Adding comments

tron/core/action.py

@@ -115,6 +115,13 @@ def serialize_namedtuple(obj):
             return obj
 
         try:
+            # NOTE: you'll notice that there's a lot of get() accesses of state_data for
+            # pretty common fields - this is because ActionCommandConfig is used by more
+            # than one type of ActionRun (Kubernetes, Mesos, SSH) and these generally look
+            # different. Alternatively, some of these fields are used by KubernetesActionRun
+            # but are relatively new and older runs do not have data for them.
+            # Once we get rid of the SSH and Mesos code as well as older runs in DynamoDB,
+            # we'll likely be able to clean this up.
             return json.dumps(
                 {
                     "command": state_data["command"],

tron/core/actionrun.py

@@ -185,6 +185,11 @@ def to_json(state_data: dict) -> Optional[str]:
                     "end_time": state_data["end_time"].isoformat() if state_data["end_time"] else None,
                     "rendered_command": state_data["rendered_command"],
                     "exit_status": state_data["exit_status"],
+                    # NOTE: mesos_task_id can be deleted once we delete all Mesos
+                    # code and run data - and kubernetes_task_id can then be
+                    # accessed unconditionally :)
+                    # (see note in ActionCommandConfig::to_json() for more
+                    # information about why we do this)
                     "mesos_task_id": state_data.get("mesos_task_id"),
                     "kubernetes_task_id": state_data.get("kubernetes_task_id"),
                 }