[Xymon] localmode, got over-size message, truncating

[Christoph Zechner]

On 09/03/2022 00:04, Jeremy Laidman wrote:
> On Tue, 8 Mar 2022 at 18:52, Christoph Zechner <zechner at vrvis.at 
> <mailto:zechner at vrvis.at>> wrote:
> 
>     It seems I celebrated prematurely, the errors are back in exactly the
>     same way :-/
> 
>     2022-03-08 08:47:19.321457 Got over-size message, truncating at 528383
>     bytes (max: 524288)
>     2022-03-08 08:47:19.339786 Dropping (more) garbled data
> 
>     I don't understand where this limit 05 512 comes from, everything on
>     the
>     server checks out (2048 before, tried 4096 as well, no change).
> 
> 
> I'm at a loss. If the xymond process is proven to have this set at 2048, 
> then I see no reason why it would give that error message with that number.
> 
> Unless it's referring to another message type and hence a different 
> maximum setting? Perhaps take a look at xymond's environment again, but 
> search for all MAXMSG_ variables. See which one is set to 512, and that 
> might be the culprit. The defaults for these max values are all 
> different, with only two of them defaulting to 512: MAXMSG_CLIENT, 
> MAXMSG_CLICHG (reference: lib/xymond_buffer.c). But it's possible one of 
> them has been set to 512.

Thanks, I tried that, but unfortunately, this did not help, since all 
the values were set correctly, according to my config.

> 
> The only other thing I can think of is that you have two copies of 
> xymond running, somehow with different values of MAXMSG_CLIENT. But I 
> can't think how this could come about. And you've already killed off any 
> rogue processes.

Right, that's not it either. :-/

> 
> Maybe run xymond in debug mode for one round of updates, until you get 
> the "Got over-size message" and review the debug logs. This might 
> provide enough additional detail to find out what's going on.
> 
> Another approach to solve the problem (truncated client data message) is 
> to modify the client script (eg xymonclient-linux.sh) to truncate the ps 
> command output, so that the total message size is less, and hopefully 
> fits within the max message size. This will mean that PROC checks might 
> not work anymore (which is likely the case now). But the current state 
> is that monitoring of the sections that come after [ps] are likely 
> broken now. On Linux this is notably the [top] and [vmstat] sections of 
> the client data message, that are used for the "cpu" status and several 
> metrics for graphing. Maybe something like adding "head -1000" will cut 
> it down to a reasonable size:
> 
> echo "[ps]"
> ps -Aww -o pid,ppid,user,start,state,pri,pcpu,time,pmem,rsz,vsz,cmd | 
> head -1000

That's actually a gread idea and I modified the [ports] section, because 
I know this is the culprit (running a proxy there and all the active 
client connections were too much for xymon to handle.

I'm not interested in client connections anyway, I just want to monitor 
my running programs and ports on that server, so I replaced the original

netstat -antuW 2>/dev/null
netstat -antuT 2>/dev/null

with

netstat -tulpenW 2>/dev/null

(adding your "| head 1000" suggestion did not work, because it cut off 
the list before it could reach the IPv6 interfaces and thus the ports 
check was always red).

Now xymon works again, although this is just a workaround, because the 
underlying problem of where exactly my messages got truncated, is still 
to be found, but I can live with this solution.

Anyway, I very much appreciate your time and efforts, thank you very much!

Cheers
Christoph

> 
> Also, review the client data message before the [ps] section to see if 
> there's actually something else pushing it over the limit, and [ps] just 
> happens to be where the truncation happens.
> 
> J
>