Thanks a LOT, raph.
Yes, indeed, I had the mis-conception that the procedure C.p
would be executed on the remote host [ like that in the ticket-connection
mechanism ].
Making sure that Open.pipe gets executed on remote host is the key!
Your suggestion works.
Thanks
HP
On Tue, 13 May 2008, Raphael Collet wrote:
> Dear HP Wei,
>
> The error you observe is due to the distributed behavior of procedures. The
> problem is: the procedure call {C.p ...} is *not* executed on the remote host,
> as you apparently expect it to do! The procedure P defined in the functor is
> *copied* from the remote host to the local one, then it is executed locally.
> The problem is that P refers to Open.pipe, a class that cannot be copied
> between sites, because it refers to site resources (OS file descriptors, etc).
> That class is thus exported as a "resource", which is an opaque unusable
> value.
>
> {R apply(X C)} %%% b -- to run on remote host
> %% procedure P is indeed created on the remote host
>
> local L Cmd in
> Cmd = "ls a_path | wc"
> {C.p Cmd L} %% the procedure is copied and run *here*
> {System.showInfo L}
> end
>
>
> The solution is to force the remote creation of objects, by using a port.
> This can be seen as an implementation of RPC for procedure P:
>
> X = functor
> import Open
> export p:P
> define
> Str Prt={NewPort Str}
> thread
> for Cmd#R in Str % process requests (on remote host)
> thread
> {{New Open.pipe init(cmd: "sh" args:['-c' Cmd])}
> read(list:R size:all)}
> end
> end
> end
> proc {P Cmd ?R}
> {Send Prt Cmd#R} % send the request on port
> end
> end
>
>
> Cheers,
> raph
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>
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