refactor(computes): the lock helpers take claims instead of file locks

webvirtcloud/middleware.py

@@ -1,9 +1,11 @@
 from django.contrib import messages
 from django.http import JsonResponse
-from django.shortcuts import render
+from django.shortcuts import redirect, render
 from django.utils.translation import gettext_lazy as _
 import libvirt
 from libvirt import libvirtError
+from operations import claims
+from operations.utils import busy_message, summary
 from vrtManager.util import ConnectionFailed
 
 API_PREFIX = "/api/"
@@ -55,9 +57,17 @@ class ExceptionMiddleware:
         if request.path_info.startswith(API_PREFIX):
             if isinstance(exception, libvirtError):
                 return JsonResponse({"detail": error_text(request, exception)}, status=400)
+            if isinstance(exception, claims.Busy):
+                return JsonResponse({"detail": busy_message(exception, request.user),
+                                     "operation": summary(exception.blocker, request.user) if exception.blocker else None},
+                                    status=409)
             if isinstance(exception, TimeoutError):
                 return JsonResponse({"detail": "Operation is busy. Please retry."}, status=409)
             return None
+        if isinstance(exception, claims.Busy) and request.method not in ("GET", "HEAD"):
+            # back to the form with the reason; a GET is never redirected to itself
+            messages.error(request, busy_message(exception, request.user))
+            return redirect(request.get_full_path())
         if isinstance(exception, libvirtError):
             messages.error(
                 request,

webvirtcloud/tests/test_busy_refusal.py

@@ -0,0 +1,52 @@
+"""A request refused because its resource is held answers at once: the API
+with 409 and the job holding it, a page with the reason on the form it came
+from. Only the job's owner and superusers see who started it."""
+
+import json
+from unittest.mock import MagicMock
+
+from django.contrib.auth import get_user_model
+from django.contrib.messages import get_messages
+from django.contrib.messages.storage.fallback import FallbackStorage
+from django.contrib.sessions.middleware import SessionMiddleware
+from django.test import RequestFactory, TestCase
+
+from operations import claims
+from operations.models import Operation
+from operations.utils import busy_message
+from webvirtcloud.middleware import ExceptionMiddleware
+
+
+class BusyRefusalTests(TestCase):
+    def setUp(self):
+        User = get_user_model()
+        self.owner = User.objects.create_user("busy-owner", password="pw")
+        self.other = User.objects.create_user("busy-other", password="pw")
+        self.job = Operation.objects.create(kind="test.noop", user=self.owner, username="busy-owner",
+                                            submission_key="k", resource="instance:u1", resource_label="c/vm")
+
+    def handle(self, path, busy):
+        request = RequestFactory().post(path)
+        SessionMiddleware(lambda r: None).process_request(request)
+        request._messages = FallbackStorage(request)
+        request.user = self.owner
+        response = ExceptionMiddleware(MagicMock()).process_exception(request, busy)
+        return response, [str(m) for m in get_messages(request)]
+
+    def test_the_api_answers_409_with_the_job(self):
+        response, _ = self.handle("/api/v1/computes/1/instances/", claims.Busy("compute:1", self.job))
+        self.assertEqual(response.status_code, 409)
+        body = json.loads(response.content)
+        self.assertIn("busy-owner", body["detail"])
+        self.assertEqual(body["operation"]["id"], str(self.job.id))
+
+    def test_a_page_is_sent_back_to_its_form_with_the_reason(self):
+        response, messages = self.handle("/computes/1/create/", claims.Busy("compute:1"))
+        self.assertEqual(response.status_code, 302)
+        self.assertEqual(response.url, "/computes/1/create/")
+        self.assertTrue(any("short operation" in m for m in messages), messages)
+
+    def test_only_the_owner_learns_who_started_the_job(self):
+        busy = claims.Busy("instance:u1", self.job)
+        self.assertIn("busy-owner", busy_message(busy, self.owner))
+        self.assertNotIn("busy-owner", busy_message(busy, self.other))