Open Stack

Since Eventlet is based on continuations instead of threads or 
processes, any call that blocks is going to lock up the webserver. That 
is any I/O at all.  Thus, when trying to figure out how best to call the 
OpenSSL functions from Eventlet, I settled on what I thought would be 
the best tested approach: spin it off as a separate process.  And it 
seemed to work.

Well, it doesn't work.  The Eventlet library does not properly Monkey 
patch the subprocess calls from Python.  While this is something we 
should patch upstream in Eventlet,  we need something to deal with the 
existing Eventlet library for Grizzly development.

I've been trying to make it possible to run Keystone (and the other 
services eventually) in Apache.  Thus, the simple solution of replacing

import subprocess

with

import eventlet.green.subprocess

Won't work.  It solves the problem in Eventlet, but not apache.

It is possible to do something like this code below:

in the file keystone/common/interop/__init__.py

import sys
if 'eventlet' in sys.modules:
     import eventlet.green.subprocess as interop_subprocess
     print sys.modules["eventlet"]
else:
     import subprocess as interop_subprocess

PIPE = interop_subprocess.PIPE
CalledProcessError = interop_subprocess.CalledProcessError
Popen = interop_subprocess.Popen
#end interop


and then, instead of
import eventlet.green.subprocess

we can import keystone.common.interop as subprocess

The problem is that the if statement is not triggered when this import 
is hit, as the eventlet code has not yet been imported elsewhere.

What is the right way of detecting what web server we are running in and 
selecting which version of the subprocess code to import?