Well, sitting at the `MemoryHigh` limit still grinds the app to a halt
anyway, lmao. I guess it's a feature designed for well-behaved processes
and not for outright leaking ones?
Let's try just having systemd basically reset the app regularly when the
RAM hits a certain threshold. I think that's what this config will do,
we'll find out!
Lol ok, as I had kinda predicted, the memory bounds I set last time
were not tight enough, and it stalled out again! (It was at 75% and
fully just not working.)
Let's try this tighter bound instead!
So, Dependabot correctly reported that this version of puma is
vulernable, which I fixed in the main app already—but I didn't notice we
also use that version in this cute tiny placeholder app we use early in
the deployment process.
There's not a real security need to upgrade this, as this placeholder
app has no access to useful data when it is run, but I think it's better
to resolve this by fixing it than by silencing Dependabot! May as well!
I just restarted the impress app in production! First I logged in to see
why it wasn't responding, and I saw that there was almost no free RAM
left, and that the Rails app had grown to eat it all up!
So in this change, we set a memory limit: if the impress app is taking
up more than 75% of the machine's RAM, systemctl will try to shrink it
down; if it can't, then it will kill the app at 80%.
I'm not totally sure whether these bounds are tight enough? I didn't
look closely enough at the numbers to see what the app's actual usage
was according to systemctl at the time (`sudo systemctl status
impress`), so my hope is this is enough. But if we run into a memory
leak crash like that again, because it turns out even existing at 75%
RAM freezes the machine when running alongside its other processes, we
can decrease these numbers!
I also don't know the nature of the memory leak, and that could be worth
investigating—the app pretty cleanly fits into ~500–600MB when it starts
up, but then does seem to slowly but steadily grow. If it could be kept
at that size, it's possible we could downgrade the server and save some
costs—but that's a question for another day, since making sure we handle
memory leaks when they *do* happen is a more important robustness fix!
Rails already creates little pre-gzipped `.gz` copies of all our assets
in the `public/assets` directory when we build. This configures nginx to
send those when available!
We weren't doing *any* gzip stuff before, so this helps a lot with those
bigger JS files, like the `wardrobe-2020` stuff. It's now at ~.5MB with
compression, which is still a bit big, but nowhere near as offensive as
the 4.5MB pre-anything, or 1.5MB post-minification, lol.
Yay it's working! We set up the box, install Ruby, upload a placeholder app, set it up as a service, and get it hooked up to nginx!
Next, we'll add the script to upload the latest version of the site. We just need to slot it into `/srv/impress/current`, run `bundle install`, and that should basically be that! (Oh, and we need to compile production assets—I wonder if it's useful to do that on the dev machine instead of on the target? That might save us from needing to install Node. Or maybe we'll have to anyway!)
