On 31 August 2016 at 23:25, Cyril Brulebois <k...@debian.org> wrote: > So it looks to me like it could be an initial DNS issue (partial and/or > no resolution depending on the domain) which happened at start-up time, > and failed/incomplete resolutions weren't attempted again later on. > > Would this seem even remotely plausible?
Yes, this is plausible. I've seen this issue before on some servers, but I haven't been able to track it down to a cause. One theory is that if you log into a freshly-started server, and you have a lot of contacts on remote domains, it triggers a burst of DNS requests. DNS being UDP, which is lossy, some of the DNS requests fail due to packet loss caused by temporary network congestion. Whether that theory is plausible I'm not sure - it doesn't seem like it would be *that* much traffic to deal with. Perhaps there are some queue sizes or something we could tweak if that is the problem though. Eventually the failed s2s connections do establish - they will be retried as soon as you change status for example, or if any of your remote contacts change status or try to send you a message.
