Deliver public assets through CDN for Rails

Summary

Cdn assets for a Rails app on Ample. Verified on Rails: a versioned, immutable-cached asset uploaded to a published bucket and served from the CDN URL. Build and start: bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rails server reading PORT on the ruby-3.4 template with RAILS_ENV=production.

Infrastructure requirements

• Compute: verified (Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.)
• CDN: verified (The CDN host serves objects from published buckets. It does not front app compute and is not a cache or key-value store.)

Prerequisites

• A Rails project (bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rails server reading PORT on the ruby-3.4 template with RAILS_ENV=production)
• A bucket from ample bucket create with credentials passed as encrypted S3_* environment variables
• An Ample account token with servers:write, buckets:read

Exact 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 rails server -b 0.0.0.0 -p $PORT

Steps

1. Build and start. bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rails server reading PORT on the ruby-3.4 template with RAILS_ENV=production; the server must bind 0.0.0.0 on PORT.

2. Publish a bucket for public assets. Publish only the asset bucket; upload versioned keys with an immutable Cache-Control header and build URLs from its public URL.

   ample bucket publish <bucket-name>
   

3. Verify. Fetch the live URL and /p/versioned-static-assets on the example; on failure read the build and runtime logs.

   ample logs <deployment_id> --kind build
   

Tested examples

• Rails pattern fixture (tests/deploy-canaries/rails-patterns): Verified CDN assets on Rails.

Success checks

• app responds on its public URL (/ on the live URL, expect ample canary rails patterns)
• versioned-static-assets check from the example (/p/versioned-static-assets on the live URL, expect see the pattern fixture checks)

Limitations

• Verified on the ruby-3.4 template at s-1vcpu-1gb; other sizes and Rails major versions are not verified.
• Region, compliance attestations and request-duration limits are unknown and not claimed.
• The CDN serves published-bucket objects only; cache rules, purge and TTL control are not verified.

Cost estimate

Estimated 5.00 USD per month (size prices from pricing.toml at build revision a1b8c38919e59cd035ebabaced73cf84ece24371).

• app server x1 s-1vcpu-1gb: 5.00 USD

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

Verification evidence

• canary_run on 2026-09-20T21:55:28Z at revision 4f7cb9813c1f-dirty (CLI 4f7cb98): Rails pattern fixture deployed on Ample (bundle install into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via rails server reading PORT on the ruby-3.4 template with RAILS_ENV=production); for this guide: a versioned, immutable-cached asset uploaded to a published bucket and served from the CDN URL. (expires 2027-03-19T21:55:28Z)

Last verified: 2026-09-20T21:55:28Z

Execution binding

MCP tool ample_deploy (registry mcp:ample_deploy), schema hash 876465fce906da0c observed 2026-09-21T03:19:59.461917+00:00 at revision 49962bcade4f, binding state current, required scopes: servers:write, buckets:read.