[Bug 1314677] [NEW] nova-cells fails when using JSON file to store cell information

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As recommended in http://docs.openstack.org/havana/config-
reference/content/section_compute-cells.html#cell-config-optional-json
I'm creating the nova-cells config with the cell information stored in a
json file. However, when I do this nova-cells fails to start with this
error in the logs:

2014-04-29 11:52:05.240 16759 CRITICAL nova [-] __init__() takes exactly 3 arguments (1 given)
2014-04-29 11:52:05.240 16759 TRACE nova Traceback (most recent call last):
2014-04-29 11:52:05.240 16759 TRACE nova   File "/usr/bin/nova-cells", line 10, in <module>
2014-04-29 11:52:05.240 16759 TRACE nova     sys.exit(main())
2014-04-29 11:52:05.240 16759 TRACE nova   File "/usr/lib/python2.7/dist-packages/nova/cmd/cells.py", line 40, in main
2014-04-29 11:52:05.240 16759 TRACE nova     manager=CONF.cells.manager)
2014-04-29 11:52:05.240 16759 TRACE nova   File "/usr/lib/python2.7/dist-packages/nova/service.py", line 257, in create
2014-04-29 11:52:05.240 16759 TRACE nova     db_allowed=db_allowed)
2014-04-29 11:52:05.240 16759 TRACE nova   File "/usr/lib/python2.7/dist-packages/nova/service.py", line 139, in __init__
2014-04-29 11:52:05.240 16759 TRACE nova     self.manager = manager_class(host=self.host, *args, **kwargs)
2014-04-29 11:52:05.240 16759 TRACE nova   File "/usr/lib/python2.7/dist-packages/nova/cells/manager.py", line 87, in __init__
2014-04-29 11:52:05.240 16759 TRACE nova     self.state_manager = cell_state_manager()
2014-04-29 11:52:05.240 16759 TRACE nova TypeError: __init__() takes exactly 3 arguments (1 given)


I have had a dig into the code and it appears that CellsManager creates an instance of CellStateManager with no arguments. CellStateManager __new__ runs and creates an instance of CellStateManagerFile which runs __new__ and __init__ with cell_state_cls and cells_config_path set. At this point __new__ returns CellStateManagerFile and the new instance's __init__() method is invoked (CellStateManagerFile.__init__) with the original arguments (there weren't any) which then results in the stack trace.

It seems reasonable for CellStateManagerFile to derive the
cells_config_path info for itself so I've patched it locally with

=== modified file 'state.py'
--- state.py	2014-04-30 15:10:16 +0000
+++ state.py	2014-04-30 15:10:26 +0000
@@ -155,7 +155,7 @@
             config_path = CONF.find_file(cells_config)
             if not config_path:
                 raise cfg.ConfigFilesNotFoundError(config_files=[cells_config])
-            return CellStateManagerFile(cell_state_cls, config_path)
+            return CellStateManagerFile(cell_state_cls)
 
         return CellStateManagerDB(cell_state_cls)
 
@@ -450,7 +450,9 @@
 
 
 class CellStateManagerFile(CellStateManager):
-    def __init__(self, cell_state_cls, cells_config_path):
+    def __init__(self, cell_state_cls=None):
+        cells_config = CONF.cells.cells_config
+        cells_config_path = CONF.find_file(cells_config)
         self.cells_config_path = cells_config_path
         super(CellStateManagerFile, self).__init__(cell_state_cls)
 


Ubuntu: 14.04
nova-cells: 1:2014.1-0ubuntu1

nova.conf:

[DEFAULT]
dhcpbridge_flagfile=/etc/nova/nova.conf
dhcpbridge=/usr/bin/nova-dhcpbridge
logdir=/var/log/nova
state_path=/var/lib/nova
lock_path=/var/lock/nova
force_dhcp_release=True
iscsi_helper=tgtadm
libvirt_use_virtio_for_bridges=True
connection_type=libvirt
root_helper=sudo nova-rootwrap /etc/nova/rootwrap.conf
verbose=True
ec2_private_dns_show_ip=True
api_paste_config=/etc/nova/api-paste.ini
volumes_path=/var/lib/nova/volumes
enabled_apis=ec2,osapi_compute,metadata
auth_strategy=keystone
compute_driver=libvirt.LibvirtDriver
quota_driver=nova.quota.NoopQuotaDriver


[cells]
enable=True
name=cell
cell_type=compute
cells_config=/etc/nova/cells.json


cells.json: 
{
    "parent": {
        "name": "parent",
        "api_url": "http://api.example.com:8774",
        "transport_url": "rabbit://rabbit.example.com",
        "weight_offset": 0.0,
        "weight_scale": 1.0,
        "is_parent": true
    }
}

** Affects: nova
     Importance: Undecided
     Assignee: Liam Young (gnuoy)
         Status: Fix Released

** Affects: nova (Ubuntu)
     Importance: Undecided
     Assignee: Liam Young (gnuoy)
         Status: New

** Affects: nova (Ubuntu Trusty)
     Importance: Undecided
     Assignee: Liam Young (gnuoy)
         Status: New


** Tags: cells patch
-- 
nova-cells fails when using JSON file to store cell information
https://bugs.launchpad.net/bugs/1314677
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