[Planetlab-devel] PLC system discussion (in the hall)

[Thierry Parmentelat]

Just so that everybody knows what we're talking about here

- we tried to come up with a scheme where the 'nodes' data structure  
would become more generic

- so we are trying to remove most of the hard-coded 'fields' in the  
node data structure, to keep only the ones that seem to belong to  
*any* kind of node; this basically can be depicted as trying to sketch  
the notion of a 'generic node', that can then be instantiated into a  
variety of node 'types'

- the various types that we are envisioning at this stage would be  
either
* plain node (read, current node)
* dummynet boxes
* PCU's
* Wifi Mesh
* IxP

- the attribute system is very similar to either
(SliceAttributeType,SliceAttribute) for slices
(NodeNetworkSettingType, NodeNetworkSetting) for network interfaces
and, simply put, allows to dynamically extend the set of fields that  
would be attached to a given type of nodes

- it will, also, allow to remove the notion of a nodegroup, that can  
now in the new system be described as a pair (attribute,value); so  
e.g. the alpha nodegroup can be seen as the set of nodes whose  
'deployment' attribute is 'alpha'; in particular the 'conf_file'  
object will not refer to a nodegroup anymore, but to a n  
(attribute,value) pair instead

- in the process we decided to remove the 'model' node field, that's  
mostly not up2date; so the few instances where this is used (typically  
the bootmanager's hardware requirements checking step) would now use  
atribute(s) instead

- I'll add to Reid's list an item about database migration, that will  
need some care in this perspective

===
in terms of impact on the rest of the system, we've identified that

- node filtering will probably need being improved, so that e.g.  
filtering on attributes would be feasible and reasonably efficient  
(efficiency is the one major reason why the node 'type' will be  
hardcoded as a static field in the database)

- BootManager will need to use the new attributes for
* figuring the bootstrapfs to be installed
* checking hardware requirements

- The NodeManager, as well as the web GUI, look like they might need  
some changes as well

- this also might imply a disruptive change in the API

===
Also, one thing that has been left out of the discussion is:
for actually eliminating the PCU stuff, I guess we'll need something  
to create relations between nodes. Like, a PCU is likely to control a  
handful of plain nodes; same for the dummynet box;

-- Thierry


On May 14, 2008, at 4:12 PM, rmoran at CS.Princeton.EDU wrote:

> basic take aways from the hall meeting:
>
> * NodeGroup becomes (node) attribute
> - map attrib to node
> * Create node attribute table
> * Remove model from node table
> - formalize model options into attributes * Add node TYPE field to  
> node table
> * Add id/value pair to conf file table
> - find node's conf files do a join (N, attrib, conf file, id/val)
>
> BootManager:
> set attributes
> - bootstrap fs + extensions
> - requirement checking
>
> nodemanager?? GUI???
>
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