Gentle shutdown feature

John Wobus jw354 at
Fri Jun 27 15:35:24 UTC 2014

Here's our situation:
We run DHCP-4.1-ESV R8 and we stop and restart the
server every 2 minutes to reconfigure.  We have about
200,000 addresses in dynamic pools and our log
grows to 20 million plus lines a day.

There are other similar sites that use the same "stop and
start frequently" strategy.  I would naturally be concerned
if the daemons had trouble ever reaching normal state.

I am surprised at two things:
(1) A new feature was put into the ESV version?
I'm wondering why such a thing exists if it is
handled like that.  Was this considered a bug fix?

(2) I always thought SIGTERM caused the server
to finish writing the lease file.  I noticed
significant delays (tenths of a second)
in dhcpd "term" time a decade ago and attributed
it to lease file writing.  I'm surprised to hear

John Wobus
Cornell University IT

On Jun 26, 2014, at 2:13 PM, Shawn Routhier wrote:

> In the 4.3.0 release cycle we added a feature to gently shutdown
> clients and servers when they received SIGINT and SIGTERM
> signals.  This feature was included in the changes back ported to
> 4.1-ESV and 4.2 and has two side effects that may affect users.
> This was done to allow any writes to the lease files to complete
> before the process stops.
> When a client receives a SIGINT or SIGTERM signal  the new
> behavior is to send a release message to the server.
> When a server receives a SIGINT or SIGTERM signal "if" failover
> is in use then when the server is restarted it may go through recover
> wait for a number of seconds (determined by the server's MCLT
> setting)  before becoming usable.
> In both of these cases the previous functionality can be gotten
> by halting the process with a different signal, for example
> "kill -9 <pid>"
> We have received a report objecting to this feature
> and we are determining the best course of action.
> 1) Are you already making use of this feature?  Or would it
> not be an issue if we disabled it?
> 2) Has this feature caused issues for you?
> 3) Any other useful comments about this issue?
> Shawn Routhier
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