AttributeError: 'NoneType' object has no attribute 'group'

[wukaiying]

when i run this command sudo kubespray prepare --nodes node1[ansible_ssh_host=192.168.33.111] node2[ansible_ssh_host=192.168.33.112] node3[ansible_ssh_host=192.168.33.113] [--etcds N+] [--masters N+]

Traceback (most recent call last):
File "/bin/kubespray", line 422, in
args.func(config)
File "/bin/kubespray", line 42, in prepare
options['etcds_list']
File "/usr/lib/python2.7/site-packages/kubespray/inventory.py", line 221, in write_inventory
inventory = self.format_inventory(masters, nodes, etcds)
File "/usr/lib/python2.7/site-packages/kubespray/inventory.py", line 194, in format_inventory
inventory_hostname = r.group(1)
AttributeError: 'NoneType' object has no attribute 'group'

my env:
python --version
Python 2.7.5

ansible --version
ansible 2.4.1.0
config file = None
configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
ansible python module location = /usr/lib/python2.7/site-packages/ansible
executable location = /usr/bin/ansible
python version = 2.7.5 (default, Nov 20 2015, 02:00:19) [GCC 4.8.5 20150623 (Red Hat 4.8.5-4)]

[makuk66]

I imagine you based that command on the instructions https://github.com/kubespray/kubespray-cli/blob/master/README.md#generate-inventory-for-a-baremetal-cluster? That line is misleading: the brackets in the --etcds and --masters options indicate that they are optional; unlike the brackets in the node specification which are part of the syntax. So with the command you used, the code is expecting a node[ansible_ssh_host=something], tries to parse out the bit before the bracket, which is empty, and falls over.

The question then becomes, what should those options be? The help text says:

  --masters N [N ...]   Number of masters, these instances will not run
                        workloads, master components only

which is unclear too: does it want a number (integer)? Multiple ones?
I believe what is needed is node names e.g.:

sudo kubespray prepare \
  --nodes node1[ansible_ssh_host=192.168.33.111] node2[ansible_ssh_host=192.168.33.112] node3[ansible_ssh_host=192.168.33.113] \
  --etcds node1 node2 node3 --masters node1

though I'm not entirely sure, as this is the first time I'm running this, but that at least got me further, and seems to generate plausible-looking yaml