[FreeNX-kNX] nxagent session gets lost, user gets new session even though one already exists

[Marcelo Boveto Shima]

The following patch fixes this bug.
http://bazaar.launchpad.net/~freenx-team/freenx-server/teambzr/revision/91

This line seems to trigger the problem.
echo "NX> 596 Error: Session $1 failed. Reason was: $line"

Running it only when the node failed to restore the session solves the bug.

Regards.
Shima

On Mon, Feb 16, 2009 at 4:50 PM, Freerk Kalsbeek
<f.kalsbeek at mindswitch.nl>wrote:

> I've implemented this patch at one of our servers. Let's see what happens
> next few days.
> Haven't had the time to analyse our issues in more detail. Hopefully this
> fixes it.
>
> Regards,
> Freerk
>
>
> On Sun, Jan 25, 2009 at 4:32 AM, Mario Becroft <mb at gem.win.co.nz> wrote:
>
>> I still don't fully understand this problem, but I have a solution.
>>
>> I am not very sure about Marcelo's patch because as far as I can see,
>> NODE_SUSPEND_STATUS is never set to "Suspending". What is this patch
>> meant to do exactly?
>>
>> I found that with slave mode disabled, everything is much easier to
>> understand, and it does not appear to make it any slower. It did not
>> exactly fix the problem though, just modified the symptoms.
>>
>> The key problem is that when the client nxssh is killed, nxserver hangs
>> in the echo inside server_nxnode_echo(). It attempts to handle this
>> situation by installing a SIGPIPE handler that sets
>> SERVER_CHANNEL=0. Unfortunately, SIGPIPE is never received in this
>> situation; instead the echo hangs forever. This is what causes it never
>> to process any more commands from nxnode.
>>
>> It is not entirely clear why it happens in this way.
>>
>> Anyway, the workaround is to change echo to /bin/echo. /bin/echo returns
>> immediately if the client is disconnected. Probably it should also check
>> the status and set SERVER_CHANNEL=0 if /bin/echo failed. However I have
>> not bothered to do this. It does not seem to matter a great deal.
>>
>> This solves the problem both with and without slave mode. I think there
>> may still be some sort of timing related potential problem here, but I
>> am not sure, it is all rather complicated.
>>
>> I have also noticed another problem that I thought might be related, but
>> is probably different. If you unplug the network from the currently
>> logged in client, it takes about 30 seconds before nxagent notices that
>> the client is gone and suspends the session. If, in this 30-second
>> window, you login from another client, everything works, but the session
>> status incorrectly remains in suspended state. I guess this is because
>> when the second client logs in, it must suspend the session before
>> restoring it on the new client. Somehow the suspended state of the
>> session is set after the resumed state. I am out of time and this
>> problem is not so serious, so I am ignoring it for now. Maybe someone
>> else has time to look into this one.
>>
>> Anyway, for anyone else who has the present problem, please try the
>> following patch and report back.
>>
>> See the patch below (the line numbers might be a bit off since my file
>> has lots of extra instrumentation):
>>
>> --8<---------------cut here---------------start------------->8---
>> --- nxserver.foo        2009-01-25 16:07:46.590977440 +1300
>> +++ nxserver    2009-01-25 16:07:54.498952944 +1300
>> @@ -967,8 +967,8 @@
>>  server_nxnode_echo()
>>  {
>>        log 6 "server_nxnode_echo: $@"
>> -       [ "$SERVER_CHANNEL" = "1" ] && echo "$@"
>> -       [ "$SERVER_CHANNEL" = "2" ] && echo "$@" >&2
>> +       [ "$SERVER_CHANNEL" = "1" ] && /bin/echo "$@"
>> +       [ "$SERVER_CHANNEL" = "2" ] && /bin/echo "$@" >&2
>>  }
>>
>>  server_nxnode_exit_func()
>> --8<---------------cut here---------------end--------------->8---
>>
>> --
>> Mario Becroft <mb at gem.win.co.nz>
>> ________________________________________________________________
>>     Were you helped on this list with your FreeNX problem?
>>    Then please write up the solution in the FreeNX Wiki/FAQ:
>>
>> http://openfacts2.berlios.de/wikien/index.php/BerliosProject:FreeNX_-_FAQ
>>
>>         Don't forget to check the NX Knowledge Base:
>>                 http://www.nomachine.com/kb/
>>
>> ________________________________________________________________
>>       FreeNX-kNX mailing list --- FreeNX-kNX at kde.org
>>      https://mail.kde.org/mailman/listinfo/freenx-knx
>> ________________________________________________________________
>>
>
>
> ________________________________________________________________
>     Were you helped on this list with your FreeNX problem?
>    Then please write up the solution in the FreeNX Wiki/FAQ:
>
> http://openfacts2.berlios.de/wikien/index.php/BerliosProject:FreeNX_-_FAQ
>
>         Don't forget to check the NX Knowledge Base:
>                 http://www.nomachine.com/kb/
>
> ________________________________________________________________
>       FreeNX-kNX mailing list --- FreeNX-kNX at kde.org
>      https://mail.kde.org/mailman/listinfo/freenx-knx
> ________________________________________________________________
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.kde.org/pipermail/freenx-knx/attachments/20090228/5e0d167e/attachment.html>