add mcp service example (#12)

* add mcp service example
* fix ruff

Author: robmsmt

backend/main.py

@@ -18,6 +18,7 @@
     metrics,
     rerank,
     tokenization,
+    mcp,
 )
 
 settings = get_settings()
@@ -69,6 +70,7 @@ async def backend_http_error_handler(request: Request, exc: BackendHTTPError):
 app.include_router(metrics.router)
 app.include_router(rerank.router)
 app.include_router(tokenization.router)
+app.include_router(mcp.router)
 
 if __name__ == "__main__":
     import uvicorn

backend/routers/mcp.py

@@ -0,0 +1,34 @@
+import aiohttp
+from fastapi import APIRouter, Request, Depends
+from fastapi.responses import Response, JSONResponse
+from backend.middleware.auth import require_auth
+from backend.services.mcp_service import mcp_proxy, list_mcp_servers
+
+router = APIRouter()
+
+
+@router.get("/v1/mcp")
+async def get_mcp_servers(token: str = Depends(require_auth)):
+    return {"servers": list_mcp_servers()}
+
+
+@router.post("/v1/mcp/{owner}/{repo}")
+async def mcp_endpoint(
+    owner: str,
+    repo: str,
+    request: Request,
+    token: str = Depends(require_auth),
+):
+    body = await request.body()
+    try:
+        data, status = await mcp_proxy(owner, repo, body)
+        return Response(
+            content=data,
+            status_code=status,
+            media_type="application/json",
+        )
+    except aiohttp.ClientError:
+        return JSONResponse(
+            status_code=404,
+            content={"error": f"MCP server '{owner}/{repo}' not reachable"},
+        )

backend/services/mcp_service.py

@@ -0,0 +1,29 @@
+import aiohttp
+
+NAMESPACE = "rob-poc"
+MCP_PORT = 8080
+
+# Hardcoded MCP server registry: owner/repo -> K8s service DNS
+MCP_SERVERS = {
+    "alan5543/calculator-mcp": f"http://tool-gym-alan5543-calculator-mcp-dev.{NAMESPACE}.svc.cluster.local:{MCP_PORT}",
+}
+
+
+async def mcp_proxy(owner: str, repo: str, body: bytes) -> tuple[bytes, int]:
+    """Forward a JSON-RPC request to the MCP server. Returns (body, status)."""
+    url = MCP_SERVERS.get(f"{owner}/{repo}")
+    if not url:
+        return b'{"error":"MCP server not found"}', 404
+    async with aiohttp.ClientSession() as session:
+        async with session.post(
+            url,
+            data=body,
+            headers={"Content-Type": "application/json"},
+            timeout=aiohttp.ClientTimeout(total=30),
+        ) as resp:
+            data = await resp.read()
+            return data, resp.status
+
+
+def list_mcp_servers() -> list[dict]:
+    return [{"owner": k.split("/")[0], "repo": k.split("/")[1]} for k in MCP_SERVERS]