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/store.py

@@ -1,53 +1,63 @@
 import asyncio
-from datetime import UTC, datetime
-from uuid import UUID
+from uuid import UUID, uuid4
 
-from app.models import CurrentStatus, Monitor, MonitorCreate, MonitorUpdate
+from app.models import CurrentStatus, Monitor, MonitorCreate, MonitorUpdate, utc_now
 
 
 class MonitorStore:
-    """Concurrency-safe process-local state; all values cross the lock as copies."""
-
     def __init__(self) -> None:
-        self._items: dict[UUID, Monitor] = {}
         self._lock = asyncio.Lock()
+        self._items: dict[UUID, Monitor] = {}
 
-    async def create(self, data: MonitorCreate) -> Monitor:
-        monitor = Monitor(name=data.name, url=data.url)
+    async def create(self, value: MonitorCreate) -> Monitor:
+        now = utc_now()
+        item = Monitor(
+            id=uuid4(), name=value.name, url=value.url, created_at=now, updated_at=now, revision=1
+        )
         async with self._lock:
-            self._items[monitor.id] = monitor
-        return monitor.model_copy(deep=True)
+            self._items[item.id] = item
+        return item.model_copy(deep=True)
 
     async def list(self) -> list[Monitor]:
         async with self._lock:
-            return [item.model_copy(deep=True) for item in self._items.values()]
+            values = sorted(self._items.values(), key=lambda item: item.created_at)
+            return [item.model_copy(deep=True) for item in values]
 
     async def get(self, monitor_id: UUID) -> Monitor | None:
         async with self._lock:
             item = self._items.get(monitor_id)
             return item.model_copy(deep=True) if item else None
 
-    async def update(self, monitor_id: UUID, data: MonitorUpdate) -> Monitor | None:
-        changes = data.model_dump(exclude_unset=True, exclude_none=True)
+    async def update(self, monitor_id: UUID, value: MonitorUpdate) -> Monitor | None:
         async with self._lock:
-            item = self._items.get(monitor_id)
-            if item is None:
+            old = self._items.get(monitor_id)
+            if old is None:
                 return None
-            updated = item.model_copy(update={**changes, "updated_at": datetime.now(UTC)})
-            self._items[monitor_id] = updated
-            return updated.model_copy(deep=True)
+            changed_url = old.url != value.url
+            item = old.model_copy(
+                update={
+                    "name": value.name,
+                    "url": value.url,
+                    "updated_at": utc_now(),
+                    "revision": old.revision + 1,
+                    "current_status": None if changed_url else old.current_status,
+                }
+            )
+            self._items[monitor_id] = item
+            return item.model_copy(deep=True)
 
     async def delete(self, monitor_id: UUID) -> bool:
         async with self._lock:
             return self._items.pop(monitor_id, None) is not None
 
-    async def set_status(self, monitor_id: UUID, status: CurrentStatus) -> Monitor | None:
+    async def set_status_if_current(
+        self, monitor_id: UUID, revision: int, status: CurrentStatus
+    ) -> bool:
         async with self._lock:
-            item = self._items.get(monitor_id)
-            if item is None:
-                return None
-            updated = item.model_copy(
-                update={"current_status": status, "updated_at": datetime.now(UTC)}
+            old = self._items.get(monitor_id)
+            if old is None or old.revision != revision:
+                return False
+            self._items[monitor_id] = old.model_copy(
+                update={"current_status": status, "updated_at": utc_now()}
             )
-            self._items[monitor_id] = updated
-            return updated.model_copy(deep=True)
+            return True