nocloud-datasource with numeric hostname

[DHPark]

When I use nocloud datasource with numeric hostname like 1234,
it shows errors as follow,
2020-07-01 06:37:49,018 - util.py[DEBUG]: Getting data from <class 'cloudinit.sources.DataSourceNoCloud.DataSourceNoCloud'> failed
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/cloudinit/sources/__init__.py", line 733, in find_source
    if s.update_metadata([EventType.BOOT_NEW_INSTANCE]):
  File "/usr/lib/python2.7/site-packages/cloudinit/sources/__init__.py", line 622, in update_metadata
    result = self.get_data()
  File "/usr/lib/python2.7/site-packages/cloudinit/sources/__init__.py", line 259, in get_data
    self.persist_instance_data()
  File "/usr/lib/python2.7/site-packages/cloudinit/sources/__init__.py", line 289, in persist_instance_data
    self._get_standardized_metadata())
  File "/usr/lib/python2.7/site-packages/cloudinit/sources/__init__.py", line 209, in _get_standardized_metadata
    local_hostname = self.get_hostname()
  File "/usr/lib/python2.7/site-packages/cloudinit/sources/__init__.py", line 566, in get_hostname
    if util.is_ipv4(lhost):
  File "/usr/lib/python2.7/site-packages/cloudinit/util.py", line 544, in is_ipv4
    toks = instr.split('.')
AttributeError: 'int' object has no attribute 'split'

In get_hostname function in cloudinit/sources/__init__.py,

601 else:
602 # if there is an ipv4 address in 'local-hostname', then
603 # make up a hostname (LP: #475354) in format ip-xx.xx.xx.xx
604 lhost = self.metadata['local-hostname']
605 if net.is_ipv4_address(lhost):
606 toks = []
607 if resolve_ip:
608 toks = util.gethostbyaddr(lhost)
609
610 if toks:
611 toks = str(toks).split('.')
612 else:
613 toks = ["ip-%s" % lhost.replace(".", "-")]
614 else:
615 toks = lhost.split(".")

before utilize lhost, it needs to convert to string type like
 -> net.is_ipv4_address(str(lhost))
 -> str(lhost).split(".")
because when hostname is numeric only, lhost type would be integer by default in python.

[Chad Smith (chad.smith)]

Thanks for filing this bug and making cloud-init better.

RFC 1123 says hostname can start with digits and contain only digits. https://tools.ietf.org/html/rfc1123
I think this is a fair feature/bug request.

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/3755