[Engine-devel] Fwd: Problem in REST API handling/displaying of logical networks

[Itamar Heim]

On 07/03/2012 10:30 AM, Livnat Peer wrote:
> On 02/07/12 17:35, Mike Kolesnik wrote:
>> Hi All,
>>
>> I would like to hear opinions about a behaviour that I think is
>> problematic in
>> REST API handling of logical networks.
>>
>> -- Intro --
>> Today in the REST API we are exposing two collections for "logical
>> network" related entities.
>>
>> First is a top level collection which is out of any context at the address
>> http://engine/api/networks.
>> Second is a sub-collection in the context of a cluster:
>> http://engine/api/cluster/xxx/networks
>>
>> The network itself is defined per DC level, so for each DC you would have
>> at least one logical network for management, which has some properties such
>> as STP, MTU, etc..
>> The top level collection is used to create/delete such network entities.
>>
>> The sub-collection in the context of a Cluster is used to attach/detach a
>> network from the DC of that cluster.
>> The network in the context of a cluster has some additional information,
>> let's
>> say for example 'status' of the network:
>>      If a network is defined on all hosts in the cluster then it's status is
>>      'Operational'.
>>      If a network is not defined on some of the hosts in the cluster then
>> it's
>>      status is 'Not Operational'[1].
>>
>>
>> -- Problem --
>> The problem is that details which are only relevant in context of a
>> cluster, are still displayed in the root context as well (e.g: 'status').
>> This can, in certain cases, cause unexpected behaviour.
>>
>> For example, let's consider this topology:
>>    Data Center A
>>          |
>>          |\____ Network 'red'
>>          |\____ Cluster A1
>>          |              \______ Network 'red' attached
>>          \____ Cluster A2
>>                         \______ Network 'red' attached
>>
>> If the 'status' is the same on all the clusters that the network is
>> attached to
>> (A1, A2) then there will be one element in the top level collection,
>> with the
>> network details and the 'status' field representing the state (which is same
>> for all networks in the cluster contexts of the cluster).
>> If, however, the status is not the same (ie. on A1 the network is
>> 'Operational' and on A2 it is 'Non Operational') then the top-level
>> collection will show two elements for the network, where all network
>> details are the same and only the 'status' field is different.
>>
>
> That sounds like a bug to me.
> I think that top collection should include only DC level properties and
> not cluster level properties, status should not be there (same as
> display required etc.)
>
>
>> This is problematic IMHO for several reasons:
>>    1. Showing one network in certain states, and multiple copies of this
>>        network in other states is not optimal, to say the least.
>>    2. In the top-level collection there is no indicator of the cluster
>> for which
>>        the network is displayed, so there is no way to differentiate
>> between the
>>        two 'red' network elements (they will have same id, name, etc.).
>>    3. There is a certain asymmetry between the remove action[2] and the
>>        result in that you would expect: you either remove a network but
>> in the
>>        result you would see several elements removed.
>>
>>
>> -- Proposed Solutions --
>> Personally I can think of several solutions to this problem:
>>    1. Declare the top-level collection as a collection of all networks
>> that are
>>        either attached to cluster or not, and if they are indeed attached
>> then
>>        show the details for each cluster, including a link to the cluster.
>>    2. Declare the top-level collection as a collection of all networks
>> that are
>>        defined in data-centers, but they will not contain any cluster
>> specific
>>        data, and thus each entry is unique.
>>
>> Solution #2 is breaking the API backwards-compatibility, since it includes
>> removing certain fields that have appeared today (namely 'status' and
>> 'display') but IMO would give a better experience since the top-level
>> collection is actually used for managing networks, and not their attachment
>> to clusters which should be done in the context of each cluster.
>>
> I really don't think top collections should include cluster networks it
> is not user-friendly to say the least.

how is that different from top collections including VMs and templates?
(or logical networks becoming main tab in the UI going forward)

>
> I vote for the second option, I don't think that having a bug in
> previous versions should drive this decision.
>
>
>> I would like to hear what suggestions you have to solve this problem or if
>> you prefer either of the above solutions.
>>
>>
>> -- Footnotes --
>> [1] In 3.1 this is slightly different, but for the sake of simplicity I
>> didn't
>>       specify the new behaviour.
>> [2] Currently you can't update the network if it's attached to any cluster,
>>       but perhaps in the future this would be possible.
>>
>> Regards,
>> Mike
>>
>>
>
>
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