decomposer: generate deliverable files for Define the service contract and project architecture for the FastAPI endpoint monitoring service.; Implement the typed monitor CRUD API and concurrency-safe in-memory state according to the service design.; Implement secure on-demand endpoint checks with status updates, latency measurement, robust error handling, and redacted structured logs.; Add operational API endpoints and environment-driven runtime configuration to the monitoring service.; Create automated tests for the monitoring service.; Package the service with Docker and developer documentation.; Validate the complete project.

app/main.py

@@ -1,101 +1,107 @@
+import logging
 from contextlib import asynccontextmanager
-from typing import AsyncIterator
 from uuid import UUID
 
-from fastapi import Depends, FastAPI, HTTPException, Request, Response, status
+from fastapi import FastAPI, HTTPException, Response, status
 
-from app.checker import EndpointChecker
+from .checker import check_url
-from app.config import Settings, get_settings
+from .config import get_settings
-from app.logging import configure_logging
+from .logging import log_event
-from app.models import CheckResponse, CurrentStatus, Monitor, MonitorCreate, MonitorUpdate
+from .models import CheckResult, CheckSnapshot, Monitor, MonitorInput
-from app.store import MonitorStore
+from .security import UnsafeDestination
+from .store import MonitorStore, StoreFullError
 
+settings = get_settings()
+logging.basicConfig(level=settings.log_level, format="%(message)s")
+logger = logging.getLogger("endpoint_monitor.api")
 
-def not_found() -> HTTPException:
-    return HTTPException(status_code=404, detail={"code": "monitor_not_found", "message": "monitor does not exist"})
-
-
-def get_store(request: Request) -> MonitorStore:
-    return request.app.state.store
-
-
-def get_checker(request: Request) -> EndpointChecker:
-    return request.app.state.checker
-
-
-def create_app(
-    settings: Settings | None = None,
-    store: MonitorStore | None = None,
-    checker: EndpointChecker | None = None,
-) -> FastAPI:
-    config = settings or get_settings()
 
 @asynccontextmanager
-    async def lifespan(app: FastAPI) -> AsyncIterator[None]:
+async def lifespan(app: FastAPI):  # type: ignore[no-untyped-def]
-        configure_logging(config.log_level)
+    app.state.store = MonitorStore(settings.max_monitors)
+    log_event(logger, "service_started", storage="process-local-memory")
     yield
 
-    app = FastAPI(title="Endpoint Monitor Service", version="0.1.0", lifespan=lifespan)
-    app.state.store = store or MonitorStore()
-    app.state.checker = checker or EndpointChecker(config)
 
-    @app.get("/health")
+app = FastAPI(title="Endpoint Monitor", version="0.1.0", lifespan=lifespan)
+
+
+def store() -> MonitorStore:
+    return app.state.store
+
+
+def missing() -> HTTPException:
+    return HTTPException(status_code=404, detail="monitor not found")
+
+
+@app.get("/healthz")
 async def health() -> dict[str, str]:
     return {"status": "ok"}
 
-    @app.get("/ready")
+
+@app.get("/readyz")
 async def ready() -> dict[str, str]:
     return {"status": "ready", "storage": "process-local-memory"}
 
-    @app.post("/monitors", response_model=Monitor, status_code=status.HTTP_201_CREATED)
+
-    async def create_monitor(value: MonitorCreate, state: MonitorStore = Depends(get_store)) -> Monitor:
+@app.post("/monitors", response_model=Monitor, status_code=201)
-        return await state.create(value)
+async def create_monitor(data: MonitorInput) -> Monitor:
+    try:
+        return await store().create(data)
+    except StoreFullError as exc:
+        raise HTTPException(status_code=503, detail="monitor capacity reached") from exc
+
 
 @app.get("/monitors", response_model=list[Monitor])
-    async def list_monitors(state: MonitorStore = Depends(get_store)) -> list[Monitor]:
+async def list_monitors() -> list[Monitor]:
-        return await state.list()
+    return await store().list()
+
 
 @app.get("/monitors/{monitor_id}", response_model=Monitor)
-    async def read_monitor(monitor_id: UUID, state: MonitorStore = Depends(get_store)) -> Monitor:
+async def get_monitor(monitor_id: UUID) -> Monitor:
-        item = await state.get(monitor_id)
+    item = await store().get(monitor_id)
     if item is None:
-            raise not_found()
+        raise missing()
     return item
 
+
 @app.put("/monitors/{monitor_id}", response_model=Monitor)
-    async def update_monitor(monitor_id: UUID, value: MonitorUpdate, state: MonitorStore = Depends(get_store)) -> Monitor:
+async def replace_monitor(monitor_id: UUID, data: MonitorInput) -> Monitor:
-        item = await state.update(monitor_id, value)
+    item = await store().replace(monitor_id, data)
     if item is None:
-            raise not_found()
+        raise missing()
     return item
 
-    @app.delete("/monitors/{monitor_id}", status_code=status.HTTP_204_NO_CONTENT)
+
-    async def delete_monitor(monitor_id: UUID, state: MonitorStore = Depends(get_store)) -> Response:
+@app.delete("/monitors/{monitor_id}", status_code=204)
-        if not await state.delete(monitor_id):
+async def delete_monitor(monitor_id: UUID) -> Response:
-            raise not_found()
+    if not await store().delete(monitor_id):
+        raise missing()
     return Response(status_code=status.HTTP_204_NO_CONTENT)
 
-    @app.post("/monitors/{monitor_id}/check", response_model=CheckResponse)
-    async def run_check(
-        monitor_id: UUID,
-        state: MonitorStore = Depends(get_store),
-        endpoint_checker: EndpointChecker = Depends(get_checker),
-    ) -> CheckResponse:
-        snapshot = await state.get(monitor_id)
-        if snapshot is None:
-            raise not_found()
-        result = await endpoint_checker.check(str(snapshot.url), str(monitor_id))
-        applied = await state.set_status_if_current(monitor_id, snapshot.revision, result)
-        return CheckResponse(monitor_id=monitor_id, status=result, applied=applied)
 
-    @app.get("/monitors/{monitor_id}/status", response_model=CurrentStatus | None)
+@app.get("/monitors/{monitor_id}/status", response_model=CheckSnapshot)
-    async def current_status(monitor_id: UUID, state: MonitorStore = Depends(get_store)) -> CurrentStatus | None:
+async def current_status(monitor_id: UUID) -> CheckSnapshot:
-        item = await state.get(monitor_id)
+    item = await store().get(monitor_id)
     if item is None:
-            raise not_found()
+        raise missing()
-        return item.current_status
+    return item.status
-
-    return app
 
 
-app = create_app()
+@app.post("/monitors/{monitor_id}/check", response_model=CheckResult)
+async def check_monitor(monitor_id: UUID) -> CheckResult:
+    item = await store().get(monitor_id)
+    if item is None:
+        raise missing()
+    timeout = item.timeout_seconds or settings.request_timeout_seconds
+    try:
+        snapshot = await check_url(str(item.url), timeout, settings)
+    except UnsafeDestination as exc:
+        snapshot = CheckSnapshot(state="error", checked_at=__import__(
+            "datetime").datetime.now(__import__("datetime").UTC), error=str(exc))
+        await store().set_status(item.id, item.revision, snapshot)
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    updated = await store().set_status(item.id, item.revision, snapshot)
+    if updated is None:
+        raise HTTPException(status_code=409, detail="monitor changed during check")
+    return CheckResult(monitor_id=item.id, **snapshot.model_dump())