[pulseaudio-discuss] Can PulseAudio "automatically start" jackd?

[Jaime T]

Hi all.

As per "man jackd", "JACK is evolving a mechanism for automatically
starting the server when needed. Any client started without a running
JACK server will attempt to start one itself...". I've got a laptop
running Debian 9 (Stretch) and this "automatic starting" mechanism for
jack works perfectly. I know this because "ps aux | grep -i jackd"
returns:

nonroot  10609  0.0  0.0   4728   852 pts/4    S+   01:08   0:00 grep -i jackd

before I run jack-play,

nonroot  10640  8.3  3.9  83412 82100 ?        SLsl 01:11   0:00
/usr/bin/jackd -T -ndefault -T -d alsa
nonroot  10650  0.0  0.0   4728   828 pts/4    S+   01:11   0:00 grep -i jackd

while I am running jack-play, and:

nonroot  10658  0.0  0.0   4728   836 pts/4    S+   01:12   0:00 grep -i jackd

(again) after jack-play has terminated.

I thought that pulseaudio might be able to use this autostart
mechanism, so I've installed pulseaudio-module-jack, but when I run
"pactl load-module module-jack-sink channels=2", I get either:
"Failure: Module initialization failed" or "Module load failed.", and
"tail -f /var/log/syslog" returns something like:

Nov 11 01:52:07 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >JACK died - calling shutdown handler<
Nov 11 01:52:29 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >connect(2) call to
/dev/shm/jack-1000/default/jack_0 failed (err=No such file or
directory)<
Nov 11 01:52:30 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >connect(2) call to
/dev/shm/jack-1000/default/jack_0 failed (err=No such file or
directory)<
Nov 11 01:52:31 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >connect(2) call to
/dev/shm/jack-1000/default/jack_0 failed (err=No such file or
directory)<
Nov 11 01:52:32 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >connect(2) call to
/dev/shm/jack-1000/default/jack_0 failed (err=No such file or
directory)<
Nov 11 01:52:33 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >connect(2) call to
/dev/shm/jack-1000/default/jack_0 failed (err=No such file or
directory)<
Nov 11 01:52:34 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >connect(2) call to
/dev/shm/jack-1000/default/jack_0 failed (err=No such file or
directory)<
Nov 11 01:52:35 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: JACK error >attempt to connect to server failed<
Nov 11 01:52:35 piano pulseaudio[887]: [pulseaudio]
module-jack-sink.c: jack_client_open() failed.
Nov 11 01:52:35 piano pulseaudio[887]: [pulseaudio] module.c: Failed
to load module "module-jack-sink" (argument: "channels=2"):
initialization failed.

Note that if I explicitly (manually) start jackd *before* running
"pactl load-module module-jack-sink channels=2", then all is good.

I have also found
https://docs-old.fedoraproject.org/en-US/Fedora/16/html/Musicians_Guide/sect-Musicians_Guide-Integrating_PulseAudio_with_JACK.html
which makes me think that this *should* work (it includes the words
"When PulseAudio starts JACK").

My question is: is pulseaudio's "not automatically starting" jackd
expected, or is it a bug?

Thank you for your help. Jaime