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["Markus Zoeller \(markus_z\)" <mzoeller@xxxxxxxxxx>]

Public bug reported:

Config options code like this doesn't generate output in the
sample.config file:

    ALL_OPTS = itertools.chain(
               compute_opts,
               resource_tracker_opts,
               allocation_ratio_opts
               )


    def register_opts(conf):
        conf.register_opts(ALL_OPTS)


    def list_opts():
        return {'DEFAULT': ALL_OPTS}

The reason is that the generator created by "itertools.chain" doesn't
get reset after getting used in "register_opts". A simple complete
example:

    import itertools

    a = [1, 2]
    b = [3, 4]

    ab = itertools.chain(a, b)

    print("printing 'ab' for the first time")
    for i in ab:
	    print(i)

    print("printing 'ab' for the second time")
    for i in ab:
	    print(i)

The combined list 'ab' won't get printed a second time. The same thing
happens when the oslo.config generator wants to print the sample.config
file. This means we use either:

    ab = list(itertools.chain(a, b))

or

    ab = a + b

** Affects: nova
     Importance: High
     Assignee: Markus Zoeller (markus_z) (mzoeller)
         Status: Confirmed

** Changed in: nova
   Importance: Undecided => High

** Changed in: nova
       Status: New => Confirmed

** Changed in: nova
     Assignee: (unassigned) => Markus Zoeller (markus_z) (mzoeller)

-- 
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https://bugs.launchpad.net/bugs/1565824

Title:
  config option generation doesn't work with itertools.chain

Status in OpenStack Compute (nova):
  Confirmed

Bug description:
  Config options code like this doesn't generate output in the
  sample.config file:

      ALL_OPTS = itertools.chain(
                 compute_opts,
                 resource_tracker_opts,
                 allocation_ratio_opts
                 )

  
      def register_opts(conf):
          conf.register_opts(ALL_OPTS)

  
      def list_opts():
          return {'DEFAULT': ALL_OPTS}

  The reason is that the generator created by "itertools.chain" doesn't
  get reset after getting used in "register_opts". A simple complete
  example:

      import itertools

      a = [1, 2]
      b = [3, 4]

      ab = itertools.chain(a, b)

      print("printing 'ab' for the first time")
      for i in ab:
  	    print(i)

      print("printing 'ab' for the second time")
      for i in ab:
  	    print(i)

  The combined list 'ab' won't get printed a second time. The same thing
  happens when the oslo.config generator wants to print the
  sample.config file. This means we use either:

      ab = list(itertools.chain(a, b))

  or

      ab = a + b

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