Murdock: Increment metric counters in _process_job

The individual job_{prepare,finalize} are expected to throw exceptions.
If one of these throw an exception, the execution continues potentially
without incrementing the metric counters. Pulling the counters outside
these functions ensure that they are always incremented.

Grouping them in the same function call makes it also easier to track
their increments

murdock/murdock.py

@@ -170,6 +170,7 @@ async def _process_job(self, job: MurdockJob):
         else:
             logger.info("Processing job")  # type: ignore[union-attr]
             self._set_worker_metric(job, "prepare")
+            self.job_start_counter.inc()
             try:
                 await self.job_prepare(job)
             except Exception as exc:
@@ -196,6 +197,7 @@ async def _process_job(self, job: MurdockJob):
                 logger.warning(
                     "Finalize step failed", exception=repr(exc), state=job.state
                 )
+            self.job_status_counter.labels(status=job.state).inc()
             self._remove_worker_metric()
             logger.info("job completed", state=job.state)
 
@@ -233,7 +235,6 @@ async def job_prepare(self, job: MurdockJob):
                 "target_url": job.details_url,
             },
         )
-        self.job_start_counter.inc()
         await self.reload_jobs()
 
     async def job_finalize(self, job: MurdockJob):
@@ -277,7 +278,6 @@ async def job_finalize(self, job: MurdockJob):
             job.state == "stopped" and self.store_stopped_jobs
         ):
             await self.db.insert_job(job)
-        self.job_status_counter.labels(status=job.state).inc()
         await self.reload_jobs()
 
     async def add_job_to_queue(self, job: MurdockJob):