Does child process fork() is same as spawn with explicit 'ipc' on Windows ?

[projektorius96]

If the answer is negative what are the differences : is it true that fork() creates new Node.js V8 instance, whereas spawn does not ?

In terms of stdio variant I mentioned in the title : stdio [null, null, null, 'ipc'] whereas null for 'pipe'

Any reference would be appreciated , thanks !

[cjihrig]

spawn() is a general purpose function for creating child processes. spawn() can be used to create Node.js child processes.

fork() is built on top of spawn(). It is only used for spawning Node.js child processes.

fork() does create an IPC channel. spawn() does not create an IPC channel by default, but can be configured to do so.

Check out the fork() docs.

[projektorius96]

With reference to given fork docs it says (citing) :

"Keep in mind that spawned Node.js child processes are independent of the parent with exception of the IPC communication channel that is established between the two. Each process has its own memory, with their own V8 instances. Because of the additional resource allocations required, spawning a large number of child Node.js processes is not recommended."

As far as I did understand, by default Node.js process is another process under OS process hierarchy (i.e. parent to child relationship), am I right ? @cjihrig

If answer is more or less positive, does it mean that workers (threads) are kinda of "child_process" optimization within single Node.js process instance : rather than forking many independent Node.js V8 process instances i.e. instead of allocating more and more resources (RAM?) per each process, instead we utitlise THREADS, that DO SHARE MEMORY ADDRESS SPACE PER SINGLE PROCESS, subsequently OS-wise context-switching is less expansive . Do I comprehend it correctly, at least conceptually ? @cjihrig

Thanks !

[cjihrig]

fork() creates a separate process at the operating system level. They are two completely separate Node.js processes that can communicate over IPC.

Worker threads are just that - threads. They are in the same Node.js process.

[projektorius96]

With reference to "Shell scripting with Node.js" by Dr. Axel Rauschmayer , @rauschma , cited :

... each worker is an V8 isolate that has its own JavaScript heap but
shares its operating system heap with other threads.

Now getting back to your last sentence : "They (i.e. threads) are in the same Node.js process" .

Both cited above are quite mutually exclusive, don't you thinks so (politely) ?

I assume Axel Rauschmayer referred specifically to JavaScript V8-wise workers, whereas your i.e. @cjihrig last statement referred to Libuv-wise threads : if so I see no more contradiction herein as threads DO run within single context (≈isolate?) of Node.js process ?

Can you confirm that "Threads Node.js libuv implementation-wise, rather than Workers V8-wise, DO run within single context (≈isolate?) of Node.js process" ?

Thank you .

[cjihrig]

The main thread and each Worker thread are separate threads in the same Node.js process. The main thread and each Worker thread has its own V8 isolate.

[projektorius96]

Last question, in terms of embedding V8 into C++ application, is there any definition for encapsulation of multiple isolates, say it "super-isolate ", "OS-wise namespace (like in Linux)" or some relevant ?

Thank you for patience & answers ! @cjihrig ♥

[cjihrig]

I have not heard of anything resembling a "super-isolate."