xs-vat-worker limited to one at a time? (hard-coded fd 3, 4)

[dckc]

context: #1407 (comment)

cc @warner

[warner]

yeah we should add command-line arguments to specify the fds that the child should use, the parent will allocate a pair for each worker process it launches and tell the child what it picked

[dckc]

I wonder... Many children can each have fd 3 and 4, no?

[warner]

Yeah, but the parent cannot. But, now you're making me wonder how this really works, and whether the FD numbers have to be the same in both child and parent (I know it's doing fork/exec, but the parent process could close/fdup to reassign the numbers before it execs the child). I wrote code to do this in Twisted 20 years ago, but for the life of me I don't remember what I did.

We'll have to check the Node.js spawn docs to see if this is strictly necessary.

[dckc]

@warner tells me he found that node does The Right Thing in the parent so that the fds in the child can stay hard-coded.

Until we learn otherwise, I'm closing this.