Worker/Fork (Nginx)

[incapdns]

How does f-stack work with fork?
I'm trying to use fork (), and F-stack doesn't work.

But it strangely works with nginx (multiple works).
I'm sorry for the question (because I'm new to C, I don't know much), but what do?

If possible I would like to request a small code as an example (specifying what was used to function with fork ()).
If you can send me a small piece of code that contains the fork solution, I would be grateful.

My question (regarding fork ()):
Can I run: ff_init // ff_run in each process?
I'm sorry for my bad english.

[jfb8856606]

F-Stack is multi-processes mode, you can modify lcore_mask in config.ini, If use nginx, the number of worker need to be modify also.
And ff_init and ff_run only can be called in main thread of every process.
See #430

[ygm521]

@jfb8856606 Can you give an Multiple core configuration examples for f-stack with Nginx ?

[jfb8856606]

Regarding fork():

At the time this was filed, F-Stack did not support fork() in the traditional sense — ff_init and ff_run had to be called in the main thread of each independently-launched process, not in forked children. Nginx's multi-worker model worked because F-Stack's Nginx integration handles the master/worker relationship specially via its own IPC mechanism.

Good news: As of PR #887 (merged 2025-05), F-Stack now supports fork() properly, similar to Linux — child processes inherit open file descriptors with reference counting, and each process gets its own FreeBSD struct thread. So fork()-based multi-process patterns should now work correctly.

Alternative: LD_PRELOAD mode (adapter/syscall)

If you want to port an existing multi-process application (one that uses fork()) to F-Stack without modifying source code, the LD_PRELOAD approach via libff_syscall.so is also available:

# Build libff_syscall.so
export FF_PATH=/data/f-stack
cd /data/f-stack/adapter/syscall
make clean && make all

# Start the F-Stack instance process first
./fstack -c config.ini

# Then run your app with LD_PRELOAD
export LD_PRELOAD=/data/f-stack/adapter/syscall/libff_syscall.so
./your_app

For fork-based multi-process apps, enable FF_MULTI_SC mode so each forked worker process gets its own socket context. See adapter/syscall/README.md for details.

Nginx multi-core configuration example:

In f-stack.conf:

[dpdk]
lcore_mask=3   # use cores 0 and 1 (binary: 11)

In nginx.conf:

worker_processes 2;   # must equal the number of lcores in lcore_mask

events {
    worker_connections 102400;
    use kqueue;
}
sendfile off;

worker_processes must equal the number of set bits in lcore_mask. Each Nginx worker is pinned to one lcore and has its own independent network stack instance.

Closing as answered.