# Host rest api with Spring Boot: streamed responses

## Summary
Deploy a rest api built with Spring Boot 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 Spring Boot: 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). Not separately tested: your event schema, reconnection strategy and any per-request duration ceiling beyond the 70 seconds measured; treat the rest api-specific behavior as your application code.

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

## Resource Requirements
- primitive:compute
- primitive:postgres

## Infrastructure Requirements
- **Compute**: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
- **Postgres**: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

## Framework
Spring Boot

## Workload
REST API

## Release Status
published

## Support Status
verified

## Execution Status
ready

## Prerequisites
1. A Spring Boot project that builds and starts with the documented commands (./mvnw -q -DskipTests package (or the Gradle wrapper) producing one application jar, then java -jar on the jvm-21 template (Temurin JDK 21) with server.port read from PORT)
2. A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env)
3. An Ample account token with servers:write, databases:read

## Tested Configuration
- **Template**: jvm-21
- **Runtime**: java
- **Size**: s-1vcpu-2gb
- **Build**: ./mvnw -q -DskipTests package
- **Start**: java -jar $(ls target/*.jar | grep -v -- '-plain' | head -n 1)

## Workflow Steps
1. **Build and start**: `./mvnw -q -DskipTests package (or the Gradle wrapper) producing one application jar, then java -jar on the jvm-21 template (Temurin JDK 21) with server.port read from PORT. 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`

## Examples
- **Spring Boot pattern fixture**: Multi-pattern Spring Boot app whose streaming response service module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

## Success Checks
1. app responds on its public URL: kind: http_get, path: /, expect: ample canary spring boot patterns
2. 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 jvm-21 template at s-1vcpu-2gb with the example fixture; other sizes, templates, and Spring Boot 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) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty
- **Components**:
  - app server: size: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: 5.0
  - managed PostgreSQL database: size: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: 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
1. **Kind**: canary_run, **Summary**: Spring Boot pattern fixture deployed on Ample; checks passed for streaming-response-service and configuration-secrets. **Observed At**: 2026-09-21T02:34:39Z
2. **Kind**: canary_run, **Summary**: The same Spring Boot app deployed with a --release-command migration; the marker it created was readable after activation. **Observed At**: 2026-09-20T22:49:19Z

## Unknowns
- region availability is unknown until a verified region fact is recorded
- compliance attestations are unknown; none are claimed

## Formats
- [HTML Format](/content/recipes/rest-api/spring-boot/response-streaming/index.html)
- [Markdown Format](/content/recipes/rest-api/spring-boot/response-streaming.md)
- [JSON Format](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Arest-api%3Aspring-boot%3Aresponse-streaming)

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