bug#53580: /var/run/shepherd/socket is missing on an otherwise functional system

[Attila Lendvai <attila@lendvai.name>]

the systems seems to work fine. Gnome is up, i can log in with my user, and everything seems to work, except herd.

i encounter this broken state every once in a while. IRC logs also mention this multiple times, but without many insights:

https://logs.guix.gnu.org/guix/search?query=%2Fvar%2Frun%2Fshepherd%2Fsocket

```
# herd status
error: connect: /var/run/shepherd/socket: No such file or directory

# ps afxu | grep shepherd
root         1  0.0  0.3 160788 43684 ?        Sl   11:51   0:00 /gnu/store/cnfsv9ywaacyafkqdqsv2ry8f01yr7a9-guile-3.0.7/bin/guile --no-auto-compile /gnu/store/vza48khbaq0fdmcsrn27xj5y5yy76z6l-shepherd-0.8.1/bin/shepherd --config /gnu/store/q4nd803lxrlkr60s8sx88gvpb6c7lxyd-shepherd.conf

# uptime
12:26:44  up   0:34,  2 users,  load average: 0.00, 0.01, 0.00
```

looking at shepherd's code:

```
(define (call-with-server-socket file-name proc)
  "Call PROC, passing it a listening socket at FILE-NAME and deleting the
socket file at FILE-NAME upon exit of PROC.  Return the values of PROC."
  (let ((sock (open-server-socket file-name)))
    (dynamic-wind
      noop
      (lambda () (proc sock))
      (lambda ()
        (close sock)
        (catch-system-error (delete-file file-name))))))
```

maybe this is caused by some call/cc magic that causes an unwind that deletes the file, but then continues?

--
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
“Above all, do not lose your desire to walk: Every day I walk myself into a state of well-being and walk away from every illness; I have walked myself into my best thoughts, and I know of no thought so burdensome that one cannot walk away from it.”
	— Søren Kierkegaard (1813–1855)