[reSIProcate] DNS not returning entries after 408?

[Byron Campen]

	If whitelisting is enabled (which, if I understand correctly, it is  
not by default), then we will continue using the good server. If we  
had a greylisting concept, we could afford to greylist for much  
longer than 32s, but I don't know if it is wise to blacklist for very  
long in the event of a timeout. (I am sure there are scenarios where  
this would be desirable behavior, but there are other scenarios where  
it would not.)

Best regards,
Byron Campen
> Good point about the 503’s – I agree.  I am a little worried about  
> only blacklisting a timeout (408) for 32 seconds, when there are  
> alternate servers that could handle requests.  Does this mean that  
> every 32 seconds we will try to send requests to the black listed  
> server again - and fail (assuming the server is down)?  Or will the  
> whitelisting logic kick in and we will continue to use the good  
> server?
>
>
>
> Scott
>
>
>
> From: Byron Campen [mailto:docfaraday at mac.com]
> Sent: Thursday, December 07, 2006 2:32 PM
> To: Scott Godin
> Cc: Jeremy Geras; resiprocate-devel at list.resiprocate.org
> Subject: Re: [reSIProcate] DNS not returning entries after 408?
>
>
>
>             We can't unblacklist stuff that was blacklisted because  
> of a 503. If all of the available servers are keeling over from  
> overload, and sending 503s, we are supposed to just shut up and  
> wait for the blacklists to expire. However, it is reasonable to say  
> that this behavior is not warranted in cases where we have  
> blacklisted due to a timeout. If we wish to treat these two  
> scenarios differently, maybe a greylisting concept is what we  
> should use.
>
>
>
> Best regards,
>
> Byron Campen
>
>
>
>
> Before the recent changes, that way I understood it the  
> blacklisting was supposed to work as follows:
>
> 1.        Only blacklist an entry if there other DNS entries to try.
>
> 2.       If we have ended up blacklisting all entries from a  
> particular lookup, then un-blacklist them all and let the next  
> request start the cycle again.
>
> Scott
>
>
>
> From: resiprocate-devel-bounces at list.resiprocate.org  
> [mailto:resiprocate-devel-bounces at list.resiprocate.org] On Behalf  
> Of Byron Campen
> Sent: Thursday, December 07, 2006 2:01 PM
> To: Jeremy Geras
> Cc: resiprocate-devel at list.resiprocate.org
> Subject: Re: [reSIProcate] DNS not returning entries after 408?
>
>
>
>           This is happening because the stack is blacklisting the  
> tuple that your server was running on, because it didn't respond.  
> This blacklist (currently) lasts 32s. I was thinking about making  
> this duration configurable. Does anyone want to have a discussion  
> about whether blacklisting on a UDP timeout is something we want to  
> be doing? It seems to me that we might need to have a concept of  
> "greylisting", where greylisted tuples will only be used if they  
> are all that remains to be tried. (This is opposed to a blacklisted  
> tuple, which we should never try, since chances are we have been  
> explicitly told, with a 503, to leave the tuple alone for a while.)  
> Any thoughts? (anyone?)
>
>
>
> Best regards,
>
> Byron Campen
>
> Hi,
>
>
>
> I’m using the latest code from SVN (updated today), and I’ve  
> encountered an issue with DNS in the following case:
>
>
>
> Client                                          Registrar
>
>       REGISTER (due to user login)------------->
>
>       <---------------------------------- 200 OK
>
>
>
> (at this point the Registrar becomes unavailable – its IP is still  
> reachable, but nothing is listening on UDP port 5060)
>
>
>
>       re-REGISTER (due to Expires timer)------->
>
>
>
> (~ 30 seconds go by and then I get a 408 from DUM)
>
> (client sits idle for ~ 30 seconds more)
>
>
>
>       REGISTER -------------------------------->
>
>
>
> (Get a 503 Service Unavailable immediately from DUM)
>
> (sit idle for any amount of time)
>
>
>
>       REGISTER -------------------------------->
>
>       <---------------------------------- 200 OK
>
>
>
>
>
> My client is set up to use only UDP as a transport.  I’m using  
> DUM.  I’ve looked at the logs, and it seems the reason I’m getting  
> the 503 is that there aren’t any DNS entries for my registrar: “Ran  
> out of dns entries for 192.168.1.172. Send 503”.  But this doesn’t  
> make sense, as there definitely should be entries (and since I can  
> register if I try once again after I get the 503).
>
>
>
> If I go back to an older revision (6609 which is from back in  
> September), I don’t have this issue – i.e. I don’t get the 503, my  
> last REGISTER actually goes out on the wire and I get my expected  
> 200 OK.
>
>
>
> Any thoughts?
>
>
>
> Thanks,
>
>  - Jeremy -
>
>
>
>
>
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