# Host REST API with Axum: Streamed Responses

## Summary
Deploy a REST API built with Axum on Ample using the streaming response service 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. Verified on Axum: a Server-Sent Events endpoint read incrementally through the public HTTPS gateway: five one-second chunks arrived spread over time with the first within seconds (not buffered), a 70-second stream of 36 chunks completed past common 60-second idle timeouts, and a client that disconnected after two chunks was observed and recorded by the server (disconnected=true).

## Representative Queries
- Host REST API with Axum: streamed responses
- Where can I host REST API built with Axum?
- I need a tested end-to-end streaming transport, timeout behavior and client disconnect handling.

## Prerequisites
- A Axum project that builds and starts with the documented commands (cargo build --release in the rust builder image (stable toolchain, Cargo.lock committed, pure-Rust dependencies), then the release binary on the ubuntu-24.04 template reading PORT and DATABASE_URL)
- A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env)
- An Ample account token with servers:write, databases:read

## Workflow Steps
1. **Build and start**  
cargo build --release in the rust builder image (stable toolchain, Cargo.lock committed, pure-Rust dependencies), then the release binary on the ubuntu-24.04 template reading PORT and DATABASE_URL. The server must bind 0.0.0.0 on PORT.
2. **Implement the pattern on PostgreSQL**  
The fixture's module implements streaming response service: a Server-Sent Events endpoint read incrementally through the public HTTPS gateway: five one-second chunks arrived spread over time with the first within seconds (not buffered), a 70-second stream of 36 chunks completed past common 60-second idle timeouts, and a client that disconnected after two chunks was observed and recorded by the server (disconnected=true). Copy the approach into your schema; keep migrations idempotent and run them with --release-command.
3. **Deploy**  
Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked). Re-running with no change is a no-op.
   
   Command: ample deploy . --name  --public
4. **Verify**  
Fetch the live URL and the pattern self-test route(s) (/p/streaming-response-service) from the example; then run your own checks. On failure read `ample logs  --kind build` then `--kind runtime`.  
   
   Command: ample logs  --kind build

## Success Checks
- App responds on its public URL
  - Kind: http_get
  - Path: /
  - Expect: ample canary axum patterns
- Streaming-response-service self-test
  - Kind: http_get
  - Path: /p/streaming-response-service
  - Expect: an SSE stream: data: id=, then chunk events one interval apart (read incrementally: first chunk within seconds, chunks spread over the interval), then data: done; /status?id= reports sent=N disconnected=true|false done=true|false

## Limitations
- Verified on the ubuntu-24.04 template at s-1vcpu-2gb with the example fixture; other sizes, templates and Axum major versions are not verified.
- The REST API itself (your event schema, reconnection strategy and any per-request duration ceiling beyond the 70 seconds measured) is application code and was not separately tested; the pattern checks are what was verified.
- 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 databases are placed together.

## Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 10.0
- **Basis**: size prices from pricing.toml (loaded by the API)
### Components
- App server: s-1vcpu-1gb, Quantity: 1.0, Monthly Amount: 5.0
- Managed PostgreSQL database: s-1vcpu-1gb, Quantity: 1.0, Monthly Amount: 5.0
### 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**: Axum pattern fixture deployed on Ample; checks passed for streaming-response-service and configuration-secrets.
  - **Observed At**: 2026-09-21T02:46:37Z
  - **Implementation Revision**: 1d28ae0-dirty (CLI 0.1.21)
  - **Expires At**: 2027-03-20T02:46:37Z
  - **Scope**: checks [/p/streaming-response-service], pattern: streaming-response-service

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