A nice feature is that journald gives you flags like "--boot" to see logs only emitted during a specific boot, or "--since '5m ago'" which is not that straightforward to do with the approach you favor. (if there is a way to do it easily, please let me know!)
On my NAS
# strace journalctl -u nginx 2>&1 |grep open |wc -l
827
# strace journalctl -u baked-potato 2>&1 |grep open |wc -l
827
It's DB implementation is utter garbage. It doesn't even organize files by time or really anything useful. If the binary database was a SQLite file with columns containing app name/log level/etc. it would actually be useful but current one is just shit.
Bonus round:
#:/var/log/journal echo 3 >/proc/sys/vm/drop_caches
#:/var/log/journal time journalctl -u nginx >/dev/null 2>&1
real 0m3,232s
user 0m0,036s
sys 0m0,292s
#:/var/log/journal echo 3 >/proc/sys/vm/drop_caches
#:/var/log/journal time ag -R nginx . >/dev/null 2>&1
real 0m2,531s
user 0m0,004s
sys 0m0,290s
> It's DB implementation is utter garbage. It doesn't even organize files by time or really anything useful.
That sounds interesting, can you please elaborate on the internal structure of journald files or link to further documentation? And why would I care if journald handles it for me?
Well, I was routinely getting multi-second wait for operations like systemctl status servicename which is not something rare, because it didn't even kept the pointer to file that has last few lines of app's logs. It's not just benchmarks
It also trashes cache with hundreds of MBs of logs instead of stuff apps running on server actually needs. An equivalent of "tail -f" can go thru hundreds of megabytes of binary logs.
https://systemd.io/JOURNAL_FILE_FORMAT/
On the other hand I agree that journald seems to call open syscall more often than I would originally expect, which can be a problem for some edge cases[1], but I don't consider this to be a real problem.
The difference is that you can use ls to find out, the same ls that you use when working with everything else, rather than needing to know some journald-specific thing that will only ever work for journald and will no doubt change again in another 5 years.
It's a big difference, not because one command, but because tail is part of the standard unix toolset that works with all files. Except now you have this one log file that is special and needs a different unique tool.
I do. I specifically want that as a more valuable and powerful feature. Undifferentiated, open-ended, general purpose, sharp tools are infinitely more useful.