Kind: `http_get`  
  Path: `/items`  
  Expect: `postgres=ok`

## Limitations
- Verified on the node-22 template at s-1vcpu-1gb; other templates and sizes are not verified by this recipe.
- Region, compliance attestations and request-duration limits are unknown and not claimed.
- Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.
- Apps and their managed databases are placed together; cross-node shared databases are unsupported.

## Cost Estimate
- **Currency**: USD  
- **Monthly Amount**: 10.00  
- **Note**: Apps and managed databases auto-pause when idle; the estimate is the always-on monthly price of the tested sizes. Plan quotas and budgets apply.

### Components  
1. **App server**  
   - Size: s-1vcpu-1gb  
   - Quantity: 1.0  
   - Monthly Amount: 5.0
2. **Managed PostgreSQL database**  
   - Size: s-1vcpu-1gb  
   - Quantity: 1.0  
   - Monthly Amount: 5.0

## Evidence Summary
- **Kind**: canary_run  
  **Summary**: Flask app (waitress) using psycopg with an auto-provisioned managed PostgreSQL database: /items reported postgres=ok and /config confirmed the encrypted secret.  
  Observed At: 2026-09-20T01:42:25Z

- **Kind**: canary_run  
  **Summary**: Node app needing PostgreSQL with no DATABASE_URL: a managed database was auto-provisioned and /db reported postgres=ok.  
  Observed At: 2026-09-19T23:55:33Z

## Next Actions
- **Browse the catalog index**  
  Action ID: `browse-catalog`  
  Operation ID: `catalog_index`  
- **Search published recipes by intent, stack and constraints**  
  Action ID: `search-recipes`  
  Operation ID: `search_recipes`  
- **Prepare a side-effect-free deployment plan for an authorized project**  
  Action ID: `plan:page:guides:flask:database-connection`  
  Operation ID: `plan_deployment`