Hello.
How to isolate the user?
Can I run the REPL in a slave process for a user without them having access to the master process’s data?
Yes.
(There are various ways to implement this. For example, Jupyter talks to a Julia process using a ZMQ-based protocol, implemented in IJulia.jl.)
ZMQ or ather is too slow, need a shared memory, but julia haven’t way to synchronize two independent julia process. Ideally, run julia in shared memory. Is it possible?
“Shared memory” and “isolated without access to data” seem like they are in opposition to one another…
Too slow for what? You were talking about a “REPL”, i.e. an interactive process — waiting for user input is usually going to make the latency of something like ZMQ irrelevant. But if you have some more specialized requirements in mind you should explain your application in more detail to get sensible advice.
the user gives access to his memory to the main process, but not vice versa