IMs and group IMs (was Re: [sldev] Frequent bugs with difficult repros)

[Lawson English]

Henri Beauchamp wrote:
> On Fri, 29 Feb 2008 17:11:05 -0700, Lawson English wrote:
>
>   
>> Tateru Nino wrote:
>>     
>>> Kelly Linden wrote:
>>>       
>>>> Tateru Nino wrote:
>>>>         
>>>>> Soft wrote:
>>>>>           
>>>>>> On Fri, Feb 29, 2008 at 2:51 AM, Callum Lerwick <seg at haxxed.com> 
>>>>>> wrote:
>>>>>>  
>>>>>>             
>>>>>>>  On Fri, 2008-02-29 at 13:24 +1100, Tateru Nino wrote:
>>>>>>>  > Double chats in IM groups? That's caused by packet loss between 
>>>>>>> the
>>>>>>>  > viewer and the sim, honey. Same as double-chat in local chat, 
>>>>>>> and in
>>>>>>>  > person-to-person IMs. It also causes out-of-order chat.
>>>>>>>
>>>>>>>  So when is our chat going to be transported by this new-fangled TCP
>>>>>>>  thing? I hear it deals with packet loss and retains ordering...
>>>>>>>     
>>>>>>>               
>>>>>> I'm pretty sure TCP is just a fad.
>>>>>>
>>>>>> Actually, I thought this had already gone TCP. I'll ask around, but if
>>>>>> any other Lindens want to chime in...
>>>>>>   
>>>>>>             
>>>>> Depends. Even if it is tcp, application level sequencing and 
>>>>> controls over messaging flow, acknowledgement and order can still 
>>>>> duplicate your data - depending on whether you're second guessing 
>>>>> the transport with your own scheme, and how you've got it implemented.
>>>>>
>>>>>           
>>>> Those would be what we would call "bugs", I hope.  :D  I'm not the 
>>>> most up to date (my head is far too deep in havok4 for the past 6 
>>>> months), but I don't think chat or IM have moved to TCP, I believe 
>>>> they still use our home brewed "reliable" UDP messaging transport layer.
>>>>
>>>>         
>>> I believe that is also the case. Reliable is such an interesting word. 
>>> Very contextual. :)
>>>
>>> That said, the algorithms that govern the UDP transport actually do a 
>>> surprisingly good job under very trying and harsh circumstances - 
>>> however circumstances and workloads just aren't what they once were. 
>>> Something I think we all recognize.
>>>
>>>       
>> As far as I know, the main issues with IM in Second LIfe have nothing to 
>> do with UDP and would be just as bad if they were implemented using TCP, 
>> as long as the same underlying design remains unchanged.
>>     
>
> The IMs and group IMs issue is indeed independant of the protocol. IMs
> used to work just fine in UDP before LL made one of its most catastrophic
> mistakes by changing the architecture for IM communications in v1.14.1
> ( http://blog.secondlife.com/2007/04/02/preview-of-second-life-11411-now-up-on-the-beta-test-grid/ )
> to try and lighten the load on the servers.
>
> Despite a HUGE amount of bug reports and complaints, LL stubbornely kept
> the changes they made and we are still now, 11 months after the problems
> were identified, suffering the same out of order IMs, spuriously reopening
> group sessions, failure to open group sessions and send group notices,
> failures to set invisble or visible status in friends list (you are marked
> either visible or not, but your friends see the opposite), failures to load
> friends or groups lists after a cache emptying, etc, etc, etc...
>
> LL, please, STOP this madness and return to the OLD, reliable architecture,
> simply using better pipes and more powerful servers to keep the IMs and
> groups CENTRALIZED !
>
> Henri Beauchamp.
> _______________________________________________
>   

The concurrency record is now 65K simultaneous users. What was it 11 
months ago and why do you think that the old way would work better with 
the current load?


Lwason