Multiple invocations of cron-job AT THE SAME MINUTE on Raspbian

[Ajay Garg]

Hi All.

Sorry for sounding desperate, but it's my earnest request to all the
experts, to kindly shed some light on this.

We are facing issues in field only on the Raspberry-Pi units, while
the units of other types running the exact same startup-script work
perfect.


Thanks and Regards,
Ajay

On Thu, Sep 15, 2016 at 11:08 AM, Ajay Garg <ajaygargnsit at gmail.com> wrote:
> Hi All.
>
> I have a raspbian-pi-3, and following is the first-level information ::
>
> ########################################
> uname -a
> Linux raspberrypi 4.4.11-v7+ #888 SMP Mon May 23 20:10:33 BST 2016
> armv7l GNU/Linux
> ########################################
>
>
>
> Following is the script that is run by the every-minute cron ::
>
> ########################################
> PID=`ps -aux | grep instamsg | grep -v grep | grep -v tail`
>
> if [ -z "${PID}" ]
> then
>     echo "Binary not running"
>     cd /home/sensegrow
>     chmod 777 instamsg
>
>     sleep 3
>     ./instamsg &
> else
>     echo "Binary running fine"
> fi
> ########################################
>
>
>
> Now, things are mostly fine, but very spuriously, I see that multiple
> instances of "instamsg" are spawned, sometimes upto 5, ALL IN THE SAME
> MINUTE.
> The occurrence of such phenomena is like once in a day.
>
> I know there are multiple posts about this on the internet, but all of
> those point to faulty-script(s) that are run as part of cron.
> However, I guess the script I am using is pretty simple, and can never
> be "long-running, longer than a minute".
>
> Please note that I may solve this by using the lock-file mechanism,
> but I wish to know the root-cause, as the same script runs without any
> issues for days the on Maestro-Wireless routers, and Lanner-systems
> running Ubuntu.
>
> In particular, could this be an issue with the cron-daemon code on
> Raspbian-kernel, which could (in spurious cases) spawn multiple
> instances of the same cron-job in the same minute?
>
>
> Thanks and Regards,
> Ajay



-- 
Regards,
Ajay