[gridrpc-wg] questions about function handles

[Hidemoto Nakada]

Laurent, 

sorry for my lazy response,

> After the last GridRPC meeting in Seoul, we promised to send a new 
> proposal for data management in GridRPC and an answer to Hidemoto's 
> comments. However, in our discussions we still face a problem on the 
> definition of function handles.
> 
> There two ways to initialize a function handle.
> 
> - first, we can do it with grpc_function_handle_init. In this case, the
>   server is explicitly given by the client. As data location is known
>   (client, server or data repository), there no problem to bind the data
>   to the server. All data management can be done by the client:
>   placement, transfers or removal. The location will be given in the data
>   management functions.
> 
> - second, the function handle could be initialized by
>   grpc_function_handle_default. In that case, the GridRPC API document
>   says: "This default could be a pre-determined server or it could be a
>   server that is dynamically chosen by the resource discovery mechanisms
>   of the underlying GridRPC implementation". Does that mean, the function
>   handle will contain a server reference in it after
>   grpc_function_handle_default call ? Or does that mean, the function
>   handle will reference a default discovery (or GridRPC server) while the
>   computational server will be chosen during grpc_call ?

It is totally implementation dependent, I believe.
In theory, you can get more chance to choose 'better' server,
if you delayed selection of the server to the actual invocation time,
since at that time you can get more information on the invocation,
such as the size of data to be transferred.

>   If the function handle contains a reference to a server, then the data
>   management can be done in the same way as for
>   grpc_function_handle_init. If the function handle does not reference
>   the computational server, there no way to know where to place data
>   before issuing grpc_call. This is the way function handles are
>   implemented in Diet and Netsolve (2.0, any changes ?)
>   GridRPC interfaces.
> 
> However, we should provide a way to dynamically choose a server...
> Any comments ?

I cannot understand your concern. Could you explain it giving
examples ?

-hidemoto