# PAGI vs ASGI Ecosystem: Deep Comparison

## Current PAGI Inventory

| Category | Count | Details |
|----------|-------|---------|
| **Server Protocols** | 3 | HTTP/1.1, WebSocket, SSE |
| **Middleware** | 31 | More than Starlette's 7 built-in |
| **Apps** | 14 | Router, File, Proxy, WrapPSGI, etc. |
| **Test Tools** | 4 | Client, Response, WebSocket, SSE |

## Feature Comparison with ASGI Ecosystem

### Server Capabilities

| Feature | Uvicorn | Hypercorn | Daphne | **PAGI** |
|---------|:-------:|:---------:|:------:|:--------:|
| HTTP/1.1 | ✅ | ✅ | ✅ | ✅ |
| HTTP/2 | ✅ | ✅ | ✅ | ❌ |
| HTTP/3 (QUIC) | ❌ | ✅ | ❌ | ❌ |
| WebSocket | ✅ | ✅ | ✅ | ✅ |
| SSE | ✅ | ✅ | ✅ | ✅ |
| TLS | ✅ | ✅ | ✅ | ✅ |
| Multi-worker | ✅ | ✅ | ✅ | ✅ |
| Graceful shutdown | ✅ | ✅ | ✅ | ✅ |
| Lifespan protocol | ✅ | ✅ | ✅ | ✅ |
| SIGHUP restart | ✅ | ✅ | ✅ | ✅ |
| Worker scaling (TTIN/TTOU) | ❌ | ❌ | ❌ | ✅ |
| Max requests/worker | ✅ | ✅ | ❌ | ✅ |

### Middleware Comparison

**Starlette built-in (7):**
- CORSMiddleware → ✅ PAGI has
- SessionMiddleware → ✅ PAGI has
- HTTPSRedirectMiddleware → ✅ PAGI has
- TrustedHostMiddleware → ✅ PAGI has
- GZipMiddleware → ✅ PAGI has
- ServerErrorMiddleware → ✅ PAGI has (ErrorHandler)
- BaseHTTPMiddleware → ✅ PAGI has (Middleware.pm)

**PAGI extras not in Starlette core:**
- CSRF, SecurityHeaders, RateLimit
- Auth::Basic, Auth::Bearer
- JSONBody, FormBody, ContentNegotiation
- ETag, ConditionalGet
- Debug, Maintenance, Healthcheck
- ReverseProxy, XSendfile, Rewrite
- WebSocket::Heartbeat, WebSocket::RateLimit, WebSocket::Compression
- SSE::Heartbeat, SSE::Retry

### Observability Gap

| Feature | Python ASGI | **PAGI** |
|---------|:-----------:|:--------:|
| OpenTelemetry middleware | ✅ | ❌ |
| Prometheus metrics | ✅ (via libs) | ❌ |
| Structured logging | ✅ | Partial |
| Distributed tracing | ✅ | ❌ |

### Testing Tools

| Feature | Starlette | **PAGI** |
|---------|:---------:|:--------:|
| TestClient | ✅ | ✅ |
| WebSocket testing | ✅ | ✅ |
| SSE testing | ❌ (manual) | ✅ |
| Lifespan testing | ✅ | ✅ |
| Async client | ✅ (httpx) | ✅ |

### Unique PAGI Strengths

1. **PSGI Bridge** - `WrapPSGI` runs legacy PSGI apps (Python has no WSGI→ASGI built-in)
2. **CGI Bridge** - `WrapCGI` for legacy CGI scripts
3. **More middleware** - 31 vs Starlette's 7 built-in
4. **Dynamic worker scaling** - SIGTTIN/SIGTTOU (unique to PAGI)
5. **SSE test client** - Starlette doesn't have one
6. **WebSocket-specific middleware** - Heartbeat, RateLimit, Compression

---

## Prioritized Roadmap

### Tier 1: Critical for Production Adoption

| Priority | Feature | Effort | Rationale |
|:--------:|---------|:------:|-----------|
| **1** | **HTTP/2 support** | High | All competitors have it. Required for modern deployments. Can be proxied via nginx, but native support expected. |
| **2** | **OpenTelemetry middleware** | Medium | Observability is table stakes for production. Python has `opentelemetry-instrumentation-asgi`. |
| **3** | **Prometheus metrics endpoint** | Low | `/metrics` endpoint with request counts, latencies, connection stats. Standard for Kubernetes. |

### Tier 2: Developer Experience

| Priority | Feature | Effort | Rationale |
|:--------:|---------|:------:|-----------|
| **4** | **Deployment documentation** | Low | systemd, Docker, nginx examples. Users need this to go to production. |
| **5** | **Hot reload (--reload)** | Medium | Uvicorn's killer feature for development. Watch files, restart workers. |
| **6** | **Structured JSON logging** | Low | AccessLog with JSON format option for log aggregators. |

### Tier 3: Nice to Have

| Priority | Feature | Effort | Rationale |
|:--------:|---------|:------:|-----------|
| **7** | **HTTP/3 (QUIC)** | Very High | Only Hypercorn has it. Low priority - proxy handles this. |
| **8** | **uvloop equivalent** | Medium | EV or similar. IO::Async::Loop::EV exists. Benchmark first. |
| **9** | **WebSocket permessage-deflate** | Medium | Autobahn compliance. Currently 71% pass rate. |

---

## Recommended Next Steps

### Immediate (Next Release)

1. **Deployment docs** - Write systemd unit file, Dockerfile, nginx proxy config
2. **Prometheus middleware** - Simple `/metrics` endpoint with basic stats

### Short-term (1-2 Releases)

3. **OpenTelemetry middleware** - Trace ID propagation, span creation
4. **Hot reload for development** - `--reload` flag watching `lib/` and app files

### Medium-term

5. **HTTP/2 support** - Use Protocol::HTTP2 or similar
6. **Performance benchmarks** - Compare with Starman, Twiggy, publish results

---

## Summary

**PAGI is ahead on:** Middleware count, PSGI compatibility, test tooling, worker scaling signals

**PAGI is behind on:** HTTP/2 (critical), observability (critical), hot reload (nice DX)

**Recommended focus:** HTTP/2 and observability are the two gaps that will block production adoption. Everything else can be worked around with proxies or external tools.

---

## References

- [2024 ASGI Server Comparison](https://medium.com/@onegreyonewhite/2024-comparing-asgi-servers-uvicorn-hypercorn-and-daphne-addb2fd70c57)
- [Starlette Middleware](https://www.starlette.io/middleware/)
- [Starlette TestClient](https://www.starlette.io/testclient/)
- [OpenTelemetry ASGI Instrumentation](https://opentelemetry-python-contrib.readthedocs.io/en/latest/instrumentation/asgi/asgi.html)
- [Uvicorn Flow Control](https://deepwiki.com/encode/uvicorn/5-http-protocol-implementations)
