refactor: Launcher poll always returns a status

Previously these methods all had to account for the potential that they
could be returning the uninitialized status, which was `None`. Default
instead to `Queued` which means that the job is ready but not yet
dispatched.

In reality this `status` variable is a bit messy; it is defined on the
base class as `None` and only set in `_post_finish` with the given
status. It is only used by `_post_finish` itself (after being set) and is
otherwise only directly used/returned by the `local`, `lsf` and `nc`
launchers, each of which do not set the value. So:
 - It initializes as `None`.
 - The `local` and `nc` launcher only use it after invoking
   `post_finish`, so it is definitely a status then.
 - The `lsf` launcher only returns the status if it has a not-None
   status, i.e. if it already finished.

So in all of these cases, `status` is only used after being set, it is
just being initialized as `None` and the type propagates. Rather than
perform typing casts or checks everywhere, lets just change this default
value to be the `Queued` status. A larger refactor is likely needed in
the future

Signed-off-by: Alex Jones <[email protected]>

Author: AlexJones0

src/dvsim/launcher/base.py

@@ -119,7 +119,7 @@ def __init__(self, job_spec: "JobSpec") -> None:
         # _check_status() method, but eventually updated by the _post_finish()
         # method, in case any of the cleanup tasks fails. This value is finally
         # returned to the Scheduler by the poll() method.
-        self.status = None
+        self.status = JobStatus.QUEUED
 
         # Return status of the process running the job.
         self.exit_code = None
@@ -259,13 +259,13 @@ def launch(self) -> None:
         self._do_launch()
 
     @abstractmethod
-    def poll(self) -> JobStatus | None:
+    def poll(self) -> JobStatus:
         """Poll the launched job for completion.
 
         Invokes _check_status() and _post_finish() when the job completes.
 
         Returns:
-            status of the job or None
+            status of the job
 
         """
 

src/dvsim/launcher/fake.py

@@ -57,7 +57,7 @@ class FakeLauncher(Launcher):
     def _do_launch(self) -> None:
         """Do the launch."""
 
-    def poll(self) -> JobStatus | None:
+    def poll(self) -> JobStatus:
         """Check status of the running process."""
         deploy_cls = self.job_spec.job_type
         if deploy_cls in _DEPLOY_HANDLER:

src/dvsim/launcher/local.py

@@ -103,7 +103,7 @@ def _do_launch(self) -> None:
 
         self._link_odir(JobStatus.DISPATCHED)
 
-    def poll(self) -> JobStatus | None:
+    def poll(self) -> JobStatus:
         """Check status of the running process.
 
         This returns a job status. If DISPATCHED, the job is still running.

src/dvsim/launcher/lsf.py

@@ -273,15 +273,15 @@ def _do_launch(self) -> None:
             job.job_id = f"{job_id}[{job.index}]"
             job._link_odir(JobStatus.DISPATCHED)
 
-    def poll(self) -> JobStatus | None:
+    def poll(self) -> JobStatus:
         """Poll the status of the job.
 
         Returns:
-            status of the job or None
+            status of the job
 
         """
         # It is possible we may have determined the status already.
-        if self.status:
+        if self.status is not JobStatus.QUEUED:
             return self.status
 
         if not self.bsub_out_fd:

src/dvsim/launcher/nc.py

@@ -168,7 +168,7 @@ def _do_launch(self) -> None:
     def minutes_since_start(self):
         return (datetime.datetime.now() - self.start_time).total_seconds() / 60
 
-    def poll(self) -> JobStatus | None:
+    def poll(self) -> JobStatus:
         """Check status of the running process.
 
         This returns a job status. If DISPATCHED, the job is still running.

src/dvsim/launcher/sge/launcher.py

@@ -97,7 +97,7 @@ def _do_launch(self) -> None:
         self._link_odir(JobStatus.DISPATCHED)
         f.close()
 
-    def poll(self) -> JobStatus | None:
+    def poll(self) -> JobStatus:
         """Check status of the running process.
 
         This returns a job status. If DISPATCHED, the job is still running.

src/dvsim/launcher/slurm.py

@@ -88,7 +88,7 @@ def _do_launch(self) -> None:
 
         self._link_odir(JobStatus.DISPATCHED)
 
-    def poll(self):
+    def poll(self) -> JobStatus:
         """Check status of the running process.
 
         This returns a job status. If DISPATCHED, the job is still running.

src/dvsim/scheduler.py

@@ -482,10 +482,6 @@ def _poll(self, hms: str) -> bool:
                     status = JobStatus.KILLED
                 level = log.VERBOSE
 
-                if status is None:
-                    msg = "Expected a valid job status but got None instead."
-                    raise ValueError(msg)
-
                 if status == JobStatus.DISPATCHED:
                     continue