Why my shell script is in standby in the background till I bring it back on the foreground? - bash

Question

I have a shell script which is executing a php script (worker for beanstalkd).
Here is the script:
#!/bin/bash
if [ $# -eq 0 ]
then
echo "You need to specify an argument"
exit 0;
fi
CMD="/var/webserver/user/bin/console $#";
echo "$CMD";
nice $CMD;
ERR=$?
## Possibilities
# 97 - planned pause/restart
# 98 - planned restart
# 99 - planned stop, exit.
# 0 - unplanned restart (as returned by "exit;")
# - Anything else is also unplanned paused/restart
if [ $ERR -eq 97 ]
then
# a planned pause, then restart
echo "97: PLANNED_PAUSE - wait 1";
sleep 1;
exec $0 $#;
fi
if [ $ERR -eq 98 ]
then
# a planned restart - instantly
echo "98: PLANNED_RESTART";
exec $0 $#;
fi
if [ $ERR -eq 99 ]
then
# planned complete exit
echo "99: PLANNED_SHUTDOWN";
exit 0;
fi
If I execute the script manually, like this:
[user#host]$ ./workers.sh
It's working perfectly, I can see the output of my PHP script.
But if I detach the process from the console, like this:
[user#host]$ ./workers.sh &
It's not working anymore. However I can see the process in the background.
[user#host]$ jobs
[1]+ Stopped ./workers.sh email
The Queue jobs server is filling with jobs and none of them are processed until I bring the detached script in the foreground, like this:
[user#host]$ fg
At this moment I see all the job being process by my PHP script. I have no idea why this is happening. Could you help, please?
Thanks, Maxime
EDIT:
I've create a shell script to run x workers, I'm sharing it here. Not sure it's the best way to do it but it's working well at the moment:
#!/bin/bash
WORKER_PATH="/var/webserver/user/workers.sh"
declare -A Queue
Queue[email]=2
Queue[process-images]=5
for key in "${!Queue[#]}"
do
echo "Launching ${Queue[$key]} instance(s) of $key Worker..."
CMD="$WORKER_PATH $key"
for (( l=1; l<=${Queue[$key]}; l++ ))
do
INSTANCE="$CMD $l"
echo "lnch instance $INSTANCE"
nice $INSTANCE > /dev/null 2> /dev/null &
done
done

Answer 1

Background processes are not allowed to write to the terminal, which your script tries to do with the echo statements. You just need to redirect standard output to a file when you put it to the background.
[user#host]$ ./workers.sh > workers.output 2> workers.error &
(I've redirected standard error as well, just to be safe.)