[Nagiosplug-devel] [Nagiosplug-help] check_ntp

[Thomas Guyot-Sionnest]

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On 11/11/07 08:29 AM, Andreas Ericsson wrote:
> Thomas Guyot-Sionnest wrote:
>>
>> Well, the options for check_ntp will remain the same, the only
>> difference it that it will return the peer's offset instead of the
>> offset between localhost and the ntp server. It will also send 8 time
>> less packets...
>>
>> We could call it check_ntpd to avoid any confusion,
> 
> Sounds good, although I still prefer check_ntp_peers, since that makes
> it obvious from a directory listing which plugin to use depending on
> ones needs.

To me it's not that obvious. OTOH check_time is a check for time offset
between ourself and a time server, so check_time_ntp for the offset
check would be the logical one.

check_ntp's description in --help is:

"This plugin checks the selected ntp server"

To me that clearly doesn't mean we're checking the local time against
the given ntp server.

>> so we would end up
>> with check_ntp (marked ad deprecated), check_ntpd and check_time_ntp...
>> Or something like that.
>>
> 
> Sounds bad.
> 
> check_ntp really should stay with its current semantics.

If we go that way, it will stay with its current semantics, but it'll
say that it's deprecated and will be removed much later (Maybe next
major release).

> check_ntp{d,_peers}
> can do the peer checking.
> 
> Deprecating check_ntp to give it a new name is nearly as user-unfriendly as
> changing its semantics, but not quite.
> 
> Think of the plugins as an API that people actively use in programs. If
> memcpy() all of a sudden was renamed to memcopy(), whole battallions of
> programs would just stop working over-night.
> 
> Changing its semantics but maintaining the arguments would be just as
> broken as if malloc() all of a sudden started returning a pointer to
> the end of the newly allocated buffer.

I'm not sure if you follow me well there. By "deprecating" check_ntp I
just mean we'll yell it all over the place without touching it (apart
from normal bugfixes). However people will have the option to use two
new checks that do what they should do.

>> I'm open to discussion but I've seen multiple times people wanting the
>> peer ofsset in check_ntp, and I feel this is the right thing anyways.
>>
> 
> The problem is that you only hear from people who want the behaviour to
> change. Those who are happy with the way check_ntp works today are much
> more likely to not say anything. Until it breaks, that is.

IMHO for many people it's already broken and they just don't realize it.
When I do a NTP check I check the $HOSTADDRESS$, which mean I want to
know about the health of the NTP server, not the offset between Nagios
and the server. Do you know many people that run check_ntp over nrpe and
specify a time server?

>> What might happen if we don't change the name is that people expecting
>> to check the offset between their server and the remote will actually
>> monitor the remote server.
> 
> Hence "check_ntp" and "check_ntp_peers". A directory listing will tell
> them which plugin to use based on their needs.

I suggest you take a look at my branch... You can svn co this:

https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/branches/dermoth_ntp_rework

Or just point your browser to the actual files and put them in your
working copy:
https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/branches/dermoth_ntp_rework/plugins/check_ntpd.c
https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/branches/dermoth_ntp_rework/plugins/check_time_ntp.c
https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/branches/dermoth_ntp_rework/plugins/Makefile.am

>> OTOH in the past (before working on
>> check_ntp) I assumed that the offset was the peer's offset and I might
>> not be alone thinking that. So either way some people won't do the
>> RightThing(tm) with check_ntp...
>>
> 
> In my experience, it's much more common that random servers get out of
> sync with the stratum >1 server than that server getting out of sync
> with its peers. I've always expected check_ntp to see if the server it's
> being run on is in sync with the ntp server.

A ntp server will loose sync if any of the servers in the path isn't
sync. The newer check specifically warn if the server isn't sync (I may
add an option to make that configurable - ok/warn/crit/unknown).

Thomas
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