Fix stall problem in pipeliner runner in environments with nice>0

This is fixing a stall problem in the pipeline runner, which was
observed on systems (GRID), where the runner was launched with an
increased nice value (>0).

In this scenario, allocated resources per task were not correctly
"un-accounted' and so the runner stalled at some moment since it couldn't
find free resources.

This commit is also adding some debugging mechanism with webhooks.
Later integration into the standard logging system would be nice.

MC/bin/o2_dpg_workflow_runner.py

@@ -40,6 +40,12 @@ def setup_logger(name, log_file, level=logging.INFO):
 # second file logger
 metriclogger = setup_logger('pipeline_metric_logger', 'pipeline_metric.log')
 
+# for debugging without terminal access
+# TODO: integrate into standard logger
+def send_webhook(hook, t):
+    if hook!=None:
+      command="curl -X POST -H 'Content-type: application/json' --data '{\"text\":\" " + str(t) + "\"}' " + str(hook) + " &> /dev/null"
+      os.system(command)
 
 # A fallback solution to getting all child procs
 # in case psutil has problems (PermissionError).
@@ -570,7 +576,6 @@ def stop_pipeline_and_exit(self, process_list):
 
         exit(1)
 
-
     def monitor(self, process_list):
         self.internalmonitorcounter+=1
         if self.internalmonitorcounter % 5 != 0:
@@ -650,6 +655,7 @@ def monitor(self, process_list):
 
             resources_per_task[tid]={'iter':self.internalmonitorid, 'name':self.idtotask[tid], 'cpu':totalCPU, 'uss':totalUSS/1024./1024., 'pss':totalPSS/1024./1024, 'nice':proc.nice(), 'swap':totalSWAP, 'label':self.workflowspec['stages'][tid]['labels']}
             metriclogger.info(resources_per_task[tid])
+            send_webhook(self.args.webhook, resources_per_task)
 
         for r in resources_per_task.values():
             if r['nice']==os.nice(0):
@@ -679,7 +685,7 @@ def waitforany(self, process_list, finished):
           if returncode!=None:
             actionlogger.info ('Task ' + str(pid) + ' ' + str(p[0])+':'+str(self.idtotask[p[0]]) + ' finished with status ' + str(returncode))
             # account for cleared resources
-            if self.nicevalues[p[0]]==0: # --> change for a more robust way
+            if self.nicevalues[p[0]]==os.nice(0):
                 self.curmembooked-=float(self.maxmemperid[p[0]])
                 self.curcpubooked-=float(self.cpuperid[p[0]])
             else:
@@ -865,6 +871,10 @@ def execute(self):
                 finished = []
                 actionlogger.debug('Sorted current candidates: ' + str([(c,self.idtotask[c]) for c in candidates]))
                 self.try_job_from_candidates(candidates, self.process_list, finished)
+                if len(candidates) > 0 and len(self.process_list) == 0:
+                    actionlogger.info("Not able to make progress: Nothing scheduled although non-zero candidate set")
+                    send_webhook(self.args.webhook,"Unable to make further progress: Quitting")
+                    break
 
                 finished_from_started = []
                 while self.waitforany(self.process_list, finished_from_started):
@@ -889,6 +899,7 @@ def execute(self):
                                 candidates.append(candid)
 
                 actionlogger.debug("New candidates " + str( candidates))
+                send_webhook(self.args.webhook, "New candidates " + str(candidates))
 
                 if len(candidates)==0 and len(self.process_list)==0:
                    break
@@ -927,6 +938,7 @@ def execute(self):
 parser.add_argument('--cgroup', help='Execute pipeline under a given cgroup (e.g., 8coregrid) emulating resource constraints. This m\
 ust exist and the tasks file must be writable to with the current user.')
 parser.add_argument('--stdout-on-failure', action='store_true', help='Print log files of failing tasks to stdout,')
+parser.add_argument('--webhook', help=argparse.SUPPRESS) # log some infos to this webhook channel
 
 args = parser.parse_args()
 print (args)