[rsyslog] HUP action

[david at lang.hm]

On Mon, 6 Oct 2008, Rainer Gerhards wrote:

>> could you do something along the lines of checking to see if the
> config
>> file changed, and if so do a full restart, otherwise just the
>> flush/close?
>>
>> if you know when you started you may be able to just check the
>> last-modified time of the config file and do a restart if it's been
>> modified after you started.
>
> That's a very interesting idea. Do you think this criterion is
> sufficient?

I was thinking of other possible items (doing a checksum of the file, 
doing a syntactic check to see if the new is equivalent to the old, etc) 
and I think that they don't end up adding noticable value

the only way the last-modified check would fail is if your clock goes 
backwards (and goes backwards far enough that the 'new' file is modified 
before you last started). two ways to deal with that

1. store the last-modified time of the file when you start up and re-read 
it if it has changed (still vunerable if the clock moved back to that 
exact second, but a very small windows)

2. document the issue and tell people that if their clock goes backwards 
and the HUP doesn't re-read the config file do a 'touch' of the file and 
try again.

David Lang