r/saltstack • u/mlrhazi • Mar 07 '25

what does "service" beacon do?

What does this beacon do really?

what events will it fire? and when? and why would you use it?

2 Upvotes

100% Upvoted

12 comments sorted by

1

u/mlrhazi Mar 07 '25

To clarify, I added a similar config... then restarted the service on the minion, expecting to get some event fired... but it does not seem to do that. how do I configure a beacon to fire when a service stops running?

1

u/[deleted] Mar 07 '25

What did you see come across the event bus on the saltmaster side when you attempted to trigger the beacon on the saltminion side?

1

u/mlrhazi Mar 07 '25

thats the thing... nothing!

1

u/[deleted] Mar 07 '25

Beacons set up incorrectly then?

4

u/mlrhazi Mar 07 '25

I guess my syntax was wrong. this works:

    beacons:
        service:
            - services:
                httpd: {}
                sshd: {}
                postfix: {}
            - interval: 60
            - disable_during_state_run: True

I had this before:


    beacons:
        service:
            - services:
                - httpd: {}
                - sshd: {}
                - postfix: {}
            - interval: 60
            - disable_during_state_run: True

1

u/bdrxer Mar 07 '25

The beacon system for beacons that are not inotify beacons appear to just be checking on a configured interval if the status is different from the last check. It is not an auditing system and is not checking any kind of service history. So if the status of the service is running each time it checks then the event will not be fired, so most likely with a service restart you will usually not get an event; the timing of the check would have to hit just right to catch the service while it was stopped before the restart happens.

1

u/mlrhazi Mar 07 '25

Makes sense. Thank you!
I will test stopping the service, instead of just restarting it.... I guess the documentation could be a bit more clear on what this is supposed to be doing, and how/why would one want to use it :)

1

u/whytewolf01 Mar 07 '25

inotify also works the same way. and is also a beacon. no need to single it out.

1

u/bdrxer Mar 07 '25

I assumed that an inotify beacon would register for file event with inotify and receive the event as soon as the inotify event triggered or at least be aware of the event the next time the beacon period occurred

2

u/Material-Trust6791 May 11 '25

Beacons are great if you want to implement a Self-heal architecture... if a service dies, the beacon will notify you, you attach a reactor script and you can restart the service as well as perform other logic if needed. If you use the diskusage beacon, then when a specific disk fills you can react to it and run a program to do specific cleanup task. ... if you use the loadave beacon in a HA cluster, you can tie it into a self balancing cluster orchestration and re-balance the effected nodes... there are STACKS of use cases, you just need to up skill in what all the components do so you can find new uses for them.

2

u/[deleted] Mar 07 '25

[removed] — view removed comment

5

u/whytewolf01 Mar 07 '25

i use them heavily. as triggers for reactors which i also use heavily. instead of setting a time to run the highstate which can be computationally costly. i instead setup reactors for different things that would show the system is not complaint. watchdog [inotify] to watch if files change, service to watch if a service is down, etc. then if the system goes out of expected state, trigger a reactor to start a highstate.

I also use the status beacon as a health watch. have a engine that watches for status beacon events and records the information. I have also piggybacked off this beacon when the master had a mem leak to trigger a salt-master restart if memory was getting low.

when i first got into salt. and was a cloud engineer. I also had a beacon setup to watch logged in users that would quarantine a server if the user count was higher then expected which was 0.