ipc pipe with fork

[Tim Kuijsten]

I would like to setup an IPC pipe with a submodule. Unfortunately it
seems impossible to provide a stdio array with fork like the way this is
done with spawn.

Two questions:

1. is the following equivalent to `fork('lib/foo')`?

spawn('node', ['lib/foo'], {
stdio: ['pipe', 'pipe', 'pipe', 'ipc']
});

2. should I use spawn when I want to share a pipe with a submodule? i.e.

spawn('node', ['lib/foo'], {
stdio: ['pipe', 'pipe', 'pipe', 'ipc', 'pipe']
});

-Tim

[Angel Java Lopez]

I never used that feature, but, why not use the "built-in" IPC channel given by fork?

http://nodejs.org/api/child_process.html#child_process_child_process_fork_modulepath_args_options

In addition to having all the methods in a normal ChildProcess instance, the returned object has a communication channel built-in. See child.send(message, [sendHandle])for details.

Then

http://nodejs.org/api/child_process.html#child_process_child_send_message_sendhandle

with examples, child.send, child.on, at parent side, and process.send, process.on at child side

I guess there are more info at:

http://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options

1. 'ipc' - Create an IPC channel for passing messages/file descriptors between parent and child. A ChildProcess may have at most one IPC stdio file descriptor. Setting this option enables the ChildProcess.send() method. If the child writes JSON messages to this file descriptor, then this will trigger ChildProcess.on('message'). If the child is a Node.js program, then the presence of an IPC channel will enable process.send() and process.on('message').

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[Tim Kuijsten]

Angel Java Lopez schreef op 26-10-14 om 21:16:

> I never used that feature, but, why not use the "built-in" IPC channel
> given by fork?
>
> http://nodejs.org/api/child_process.html#child_process_child_process_fork_modulepath_args_options
>
> In addition to having all the methods in a normal ChildProcess instance,
> the returned object has a communication channel built-in. See

> |child.send(message, [sendHandle])|for details.

>
> Then
> http://nodejs.org/api/child_process.html#child_process_child_send_message_sendhandle
> with examples, child.send, child.on, at parent side, and process.send,
> process.on at child side
>
> I guess there are more info at:
>
> http://nodejs.org/api/child_process.html#child_process_child_process_spawn_command_args_options
>

> 1. |'ipc'| - Create an IPC channel for passing messages/file

> descriptors between parent and child. A ChildProcess may have at

> most /one/ IPC stdio file descriptor. Setting this option enables

> the ChildProcess.send() method. If the child writes JSON messages to
> this file descriptor, then this will trigger
> ChildProcess.on('message'). If the child is a Node.js program, then
> the presence of an IPC channel will enable process.send() and
> process.on('message').

I'm already using the builtin IPC channel for messaging and passing
named sockets around. But because I use privilege separation within my
server I also like to have an efficient pipe, like the socketpair that
is used when specifying 'pipe' in stdio, to push some binary data to the
child (in the form of BSON).

-Tim

>
>
> On Sun, Oct 26, 2014 at 2:53 PM, Tim Kuijsten <in...@netsend.nl
> <mailto:in...@netsend.nl>> wrote:
>
> I would like to setup an IPC pipe with a submodule. Unfortunately it
> seems impossible to provide a stdio array with fork like the way
> this is done with spawn.
>
> Two questions:
>
> 1. is the following equivalent to `fork('lib/foo')`?
>
> spawn('node', ['lib/foo'], {
> stdio: ['pipe', 'pipe', 'pipe', 'ipc']
> });
>
> 2. should I use spawn when I want to share a pipe with a submodule? i.e.
>
> spawn('node', ['lib/foo'], {
> stdio: ['pipe', 'pipe', 'pipe', 'ipc', 'pipe']
> });
>
> -Tim
>
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