Thank you, actually I found out about this behaviour just after I posted here. Strangely, I don't see tcp connections with either nslookup of dig, though response is about 860 bytes, but UDP outgoing traffic is present. When I probe with blackbox there is also tcp.
How blackbox performs such probes? In parallel or successively? Is there a way to suspend such behaviour, analogue to +notcp option of dig? On Thursday, August 25, 2022 at 2:03:27 PM UTC+10 [email protected] wrote: > DNS lookups will switch to TCP if the response is larger than can fit in a > single packet. But that should happen immediately. > > > > On Thu, Aug 25, 2022 at 5:56 AM terrible person <[email protected]> > wrote: > >> Hi. I'm currently debugging DNS Lookup warnings (more that 3 sec) and >> need to figure out whether our network/our DNS/or exporter is misbehaving. >> So I'm checking ssh endpoints with tcp module: >> >> [image: 2022-08-25_13-22-13.png] >> >> but experience 3+ seconds delay on resolving ssh hostnames, which >> triggers alerts DNSLookupDuration3s. >> >> [image: 2022-08-25_13-26-19.png] >> problem looks something like this on different hosts - 3.0s+ seconds of >> timeout, which looks very much like a generic tcp timeout. >> >> I checked on DNS server and yes, after UDP queries there is a TCP DNS >> query for A record. I don't see any UDP checksum corruption or delays for >> such failover. Is this intended? Can someone help me out on this. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Prometheus Users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/prometheus-users/16d8f137-a7e3-4361-a624-6719d71b1d29n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/prometheus-users/16d8f137-a7e3-4361-a624-6719d71b1d29n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "Prometheus Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/prometheus-users/5f7bc297-5130-433b-b70c-6de34186a9e8n%40googlegroups.com.
