X2Go Bug report logs - #692
select_session offers offline servers to X2Go Client

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Date: Sun, 7 Dec 2014 03:45:28 +0400 (MSK)
From: Sergey Savko <savko@tophouse.ru>
To: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>, 684@bugs.x2go.org
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Subject: Re: [X2Go-Dev] Bug#684: select_session offers offline servers to
 X2Go Client
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Thread-Topic: Bug#684: select_session offers offline servers to X2Go Client
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If the server will give the address to which it can not connect, there will be no load balancing works. 
Since the server is connected to receive the coefficient of loading.


----- Исходное сообщение -----
От: "Mike Gabriel" <mike.gabriel@das-netzwerkteam.de>
Кому: "Sergey Savko" <savko@tophouse.ru>, 684@bugs.x2go.org
Отправленные: Воскресенье, 7 Декабрь 2014 г 1:56:05
Тема: Re: [X2Go-Dev] Bug#684: select_session offers offline servers to X2Go Client

Control: clone -1 -2 -3
Control: reassign -2 x2goclient
Control: reassign -3 python-x2go
Control: retitle -1 add exclude-hosts parameter to selectsession task
Control: retitle -2 request another server from broker provided server is down
Control: retitle -3 request another server from broker provided server is down
Control: severity -1 wishlist
Control: severity -2 wishlist
Control: severity -3 wishlist
Control: block -2 by -1
Control: block -3 by -1
Control: tag -1 - patch

Hi Sergey,

On  Fr 05 Dez 2014 17:14:51 CET, Sergey Savko wrote:

> This patch work after patch from  
> http://bugs.x2go.org/cgi-bin/bugreport.cgi?bug=686

After thinking this through a little, I come to the conclusion that  
the broker cannot decide if a machine is down or not.

We have to think very generically. There may be a scenario where the  
broker machine may be on an network segment where it cannot ping/reach  
the X2Go Servers.

The X2Go Clients can reach the X2Go Broker. The broker provides an  
X2Go Server address on the "selectsession" broker task to the X2Go  
Client. Then the X2Go Client should test if that X2Go Server address  
works (via a simple ping6/ping command, machines should always be  
pingable!!!). If the ping fails, X2Go Client should go back to the  
broker and say: hey, that server failed for me, give me another one  
(but not the one you already gave me).

I fear we need to do four things for this bug to get fixed:

   1. extend broker/client communication protocol (second/third/...  
selectsession
      call with a list of hosts that did not work on previous attempts)
   2. extend X2Go Session Broker with an exclude-hosts (or so)  
parameter for the
      selectsession task
   3. Adapt X2Go Client: ping X2Go Server, go back to the broker if  
server is down
      and request another server
   4. Adapt Python X2Go: dito

Regards,
Mike

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