[systemd-devel] reacting to unit failures (OnFailure)

[Lennart Poettering]

On Tue, 02.12.14 08:00, Nekrasov, Alexander (alexander.nekrasov at emc.com) wrote:

> Meaning that I have to create a myfailureunit<name>.service
> file/unit for every unit I want to register for? Which in my case is
> going to be almost all of them, in a high availability system

No. systemd has a concept of "template" units, that can be
instantiated a number of times. The unit names with "@" in the name
are such templated units. The files on disk are name foo at .service, and
at runtime you can then instantiate them as foo at bar.service,
foo at waldo.service and so on. The "foo" in this scheme is the template
name, while bar/waldo/... is the instance id. In my proposal below I
suggested using one template and then instantiate them once for each
failed unit, using the faile unit's name as the instance id.

> > -----Original Message-----
> > From: Lennart Poettering [mailto:lennart at poettering.net]
> > Sent: Monday, December 01, 2014 5:46 PM
> > To: Nekrasov, Alexander
> > Cc: systemd-devel at lists.freedesktop.org
> > Subject: Re: [systemd-devel] reacting to unit failures (OnFailure)
> > 
> > On Mon, 01.12.14 17:10, Nekrasov, Alexander (alexander.nekrasov at emc.com)
> > wrote:
> > 
> > > Hello,
> > >
> > > While converting from Upstart to SystemD, came upon this issue. Is
> > this case not covered or am I missing something?
> > >
> > > In Upstart, I can start a job when another job fails, and there's a
> > $JOB variable that tells me what was the job that failed.
> > >
> > > start on (stopped RESULT=failed PROCESS=post-stop)
> > >
> > > script
> > >     echo "this just failed: $JOB"
> > > end script
> > >
> > > In SystemD I can register a unit to be started when another unit
> > > fails. But there seems to be no way of knowing what unit failed. Is
> > > that correct?
> > 
> > The idea is that you use "OnFailure=myfailureunit@%n.service". %n is
> > automatically replaced by the name of the unit you place this
> > in. Then, in the failure unit you can identify the instance again with
> > %i or %I.
> > 
> > Lennart
> > 
> > --
> > Lennart Poettering, Red Hat
> 


Lennart

-- 
Lennart Poettering, Red Hat