Show HN: Nerdlog – Fast, multi-host TUI log viewer with timeline histogram

For more background and technical details, I wrote this up as well: https://dmitryfrank.com/projects/nerdlog/article

Show HN: Nerdlog – Fast, multi-host TUI log viewer with timeline histogram
github.com

journalctl is mentioned once in the landing page and it seems to imply that journalctl is not supported per se, as logs need to be stored plaintext to legacy syslog (?).

I do not want to store plaintext logs and use ancient workarounds like logrotate. journald itself has the built-in ability to receive logs from remote hosts (journald remote & gateway) and search them using --merge.

Nice work! The TUI looks really sharp and I like the histogram on top. Going to play with this today.

TIL awk patterns can be more than just regexes and can be combined with boolean operators. I've written a bit of awk and never realized this.

That's true, as of today nerdlog doesn't use journalctl, and needs plain log files. There were a few reasons of that, primarily related to the sheer amount of logs that we were dealing with.

As mentioned in the article, my original use case was: having a fleet of hosts, each printing pretty sizeable amount of logs, e.g. having more than 1-2GB log file on every host on a single day was pretty common. My biggest problem with journalctl is that, during some intensive spikes of logs, it might drop logs; we were definitely observing this behavior that some messages are clearly missing from the journalctl output, but when we check the plain log files, the messages are there. I don't remember details now, but I've read about some kind of ratelimiting / buffer overflow going on there (and somehow the part which writes to the files enjoys not having these limits, or at least having more permissive limits). So that's the primary one; I definitely didn't want to deal with missing logs. Somehow, old school technology like plain log files keeps being more reliable.

Second, at least back then, journalctl was noticeably slower than simply using tail+head hacks to "select" the requested time range.

Third, having a dependency like journalctl it's just harder to test than plain log files.

Lastly, I wanted to be able to use any log files, not necessarily controlled by journalctl.

I think adding support for journalctl should be possible, but I still do have doubts on whether it's worth it. You mention that you don't want to store plaintext logs and using logrotate, but is it painful to simply install rsyslog? I think it takes care of all this without us having to worry about it.

You'll go broke doing that, as those API calls are not free. Best to configure cloudwatch to dump into some sane place (S3, SigNoz, whatever) so you only pay the api call once and not every time for interactive viewing

I went spelunking around in the codebase trying to get the actual answer to your question and it seems it's like many things: theoretically yes with enough energy expended but by default it seems to be ssh-ing into the target hosts and running a pseudo agent over its own protocol back through ssh. So, "no"