[tor-bugs] #20504 [Metrics/Torflow]: When there is only one slice and one scanner, a bwauth runs a second empty slice

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#20504: When there is only one slice and one scanner, a bwauth runs a second empty
slice
---------------------------------+--------------------
     Reporter:  teor             |      Owner:  aagbsn
         Type:  defect           |     Status:  new
     Priority:  Medium           |  Milestone:
    Component:  Metrics/Torflow  |    Version:
     Severity:  Normal           |   Keywords:
Actual Points:                   |  Parent ID:
       Points:                   |   Reviewer:
      Sponsor:                   |
---------------------------------+--------------------
 When I run a single bandwidth scanner on less than 50 nodes, configured
 with:
 {{{
 start_pct = 0
 stop_pct = 100
 nodes_per_slice = 50
 }}}

 I get the following log message:
 {{{
 NOTICE[Mon Oct 31 04:31:46 2016]:Starting slice for percentiles 100-200
 NOTICE[Mon Oct 31 04:31:47 2016]:Only 0 exits remain in slice 100-200
 after restrictions. ...
 NOTICE[Mon Oct 31 04:31:47 2016]:No routers left after restrictions
 applied: NodeRestrictionList(['UnmeasuredPercentileRestriction(100,200)',
 'OrNodeRestriction(["FlagsRestriction([\'BadExit\'],[])",
 \'ConserveExitsRestriction()\'])', "FlagsRestriction(['Running'],[])"])
 }}}
 as well as a successful message for the 0-100 slice.

 It seems likely that there is an off by one error, either in the handling
 of start_pct & stop_pct, or in the handling of nodes_per_slice.

--
Ticket URL: <https://troodi.torproject.org/projects/tor/ticket/20504>
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