Jonathan Hammer:
> Hi,
>
> We are running Postfix on macOS and making use of `maillog_file =
> /dev/stdout` and `postfix start-fg` to send our logs to stdout. Not using
> Docker.
>
> We would like to pipe the logs from stdout to another process to do some
> analysis and post-processing, like so:
>
> $ postfix start-fg | our-custom-log-analyzer?
>
> However, in this configuration, Postfix fails to start and logs this error:
>
> fatal: open logfile ?/dev/stdout?: file has 0 hard links
Here is one suggestion to make this more robust. Insteead of
postfix start-fg | analyzer
which requires restarting Postfix when the analyzer needs to be restarted.
use a named pipe, like thisL
test -e /path/to/fifo || mkfifo /path/to/fifo
analyzer < /path/to/fifo &
postfix start-fg > /path/to/fifo
With this, you can restart the analyzer independently from Postfix.
It also avoids the nonsense with stdout having a zero link count.
Quick demo on Macos:
$ mkfifo fifo
$ cat <fifo&
[1] 45582
$ ls -lL /dev/stdout >fifo
prw-r--r-- 1 wietse eng 0 Sep 24 10:22 /dev/stdout
[1]+ Done cat < fifo
$
Note the link count of '1'.
That said, stdout logging is intended for containers that don't run
other programs. It does not work when a non-root user runs a Postfix
command; in that case, stdout logging may be intermingled with
normal command output.
Wietse
