Re: [Openvpn-devel] Multi Cache TTL Usage

[James Y. <ji...@yo...>]

Harris, Jeff wrote:
> Does anyone know the effect of lowering the MULTI_CACHE_ROUTE_TTL
> constant in multi.h from 60 seconds to say 10?  Will it cause extra
> network traffic or anything if the routes are purged more often?
>
> I am trying to work around an issue I'm seeing with spikes in the number
> of multi_instance objects.  I have 125 connected clients and after a
> number of restarts of all the clients, the number of multi_instance
> objects on my server spikes to over 600 leading to an eventual
> exhaustion of memory.  I am using keep-alive settings of 5 second pings
> and 30 seconds of inactivity.
>
> Lowering the value to 30 seems to hold off the spikes for a bit.  With a
> value of 10 I have not seen the spikes.
>
> Any help would be appreciated.
>
>   

OpenVPN caches routes in a hash table for efficiency, so that it doesn't 
need to iterate through the whole routing table in order to find a 
match.  The problem appears to be that cache entries may prolong the 
life of a marked-for-delete multi-instance object by holding references 
to it until the cache entry expires.  So timing out the cached routes 
earlier appears to be a good solution, and will not increase network 
traffic.

James