Re: [gpsd-users] Control Gpsd

[Alexander Carver]

There's no guarantee that the PID file will go away if gpsd stops.

On 2016-03-15 10:59, bruno suarez wrote:
> Another solution without programming is to use watchdog and monitoring
> the pid file of gpsd
> 
> This works for me, if gpsd stops the system reboot
> 
> Bruno
> 
> Le 15/03/2016 18:01, bruno suarez a écrit :
>> Thanks for the help.
>> This is a good start for me ...
>> I'll try this, I think in the script (cron) I will restart Pi directly
>> because if there is a problem it may be the receiver or other items
>>
>> Bruno
>>
>> Le 15/03/2016 17:01, Alexander Carver a écrit :
>>> I can't really give you an example because there's many ways of doing
>>> it.  It's all up to the programming languages you are most familiar with
>>> (and those that run on the Raspberry Pi).  It's also not exactly a one
>>> or two line script although there are some very rough ways of doing it
>>> in a small script, they're not very robust.
>>>
>>> But in general you need to write a small program that connects to gpsd,
>>> sends the WATCH command so that data streams from the attached GPS
>>> receiver and then detect if that data stops flowing (because gpsd
>>> crashed) or the data isn't updating (because the GPS receiver failed or
>>> disconnected).  In that case you send a system call to kill the PID of
>>> the gpsd process then start a new copy.
>>>
>>>
>>> The small script version would be something like (this is completely
>>> untested, don't use it)
>>>
>>> #!/bin/bash
>>> GPSDPID=$(ps ax | grep gpsd | grep -v grep | awk '{print $1}')
>>> GPSDSTATE=$(ps ax | grep gpsd | grep -v grep | awk '{print $3}'
>>> GPSDCMD="/path/to/gpsd --with-parameters"
>>> if [ "$GPSDSTATE" == 'Z' ] || [ -z "$GPSDPID" ];
>>> then
>>>     echo 'gpsd is a zombie or it's completely missing, kill it'
>>>     if [ -n "$GPSDPID" ];
>>>     then
>>>         kill -KILL $GPSDPID
>>>         sleep 1
>>>     fi
>>>
>>>     $GPSDCMD
>>> fi
>>>
>>> Basically that script would look at the process list to see if gpsd was
>>> there, pull out the PID and the state and then see if the state is a Z
>>> (zombie process) or an empty string (the -z) in which case it died and
>>> needs to be restarted.  This is a bad script because it can't catch many
>>> problems that might leave gpsd running but not really functioning.
>>>
>>> You are better off using something else to connect directly to gpsd's
>>> TCP port and taking action if the data isn't there, the port closes or
>>> some other detail you don't like.
>>>
>>>
>>> On 2016-03-14 23:51, bruno suarez wrote:
>>>> Hello,
>>>>
>>>> Thank you for the reply and the idea of chemical heat packs.
>>>> The watchdog is expected.
>>>>
>>>> On monitoring GPSD, ok for the principle, but a sample script would
>>>> help
>>>> me (I am not a man of script!).
>>>>
>>>>
>>>> Thank you for your answers and tips
>>>> cordially
>>>> Bruno
>>>>
>>>> Le 15/03/2016 07:36, Alexander Carver a écrit :
>>>>> On 2016-03-14 12:06, bruno suarez wrote:
>>>>>> Hello,
>>>>>> For a stratospheric balloon project, I usea raspberry Rasbian
>>>>>> Jessie and
>>>>>> a USB GPS receiver.
>>>>>>
>>>>>> Everything is OK with gpsd and my GPS receiver.
>>>>>> When I plug everything works correctly, gpsd start on the correct
>>>>>> port
>>>>>> /dev/ttyUSB0.
>>>>>>
>>>>>> However, I want to make sure that everything works properly during
>>>>>> 2/3
>>>>>> hours to extremely cold temperature
>>>>>>
>>>>>> What is the easiest way to automatically control the operation of
>>>>>> GPSD
>>>>>> and relaunch it(on the same port detected ) if it is stopped or if
>>>>>> it is
>>>>>> in error.
>>>>>>
>>>>>> Thank you for your answers and tips
>>>>>>
>>>>>> Cordially
>>>>>> Bruno
>>>>> First, pack your payload with heaters.  You can use chemical heat
>>>>> packs
>>>>> from a pharmacy that are normally used for heating muscles and joints
>>>>> (these are the plastic bags that you smash to mix the chemicals and
>>>>> they
>>>>> get warm.)  In an insulated container you should stay within your
>>>>> operating limits of the Pi (the lower limit is approximately -20
>>>>> Celsius).
>>>>>
>>>>> After that, just set up a script that watches for data coming from
>>>>> gpsd
>>>>> and, if there is no data, issue a kill for the PID of gpsd and restart
>>>>> it.  Since gpsd can support more than one connection you can get data
>>>>> for your recording/telemetry program and have a completely separate
>>>>> program running to watch for a loss of communication.
>>>>>
>>>>> Also make sure to enable the watchdog timer in the Pi so that it will
>>>>> reboot if the whole system fails.  Make sure gpsd will start at
>>>>> boot as
>>>>> well as your data logging/telemetry program and the monitoring script.
>>>>>
>>>>
>>>>
>>>
>>
>>
> 
> 
>