Try adjust LimitNOFILE on systemd unit
If this will help then create ticker and i will create PR
Example

чт, 28 сент. 2017 г. в 8:51, Jurijs Ivolga <jurijs.ivolga@gmail.com>:
Hi Guys,

I recently tried to use Debian Stretch in production and it didn't went well. On load(500k-700k SIP messages per day) I get a problem that at some point there was a pike of CLOSE_WAIT connections(up to 2k of CLOSE_WAIT connections) and no new connections was possible, I tried to figure out where problem is, but I didn't found anything in system or Kamailio logs, Kamailio just stopped to receive traffic via TCP, but UDP continued to work. Test environment where was no load I didn't faced such issue.

Just curious is there anybody who are using Debian Stretch in production without issues?

Jurijs
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