[tor-relays] Failing because we have 4063 connections already // Number of file descriptors

[Ralph Seichter]

Since a couple of days ago, one of my relay nodes keeps logging messages
like this:

  Tor[3534]: Failing because we have 4063 connections already. Please
  read doc/TUNING for guidance. [over 16000001 similar message(s)
  suppressed in last 21600 seconds]

I found https://trac.torproject.org/projects/tor/ticket/16929 and an
older mailing list thread (and doc/TUNING) that suggest increasing the
maximum number of open file descriptors. I now use

  # /etc/security/limits.conf
  *  -  nofile  65535

to raise 'nofile' from 1024 to 65535, which does not seem to make any
difference (the logged error message does not change).

My relay uses Gentoo Linux kernel version 4.14.5 and Tor 0.3.2.6 alpha.
I also tried older versions of the kernel and Tor 0.3.1.9, in several
combinations, without success. I also other relays running just fine
with the default number of file descriptors (1024).

As I mentioned, the problems started a few days ago, around the time I
upgraded from Gentoo system profile default/linux/amd64/13.0 to
default/linux/amd64/17.0, rebuilding many system packages in the
process. Unfortunately I cannot tell what exactly changed. Since the
profile upgrade was deliberate and I cannot roll back, I wonder if
I can overcome Tor's problems via configuration options only?

-Ralph