Issue: PulseAudio command working with console but not in Exec node

[janedoe123]

Hi All,

I'm having an issue that I'm not able to fix when using a | (pipe) in an exec node. The full command I am trying to exec is:

pactl load-module module-loopback latency_msec=1 source=2 sink=1 | multimon-ng -a DTMF /dev/stdin

But the command will not get executed and the error message thrown is:
Failure: Module initialization failed

However if I just exec the below command in the exec node, it works:
pactl load-module module-loopback latency_msec=1 source=2 sink=1

And if I just exec the below command in the exec node, it also works:
multimon-ng -a DTMF

So I tried the above two commands that are failing in node-red, by executing them directly in the console. Both work:

pi@raspberrypi:~ $ pactl load-module module-loopback latency_msec=1 source=2 sink=1 | multimon-ng -a DTMF /dev/stdin
multimon-ng 1.1.8
  (C) 1996/1997 by Tom Sailer HB9JNX/AE4WA
  (C) 2012-2019 by Elias Oenal
Available demodulators: POCSAG512 POCSAG1200 POCSAG2400 FLEX EAS UFSK1200 CLIPFSK FMSFSK AFSK1200 AFSK2400 AFSK2400_2 AFSK2400_3 HAPN4800 FSK9600 DTMF ZVEI1 ZVEI2 ZVEI3 DZVEI PZVEI EEA EIA CCIR MORSE_CW DUMPCSV X10 SCOPE
Enabled demodulators: DTMF

So I suspect the exec-node does not handle the pipe properly.

I hope someone has faced the same issue and can help me.

PS: It is not a matter of appending the msg.payload as I am even trying by passing the entire command manually in the exec node to make sure the command is executed properly.

Thanks all

[Colin]

Welcome to the forum @janedoe123

I am not at my computer so cannot test at the moment. Have you tried a simple command with pipe such ascat piping into grep to check that it is the pipe that is the problem?

[Steve-Mcl]

It is more likely an environment thing.

How do you launch node-red? From command line terminal? run as a service? PM2?

Also, what account runs node-red?

Try adding this flow - what do you see in debug window?

printenv...

[{"id":"67000189.da769","type":"inject","z":"5e6c8b.7f38b374","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":1420,"y":880,"wires":[["7e0062b2.c73adc"]]},{"id":"7e0062b2.c73adc","type":"exec","z":"5e6c8b.7f38b374","command":"printenv","addpay":false,"append":"","useSpawn":"false","timer":"","oldrc":false,"name":"","x":1578,"y":880,"wires":[["bd65cfa7.0626a"],[],[]]},{"id":"bd65cfa7.0626a","type":"function","z":"5e6c8b.7f38b374","name":"","func":"var lines = msg.payload.split(\"\\n\")\nvar envvars = {};\nfor(let i = 0; i < lines.length; i++) {\n    let line = lines[i];\n    let parts = line.split(\"=\");\n    envvars[parts[0]]=parts[1];\n}\nmsg.payload = envvars;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","x":1754,"y":880,"wires":[["36b59d59.44c5a2"]]},{"id":"36b59d59.44c5a2","type":"debug","z":"5e6c8b.7f38b374","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":1924,"y":880,"wires":[]}]

then from a terminal where your command works, enter printenv - how do the env vars differ?

lastly,

stop node-red service (assumption) and from the terminal where your command works, enter node-red to start up node-red. run the above flow once more - do the correct env vars appear this time?

If so, then you can modify the service to include extra env vars required.

[janedoe123]

Thank you Steve !

Node-RED is automatically launched on boot.

Standard user runs Node-RED (in my case, it is "pi" account as I am use a Raspberry Pi), I have checked in the service file.

Running your flow gives the below result:

And executing printenv in the console where the command works gives:

The only difference I can see is SHLVL=1 in the console, and SHLVL=0 in node-RED.

The environment vars seem to be ok... Is there something I am missing out?

[Steve-Mcl]

@janedoe123

SHLVL=1 in the console, and SHLVL=0 in node-RED.

I dont think the Shell Level will matter.

@janedoe123

The environment vars seem to be ok... Is there something I am missing out

Hmm, there are also a few env vars missing (NO_AT_BRIDGE, XDG_SESSION, DISPLAY, LC_ALL, DBUS_SESSION) and slight difference in path (that shouldnt matter tho) - one of these might be important to the execution?

Did you try Colins simple pipe test to rule that out?

[dceejay]

A simple ps -ef | grep node works fine so no not an issue with exec node and pipe.

[janedoe123]

Thanks Steve,

Indeed there are few env vars missing: NO_AT_BRIDGE, XDG_SESSION, DISPLAY, LC_ALL, DBUS_SESSION

The cat | grep command works as suggested by Colin:

So the question is: How to add the missing env vars to make sure they are taken into account by Node-RED?

[janedoe123]

@janedoe123

NO_AT_BRIDGE, XDG_SESSION, DISPLAY, LC_ALL, DBUS_SESSION

Indeed. Do you know how to add the missing end vars NO_AT_BRIDGE, XDG_SESSION, DISPLAY, LC_ALL, DBUS_SESSION in order to make sure my command is executed?

[Steve-Mcl]

@janedoe123

in order to make sure my command is executed

Just a heads up - this is only a suggestion & may not be the cause/fix (i.e. lets rule out env vars before digging)

As a quick and dirty test, you could set the env vars before the command in the exec node e.g. export DISPLAY=:0 _MY_COMMAND_XXXX YYYY ZZZZ

e.g. if you change my demo flow to exec DISPLAY=:0 printenv you will see DISPLAY is now one of the env vars.

[janedoe123]

I just ran into this post from knolleary

Nov '19

One way of setting environment variables is in your settings.js file.

The following will set the env var MY_ENV_VAR :

process.env.MY_ENV_VAR = "Hello World";

You can add lines like that to the top of your settings file.

---

Does it mean I need to force them all in settings.js ?

[Steve-Mcl]

I dont think that setting env vars in settings.js will cause exec to inherit them - I am pretty sure thats for function nodes / change nodes to access additional variables about its "env".

I might be wrong though - you could always try modifying settings.js, re-run the flow i posted - does printenv show your new variables?

[janedoe123]

@Steve-Mcl

NO_AT_BRIDGE, XDG_SESSION, DISPLAY, LC_ALL, DBUS_SESSION

Here is what I just tried in the exec node. The command is successfully executed:
multimon-ng -a DTMF

However if I force the below env var in the exec node, with exactly the same command, it fails with the node returning rc:-2:
NO_AT_BRIDGE=1 XDG_SESSION_TYPE=tty DISPLAY=:0 LC_ALL=en_US.UTF-8 DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus multimon-ng -a DTMF

I've tried the env var one by one, same result:
NO_AT_BRIDGE=1 multimon-ng -a DTMF
XDG_SESSION_TYPE=tty multimon-ng -a DTMF
DISPLAY=:0 multimon-ng -a DTMF
LC_ALL=en_US.UTF-8 multimon-ng -a DTMF
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus multimon-ng -a DTMF

Am I doing something wrong?

[janedoe123]

Ok so I have tried something else.

In the console, I am executing the below comand:

pi@raspberrypi:~ $ pactl load-module module-loopback latency_msec=1 source=1 sink=0 | multimon-ng -a DTMF /dev/stdin

It is successfully working:

multimon-ng 1.1.8
  (C) 1996/1997 by Tom Sailer HB9JNX/AE4WA
  (C) 2012-2019 by Elias Oenal
Available demodulators: POCSAG512 POCSAG1200 POCSAG2400 FLEX EAS UFSK1200 CLIPFSK FMSFSK AFSK1200 AFSK2400 AFSK2400_2 AFSK2400_3 HAPN4800 FSK9600 DTMF ZVEI1 ZVEI2 ZVEI3 DZVEI PZVEI EEA EIA CCIR MORSE_CW DUMPCSV X10 SCOPE
Enabled demodulators: DTMF

If I try to launch the very same command using Node-RED and having a look at the logs, I am getting the below error message:

Failed to parse module arguments
Failed to load module "module-loopback" (argument: "latency_msec=1 source=1 sink=0 | multimon-ng -a DTMF /dev/stdin"): initialization failed.
^C

I also found a similar thread here: Exec Node and Terminal Problem ( Alsa)
Not sure it is related to the same issue...

I am really clueless... Why would it work with the console, and not node-Red ?

[janedoe123]

Ok folks,

I think I got it work but I don't know why... Is this a bug in node-red ?

I took the command pactl load-module module-loopback latency_msec=1 source=1 sink=0 | multimon-ng -a DTMF /dev/stdin and created a pulse.sh script as follows:

#!/bin/sh

pactl load-module module-loopback latency_msec=1 source=1 sink=0 | multimon-ng -a DTMF /dev/stdin

In the node-red exec node, I am calling the pulse.sh as follows:
/home/pi/Documents/pulse.sh

Guess what ? It works!

I really don't know why... That's worrying actually... Does anyone have any idea?

[janedoe123]

Small up Is this a Node-Red bug?

PS: I haven't even added/modified any env var for that to work.

[9886815d5d5c584c03d8]

I was having trouble with pulseaudio commands from the exec node and found that it was an environment issue.

To solve it i used... XDG_RUNTIME_DIR=/run/user/1000 pactl info

This worked on a headless Raspberry Pi and my desktop machine.