handling inotify based cases in older upstart withouut file bridge.

[Suvir Bhargav]

Hi,

I have a update job for updating the system (let's say it engine for now). Now i need to invoke it during wifi up only. On other states, update job must be in stop state.
The problem is my system is pretty old and i don't have access to nice upstart-file-bridge. Hence i'm calling a script from the job to chehck for status and controlling the update job from the script itself.

For the whole sc, i have two jobs and one script. as:

The engine job .conf file:
------------------------------------------------------------------------------

# engine update
#
# Takes care of updating of the system.

description     "engine update"

# removing start, it will be started by wifi-job
#start on file FILE_PATH=/var/run/engine/wifiState and started engine
stop on stopped engine or rw_mode

respawn# sinnce its a network job, hence keeping it respawn
respawn limit 10 5

------------------------------------------------------------------------------


Chechk wifi_status job
------------------------------------------------------------------------------

start on started engine
stop on stopped engine or rw_mode



respawn
respawn limit 10 5

script
        sleep 10;
        /etc/engine/wifi_update.sh
end script

------------------------------------------------------------------------------



And, finally the wifi_update.sh script which basically chehcks for the status and calls engine update job.
------------------------------------------------------------------------------------------------------------------------------------------------------------


#!/bin/bash
# we check for wifistate and stop/start service based on it.

WIFI_FILE='/var/run/engine/wifiState' #chehck the status here

function update_onwifi () {
    if grep -q "^up" /var/run/engine/wifiState && \
       initctl status engine | grep -q "start/running"
    then
        start engine-update
    elif grep -q "^down" /var/run/engine/wifiState; then
        stop engine-update
    fi
}

#check if inotify-tools is installed
type -P inotifywait &>/dev/null || { echo "inotifywait command not found."; }


# it takes some time for wifi status to appear. so we read the directory for changes.
while inotifywait --format '%f' -e modify,attrib,close_write,move,create,delete /var/run/engine/ ; do


# it takes some time after boot for the file to appear, hence check.
if [ -f "$WIFI_FILE" ]; then
        # we basically chehck everytime someone touch the directory var/run/engine.
        update_onwifi
else
        echo "$WIFI_FILE not found."
fi

done
------------------------------------------------------------------------------------------------------------------------------------------------------------


Upon boot, my wifi status job keeps respwaning as it says it has been terminated. I tested the script independently and it works fine.
May be my appraoch to handle inotify case isn't the right one. Would be happy if someone has any suggestion


/Suvir

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