blueprint <multi-process-api-service>

Add multiprocess support for API serivces (EC2/OSAPI_Compute/OSAPI_Volume/Metadata).

2012-06-1 v7:
    * Add unittest to cover worker recovery, service termination functionality
    in wsgi.py, fix python 2.6 compatibility issue.
    * Modify generate_uid() to introduce per-process seeds in utils.py to avoid
    collisions.
    * Add worker session to nova.conf.sample.
2012-05-21 v6:
    * Fix 'test_wsgi' unittest error.
2012-04-28 v5:
    * Add SIGINT handler and fix child-parent race condition when Ctrl+C is
    pressed.
2012-03-31 v4:
    * Fixed typo, removed debug code.
2012-03-30 v3:
    * Fixed localization/pep8 error in unittest, add metadata test.
    * nova/wsgi.py:Server: use the greenthread pool created for each process.
    * nova/service.py: remove debug code
2012-03-27 v2:
    * Fixed unittest error.
    * nova/wsgi.py:Server: Use self._logger to do logging in multiprocess mode.
    * nova/wsgi.py:Server: Move self._pool creation into proper place.
    * code style fix.
2012-03-25 v1:
    * Modification to nova/service.py and nova/wsgi.py in order to support
    multiprocess (a.k.a. workers) for various API services.  If multiprocess
    mode is enabled, (i.e. flags 'APINAME_workers' set to positive numbers),
    corresponding API service will run in target number of process(es). There
    is also a master_worker process spawned for managing all workers (handling
    signal/termination).
    * Add unittest for multiprocess API service, also alter testing/runner.py
    to adopt new unittest.

Change-Id: Ia045e595543ddfd192894b2a05801cc4b7ca90cb

nova/utils.py

@@ -63,6 +63,7 @@ LOG = logging.getLogger(__name__)
 ISO_TIME_FORMAT = "%Y-%m-%dT%H:%M:%S"
 PERFECT_TIME_FORMAT = "%Y-%m-%dT%H:%M:%S.%f"
 FLAGS = flags.FLAGS
+RESEED = True
 
 FLAGS.register_opt(
     cfg.BoolOpt('disable_process_locking', default=False,
@@ -290,6 +291,13 @@ def debug(arg):
 
 
 def generate_uid(topic, size=8):
+    global RESEED
+    if RESEED:
+        random.seed("%d%s%s" % (os.getpid(),
+                            socket.gethostname(),
+                            time.time()))
+        RESEED = False
+
     characters = '01234567890abcdefghijklmnopqrstuvwxyz'
     choices = [random.choice(characters) for _x in xrange(size)]
     return '%s-%s' % (topic, ''.join(choices))