### Host CSV Import Tool with Flask: File Attachments

#### Summary
Deploy a CSV import tool built with Flask on Ample using the browser file uploads pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL. A managed PostgreSQL 16 database is auto-provisioned and injected as `DATABASE_URL`. A private S3-compatible bucket holds objects with credentials delivered as encrypted environment variables. Verified on Flask:

- Content-type and size validation that rejects disallowed files.
- An object written to a private bucket.
- A row linking the record to the object key.

**Treat the CSV import tool-specific behavior as your application code.**

#### Representative Queries
- Host CSV import tool with Flask: file attachments
- Where can I host a CSV import tool built with Flask?
- I need a restricted upload flow, file validation, and record-to-object linkage.

#### Prerequisites
- A Flask project that builds and starts with the documented commands (pip install into .ample/python from `requirements.txt`, then `waitress` from `app.py` reading `PORT` on the python-3.12 template).
- A PostgreSQL driver reading `DATABASE_URL` at runtime (auto-provisioned when omitted, or supplied with `--env`).
- A bucket from `ample bucket create` with its credentials passed as encrypted `S3_*` environment variables.
- An Ample account token with `servers:write`, `databases:read`, `buckets:read`.

#### Workflow Steps
1. **Build and Start**  
   pip install into .ample/python from `requirements.txt`, then waitress from `app.py` reading `PORT` on the python-3.12 template. The server must bind `0.0.0.0` on `PORT`.

2. **Implement the Pattern on PostgreSQL**  
   The fixture's module implements browser file uploads: content-type and size validation that rejects disallowed files. An object is written to a private bucket and a row links the record to the object key.

3. **Wire Object Storage**  
   Create the bucket(s), then pass endpoint, region, bucket, and keys as `--env` values.

4. **Deploy**  
   Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked).

5. **Verify**  
   Fetch the live URL and the pattern self-test route(s) (`/p/browser-file-uploads`) from the example, then run your own checks.

#### Success Checks
- **App responds on its public URL**  
   `GET /` expects `ample canary flask patterns`.
- **Browser-file-uploads self-test**  
   `GET /p/browser-file-uploads` expects `reject=ok upload=ok linked=ok`.

#### Limitations
- Verified only on the python-3.12 template at `s-1vcpu-1gb` with the example fixture; other sizes, templates, and Flask major versions are not verified.
- The CSV import tool itself (your upload UI, allowed types, size limits, and virus scanning) is application code and was not separately tested.

#### Cost Estimate
**Monthly Amount:** $10.00 (USD)

- **Components:**
  - App server: `s-1vcpu-1gb`, Monthly Amount: $5.00
  - Managed PostgreSQL database: `s-1vcpu-1gb`, Monthly Amount: $5.00

**Note:** Always-on monthly price of the tested sizes; apps and databases auto-pause when idle. Buckets are allocation-priced per quota and not included.

#### Evidence Summary
- **Kind:** canary_run  
  **Summary:** Flask pattern fixture deployed on Ample; checks passed for browser-file-uploads and configuration-secrets.
  **Observed At:** 2026-09-21 01:14:18  
  **Expires At:** 2027-03-20 01:14:18
  
- **Kind:** canary_run  
  **Summary:** The same Flask app deployed with a `--release-command` migration.
  **Observed At:** 2026-09-20 01:54:51  
  **Expires At:** 2027-03-19 01:54:51

#### Formats
- [HTML Version](/content/recipes/csv-import-tool/flask/attachments/index.html)
- [Markdown Version](/content/recipes/csv-import-tool/flask/attachments.md)
- [JSON Version](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Acsv-import-tool%3Aflask%3Aattachments)