[Dnsmasq-discuss] How does DNSMASQ handle large concurrent configure file updating request requests

Simon Kelley simon at thekelleys.org.uk
Wed Jan 14 22:10:21 GMT 2015


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Dnsmasq  checks for incoming network packets and signals in the same
event loop, so the maximum delay to DHCP packets will be the time to
read a configuration file once, even if you send 10000 SIGUSER1
signals, because the code will interleave handling DHCP and DNS
packets with the config file reading. Batching changes would be good,
if you can do it, but I'd not go looking for trouble here.


Cheers,

Simon.

On 14/01/15 15:49, Brian Haley wrote:
> On 01/14/2015 04:48 AM, Yongkang You wrote:
>> Hi,
>> 
>> We have a cloud environment which uses DNSMASQ as DHCP/DNS
>> server; in the cloud, it usually starts lots of VMs concurrently,
>> for example, 10000 VM; for each VM, we will configure a static
>> DHCP entry in DNSMASQ configuration and send SIGUSER1 to reload.
>> we observe DNSMASQ becomes very busy of reloading, for example,
>> it seems to reload 10000 times if we send for 10000 SIGUSER1.
>> 
>> Is this expected behavior? Is there any way to avoid this?
>> because it keep reloading, we don't know if this will effect VM
>> getting IP address.
> 
> Just for completeness, is this on Openstack?  I can see that code
> doesn't buffer anything when a port is plugged-in, so each triggers
> a reload.  Could maybe tweak things there to wait a few seconds
> between the HUPs.  I'm not sure it's a bug in dnsmasq though.
> 
> -Brian
> 
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