fix: increase server heartbeat TTL to 20 seconds (#109)

Author: corp-0

src/baby_serverlist/models.py

@@ -6,10 +6,10 @@
 from django.db import models
 
 from accounts.models import Account
-from commons.cache import BABY_SERVER_HEARTBEAT_TTL_SECONDS, get_baby_server_heartbeat
+from central_command.settings import BABY_SERVER_STATUS_TTL_SECONDS
+from commons.cache import get_baby_server_heartbeat
 
 SERVERLIST_TOKEN_SALT = "baby_serverlist.serverlist_token"
-LIVE_HEARTBEAT_GRACE_SECONDS = 2
 
 
 class BabyServer(models.Model):
@@ -52,6 +52,4 @@ def is_live(self) -> bool:
         if heartbeat_time.tzinfo is None:
             heartbeat_time = heartbeat_time.replace(tzinfo=UTC)
 
-        # live if last heartbeat within the cache TTL plus a small grace buffer
-        ttl_with_grace = BABY_SERVER_HEARTBEAT_TTL_SECONDS + LIVE_HEARTBEAT_GRACE_SECONDS
-        return datetime.now(tz=UTC) - heartbeat_time <= timedelta(seconds=ttl_with_grace)
+        return datetime.now(tz=UTC) - heartbeat_time <= timedelta(seconds=BABY_SERVER_STATUS_TTL_SECONDS)

src/central_command/settings.py

@@ -40,6 +40,7 @@
 
 _csrf_origins = os.environ.get("CSRF_TRUSTED_ORIGINS", "")
 CSRF_TRUSTED_ORIGINS = [origin.strip() for origin in _csrf_origins.split(",") if origin.strip()]
+BABY_SERVER_STATUS_TTL_SECONDS = 20
 
 INSTALLED_APPS = [
     "django.contrib.admin",

src/commons/cache.py

@@ -3,8 +3,7 @@
 
 from django.core.cache import cache
 
-BABY_SERVER_STATUS_TTL_SECONDS = 10
-BABY_SERVER_HEARTBEAT_TTL_SECONDS = 10
+from central_command.settings import BABY_SERVER_STATUS_TTL_SECONDS
 
 SERVER_STATUS_KEY_PREFIX = "baby_server_status:"
 SERVER_HEARTBEAT_KEY_PREFIX = "baby_server_heartbeat:"
@@ -42,7 +41,7 @@ def get_many_baby_server_statuses(server_ids: Iterable[str]) -> dict[str, dict[s
 
 def set_baby_server_heartbeat(server_id: str, timestamp: str) -> None:
     """Persist the last-reported timestamp for a server."""
-    cache.set(_heartbeat_key(server_id), timestamp, timeout=BABY_SERVER_HEARTBEAT_TTL_SECONDS)
+    cache.set(_heartbeat_key(server_id), timestamp, timeout=BABY_SERVER_STATUS_TTL_SECONDS)
 
 
 def get_baby_server_heartbeat(server_id: str) -> str | None:

src/tests/baby_serverlist/test_api.py

@@ -7,9 +7,9 @@
 from rest_framework.test import APITestCase
 
 from accounts.models import Account
-from baby_serverlist.models import LIVE_HEARTBEAT_GRACE_SECONDS, BabyServer
+from baby_serverlist.models import BabyServer
+from central_command.settings import BABY_SERVER_STATUS_TTL_SECONDS
 from commons.cache import (
-    BABY_SERVER_HEARTBEAT_TTL_SECONDS,
     get_baby_server_heartbeat,
     get_baby_server_status,
     set_baby_server_heartbeat,
@@ -155,9 +155,7 @@ def test_list_owned_baby_servers_live_flag(self) -> None:
         response = self.client.get(reverse("baby_serverlist:list-owned"))
         self.assertTrue(response.json()[0]["live"])
 
-        stale_time = datetime.now(tz=UTC) - timedelta(
-            seconds=BABY_SERVER_HEARTBEAT_TTL_SECONDS + LIVE_HEARTBEAT_GRACE_SECONDS + 1
-        )
+        stale_time = datetime.now(tz=UTC) - timedelta(seconds=BABY_SERVER_STATUS_TTL_SECONDS + 1)
         set_baby_server_heartbeat(str(baby_server.id), stale_time.isoformat())
 
         response = self.client.get(reverse("baby_serverlist:list-owned"))
@@ -191,15 +189,11 @@ def test_list_baby_servers_ignores_non_whitelisted(self) -> None:
     def test_baby_server_is_live_respects_heartbeat_ttl(self) -> None:
         baby_server = BabyServer.objects.create(owner=self.user)
 
-        fresh_time = datetime.now(tz=UTC) - timedelta(
-            seconds=BABY_SERVER_HEARTBEAT_TTL_SECONDS + LIVE_HEARTBEAT_GRACE_SECONDS - 1
-        )
+        fresh_time = datetime.now(tz=UTC) - timedelta(seconds=BABY_SERVER_STATUS_TTL_SECONDS - 1)
         set_baby_server_heartbeat(str(baby_server.id), fresh_time.isoformat())
         self.assertTrue(baby_server.is_live())
 
-        stale_time = datetime.now(tz=UTC) - timedelta(
-            seconds=BABY_SERVER_HEARTBEAT_TTL_SECONDS + LIVE_HEARTBEAT_GRACE_SECONDS + 1
-        )
+        stale_time = datetime.now(tz=UTC) - timedelta(seconds=BABY_SERVER_STATUS_TTL_SECONDS + 1)
         set_baby_server_heartbeat(str(baby_server.id), stale_time.isoformat())
         stored = get_baby_server_heartbeat(str(baby_server.id))
         self.assertEqual(stored, stale_time.isoformat())

src/tests/commons/test_cache.py

@@ -2,11 +2,13 @@
 
 from django.test import SimpleTestCase
 
+from central_command.settings import BABY_SERVER_STATUS_TTL_SECONDS
 from commons import cache as cache_module
 
 
 class CommonsCacheTests(SimpleTestCase):
-    def test_set_baby_server_status_uses_ephemeral_timeout(self) -> None:
+    @staticmethod
+    def test_set_baby_server_status_uses_ephemeral_timeout() -> None:
         payload = {"ServerName": "test"}
         server_id = "server-123"
 
@@ -19,7 +21,8 @@ def test_set_baby_server_status_uses_ephemeral_timeout(self) -> None:
             timeout=cache_module.BABY_SERVER_STATUS_TTL_SECONDS,
         )
 
-    def test_set_baby_server_heartbeat_uses_ephemeral_timeout(self) -> None:
+    @staticmethod
+    def test_set_baby_server_heartbeat_uses_ephemeral_timeout() -> None:
         timestamp = "2024-01-01T00:00:00+00:00"
         server_id = "server-456"
 
@@ -29,5 +32,5 @@ def test_set_baby_server_heartbeat_uses_ephemeral_timeout(self) -> None:
         fake_cache.set.assert_called_once_with(
             f"{cache_module.SERVER_HEARTBEAT_KEY_PREFIX}{server_id}",
             timestamp,
-            timeout=cache_module.BABY_SERVER_HEARTBEAT_TTL_SECONDS,
+            timeout=BABY_SERVER_STATUS_TTL_SECONDS,
         )