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Low-end status monitors
I've realized that the world of status monitoring has changed in the past couple of years. I'm seeing occasional screenshots on LET of things I'm not very familiar with and I've had a couple of services that I got years ago start disappearing (not that most of them ever gained traction in the community and it was a matter of time for those Lifetimes to end).
I realize that people are sometimes rabid about their favorite choice in this space; I appreciate enthusiastic responses, but I would like to know how they actually compare against each other.
So, what's the current favorite services for low-end use? Does your favorite support more than HTTP (e.g. ICMP, arbitrary user-defined protocol handshakes, etc.)? Does it have some way to track uptime (graph, CSV, etc.)? Does it support webhooks or other automation when things enter/leave "problem" states? What's it's browser compatibility like (e.g. Would it load on IE 3 if IE 3 could speak TLS? This is useful for determining how likely you're going to get to your monitor when your own connection is flaky. Tons of scripts and no degraded mode could mean no visibility, which could be more important to some than e.g. animated graphs.)? Does it, itself, have good uptime? What makes it worth a look amongst an admittedly crowded field? Any other potential decision makers I missed?
I haven't seen a thread for this topic for quite some time, so while being useful for my current project (researching the options is what made me think of checking LET), there's always a fresh batch of people on the site who could benefit from a discussion of the current options. Keeping an eye on your idlers (or not-so-idlers) is often a blind spot for community members. So, please, let's keep this one civil and helpful for those who are finding it later. 
No poll, as there are altogether too many options and I would assuredly miss at least one choice people might suggest while listing some that aren't necessarily well known in the LET community (and which I may have not used myself, so really no value).
And if you have a personal favorite that is decidedly not low-end (there are many), may as well drop it here as well. Just because we, as a community, like to make the most of the low end of the pool doesn't mean that we don't like seeing what's lurking in the deep end. 
Comments
HetrixTools itself has very good uptime, there's definitely some magic / very well HA design going on behind the scene to ensure this level of availability that runs every 1 minute.
For me myself personally I also use Smokeping, once you go Smokeping you wish everything is monitored there lol.
In terms of server resources, Node Exporter + Prometheus + Grafana wins almost every other things.
I had a public instance of Night-Sky at some point, its open source on github.
However, I ended up using it only internally.
Still runs fine on PHP 8.1 and higher.
The Project itself is roughly 8 years old.
Uptime kuma (free, open source) or use LET members as uptime checkers and LET as your status page.
I've been working on https://uptime.gd for a bit, it's getting there, but currently there's no alerting transports available, checks run every 1 minute, basic ICMP checks for now.
Github https://github.com/Ne00n/Night-Sky/tree/Experimental
Works reliable enough for me, needs only a bit of maintenance.
At some point this year, I am going to prep the Project for PHP 8.2 and 8.3 and drop the rest.
It's free but does not have an official api.
I like updown.io since its pay as you go and only pay for what you use. Plus the public status pages are a nice feature and setup instantly for you once you make a cname subdomain for it.
uptimerobot
nixstats.com
Happy enough with Hetrix agents (simplicity, stability, and enough detail). Though, I might need to see about some sort of community harassment support for a sale as it can get expensive
Speaking with some other hosts Netdata seems like a good option as well. In particular the ability to view resources specific to each KVM. I know we had very briefly looked at it internally quite awhile ago and just felt it was "too overwhelming" at that time, however as you grow and learn some of those features would definitely be helpful by now.
I can't speak to Netdata directly, but both of the above support monitoring/alerts and have been pretty flawless. Hetrix even picked up and alerted with a weird issue on a RAID array indirectly that was useful in troubleshooting a very intermittent and micro power delivery issue for an internal server.
Looks pretty clean, nice job. Will definitely follow this project.
I use netdata, only downside is the health metrics are stored on the actual server itself. So when you try to retrieve stats on a machine that can't connect to netdata or the server is borked, there no way to tell if you the CPU went 100% or your Network spiked to 100%.
Looks nice. Just FYI there's a typo on the main page: Monitor whats imporant -> Monitor what's important
Netdata is a resource hog. I like Linode's Longview for server resource monitor, it's simple and easy and lightweight and 10 free monitors you can use on a server anywhere. I got a sweet appsumo deal on unlimited lifetime betteruptime (now betterstack) and its awesome. I'm not sure what the pricing for betterstack is since I got the sweet LTD, but it should be worth paying for all its amazing features for uptime monitoring - lots of options, easy config settings, nice status pages, multi branding, teams, etc.
Anyone know of a monitoring tool like Hetrix with support for ZFS RAID monitoring?
@HBAndrei with the ZFS kinda fast popularity rise (in comparison to rest of fs) I assume this is already somewhere on #TODO, any ETA? ;-)
uptimerobot. been using it for years
Thanks -- fixed/updated now
Thank you! I aim to get alert transports up and working this month