SIGHUP's effect on parameters is not well defined

If I start the api server using:

 $ cd /opt/stack/cinder && /usr/local/bin/cinder-api --config-file /etc/cinder/cinder.conf &

and, using a debug statement, print out the value of the 'glance_core_properties' parameter:

 +++ b/cinder/volume/api.py
 @@ -330,6 +330,8 @@ class API(base.Base):

         if filters:
             LOG.debug("Searching by: %s" % str(filters))
+ LOG.debug("CONF %s" % str(CONF.glance_core_properties))

then do a 'cinder list' to trigger the debug I see the default values for this parameter:

 5f00a82aa4004bfd90c0f02a8d118d96 2dcea26aa97a41fa9547a133f6c7f5b4] CONF ['checksum', 'container_format', 'disk_format', 'image_name', 'image_id', 'min_disk', 'min_ram', 'name', 'size'] from (pid=24052) get_all /opt/stack/cinder/cinder/volume/api.py:334

If I then edit /etc/cinder/cinder.conf to add a custom definition of 'glance_core_properties' (adding 'blah' on the end):

 glance_core_properties = checksum,container_format,disk_format,image_name,image_id,min_disk,min_ram,name,size,blah

and finally do a SIGHUP on the parent cinder api process:

 cinder$ ps auwx |grep cinder-api |grep -v grep
 ubuntu 24044 0.6 0.3 215004 61040 pts/23 S 15:08 0:07 /usr/bin/python /usr/local/bin/cinder-api --config-file /etc/cinder/cinder.conf
 ubuntu 24052 0.0 0.4 305112 65736 pts/23 S 15:08 0:00 /usr/bin/python /usr/local/bin/cinder-api --config-file /etc/cinder/cinder.conf

cinder$ kill -HUP 24044

(and check the same process ids exist as before):

 cinder$ ps auwx |grep cinder-api |grep -v grep
ubuntu 24044 0.6 0.3 215004 61040 pts/23 S 15:08 0:07 /usr/bin/python /usr/local/bin/cinder-api --config-file /etc/cinder/cinder.conf
 ubuntu 24052 0.0 0.4 305112 65736 pts/23 S 15:08 0:00 /usr/bin/python /usr/local/bin/cinder-api --config-file /etc/cinder/cinder.conf

what I find is that the new value of the glance_core_properties parameter is in effect, ie the debug shows:

 2014-09-02 15:10:34.561 DEBUG cinder.volume.api [req-0c29fa25-cd9a-442e-ae61-3b74275e7291 5f00a82aa4004bfd90c0f02a8d118d96 2dcea26aa97a41fa9547a133f6c7f5b4] CONF ['checksum', 'container_format', 'disk_format', 'image_name', 'image_id', 'min_disk', 'min_ram', 'name', 'size', 'blah'] from (pid=24052) get_all /opt/stack/cinder/cinder/volume/api.py:334

but ... the entries in /etc/cinder/cinder.conf are not treated consistently.

For example, if osapi_volume_listen_port is changed and a SIGHUP is sent, the port the service is listening on is not changed. Similarly, a change to osapi_volume_workers doesn't change the number of workers.

Changes to any parameters which are configured at start up of the service (including debug = True/False) do not get picked up after a SIGHUP. The impact of a change to some parameters (eg 'lock_path') is not clear. The only way for an operator to figure out which parameters will be updated after a SIGHUP is by looking through the code, or trial and error. If a SIGHUP does pick up a change to a parameter an operator still can't be sure that it's safe to make that change or not (eg 'lock_path').