Wandering Thoughts archives


Some thoughts on having set up a personal Alertmanager instance

I've been running a personal Prometheus instance on my desktop machines for long enough that I don't remember exactly how long (probably since December of 2018). Recently, I extended that by setting up a personal Alertmanager on my work desktop. The direct trigger of this was concerns about the kernel turning off the GPU fan and melting down the GPU if I didn't catch it in time, but once I'd set up Alertmanager and written the initial alert rule, I came up with a number of other problems I wanted to know about.

All of this was pretty easy because I could mostly copy the Alertmanager configuration and alerting rules from our production Prometheus setup, with only minor edits. If I'd had to write a full setup from scratch, I might not have bothered (or it would have been a very minimal and relatively little customized one). This does have the modest downside that the emails about my personal alerts look an awful lot like our production alerts, but I'm relatively confident I can keep them straight.

On the one hand, all of this is useful, partly because it gives me a test environment. I routinely pilot new versions of many Prometheus components on my own machines, but until now that didn't include Alertmanager; now it does. It's also useful to know about problems on my work machine, especially at the moment when I'm not in the office to notice various issues in person. And some problems I'm checking for (like Prometheus exporters that have failed to start) are ones I've had before on both my home and my work machine.

On the other hand, this is a lot of duplication of effort to get monitoring and alerts for my office machine, since I've set up most of a copy of our production Prometheus setup. But I can't easily include my work machine in our production setup without causing a bunch of administrative issues, and this actually points out a general issue with (our) Prometheus.

The core issue is that our Prometheus setup is not designed or set up for multi-tenant operation, and I'm not sure there's any easy path to make a Prometheus setup work that way. My office desktop is not the only additional 'tenant' we might want to support; for example, it's quite possible that there are research groups (supported by other people) who want to monitor and alert about their own machines. Right now, all we can offer to them is to tell them how we set up our own Prometheus server and clients. We can't let them actually use our Prometheus, our Grafana, our Alertmanager, and so on; they have to provision their own machine and run their own instances.

I don't think this is necessarily within Prometheus's scope (although some people do build setups that work this way). But I do sometimes wish it was something Prometheus and Grafana supported, even if it's not clear to me how they could (or if we would take advantage of it if they did).

(One big problem with a multi-tenant environment is storage space for metrics. Our server's available storage is dedicated to our own metrics and we need all the space there. Even on a bigger server that could take more disk drives we'd have issues of allocating and handling space.)

sysadmin/AlertmanagerPersonalInstance written at 23:26:27; Add Comment

Being able to see links I've visited in Firefox is startlingly better

I recently wrote about how I wanted to make links that I'd already visited be clearly visible in Firefox. At the time I was hoping for a general style that I could temporarily enable on anywhere and have work regardless of the site's choice of colours, link decorations, and other details. In writing the entry I discovered that Firefox supported the special colour name of 'VisitedText' for your standard visited link colour. While I considered general solutions, this led me to start writing some very quick site-specific styles with Stylus to use this on suitable sites. Each site style is the same:

a:visited {
  color: VisitedText !important;

There are a lot of sites that this very simple style works on, because it turns out that there are a lot of sites that are basically black text on white background; they've just decided to suppress visited links as a separate color (and sometimes fiddle with the link style too). At this point I've added Stylus styles for about a dozen sites.

(It turns out that Stylus has an interface for adding additional domains to a style so I theoretically don't need one style per site. In practice it's probably still easier to type this out anew for each new site I apply this to rather than find and add the domain name to an existing site. And this way, I can change the site-specific style if the site does something odd later.)

It's been startling how much better this has made my experience on these sites. It's encouraged my exploration of their links, has made re-visiting far less of an annoying experience, and in general has removed a source of friction that I didn't consciously realize existed. Each site is clearly nicer this way (and less quietly irritating). It at least feels as if the sites are more legible and easier to navigate.

(One of my guesses for why is that before, every time I considered opening a link I'd hover over it and try to remember if I'd already read it. Now I don't have to try that; the site tells me.)

On the one hand I feel happy that this has validated my effort. On the other hand, this vividly demonstrates that so many (other) sites are clearly damaging their own usability (at least for me) by deliberately hiding this information in the name of some design principle.

(Of course this fix isn't complete, because some sites also put their own tracking additions on their outbound links. This makes Firefox consider the full link to be 'not visited', even though I've already visited the link without the extra tracking goo. But that's life on the modern web.)

web/SeeingVisitedLinksGreat written at 00:25:37; Add Comment

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