Update __init__.py

snakemake_executor_plugin_kubernetes/__init__.py

@@ -185,6 +185,7 @@ def run_job(self, job: JobExecutorInterface):
         # Node selector
         node_selector = {}
         if "machine_type" in job.resources.keys():
+            # Kubernetes labels a node by its instance type using this node_label.
             node_selector["node.kubernetes.io/instance-type"] = job.resources["machine_type"]
             self.logger.debug(f"Set node selector for machine type: {node_selector}")
 
@@ -315,6 +316,20 @@ def run_job(self, job: JobExecutorInterface):
     async def check_active_jobs(
         self, active_jobs: List[SubmittedJobInfo]
     ) -> Generator[SubmittedJobInfo, None, None]:
+        # Check the status of active jobs.
+
+        # You have to iterate over the given list active_jobs.
+        # For jobs that have finished successfully, you have to call
+        # self.report_job_success(job).
+        # For jobs that have errored, you have to call
+        # self.report_job_error(job).
+        # Jobs that are still running have to be yielded.
+        #
+        # For queries to the remote middleware, please use
+        # self.status_rate_limiter like this:
+        #
+        # async with self.status_rate_limiter:
+        #    # query remote middleware here
         self.logger.debug(f"Checking status of {len(active_jobs)} jobs")
         for j in active_jobs:
             async with self.status_rate_limiter:
@@ -377,6 +392,8 @@ async def check_active_jobs(
                     yield j
 
     def cancel_jobs(self, active_jobs: List[SubmittedJobInfo]):
+        # Cancel all active jobs.
+        # This method is called when Snakemake is interrupted.
         for j in active_jobs:
             self._kubernetes_retry(
                 lambda: self.safe_delete_pod(j.external_jobid, ignore_not_found=True)
@@ -423,7 +440,7 @@ def unregister_secret(self):
                 body=kubernetes.client.V1DeleteOptions(),
             )
         )
-
+    # In rare cases, deleting a pod may raise 404 NotFound error.
     def safe_delete_pod(self, jobid, ignore_not_found=True):
         import kubernetes.client
 
@@ -432,16 +449,27 @@ def safe_delete_pod(self, jobid, ignore_not_found=True):
             self.kubeapi.delete_namespaced_pod(jobid, self.namespace, body=body)
         except kubernetes.client.rest.ApiException as e:
             if e.status == 404 and ignore_not_found:
+                # Can't find the pod. Maybe it's already been
+                # destroyed. Proceed with a warning message.
                 self.logger.warning(
                     "[WARNING] 404 not found when trying to delete the pod: {jobid}\n"
                     "[WARNING] Ignore this error\n".format(jobid=jobid)
                 )
             else:
                 raise e
-
+    # Sometimes, certain k8s requests throw kubernetes.client.rest.ApiException
+    # Solving this issue requires reauthentication, as _kubernetes_retry shows
+    # However, reauthentication itself, under rare conditions, may also throw
+    # errors such as:
+    #   kubernetes.client.exceptions.ApiException: (409), Reason: Conflict
+    #
+    # This error doesn't mean anything wrong with the k8s cluster, and users can safely
+    # ignore it.
     def _reauthenticate_and_retry(self, func=None):
         import kubernetes
-
+        # Unauthorized.
+        # Reload config in order to ensure token is
+        # refreshed. Then try again.
         self.logger.info("Trying to reauthenticate")
         kubernetes.config.load_kube_config()
         subprocess.run(["kubectl", "get", "nodes"])