[Xymon] Intermittent HTTP Status 0 - Reason?

Jeremy Laidman jeremy at laidman.org
Sat Aug 4 18:13:30 CEST 2018

This may indicate an SSL negotiation failure or timeout. Running tcpdump
may confirm a timeout.

Packets from an SSL session can be inspected in Wireshark and ssldump, if
you can get access to the private key.

If this happens only a few times a week, you may want to just use
"DELAYRED" (see hosts.cfg) to allow xymonnet to try again a minute later.


On 2 July 2018 at 20:53, Jonas Weber <mail at jonasw.de> wrote:

> Hello,
> in our Xymon installation we are experiencing red HTTP status 0 alerts
> repeatedly, about a few times per week. This phenomenon started appearing
> when we switched the backend from Apache to nginx. The monitored service is
> checked over an SSL connection, making tcpdump et al. difficult to use.
> Additionally, this only appears on our production monitoring; a secondary
> installation with only this check does not show this issue. So, debug
> logging isn't really feasible, either (although I've tried).
> At this point, we are quite certain that it is a monitoring artifact and
> not a problem of the service, as there are no errors on the nginx side of
> things, and no customers have complained, either.
> I've looked in the code of xymonnet. I think status code 0 might mean that
> no HTTP/1.x response has been received, or at least that Xymon was unable
> to parse it. Is that correct? Does/did anybody else face this problem?
> Best regards,
> Jonas
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> Xymon at xymon.com
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