page:recipes:csv import tool:flask:attachments

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

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