[systemd-devel] directive for executing a script on service failure

[George Karakougioumtzis]

Interesting point, thanks for the clarifications. I thought that it
would be as simple as setting the environmental variables
DBUS_SESSION_BUS_ADRESS and DISPLAY at each unit file that you would
want to receive notifications from.I thought that i might have not seen
all the directives of systemd and perhaps there was one already to call
an external script. But thanks anyway
On 02/06/2015 09:23 PM, Mantas Mikulėnas wrote:
> On Fri, Feb 6, 2015 at 5:26 PM, George Karakougioumtzis
> <mad-proffessor at hotmail.com <mailto:mad-proffessor at hotmail.com>> wrote:
>
>     Hi. Congrats for the near perfect job on systemd! I was searching
>     for a
>     directive to execute a script upon systemd service failure. I
>     would like
>     to receive desktop notifications about such  failures. I stumbled upon
>     OnFailure and FailureAction but these have hardcoded list of actions?
>
>
> One of those actions is "start an arbitrary unit", which could handle
> notifications... Unfortunately it doesn't actually pass any failure
> information to that unit. So, instead, you might have to watch the
> system log (journal) for unit failure notices. (I would normally have
> said that the journal makes it easy to filter for them, but quite
> strangely, these ones don't have a MESSAGE_ID attached...)
>
> Maybe others will have better suggestions.
>  
>
>     Any hints how to get notified (with notify-send most likely)?
>
>
> systemd calling notify-send isn't going to happen – as a service, it
> runs "outside" your desktop session, and has no access to its D-Bus
> session bus, which tends to be started at a random address. (There
> might even be several sessions, not just one!) And even considering
> the future "user bus" plans (which would put the session bus at a
> known fixed location), the whole idea of having a service inject
> something into a desktop session is really ugly. Even Microsoft
> realized that and implemented "session 0 isolation" in VIsta.
>
> In other words, such a notifier would need to be started from within
> your desktop session, connect /to/ systemd (either by waiting for
> signals on the system bus or by watching the journal messages), and
> idle in background waiting for some unit to fail. With DBus it could
> be a simple 10-line script, waiting for signals on one bus and calling
> Notify() on another...
>
> -- 
> Mantas Mikulėnas <grawity at gmail.com <mailto:grawity at gmail.com>>

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