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[Elena Ezhova <eezhova@xxxxxxxxxxxx>]

Public bug reported:

The following commit to oslo-incubator [1], that was supposed to optimize waiting for children processes
to exit, will break neutron-server behavior (i.e. signal handling).

1. In neutron-server eventlet monkey-patching (including patching os
module) is done in parent process. That is why os.waitpid(0, 0) in
_wait_child method also     gets monkey-patched and eventlet goes crazy.
Connecting to parent process with strace shows that os.waitpid(0,
os.WNOHANG) is called, yet it is difficult to say what is really
happening because the process does not react on termination signals
(SIGTERM, SIGHUP, SIGINT).

2. Due to the fact that neutron-server initializes two instances of
ProcessLauncher in one parent process, calling
eventlet.greenthread.sleep(self.wait_interval) seems to be the only way
for the process to switch contexts and allow another instance of
ProcessLauncher to call _wait_child. It is important to mention that
ProcessLauncher is not supposed to be used in this way (2 instances in
one parent process) at all.

This bug is intended to track fixing the outlined problems on Neutron
side.

[1] https://github.com/openstack/oslo-
incubator/commit/bf92010cc9d4c2876eaf6092713aafa94dcc8b35

** Affects: neutron
     Importance: Undecided
     Assignee: Elena Ezhova (eezhova)
         Status: New

** Changed in: neutron
     Assignee: (unassigned) => Elena Ezhova (eezhova)

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https://bugs.launchpad.net/bugs/1438321

Title:
  Fix process management for neutron-server

Status in OpenStack Neutron (virtual network service):
  New

Bug description:
  The following commit to oslo-incubator [1], that was supposed to optimize waiting for children processes
  to exit, will break neutron-server behavior (i.e. signal handling).

  1. In neutron-server eventlet monkey-patching (including patching os
  module) is done in parent process. That is why os.waitpid(0, 0) in
  _wait_child method also     gets monkey-patched and eventlet goes
  crazy. Connecting to parent process with strace shows that
  os.waitpid(0, os.WNOHANG) is called, yet it is difficult to say what
  is really happening because the process does not react on termination
  signals (SIGTERM, SIGHUP, SIGINT).

  2. Due to the fact that neutron-server initializes two instances of
  ProcessLauncher in one parent process, calling
  eventlet.greenthread.sleep(self.wait_interval) seems to be the only
  way for the process to switch contexts and allow another instance of
  ProcessLauncher to call _wait_child. It is important to mention that
  ProcessLauncher is not supposed to be used in this way (2 instances in
  one parent process) at all.

  This bug is intended to track fixing the outlined problems on Neutron
  side.

  [1] https://github.com/openstack/oslo-
  incubator/commit/bf92010cc9d4c2876eaf6092713aafa94dcc8b35

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