CPG_FD_GET(3)

💖 CPG_FD_GET(3) 💖

okay bestie, sit down, hydrate, and let me tell you about cpg_fd_get — it's a lil function from the Corosync Cluster Engine Programmer's Manual and it's honestly kind of a big deal for anyone doing CPG stuff. 🦋

✨ NAME ✨

cpg_fd_get — Dispatches callbacks from the CPG service

no fr, that's the whole name line, we're not editing the sacred texts 💅

🌸 SYNOPSIS 🌸

#include <corosync/cpg.h>

int cpg_fd_get(cpg_handle_t handle, int *fd);

like, that's it. two args. she's low maintenance 👑

🎀 DESCRIPTION 🎀

So the way this works, bestie: cpg_fd_get is the function you call to retrieve the file descriptor that you can hand off to the poll system call. Why tho? Because you wanna know exactly when cpg_dispatch(3) won't block. That's the whole point. No more guessing, no more vibes-based polling. 😌✨

and here's the part people get wrong every single time, so listen up:

the handle argument may not be used directly with poll 🙅‍♀️

why not?? because it's literally not the file descriptor. it's an internal identifier that the CPG library uses for itself. it's giving "cute nickname that only the library understands," not "real OS-level fd." so if you pass handle straight into poll, that's not it, bestie. get the fd first. periodt. 💀

⭐ RETURN VALUE ⭐

this call returns the CS_OK value if successful 🫶 otherwise, an error is returned. that's the deal.

💀 ERRORS 💀

the errors are undocumented. yeah. that's it. that's the whole section. we don't know. nobody wrote it down. iconic behaviour honestly 😭

🌈 SEE ALSO 🌈

go read these too, they're all in the same friend group:

• cpg_overview(3)
• cpg_initialize(3)
• cpg_finalize(3)
• cpg_fd_get(3)
• cpg_dispatch(3)
• cpg_join(3)
• cpg_leave(3)
• cpg_mcast_joined(3)
• cpg_membership_get(3)
• cpg_zcb_alloc(3)
• cpg_zcb_free(3)
• cpg_zcb_mcast_joined(3)
• cpg_context_get(3)
• cpg_context_set(3)
• cpg_local_get(3)

and the error code squad, all listed here verbatim so you know exactly what you're catching:

• CS_ERR_TRY_AGAIN Resource temporarily unavailable
• CS_ERR_INVALID_PARAM Invalid argument
• CS_ERR_ACCESS Permission denied
• CS_ERR_LIBRARY The connection failed
• CS_ERR_INTERRUPT System call interrupted by a signal
• CS_ERR_NOT_SUPPORTED The requested protocol/functionality not supported
• CS_ERR_MESSAGE_ERROR Incorrect auth message received
• CS_ERR_NO_MEMORY Not enough memory to complete the requested task

🧚 a lil sign-off 🧚

this page came from the corosync Man Page, dated 2004-08-31 — yes she's vintage, yes she still slays, we stan an elder 💜

now go poll that fd properly. main character energy only. byeee 🎀✨💖