[FreeNX-kNX] load balancing + shadowing?

[Julie Ashworth]

hi all,
I maintain some linux workstations at UC Berkeley, and
would really like to use shadowing and load-balancing
simultaneously.
I can use them independently, but shadowing fails when
I try to use it with load-balancing. 

Below is a working config (i.e. node.conf) on a 
freenx-0.7.3-3.el5.centos server (w/ no load-balancing);
DISPLAY_BASE=1000
SESSION_LOG_CLEAN=0
NX_LOG_LEVEL=6
NX_LOGFILE=/var/log/nxserver.log
SESSION_HISTORY=604800
ENABLE_SESSION_SHADOWING_AUTHORIZATION=0
ENABLE_INTERACTIVE_SESSION_SHADOWING=0

(I disabled auth checking and interactive sessions while
testing.)

On my load-balancing gateway server 
(freenx-0.7.3-2.el5.centos) I have the same config as 
above, plus the following:
LOAD_BALANCE_SERVERS="10.0.1.1 10.0.1.2"
LOAD_BALANCE_ALGORITHM="load"


The steps I use to shadow a session (using the load-
balancer config) are:

start a nx session as user 'julie', which starts 
successfully on 10.0.1.1:1353.
Just for kicks, I run 'xhost +' in a terminal window in 
that session. 
Then I open another nx session (I try as both 'julie', and 
a different user) with the settings: 
Desktop: Shadow, 
Display: 'As on the server'. 
I am prompted for the session to shadow, and I choose 1353
display.
The session fails w/o any information on the screen. In the
logs, I see the following:

NXCreatePoller: WARNING! Failed to initialize poller.
NXShadowCreate: WARNING! NXCreatePoller failed.
Error: Aborting session with 'Failed to connect to display '10.0.1.1:1353''.

I cannot find any reference to 'NXCreatePoller' or 
'NXShadowCreate' in the nx scripts (which are installed in 
/usr/bin):
# egrep "NXCreatePoller|NXShadowCreate" /usr/bin/nx*
# strings /usr/bin/nxserver-helper | egrep "NXCreatePoller|NXShadowCreate" 


Some additional information:
Running 'nxdialog' from the load-balancing gateway to the 
nx session (10.0.1.1:1353) fails, even after running 'xhost +',
e.g.:
[root at nxgw ~]# nxdialog -display 10.0.1.1:1353 -dialog yesno
Error: Can't open display: 10.0.1.1:1353

I get mixed results when I open a terminal session (via ssh) to 
10.1.1.1, and run nxdialog. (It fails when I include the IP 
address as an argument to the display option):
[root at 10.0.1.1]# nxdialog -display 10.0.1.1:1353 -dialog yesno
/usr/bin/Xdialog: Error initializing the GUI...
Do you run under X11 with GTK+ v1.2.0+ installed ?

[root at 10.0.1.1 ~]# nxdialog -display :1353 -dialog yesno
works fine

At this point, I'm not sure if I should spend more time on 
this ;P. I may provide information about how to use nxssh as a 
tunnel (to avoid the load-balancer), e.g.
# nxssh -o 'Compression=no' -L 2221:10.0.1.1:22 -f -N <loadbalancer>
...but this isn't ideal, and  probably too complicated for most. 

Thanks in advance for any advice.
Best,
Julie


-- 
Julie Ashworth <julie.ashworth at berkeley.edu>
Computational Infrastructure for Research Labs, UC Berkeley 
http://cirl.berkeley.edu/
PGP Key ID: 0x17F013D2