[systemd-devel] Antw: [EXT] Re: Samba Config Reload

[Ulrich Windl]

Hi!

I thin Lennart had pointed it out: If the sapplication being reloaded does not provide any feedback when the reloading is complete, you can never be sure what it did complete.
Adding some sleep may catch a grat number of cases whule waiting too long in most cases.

So before discussing systemd meachnisms: How do you know when reload is complete?

Regards,
Ulrich

>>> Wols Lists <antlists at youngman.org.uk> schrieb am 09.04.2022 um 17:10 in
Nachricht <fcce76c5-d376-bbcc-10b0-c325d084ad6d at youngman.org.uk>:
> On 09/04/2022 09:00, Yolo von BNANA wrote:
>> Can you please explain this in more Detail?
>> 
>> What does this mean: " "systemctl reload" will basically return
>> immediately without the reload being complete"?
>> 
>> And what is an Example for an synchronous command for ExecReload=
>> 
> Do you understand the difference between "synchronous" and 
> "asynchronous"? The words basically mean "aligned in time" and "without 
> timed alignment".
> 
> Think of writing to files. In the old days of MS-DOS et al, when your 
> program called "write", the CPU went off, saved the data to disk, and 
> returned to your program. That's "synchronous", all nicely ordered in 
> time, and your program knew the data was safe.
> 
> Now, when your linux program calls write, linux itself replies "got it", 
> and your program goes off knowing that something else is going to take 
> care of actually saving the data to disk - that's "asynchronous". Except 
> that sometimes the program needs to know that the data HAS been safely 
> squirreled away (hence all these fsync calls).
> 
> So when systemd calls ExecReload *A*synchronously, it goes off and fires 
> off a load more stuff, knowing that the ExecReload IS GOING (future 
> tense) to happen. What the previous poster wanted was a synchronous 
> ExecReload, so that when systemd goes off do the next thing, the 
> ExecReload HAS ALREADY HAPPENED (past tense). (Which in general is a bad 
> thing because it *seriously* knackers performance).
> 
> Cheers,
> Wol