Fix job queue behaviour when loading jobs

Currently, if loading a job fails, the job queue code raises an
exception and prevents the proper processing of the jobs in the queue.
We change this so that unparseable jobs are instead archived (if not
already).

Reviewed-by: imsnah

lib/jqueue.py

@@ -382,6 +382,10 @@ class JobQueue(object):
     self.acquire()
     try:
       for job in self._GetJobsUnlocked(None):
+        # a failure in loading the job can cause 'None' to be returned
+        if job is None:
+          continue
+
         status = job.CalcStatus()
 
         if status in (constants.JOB_STATUS_QUEUED, ):
@@ -553,7 +557,19 @@ class JobQueue(object):
     finally:
       fd.close()
 
-    job = _QueuedJob.Restore(self, data)
+    try:
+      job = _QueuedJob.Restore(self, data)
+    except Exception, err:
+      new_path = self._GetArchivedJobPath(job_id)
+      if filepath == new_path:
+        # job already archived (future case)
+        logging.exception("Can't parse job %s", job_id)
+      else:
+        # non-archived case
+        logging.exception("Can't parse job %s, will archive.", job_id)
+        self._RenameFileUnlocked(filepath, new_path)
+      return None
+
     self._memcache[job_id] = job
     logging.debug("Added job %s to the cache", job_id)
     return job