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[Sergio Durigan Junior <1466926@xxxxxxxxxxxxxxxxxx>]

Xenial has reached its end of standard support.

** Changed in: apache2 (Ubuntu Xenial)
       Status: Triaged => Won't Fix

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https://bugs.launchpad.net/bugs/1466926

Title:
  reload apache2  with mpm_event cause  scoreboard is full

Status in apache2 package in Ubuntu:
  Fix Released
Status in apache2 source package in Trusty:
  Won't Fix
Status in apache2 source package in Xenial:
  Won't Fix
Status in apache2 source package in Zesty:
  Fix Released

Bug description:
  [Impact]

   * apache2 reload can fill up the scorecard with graceful reastarting
     workers to an amount that it is unable to serve more requests.

   * Backport fix from upstream to avoid the issue

  [Test Case]

   * In comment #8 I outlined some steps to fill up the scorecard with
     Gracefully stopping processes. But that never triggered the reported
     bug of eventually breaking new requests for me (It is still good to
     verify some busy tests on this part of the apache code)
     -> Therefore one of the reporters of the bug tested the ppa quite a
        while on his main machines that formerly were affected by the issue.
     -> no clear "do this then X happens" test case steps
   * Perform arbitrary additional functional tests on the package to make sure no regressions are visible

  [Regression Potential]

   * It is a rather complex code change in the mpm event handling.
     Only the first change is to code, the other two are for the
     documentation to match.
     We tested some apache benchmarks to check the effect, but found neither
     a positive nor negative impact in general (other than the bug being
     resolved). Yet if people rely on very specific behavior of the mpm
     handling that might change a bit.
     It will change for the good of it, but always remember xkcd.com/1172

     TL;DR: IMHO it clearly has a ">none" regression potential on the mpm
     event handling

  [Other Info]

   * Since this is hard to test we had a 2+ week test on the ppa, see
     comments c#8 - c#15

   * It clearly is a fix for some (e.g. the reporter of the bug), but I'd
     understand if the SRU Team would rate it as feature and deny it for an
     SRU - depends on the POV, certainly worth to be reviewed at least.

  ----

  On the clean install Ubuntu 14.04 with Apache without almost any
  client load the Apache server with the command "service apache2
  reload" itself allocates slots marked with "Gracefully finishing" for
  which rejects new connections.

  For full rejection of new requests is sufficient to perform 4x command
  "service apache2 reload".

  Ubuntu 14.04.2 LTS
  Apache 2.4.7-ubuntu4.4 (mpm_event)
  Kernel 2.16.0-30-generic

  Reproduce problem:
  #################################################
  1/ service apache2 start
  ______________________________________________________W_________
  ___________.....................................................
  ......................

  2/ service apache2 reload

  .........................GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG
  GGGGGGGGGGG__________________________________________________W__
  ______________________

  3/ service apache2 reload

  ___W_____________________GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG
  GGGGGGGGGGG__________________________________________________...
  ......................

  4/ service apache2 reload

  GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG
  GGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG___
  W_____________________

  5/ service apache2 reload -> Server Apache not responding
  With logs in apache error log file:
  ... [mpm_event:error] [pid 9381:tid 1234563234] AH00485: scoreboard is full, not at MaxRequestWorkers
  ...
  #################################################

  My workaround was change to  MPM module  from "mpm_event" to
  "mpm_worker".

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