[reSIProcate] DNS not returning entries after 408?

[Byron Campen]

	This case has been handled, by deferred destruction of the  
DnsResult. TransactionState never calls delete explicitly on its  
DnsResult, instead it calls DnsResult::destroy(). (when  
DnsResult::destroy() is called, the DnsResult checks if it has  
outstanding queries, and if so it will wait for these to come in  
before deleting itself.)

Best regards,
Byron Campen

> What if the Transaction State Obj expired (deleted about 32  
> seconds) before DNS look up returns?
>
> This may cause core dump since the DNS Result used by DNS lookup is  
> deleted when Transaction State Obj is deleted.
>
> Regards,
>
> Frank Yuan
>
>
>
> 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 1:32 PM
> To: Scott Godin
> Cc: 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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>>
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>>
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>>
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>>
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