[Pacemaker] RFC: Any interesting in 2.0.0 betas?

[Andrew Beekhof]

On Tue, Oct 30, 2012 at 5:13 PM, Vladislav Bogdanov
<bubble at hoster-ok.com> wrote:
> 30.10.2012 04:27, Andrew Beekhof wrote:
>> On reflection, I think making this configurable is going to cause more
>> trouble than its worth.
>> Any sysconfig mismatch between the nodes would result in major breakage.
>>
>> We need to pick one way and make it the default - if people want/need
>> anything else, they need to use the corosync node list.
>> For consistency with older releases, I think your original "strip
>> everything" patch is the best way to go.
>
> That is OK for me as I currently use it.
>
> Although I'd ask you to think again about stripping "known" domain name
> part from resolver-provided FQDN if uname and FQDN of local node match
> at the beginning.

Again though, uname() only works for the current node.
You can't know what the other nodes are using - and by extension if
you should strip their name as well.

> Something says me this would provide better backwards
> compatibility, while visible result for the discussed use-case will be
> exactly the same. I know at least one cluster (not mine) which will be
> broken if just to strip everything at the first dot - it uses long
> hostnames (and this is the default for a fresh-installed redhat/fedora
> if you enter FQDN in the anaconda prompt when installing a node).

How do they configure corosync.conf / cluster.conf though?
The stripping only applies when people put IP addresses in there (or
use multicast without a node list).

If people put node names we will use them unmodified.
Adding a node list is recommended by upstream corosync, so it makes
sense for us to use it as the official way to use a non-default naming
scheme.

>
> Also, way I propose provides better flexibility

It feels more fragile to me.  Its going to break really badly if some
nodes use FQDN and some dont.

> - assume that one sets
> hostname using two lexems from FQDN - node01.cluster01 (or n01.c01)
> instead of just node01 or n01. FQDN itself could be
> n01.c01.some.location.domain.com. That could be done just to add safety
> for shell actions - hostname is usually shown in the shell prompt (I
> recall many cases when I issued command on a different host from I
> thought I do it on). The same applies to cluster commands. If visible
> nodenames have some (administrator controlled) hints, cluster could be
> safer to operate. And this way should not cause any breakage - cluster
> node are usually named the same way and no additional configuration is
> involved.
>
> I can develop patch for that if you want. It would introduce one global
> var (domain name), and will have one extra call to uname() and three or
> less calls to string-handling functions.
>
>>
>> On Fri, Oct 26, 2012 at 9:57 PM, Vladislav Bogdanov
>> <bubble at hoster-ok.com> wrote:
>>> 26.10.2012 13:38, Vladislav Bogdanov wrote:
>>>> 26.10.2012 12:43, Andrew Beekhof wrote:
>>>> ...
>>>>>> May be also set it forcibly to uname if uname contains full lexem found
>>>>>> in dns name?
>>>>>
>>>>> Run that past me again?
>>>>
>>>> I mean that if ip address resolves to fqdn, and that fqdn begins with
>>>> what uname call returns (so both node itself and DNS agree on a node
>>>> name for a node with give IP address), then that value from uname could
>>>> be safely used directly.
>>>
>>> Ah, that is for local node only...
>>> For remote nodes I would strip FQDN part which begins right at that dot
>>> where FQDN of local node and its uname differ.
>>>
>>> my_ring_address == 10.0.0.XXX
>>> my_uname() == "host232"
>>> getaddinfo(my_ring_address) == host232.some.very.long.domain.name.com.
>>>
>>> my_node_name = "host232"
>>> my_domain = "some.very.long.domain.name.com."
>>>
>>> his_ring_address == 10.0.0.YYY
>>> getaddinfo(his_ring_address) == host238.some.very.long.domain.name.com.
>>>
>>> strstr("host238.some.very.long.domain.name.com.", my_domain) != NULL
>>>
>>> his_node_name = "host238"
>>>
>>>
>>>>
>>>> To illustrate:
>>>> ring_address == 10.0.0.XXX
>>>> uname() == "host232"
>>>> getaddinfo(ring_address) == host232.some.very.long.domain.name.com.
>>>>
>>>> then "host232" could be safely used as a node name (but not "host23" and
>>>> not "host232.s")
>>>>
>>>> Of course, it would be even more safe if gentnameinfo("host232") or
>>>> getnameinfo("host232.some.very.long.domain.name.com.") returns
>>>> 10.0.0.XXX, so additional check may be introduced.
>>>>
>>>> That is normal for "correct" static DNS setups, where PTR record is
>>>> consistent with what node has configured as a hostname internally.
>>>>
>>>> That is also what I have for DHCP-based static address assignments
>>>> (central configuration place for a whole cluster network), where node
>>>> usually sets (or at least can be configured to set) its name to what
>>>> DHCP server says. And DHCP server is usually set up to update A and PTR
>>>> records in DNS zone.
>>>>
>>>> Also that should work correctly when FQDN is used as an uname (long
>>>> hostname), like redhat setups usually do.
>>>>
>>>> Anyways, if FQDN does not begin with uname, then DNS info should be used
>>>> for node name (like it is now), possibly with that "strip" hack. That
>>>> could be useful for multi-ring setups I think.
>>>>
>>>> Vladislav
>>>>
>>>>
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>>>
>>>
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>>
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>
>
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