feat(host-protocol): long poll assignments

packages/cloud-platform/cloud/internal_api/api.py

@@ -1,5 +1,8 @@
 from __future__ import annotations
 
+import asyncio
+from collections.abc import Awaitable, Callable
+from time import monotonic
 from typing import TYPE_CHECKING
 
 from fastapi import APIRouter, HTTPException, Request, status
@@ -8,7 +11,13 @@ from cloud.auth import (
     AuthProvider,
     HostAuthorizationError,
 )
-from cloud.internal_api.models import HeartbeatRequest, HeartbeatResponse
+from cloud.internal_api.models import (
+    AssignmentModel,
+    ClaimRequest,
+    ClaimResponse,
+    HeartbeatRequest,
+    HeartbeatResponse,
+)
 from core.models import Device, utc_now
 
 if TYPE_CHECKING:
@@ -20,7 +29,11 @@ def create_internal_router(
     pool: DevicePool,
     auth_provider: AuthProvider,
     version_prefix: str = "/internal/v1",
+    claim_poll_interval_seconds: float = 0.1,
+    sleep: Callable[[float], Awaitable[None]] = asyncio.sleep,
 ) -> APIRouter:
+    if claim_poll_interval_seconds <= 0:
+        raise ValueError("claim_poll_interval_seconds must be greater than zero")
     router = APIRouter(prefix=version_prefix, tags=["host-agent"])
 
     def authorize_host(request: Request, host_id: str) -> None:
@@ -66,6 +79,44 @@ def create_internal_router(
             received_at=utc_now(),
         )
 
+    @router.post(
+        "/hosts/{host_id}/assignments/claim",
+        response_model=ClaimResponse,
+    )
+    async def claim_assignment(
+        host_id: str,
+        payload: ClaimRequest,
+        request: Request,
+    ) -> ClaimResponse:
+        authorize_host(request, host_id)
+        if payload.host_id != host_id:
+            raise HTTPException(
+                status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+                detail="claim host_id must match the request path",
+            )
+
+        deadline = monotonic() + payload.timeout_seconds
+        while True:
+            assignment = pool.store.claim_assignment(host_id=host_id, now=utc_now())
+            if assignment is not None:
+                return ClaimResponse(
+                    assignment=AssignmentModel(
+                        task_id=assignment.task_id,
+                        attempt=assignment.attempt,
+                        lease_id=assignment.lease_id,
+                        lease_expires_at=assignment.lease_expires_at,
+                        host_id=assignment.host_id,
+                        device_id=assignment.device_id,
+                        goal=assignment.goal,
+                        workflow_definition_id=assignment.workflow_definition_id,
+                    )
+                )
+
+            remaining = deadline - monotonic()
+            if remaining <= 0:
+                return ClaimResponse(timed_out=True)
+            await sleep(min(claim_poll_interval_seconds, remaining))
+
     return router