mbuffer: "operation not supported" message and not sure how to troubleshoot

[emory]

hello,

i'm using mbuffer on macOS in my znapzend configuration via:

 mbuffer=/usr/local/bin/mbuffer
 mbuffer_size=1G

and when i'm running znapzend --debug i see error messages for my configurations using mbuffer, ==redaction via …==:

# zfs send -I cascade/…/notes@2023-07-26-113000 cascade/…/notes@2023-07-26-114500|/usr/local/bin/mbuffer -q -s 256k -W 600 -m 1G|zfs recv -F succor/localbackup/iow/icon/cascade/…/notes
mbuffer: warning: unable to sync <stdout>: Operation not supported
mbuffer: warning: unable to sync <stdout>: Operation not supported
# zfs list -H -o name -t snapshot cascade/av@2023-07-26-114500

my mbuffer binary i built myself per the instructions in a GitHub issue: ilovezfs/mbuffer-osx#1

the version of my local mbuffer is 20141227, i've built it on Apple Silicon and intel and i use openzfs for macOS on two workstations. i use znapzend for local pool-to-pool backups and plan to begin using it for host-to-host, i hadn't noticed the error until recently. i haven't setup any launchd jobs or anything yet, i foreground and --debug in a tmux pane while i get familiar still.

[lundman]

comes from
err = fsync(fd);
spit out by
warningmsg("unable to sync %s: %s\n",d->arg,strerror(errno));

but you are already in terminateSender() at this point. So either it worked, and you are getting noise at the end, or something else went wrong.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[xenophon61]

Sorry for the noob question - is it still possible to compile mbuffer for MacOS?

If so, how? (the 2018 instructions by ilovezfs don't appear to work).

TIA