Use UTC time for heartbeat mechanism

ucloud/common/host.py

@@ -26,13 +26,13 @@ class HostEntry(SpecificEtcdEntryBase):
 
     def update_heartbeat(self):
         self.status = HostStatus.alive
-        self.last_heartbeat = time.strftime("%Y-%m-%d %H:%M:%S")
+        self.last_heartbeat = datetime.utcnow().strftime("%Y-%m-%d %H:%M:%S")
 
     def is_alive(self):
         last_heartbeat = datetime.strptime(
             self.last_heartbeat, "%Y-%m-%d %H:%M:%S"
         )
-        delta = datetime.now() - last_heartbeat
+        delta = datetime.utcnow() - last_heartbeat
         if delta.total_seconds() > 60:
             return False
         return True

ucloud/scheduler/main.py

@@ -8,7 +8,6 @@ from ucloud.common.request import RequestEntry, RequestType
 from ucloud.shared import shared
 from ucloud.settings import settings
 from .helper import (
-    get_suitable_host,
     dead_host_mitigation,
     dead_host_detection,
     assign_host,