Move code formatting job ID into a base class

A later patch will add a memory based job storage class, hence this
code is going into a separate class. It also changes the number format
to always use at least 10 digits, allowing up to 9'999'999'999 jobs to
be sorted without using a custom function.

Reviewed-by: iustinp

lib/jqueue.py

@@ -264,10 +264,41 @@ class _JobQueueWorkerPool(workerpool.WorkerPool):
     self.context = context
 
 
-class DiskJobStorage(object):
+class JobStorageBase(object):
+  def __init__(self, id_prefix):
+    self.id_prefix = id_prefix
+
+    if id_prefix:
+      prefix_pattern = re.escape("%s-" % id_prefix)
+    else:
+      prefix_pattern = ""
+
+    # Apart from the prefix, all job IDs are numeric
+    self._re_job_id = re.compile(r"^%s\d+$" % prefix_pattern)
+
+  def OwnsJobId(self, job_id):
+    return self._re_job_id.match(job_id)
+
+  def FormatJobID(self, job_id):
+    if not isinstance(job_id, (int, long)):
+      raise errors.ProgrammerError("Job ID '%s' not numeric" % job_id)
+    if job_id < 0:
+      raise errors.ProgrammerError("Job ID %s is negative" % job_id)
+
+    if self.id_prefix:
+      prefix = "%s-" % self.id_prefix
+    else:
+      prefix = ""
+
+    return "%s%010d" % (prefix, job_id)
+
+
+class DiskJobStorage(JobStorageBase):
   _RE_JOB_FILE = re.compile(r"^job-(%s)$" % constants.JOB_ID_TEMPLATE)
 
-  def __init__(self):
+  def __init__(self, id_prefix):
+    JobStorageBase.__init__(self, id_prefix)
+
     self._lock = threading.Lock()
     self._memcache = {}
     self._my_hostname = utils.HostInfo().name
@@ -383,7 +414,7 @@ class DiskJobStorage(object):
       if not result[node]:
         logging.error("copy of job queue file to node %s failed", node)
 
-    return str(serial)
+    return self.FormatJobID(serial)
 
   def _GetJobPath(self, job_id):
     return os.path.join(constants.QUEUE_DIR, "job-%s" % job_id)
@@ -400,7 +431,7 @@ class DiskJobStorage(object):
 
     """
     jfiles = self._ListJobFiles()
-    jlist = [int(m.group(1)) for m in
+    jlist = [m.group(1) for m in
              [self._RE_JOB_FILE.match(name) for name in jfiles]]
     jlist.sort()
     return jlist
@@ -510,10 +541,10 @@ class DiskJobStorage(object):
 class JobQueue:
   """The job queue.
 
-   """
+  """
   def __init__(self, context):
     self._lock = threading.Lock()
-    self._jobs = DiskJobStorage()
+    self._jobs = DiskJobStorage("")
     self._wpool = _JobQueueWorkerPool(context)
 
     for job in self._jobs.GetJobs(None):