[PVE-User] HA question

Eneko Lacunza elacunza at binovo.es
Thu Oct 6 11:01:38 CEST 2016


About the "disable" thing, wouldn't it be much clearer and less prone to 
confusion to rename it to "disable-ha-and-stop"? And I guess, 

El 06/10/16 a las 09:39, Thomas Lamprecht escribió:
> On 10/06/2016 09:08 AM, Kevin Lemonnier wrote:
>>> He wanted to remove it from HA managed but said to HA it should be
>>> stopped, nothing to do with the stop/shutdown button confusion :)
>> Yeah sorry about that, I hijacked this thread with my somewhat 
>> un-related
>> complaint, that's my bad :).
> No worries, and I hope also that I didn't discourage any from giving 
> feed back.
> The ha-manager did not received that much feedback, besides obvious 
> bug reports.
> So thanks for yours.
>> The HA enable / disable is a bit confusing, it just doesn't work as 
>> you'd
>> expect. Now that I used HA a lot more I get it, but it's a bit of a trap
>> when you are starting with HA, just like the fact that only one task can
>> be carried out at the same time on HA enabled VMs. I understood that 
>> only
>> a few weeks ago when gluster froze a VM and that stuck HA on a task 
>> forever,
>> took me a while to understand why I couldn't do anything about all of 
>> the
>> other VMs.
> That's the nature of the finite state machine (FSM) in the HA manager, 
> you
> can be in only one state at a time.  We think one task per time is 
> good for
> HA as multiple at the same time can have side effects, which is not good.
> We want that a service is always in a defined and if possible good state.
>> Or why on some VMs the live migration has an output and for others it 
>> doesn't,
>> it's because for HA enabled VM you just add a task, the output is in 
>> a separate
>> task.
> Yes that is can be confusing I guess, it came with the architecture of 
> the
> ha-manager.
> The ha-manager has quite simple mechanics internal, this makes in 
> generally
> more stable (hopefully ;)).
> When it was combined it with the rest of the PVE ecosystem we tried to
> integrate it without much changes there, to avoid new bugs and new 
> code to
> maintain.
> that lead to things like two task per real task as the interface has 
> not to
> care if it triggers a task for a ha-managed or non-ha VM.
> For the double task list I have an idea in my head, I have to try it 
> if it works and
> evaluate it if the changes are justified.
>> Maybe it'd be good to add a visual hint about that, you aren't actually
>> stoping, starting or migrating a VM, you are just adding a task for 
>> the HA to
>> carry out later, and that's where you should look to see the output ? 
>> Same thing
>> in HA, the enable / disable tick box could maybe be labelled "keep 
>> powered on" or
>> something similar ?
> The hint in the ha-managers task output is a good idea!:)
> For the enable/disable things I'm hesitating, its good documented and 
> from
> the point of how the ha-manager works it makes sense, imo.
> We talked internally about an "unmanaged" state in the FSM, it was 
> just an
> idea from my side and not a real need were here we decided against doing
> it to let things be as simple as possible.
> cheers,
> Thomas
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