Jitter and delay for svcbundle generated SMF manifests

I feel obliged to point out that this blog post is roughly 5 years old. People change, opinions evolve. In just a few years, vast technological landscapes can shift. And don't get me started on config files. Please consider this text in the context of its time.

Another extension to the svcbundle tool is the introduction of -s delay= and -s jitter= for periodic SMF services. If you have something to start in a periodic manner it’s really easy to create a service with svcbundle.

Let’s assume you have a small script called /root/demo_periodic.sh:

root@solaris:~# cat demo_periodic.sh
#!/bin/bash
date >> /root/periodic_service

You want to run it every minute. As the script needs some other stuff running, you don’t want to start it right after startup of the system or the restart of the services, but only three minutes later. And you don’t want to start it every minute sharp as you anticipate too many processes would start at right that moment, as many other users have such a periodic job as well.

The periodic service already knew concepts like jitter and delay. Jitter controls how many seconds a periodic service additionally waits with the execution after period has passed.

Delay controls how long it should wait with the first execution of the script in the periodic service after the service transitioned into online for example after boot.

This was available in SMF for quite a while. However with this recent addition via an SRU you can now control jitter and delay with svcbundle as well.

So now it’s really simple to create such a service. With -i you can even install it right with the command. It starts at once based on the configuration.

svcbundle -i -s service-name=site/demoservice \
 -s start-method=/root/demo_periodic.sh \
 -s jitter=10 \
 -s delay=180 \
 -s period=60

I asked for the time right after executing the last command. The service was already enabled at this moment.

root@solaris:~# date
Montag,  8. März 2021 um 18:38:58 Uhr UTC

In the following output you see the consequence of jitter and delay at once:

root@solaris:~# head -n4 periodic_service
Monday, March  8, 2021 at  3:42:02 PM UTC
Monday, March  8, 2021 at  3:42:57 PM UTC
Monday, March  8, 2021 at  3:44:06 PM UTC
Monday, March  8, 2021 at  3:45:04 PM UTC

The service only starts after three minutes since we enabled the service (first line). This is the consequence of delay. When you look at the varying time differences between the executions, you see the consequence of jitter.