cloud-init-dev team mailing list archive

[Ryan Harper <ryan.harper@xxxxxxxxxxxxx>]

I've a bit of a quibble with the description.  Mostly because cloud-init has _no_ control over how DNS or DHCP servers react to dhcp client requests coming from an instance.

What we (cloud-init) can do is set instance specified hostnames as _soon_ as we know it, which may be of help to some situations where Dynamic DNS via dhcp client hostname value.

This is an environment specific issue and having cloud-init set hostname as soon as possible does not ensure that there won't be issues with DNS, DHCP outside of cloud-init control.


Some inline comments too.

Diff comments:

> diff --git a/cloudinit/cmd/main.py b/cloudinit/cmd/main.py
> index d2f1b77..120c3cc 100644
> --- a/cloudinit/cmd/main.py
> +++ b/cloudinit/cmd/main.py
> @@ -354,7 +355,17 @@ def main_init(name, args):
>      LOG.debug("[%s] %s will now be targeting instance id: %s. new=%s",
>                mode, name, iid, init.is_new_instance())
>  
> -    init.apply_network_config(bring_up=bool(mode != sources.DSMODE_LOCAL))
> +    if mode == sources.DSMODE_LOCAL:
> +        # Before network comes up, set any configured hostname to allow
> +        # dhcp clients to advertize this hostname to any DDNS services
> +        # lp:1746455.
> +        cloud = init.cloudify()
> +        (hostname, _fqdn) = util.get_hostname_fqdn(

doesn't this sometime return None ?  Isn't that going to break your named _fqdn ?

> +            init.cfg, cloud, metadata_only=True)
> +        if hostname:  # Either metadata or user-data provided hostname content
> +            cc_set_hostname.handle(
> +                'pre-network-set-hostname', init.cfg, cloud, LOG, None)
> +    init.apply_network_config(bring_up=bring_up)
>  
>      if mode == sources.DSMODE_LOCAL:
>          if init.datasource.dsmode != mode:
> diff --git a/cloudinit/sources/__init__.py b/cloudinit/sources/__init__.py
> index a05ca2f..d1a213f 100644
> --- a/cloudinit/sources/__init__.py
> +++ b/cloudinit/sources/__init__.py
> @@ -276,21 +276,34 @@ class DataSource(object):
>              return "iid-datasource"
>          return str(self.metadata['instance-id'])
>  
> -    def get_hostname(self, fqdn=False, resolve_ip=False):
> +    def get_hostname(self, fqdn=False, resolve_ip=False, metadata_only=False):
> +        """Get hostname or fqdn from the datasource. Look it up if desired.
> +
> +        @param fqdn: Boolean, set True to return hostname with domain.
> +        @param resolve_ip: Boolean, set True to attempt to resolve an ipv4

hostnames aren't ipv4 or ipv6; the just map to ip addresses.

> +            address provided in local-hostname metadata.
> +        @param metadata_only: Boolean, set True to avoid looking up hostname
> +            if metadata doesn't have local-hostname present.
> +
> +        @return: hostname or qualified hostname. Optionally return None when
> +            metadata_only is True and local-hostname data is not available.
> +        """
>          defdomain = "localdomain"
>          defhost = "localhost"
>          domain = defdomain
>  
>          if not self.metadata or 'local-hostname' not in self.metadata:
> +            if metadata_only:
> +                return None

Can't we just return (None, None)?

>              # this is somewhat questionable really.
>              # the cloud datasource was asked for a hostname
>              # and didn't have one. raising error might be more appropriate
>              # but instead, basically look up the existing hostname
>              toks = []
>              hostname = util.get_hostname()
> -            fqdn = util.get_fqdn_from_hosts(hostname)
> -            if fqdn and fqdn.find(".") > 0:
> -                toks = str(fqdn).split(".")
> +            hosts_fqdn = util.get_fqdn_from_hosts(hostname)
> +            if hosts_fqdn and hosts_fqdn.find(".") > 0:
> +                toks = str(hosts_fqdn).split(".")
>              elif hostname and hostname.find(".") > 0:
>                  toks = str(hostname).split(".")
>              elif hostname:


-- 
https://code.launchpad.net/~chad.smith/cloud-init/+git/cloud-init/+merge/339720
Your team cloud-init commiters is requested to review the proposed merge of ~chad.smith/cloud-init:set-hostname-before-network into cloud-init:master.