"Discarding timed-out partial msg" Error Messages
Hi J.C.,
Thanks for the e-mail and advice!
A couple of questions:
What's the default --lqueue value that Xymon uses? (Is there a way to see what it's using?)
What exactly is your definition of "tons of simultaneous connections" here? Can you give me a number or range that you think would warrant increasing the --lqueue value?
Could it be from clients/senders with longer than usual process listings? Or other clientlog statistics? (But still under the max client message value.)
How would I be able to tell if there are long messages being sent in if the long messages are being discarded?
The clients/senders are all different and there doesn't seem to be a pattern that I can see. Some hosts are showing up more then once though. All the connections to these machines SHOULD be coming in at the same connection speed....
I'm not seeing any network issues over any of our switches. And I'm not seeing any significant or unusual network traffic on the machines in question around the time of the time-out error messages (although it could be a very brief spike in traffic that isn't being seen since the status message is being discarded).
I'll definitely look into the possibility of doing some TCP tuning on the Xymon server machine!
Thanks again!
-- Matt Vander Werf
On Tue, Nov 24, 2015 at 3:17 PM, J.C. Cleaver <cleaver at terabithia.org> wrote:
On Tue, November 24, 2015 6:29 am, Matt Vander Werf wrote:
Hey all,
Lately, I've been seeing quite a few error messages show up in xymond indicating that it was discarding a timed-out partial message from some machine.
i.e.
Latest error messages: Discarding timed-out partial msg from X.X.X.X
They seem to be happening sporadically but more often than usual as of late. Maybe one or two every couple of days or so. They don't seem to be coming from the same machine/machines either.
Is this something I should be worried about? Are there any side-effects from this happening too much?
What are the causes of this happening? Any way to make it not happen as much?
Any ideas or advice is greatly appreciated!
Thanks!!
Broadly speaking, this is a result of the entire message not making it in in the time allotted by xymond, which is 10s by default. It could be the result of network congestion issues or packet loss, slow sender performance, or slow xymon server performance.
A quick fix might be to increase the --timeout= option to xymond to something like 15 or 20s.
If a netstat shows tons of simultaneous connections, you could also increase --lqueue= to 768 or 1024.
Are there any patterns on the clients/senders that are affected? Unusually huge messages being sent over slow connections?
If there isn't a network issue per se, and there are no local network errors (or you're seeing the reports about messages from all over the place), then it's time to look at network performance tuning on the xymon box. Consider the various tcp* options via sysctl (recycle and reuse in particular). If xymonnet is running on the same system (and you're doing) high concurrency testing, be sure to increase your ip_local_port_range for outbound connections.
http://www.lognormal.com/blog/2012/09/27/linux-tcpip-tuning/ is a nice resource for that.
HTH,
-jc
Hi Matt,
Sorry for the delay. Had some unexpected time away from the keyboard this weekend.
Responses inline.
On Fri, December 4, 2015 3:49 am, Matt Vander Werf wrote:
Hi J.C.,
Thanks for the e-mail and advice!
A couple of questions:
What's the default --lqueue value that Xymon uses? (Is there a way to see what it's using?)
What exactly is your definition of "tons of simultaneous connections" here? Can you give me a number or range that you think would warrant increasing the --lqueue value?
The default is 512, which is compiled in. This really won't need to be increased unless xymond is being bogged down with lots of *literally* simultaneous waiting connections. It can be increased, but there's probably another sort of problem happening: either slow connectivity, high CPU load, or "backpressure" from too many channel workers causing xymond itself to be unable to keep up. I'm trying to think back and I don't think I had cause to increase it until SN was regularly hitting the 2500 msgs/s range, and it was lowered back down once other performance bottlenecks and some packet loss were identified.
Try stracing xymond and seeing what it's doing. If there's a lot of waiting happening for network reading, that might be a sign that lqueue increasing could help. 768 or 1024 should be more than sufficient. Anything more than that except at bursts means there's some other backlog.
Could it be from clients/senders with longer than usual process listings? Or other clientlog statistics? (But still under the max client message value.)
It's possible, but unless you're bandwidth restricted somewhere senders should generally still be able to complete in the default time frame. If you *are* bandwith restricted then that's definitely something to consider, especially if the machines you're having problems with have a lot of burst network activity. (Speaking of burst network activity, try commenting out the 'netstat' output in the client if you don't have any port checks against the host.)
How would I be able to tell if there are long messages being sent in if the long messages are being discarded?
Yeah, this should probably be added in. Truncated messages have their first line displayed, but it's not so much a 'discard' here as it is a network timeout first and foremost.
An strace with the -s 4096 (or some high number) might be able to catch the first bit of a read from the client if you're lucky there...
HTH, -jc
participants (2)
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cleaver＠terabithia.org
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matt1299＠gmail.com