Provide a "System metrics" entry in the status page, to show disk space, RAM usage, and database size

[klonos]

This feature request was inspired by this discussion in Zulip around "Minimal Backdrop", which touched on topics around what would be the very minimum system specs where Backdrop core would run, and how well it would perform.

Something like this might be helpful to allow determining requirements when:

• moving a locally-built site to an actual hosting provider
• moving a live site to a different provider
• upgrading the hosting plan of an existing site (when certain specs seem to have been reaching capacity/limits)

[klonos]

I'm creating this issue here after @cellear's request, and looking for feedback around its potential usefulness and whether it is core-worthy, or something best placed in contrib.

PR with a sandbox that will allow people to play with this and view the code coming up soon...

[cellear]

I'm @cellear, and I approve this message.

Seriously, I think built-in metrics like this would be super useful. Hosting providers use tools like Sumo Logic and Drutiny to pull out information like this, but if we could give people a bit of that just by looking at the status report...how cool is that!

[klonos]

PR and sandbox available here: backdrop/backdrop#4254

Some thoughts/observations:

• Certain things such as disk usage, db size, and PHP memory size have native PHP functions/ways to grab them, but other things like RAM usage need to be parsed via commands that are operating-system-specific.
• There are ways to grab stats for instances of Backdrop installed on Windows, but our telemetry shows that over 95% of sites run on linux. Should we bother? Would these system metrics be of value in cases where for example the site is being built on a Windows machine, but is then to be moved to a linux host?
• Certain metrics, such as disk space and db size are fairly "persistent", in that they usually grow over time. So it makes sense to provide those as an indication (site admins can keep an eye for when these are running low, or in the case of the db when it grows too big). Other metrics though, such as system RAM usage and CPU load, only make sense if monitored over a period of time (because the server may be getting spikes of usage at some points, but otherwise sailing smoothly the rest of the time).
• Is it useful to show actual disk usage (which apparently includes operating system files etc.), or should we be showing something like media asset size instead? (how much space the documents/videos/images uploaded on the site take)

[klonos]

...should we be showing something like media asset size instead?

PR updated to show the size of the various files directories:

[klonos]

...OK, I'm gonna stop here for now, and wait for feedback/thoughts.

In the meantime, I'll spin up a Windows installation when I get a chance, and try things there. ...see if we can pull the same kind of metrics reliably on Windows.

[klonos]

...more thoughts:

• Compared to other entries in the status report page, this section is lengthy/dominant. Can anybody suggest a good way to provide some sort of "summary", so that everything else can be hidden away in a "more" toggle?
• Dashboard block to go with this?

[bugfolder]

As this is growing (and it's really nice to have!), should it perhaps be a separate report at admin/reports/system-metrics? The nature of the Status Report seems to be stuff that takes up only a line or so, and most "more" links only expand by another line or few. This listing is as long as, for example, the Telemetry separate report (admin/reports/telemetry).