[FreeNX-kNX] A Fix for the problem of multiple attempts needed to login to FreeNX after a re-boot

[Aidan Marks]

Hi Chris

while there seems to be debate as to the implementation of the fix, it
certainly did resolve this very annoying nx issue for me on gentoo.
thanks for chasing it down.

regards
Aidan

Il 08/04/2010 00:26, chris at ccburton.com ha scritto:
> Some people are reporting having to make several attempts
> to login to FreeNX after a server re-boot, before the first
> successful login takes place.
> 
> After this, things are reported as being fine, until the next
> OS restart.
> ( I'm not sure that this is the full picture, as I'll explain )
> 
> 
> I've had a run through the code, and watched some startups
> Here's what I see happening.
> 
> 
> For a new session, FreeNX runs the nxagent in the 
> background from an instance of nxnode 
> ( node_start_agent & )
>  
>  . . then immediately . .
> 
> runs what it calls "The Application", also in the background,
> ( node_start_applications & )
> 
> The Application can be "startkde" ( or whatever ) for a
> desktop session, or a user application eg. ooo-writer
> for a rootless session.
> 
> Before starting kde, the script runs xrdb -merge which
> is normally launched as part of the X client, startx etc. 
> 
> 
> This is causing a problem, because the xrdb and the
> application, kde ( for example ) are starting before
> the display port is open, failing, and terminating the
> whole FreeNx session, including the agent.
> 
> The reason for this failure is that the script takes 
> some time to launch nxagent, and then nxagent takes
> some time to load its shared libraries, the first time
> it is run.
> 
> These libraries stay in memory, unless thay are flushed
> out, so subsequent logins are quicker and don't fail.
> 
> 
> This is why I say I don't think that the re-boot senario
> is the whole picture.
> 
> In fact, I expect that a machine also used for other tasks
> will, if there is no FreeNX activity, revert to the 
> "multiple login attempts required" state, due to other
> jobs causing unused shared libraries to be flushed out
> of memory.
> 
> No one has reported this however.
> 
> I also expect that xrdb fails quite often.
> 
> It is subsequently run if needed by the kde session after
> it is started, and it is possible that things have only been
> working up to now because of the delay caused by 
> the launching of xrdb.
> 
> Note.
> 
> The reason it takes several runs to complete is that although
> the nxagent is terminated after part loading its libraries, any
> libraries which have been loaded are available for the next
> attempt, which can therefore get a little nearer to completion.
> 
> After a few tries, they are all in memory, and no more
> issues.
> 
> 
> The fix is very simple.
> 
> The rule is very golden.
> 
> When backgrounding a script to launch something upon which
> something else depends, bear in mind that the the script launch
> will return straight away, then continue with the load. 
> 
> To emulate synchronous launching, a delay must be introduced.
> 
> 
> 
> Patch for nxnode 0.7.3
> 
> Watch out for line wraps messing up the diff.
> 
> It will probably be easier to look for xrdb -merge in an editor
> and add the sleep.
> 
> --- nxnode.orig 2008-11-28 12:18:13.000000000 +0000
> +++ nxnode.mod  2010-04-07 14:44:18.000000000 +0100
> @@ -328,6 +328,9 @@
>                 NODE_WM_PID=$!
>         fi
> 
> +       # Patch - delay to allow nxagent to complete lauching. ccb 
> 20100407
> +       sleep 4
> +
>         echo "Xft.dpi: 96" | DISPLAY=:$display xrdb -merge 
>>> "$USER_FAKE_HOME/.nx/C-$sess_id/session" 2>&1
>         [ -d /etc/X11/Xresources ] && xrdb -display :$display -merge 
> /etc/X11/Xresources/* >>"$USER_FAKE_HOME/.nx/C-$sess_id/session" 2>&1
> 
> 
> 
> If this works for you, please let us know so the next 
> people with this problem have some idea if it is a fix
> for them or not !!
> 
> If it doesn't work I'm sure you will say something!!
> 
> 
> cb
> 
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> 
> ________________________________________________________________
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> 
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>   
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