Re: new wifi connection = nntp timeout = Emacs restart?

[Eric Abrahamsen <eric@ericabrahamsen.net>]

Robert Pluim <rpluim@gmail.com> writes:

>>>>>> On Mon, 20 Apr 2020 08:45:06 -0700, Eric Abrahamsen <eric@ericabrahamsen.net> said:
>
>     Eric> Andreas Schwab <schwab@linux-m68k.org> writes:
>     >> On Apr 19 2020, Eric Abrahamsen wrote:
>     >>
>     >>> I just started watching Emacs' nntp connections, and immediately noticed
>     >>> that closing all servers ("z")
>     >>
>     >> Why do you think that gnus-group-suspend closes servers?
>     >> gnus-close-all-servers does.
>
>     Eric> Because gnus-group-suspend literally includes all the code in
>     Eric> gnus-close-all-servers...
>
> It even says:
>
>     ;; Closing all the backends is useful (for instance) when when the
>     ;; IP addresses have changed and you need to reconnect.

Okay, progress! Glad I'm inflicting this on all of you in the group,
rather than embarrassing myself in a bug report.

First of all, refreshing Gnus after moving to a new wifi network showed
the nntp connection going from this:

tcp 0 0 192.168.1.39:42194 159.69.161.202:nntp users:(("emacs",pid=143327,fd=18)) timer:(keepalive,94min,0)

to this:

tcp 0 1558 192.168.1.39:42194 159.69.161.202:nntp users:(("emacs",id=143327,fd=18)) timer:(persist,4.800ms,3)

Dunno if that means anything!

But left-behind nntp connections don't seem to be the source of the
problem: Once Gnus fails to reconnect, and I hit "g" again, all the old
connections are killed. (FWIW, I'm still pretty sure it's a bug that
gnus-suspend and close-servers don't kill the nntp connection, there
should never be more than one per server.) So my original hunch was
wrong, as most of my hunches seem to be.

Edebugging `nntp-open-connection', it turns out the condition-case, with
nnheader-report in the error clause, was swallowing real errors -- it
never occurred to me to ask the nntp server for its "report string". The
first error I saw was:

nntp-with-open-group-function: Wrong type argument: stringp, nil

which is my favorite Gnus error. i'm not sure where that came from. The
real problem seems to be:

(error "news.gmane.io/nntp Temporary failure in name resol...")

And I think that's our culprit! The DNS lookup fails, and continues to
fail until I restart Emacs. So I'm assuming Emacs has some sort of dns
caching going on, or something, that presumably we could flush if we
wanted to.

I'm going to leave this here for a day or two, then open a proper bug
report.

E