page:guides:sinatra:private file access

Enforce private-file authorization for Sinatra

Summary

Private file access for a Sinatra app on Ample. Verified on Sinatra: a role-to-document access model with negative tests (401, 403) and an authorized private-bucket round-trip (private=ok). Build and start: bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rackup (config.ru) reading PORT on the ruby-3.4 template.

Representative Queries

• Enforce private-file authorization for Sinatra
• Where can I host Enforce private-file authorization built with Sinatra?
• I need application identity integration, per-file access rules and negative authorization tests.

Resource Requirements

• primitive:compute
• primitive:postgres
• primitive:s3-compatible-object-storage

Infrastructure Requirements

1. Compute
   • Status: verified
   • Summary: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
2. Postgres
   • Status: verified
   • Summary: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.
3. S3-compatible object storage
   • Status: verified
   • Summary: Buckets are S3-compatible with issued credentials; PutObject and GetObject are verified by canary. Other S3 operations are not verified.

Prerequisites

• A Sinatra project (bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rackup (config.ru) reading PORT on the ruby-3.4 template).
• A PostgreSQL driver reading DATABASE_URL at runtime.
• A bucket from ample bucket create with credentials passed as encrypted S3_* environment variables.
• An Ample account token with servers:write, databases:read, buckets:read.

Tested Configuration

• Template: ruby-3.4
• Runtime: ruby
• Size: s-1vcpu-1gb
• Install: bundle config set --local path vendor/bundle && bundle config set --local without 'development test' && bundle install
• Start: bundle exec rackup -o 0.0.0.0 -p $PORT

Workflow Steps

1. Build and start
   bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rackup (config.ru) reading PORT on the ruby-3.4 template; the server must bind 0.0.0.0 on PORT.
2. Create the bucket and pass its credentials
   Create it once with ample bucket create, then pass endpoint, region, bucket and keys with --env; use path-style addressing.
   Command: ample deploy . --name --public --env S3_ENDPOINT=... --env S3_REGION=... --env S3_BUCKET=... --env S3_ACCESS_KEY_ID=... --env S3_SECRET_ACCESS_KEY=...
3. Authorize before touching storage
   Return 401 for unauthenticated requests and 403 for the wrong role; keep the bucket unpublished and stream objects through the app.
4. Verify
   Fetch the live URL and /p/private-document-library on the example; on failure read the build and runtime logs.
   Command: ample logs --kind build

Examples

• Sinatra pattern fixture: Verified private file access on Sinatra.
  Source Reference: tests/deploy-canaries/sinatra-patterns

Success Checks

1. App responds on its public URL
   • Kind: http_get
   • Path: /
   • Expect: ample canary sinatra patterns
2. Private-document-library check from the example
   • Kind: http_get
   • Path: /p/private-document-library
   • Expect: see the pattern fixture checks

Limitations

• Verified on the ruby-3.4 template at s-1vcpu-1gb; other sizes and Sinatra major versions are not verified.
• Region, compliance attestations and request-duration limits are unknown and not claimed.
• Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.
• PutObject and GetObject with path-style addressing are verified; other S3 operations are not.

Cost Estimate

• Currency: USD
• Monthly Amount: 10.0
• Basis: size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty
• 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: Always-on monthly price of the tested sizes; apps auto-pause when idle. Buckets are allocation-priced per quota and not included.

Evidence Summary

• Kind: canary_run
  Summary: Sinatra pattern fixture deployed on Ample (bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rackup (config.ru) reading PORT on the ruby-3.4 template); for this guide: a role-to-document access model with negative tests (401, 403) and an authorized private-bucket round-trip (private=ok).
  Observed At: 2026-09-20T23:45:31Z
  Implementation Revision: 4d1511e574302f3904b75088bd4048a0975218b3-dirty (CLI 0.1.21)
  Expires At: 2027-03-19T23:45:31Z
  Scope: checks: ['/p/private-document-library'], template: ruby-3.4

Last Verified At

2026-09-20T23:45:31Z

Unknowns

• Region availability is unknown until a verified region fact is recorded.
• Compliance attestations are unknown; none are claimed.

Formats

• HTML: View
• Markdown: View
• JSON: View

Next Actions

1. Browse the catalog index
   Method: GET
   Relative Path: /v1/catalog
   Requires Authentication: false
2. Search published recipes by intent, stack and constraints
   Method: POST
   Relative Path: /v1/catalog/search
   Body: {"limit":5,"query":"Enforce private-file authorization for Sinatra"}
   Requires Authentication: false
3. Prepare a side-effect-free deployment plan for an authorized project
   Method: POST
   Relative Path: /v1/catalog/plan
   Body: {"inputs":{},"projectId":"","recipeId":"page:guides:sinatra:private-file-access","recipeRevision":"r1"}
   Requires Authentication: true
4. Read the existing agent authentication setup
   Method: GET
   Relative Path: /mcp/setup
   Requires Authentication: false
5. Browse Sinatra
   Method: GET
   Relative Path: /v1/catalog/nodes/stack%3Aframework-sinatra
   Requires Authentication: false
6. Browse Connect app to storage
   Method: GET
   Relative Path: /v1/catalog/nodes/intent%3Aconnect-app-to-storage
   Requires Authentication: false
7. Browse Private document library
   Method: GET
   Relative Path: /v1/catalog/nodes/pattern%3Aprivate-document-library
   Requires Authentication: false