[ovirt-devel] [ovirt-users] Feature Page: Mac Pool per DC

Wed Apr 23 20:32:33 UTC 2014

On 04/23/2014 11:12 AM, Martin Mucha wrote:
> Hi,
>
> I was describing current state, first iteration. Need of restart is something which should not exist, I've removed that necessity meantime.
> Altered flow: You allocate mac address for nic in data center without own pool, it gets registered in global pool. Then you modify settings of that data center so that new pool is created for it. All NICs for that data center is queries from DB, it's macs released from global pool and added to data center scope pool. And other way around. When you delete this scoped pool, all its content will be moved to global pool. Feature page is updated.
>
> Note: *previously* there was MAC placed in wrong pool only after modification of existing data center, which caused entirely new pool to be created (there wasn't pool for this scope, after modification there is). All other operations were fine. Now all manipulation with scoped pools should be ok.
>
> Note2: all that scoped pool handling is implemented as strategy. If we are unsatisfied with this implementation we could create another one and switch to it without modifying 'calling' code. Also many implementation may coexist and we can switch between them (on app start up) upon config.
>
> Question: When allocating MAC, not one specified by user, system picks available mac from given mac pool. Imagine, that after some time then mac pool ranges changes, and lets say that whole new interval of macs is used, not overlapping with former one. Then all previously allocated macs will be present in altered pool as a user specified ones -- since they are outside of defined ranges. With large number of this mac address this have detrimental effect on memory usage. So if this is a real scenario, it would be acceptable(or welcomed) for you to reassign all mac address which were selected by system? For example on engine start / vm start.

no. you don't change mac addresses on the fly.
also, if the mac address isn't in the range of the scope, i don't see 
why you need to keep it in memory at all?

iiuc, you keep in memory the unused-ranges of the various mac_pools.
when a mac address is released, you need to check if it is in the range 
of the relevant mac_pool for the VM (default, dc, cluster, vm_pool).
if it is, you need to return it to that mac_pool. otherwise, the 
mac_pool is not relevant for this out-of-range mac address, and you just 
stop using it.

remember, you have to check the released mac address for the specific 
associated mac_pool, since we do (read: should[1]) allow overlapping mac 
addresses (hence ranges) in different mac_pool.

so cases to consider:
- mac_pool removed --> use the relevant mac_pool (say, the default one)
   for the below
- mac_pool range extended - need to check if any affected VMs have mac
   addresses in the new range to not use them
- mac_pool range reduced - just need to reduce it, unrelated to current
   vm's
- mac_pool range changed all-together / new mac_pool defined affecting
   the VM (instead of the default one) - need to review all mac
   addresses in affected vm's to check if any are in the range and
   should be removed from the mac_pool ranges.

the last 3 all are basically the same - on any change to mac_pool range 
just re-calculate the ranges in it by creating sub-ranges based on 
removing sorted groups/ranges of already allocated mac addresses?

[1] iirc, we have a config allowing this today for manually configured 
mac addresses.

>
> M.
>
> ----- Original Message -----
> From: "Itamar Heim" <iheim at redhat.com>
> To: "Martin Mucha" <mmucha at redhat.com>
> Cc: users at ovirt.org, devel at ovirt.org
> Sent: Tuesday, April 22, 2014 5:15:35 PM
> Subject: Re: [ovirt-users] Feature Page: Mac Pool per DC
>
> On 04/18/2014 01:17 PM, Martin Mucha wrote:
>> Hi,
>>
>> I'll try to describe it little bit more. Lets say, that we've got one data center. It's not configured yet to have its own mac pool. So in system is only one, global pool. We create few VMs and it's NICs will obtain its MAC from this global pool, marking them as used. Next we alter data center definition, so now it uses it's own mac pool. In system from this point on exists two mac pools, one global and one related to this data center, but those allocated MACs are still allocated in global pool, since new data center creation does not (yet) contain logic to get all assigned MACs related to this data center and reassign them in new pool. However, after app restart all VmNics are read from db and placed to appropriate pools. Lets assume, that we've performed such restart. Now we realized, that we actually don't want that data center have own mac pool, so we alter it's definition removing mac pool ranges. Pool related to this data center will be removed and it's content will!
  !
>   be moved t
> o a scope above this data center -- into global scope pool. We know, that everything what's allocated in pool to be removed is still used, but we need to track it elsewhere and currently there's just one option, global pool. So to answer your last question. When I remove scope, it's pool is gone and its content moved elsewhere. Next, when MAC is returned to the pool, the request goes like: "give me pool for this virtual machine, and whatever pool it is, I'm returning this MAC to it." Clients of ScopedMacPoolManager do not know which pool they're talking to. Decision, which pool is right for them, is done behind the scenes upon their identification (I want pool for this logical network).
>>
>> Notice, that there is one "problem" in deciding which scope/pool to use. There are places in code, which requires pool related to given data center, identified by guid. For that request, only data center scope or something broader like global scope can be returned. So even if one want to use one pool per logical network, requests identified by data center id still can return only data center scope or broader, and there are no chance returning pool related to logical network (except for situation, where there is sole logical network in that data center).
>>
>> Thanks for suggestion for another scopes. One question: if we're implementing them, would you like just to pick a *sole* non-global scope you want to use in your system (like data center related pools ONLY plus one global, or logical network related pools ONLY plus one global) or would it be (more) beneficial to you to have implemented some sort of cascading and overriding? Like: "this data center uses *this* pool, BUT except for *this* logical network, which should use *this* one instead."
>>
>> I'll update feature page to contain these paragraphs.
>
> I have to say i really don't like the notion of having to restart the
> engine for a change done via the webadmin to apply.
> also, iiuc your flow correctly, mac addresses may not go back to the
> pool anyway until an engine restart, since the change will only take
> effect on engine restart anyway, then available mac's per scope will be
> re-calculated.
>
>
>
>>
>> M.
>>
>>
>> ----- Original Message -----
>> From: "Itamar Heim" <iheim at redhat.com>
>> To: "Martin Mucha" <mmucha at redhat.com>, users at ovirt.org, devel at ovirt.org
>> Sent: Thursday, April 10, 2014 9:04:37 AM
>> Subject: Re: [ovirt-users] Feature Page: Mac Pool per DC (was: new feature)
>>
>> On 04/10/2014 09:59 AM, Martin Mucha wrote:
>>> Hi,
>>>
>>> I'd like to notify you about new feature, which allows to specify distinct MAC pools, currently one per data center.
>>> http://www.ovirt.org/Scoped_MacPoolManager
>>>
>>> any comments/proposals for improvement are very welcomed.
>>> Martin.
>>> _______________________________________________
>>> Users mailing list
>>> Users at ovirt.org
>>> http://lists.ovirt.org/mailman/listinfo/users
>>>
>>
>>
>> (changed title to reflect content)
>>
>>> When specified mac ranges for given "scope", where there wasn't any definition previously, allocated MAC from default pool will not be moved to "scoped" one until next engine restart. Other way, when removing "scoped" mac pool definition, all MACs from this pool will be moved to default one.
>>
>> cna you please elaborate on this one?
>>
>> as for potential other "scopes" - i can think of cluster, vm pool and
>> logical network as potential ones.
>>
>> one more question - how do you know to "return" the mac address to the
>> correct pool on delete?
>>