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[sean mooney <2103811@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

In previous releases we addressed https://bugs.launchpad.net/nova/+bug/1882094
    (a bug with how mod_wsgi reloads wsgi applications into the same python
    interpreter on error) by wrapping the initialization of global data in
    a run_once decorator. The run_once decorator solves the reentrancy problem
    for the initialization of the config objects or other global state that
    can only be setup once in a given python interpreter.
    This allows the nova wsgi application to be reloaded and retried when
    transient errors, such as the db being unavailable when the api starts,
    to heal overtime.
    The run_once decorator also had an unplanned side-effect. If the nova-api
    raised an error for an non-transient issue such as invalid config that would
    be raised only once and nova would serve subsequent requests with a partly
    initialized config. This will lead to undefined behavior and is
    obviously a bug. When run under other wsgi servers config errors cause
    the hosting python interpreter to exit, this is not the behavior of mod_wsgi.

** Affects: nova
     Importance: Medium
     Assignee: sean mooney (sean-k-mooney)
         Status: In Progress


** Tags: api

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https://bugs.launchpad.net/bugs/2103811

Title:
  nova (metadata)api does not exit on fatal errors under mod_wsgi

Status in OpenStack Compute (nova):
  In Progress

Bug description:
  In previous releases we addressed https://bugs.launchpad.net/nova/+bug/1882094
      (a bug with how mod_wsgi reloads wsgi applications into the same python
      interpreter on error) by wrapping the initialization of global data in
      a run_once decorator. The run_once decorator solves the reentrancy problem
      for the initialization of the config objects or other global state that
      can only be setup once in a given python interpreter.
      This allows the nova wsgi application to be reloaded and retried when
      transient errors, such as the db being unavailable when the api starts,
      to heal overtime.
      The run_once decorator also had an unplanned side-effect. If the nova-api
      raised an error for an non-transient issue such as invalid config that would
      be raised only once and nova would serve subsequent requests with a partly
      initialized config. This will lead to undefined behavior and is
      obviously a bug. When run under other wsgi servers config errors cause
      the hosting python interpreter to exit, this is not the behavior of mod_wsgi.

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