[pve-devel] [RFC cluster/ha-manager 00/16] HA colocation rules

[Daniel Kral]

On 3/25/25 16:12, Daniel Kral wrote:
> Colocation Rules
> ----------------
> 
> The two properties of colocation rules, as described in the
> introduction, are rather straightforward. A typical colocation rule
> inside of the config would look like the following:
> 
> colocation: some-lonely-services
> 	services vm:101,vm:103,ct:909
> 	affinity separate
> 	strict 1
> 
> This means that the three services vm:101, vm:103 and ct:909 must be
> kept separate on different nodes. I'm very keen on naming suggestions
> since I think there could be a better word than 'affinity' here. I
> played around with 'keep-services', since then it would always read
> something like 'keep-services separate', which is very declarative, but
> this might suggest that this is a binary option to too much users (I
> mean it is, but not with the values 0 and 1).

Just to document this, I've played around with using a score to decide 
whether the colocation rule is positive/negative, how strict and to 
allow specifying a value on how much it is desired to meet the 
colocation rule in case of an optional colocation rule, much like 
pacemaker's version.

But in the end, I ditched the idea, since it didn't integrate well and 
it was also not trivial to find a good scale for this weight value that 
would correspond similarly as the node priority in HA groups, for 
example, especially when we select for each service individually.

On 3/25/25 16:12, Daniel Kral wrote:
> [0] https://clusterlabs.org/projects/pacemaker/doc/3.0/Pacemaker_Explained/html/constraints.html#colocation-properties
> [1] https://bugzilla.proxmox.com/show_bug.cgi?id=5260
> [2] https://bugzilla.proxmox.com/show_bug.cgi?id=5332
> [3] https://lore.proxmox.com/pve-devel/c8fa7b8c-fb37-5389-1302-2002780d4ee2@proxmox.com/

I forgot to update the footnotes here when sending this. The first 
footnote was to the initial inspiration of a score-based colocation 
rule, but as already said this was dropped.

So the references for the two quotes from our Bugzilla [0] and [1] map 
to the foot note [1] and [2] here respectively.