Hello.
On Fri, Oct 28, 2022 at 12:39:01PM +0200, Simon Mullis <simon@xxxxxxxxxxxx> wrote:
> Step 0
> - service_data_gen => creates N outputs
>
> Step 1
> - service1@.service => N instances are created but don't actually need
> to do anything.
> - service1@.socket => N sockets are created which are the target FIFOs
> for the output of - service_data_gen above.
What processes the data flowing into step1@.socket (==service1@.socket)?
> I don't need any service to actually run in step1, I would like
> systemd to manage the sockets and the dependencies (as it is for the
> rest of the chain).
So why don't you just shift the rest of the pipeline/numbering?
step1@.socket would trigger step1@.service and it'd do job that your
current step2@.service does.
And you'd initiate your pipeline with
eval systemctl start step1@{1..${cpu_cores}}.socket
and trigger by writes into the sockets from the single
service_data_gen.
> What is the best practise for an ExecStart= entry to act as a dummy,
> where no service is actually required? At the moment I am using:
>
> ExecStart=/usr/bin/sh -c "sleep infininty" in the service template for
> service1@.service
ExecStart=/bin/true
RemainAfterExit=true
is slightly better in terms of system resource use.
> I think the crux of this is entirely related to the use of instance
> templates and linking one unconnected single parent service to many
> child services (and sockets).
FTR, not related to templates in particular, as systemd.socket(5) says:
"For each socket unit, a matching service unit must exist".
HTH,
Michal
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