set (at exit) hostname = '' of vms running on this host + hints of migration implementation

main.py

@@ -60,6 +60,13 @@ def goodbye(host):
     host.value["status"] = "DEAD"
     host.value["last_heartbeat"] = datetime.utcnow().isoformat()
     client.put(host.key, json.dumps(host.value))
+    
+    vms = client.get_prefix("/v1/vm", value_in_json=True)
+    vms = filter(lambda v: v.value["hostname"] == host.key, vms)
+    for vm in vms:
+        vm.value["hostname"] = ""
+        client.put(vm.key, vm.value, value_in_json=True)
+    
     logging.info(f"Host {host.key} dead! at {host.value['last_heartbeat']}")
     os.kill(os.getpid(), signal.SIGKILL)
 
@@ -203,9 +210,18 @@ def get_vm(vm_list: list, vm_key) -> Union[VM, None]:
 
 
 def maintenence(e, host):
+    
+    # VMs on this Host
     _vms = filter(lambda v: v.value["hostname"] == host.key, client.get_prefix("/v1/vm", value_in_json=True))
     alleged_running_vms = filter(lambda v: v.value["status"] == "RUNNING", _vms)
-    should_be_running = filter(lambda v: v.value["status"] == "REQUESTED_START", _vms)
+    
+    # TODO: Delete this. This was intended to start VMs that
+    #       requested to be started when ucloud-vm is not running.
+    #       This is no longer needed as we check for pending requests
+    #       at the start and handle them.
+    
+    # should_be_running = filter(lambda v: v.value["status"] == "REQUESTED_START", _vms)
+    
     for vm in alleged_running_vms:
         _vm = get_vm(running_vms, vm.key)
         if (_vm and not _vm.vm.is_running()) or _vm is None:
@@ -215,9 +231,18 @@ def maintenence(e, host):
             vm.value["status"] = "KILLED"
             client.put(vm.key, json.dumps(vm.value))
 
-    for vm in should_be_running:
+    # TODO: Delete this. This was intended to start VMs that
-        vm_path = f"rbd:uservms/{vm.key.split('/')[-1]}"
+    #       requested to be started when ucloud-vm is not running.
-        start_vm(vm_path, e)
+    #       This is no longer needed as we check for pending requests
+    #       at the start and handle them.
+    
+    # for vm in should_be_running:
+    #     vm_path = f"rbd:uservms/{vm.key.split('/')[-1]}"
+    #     start_vm(vm_path, e)
+
+
+    # TODO: Check whether a vm is running on this host that
+    # is not supposed to be running on this host
     
     host.value["status"] = "ALIVE"
     host.value["last_heartbeat"] = datetime.utcnow().isoformat()
@@ -244,6 +269,9 @@ def main():
     for events_iterator in [client.get_prefix("/v1/vm/"),
                             client.watch_prefix("/v1/vm/", timeout=10)]:
         for e in events_iterator:
+            # TODO: Should we disable timeout alarm inside
+            # event handling code and enable it while going outside
+            
             try:
                 e.value = json.loads(e.value)
             except json.JSONDecodeError:
@@ -258,12 +286,17 @@ def main():
                 continue
 
             e_hostname = e.value["hostname"]
+            if hasattr(e.value, "migration_destination"):
+                e_migration_destination = e.value["migration_destination"]
+            else:
+                e_migration_destination = ""
+            
             vm_uuid = e.key.split("/")[-1]
 
-            # If it is not for me then skip it
+            # If the event is directed toward me or
-            if e_hostname != args.hostname:
+            # I am destination of a REQUESTED_MIGRATION
-                continue
+            if e_hostname == host.key or\
-
+                e_migration_destination == host.key:
                 logging.debug(f"EVENT: {e}")
 
                 if e_status == "SCHEDULED_DEPLOY":
@@ -285,6 +318,9 @@ def main():
                 elif e_status == "DELETED":
                     delete_vm(e)
 
+                # elif e_status == "REQUESTED_MIGRATION":
+                #     if e.value["migration_destination"]
+                
                 logging.info(f"Running VMs {running_vms}")