# Prometheus Label Bookmarklet Rabbit Hole

Following on from my previous post where I showed the bookmarklet I created to allow users to persist labels on Prometheus' targets page, I wanted to write a post explaining how I arrived at the point of the bookmarklet.

Warning
I’m not a frontend developer and haven’t really written javascript in a good few years, the below is just meant to showcase my approach to solving a problem rather than my prowess in making browsers do my bidding.

Quick summary of the problem, I saw the “before” labels as a means of deciding what relabel configurations I wanted to introduce into each scrape configuration I was creating, however the “before” labels were only visible during a mouseover event which was frustrating me no end.

Digging into the source code to understand how the mouseover tooltip is generated, I noticed that the list of “before” labels was not a dynamic page element, the content of the tooltip is embedded within the pages' HTML, so I knew I just needed a way to get to the underlying HTML.

Initially this was achieved using the inspect element tool, this was ok if a bit clunky.

While inspecting the list of labels I noticed a snippet of code data-toggle="tooltip", surely we could change tooltip for something else.

Chucking that snippet into Google, the search results all pointed to something called Bootstrap. I knew it was a javascript library, so I went over to the Bootstrap documentation to find out more.

It just so happens that Bootstrap can provide a number of components to your page, I didn’t really know what I was after at the time so there was a bit of trial and error involved in finding the component with the behaviour that would suit my use case, but eventually I came across Popovers and they seemed to do what I wanted. The example code provided in the documentation also looked pretty similar to the tooltip code, so it felt like a pretty good replacement.

Tooltips

 1 2 3  $(function () {$('[data-toggle="tooltip"]').tooltip() }) 

Popovers

 1 2 3  $(function () {$('[data-toggle="popover"]').popover() }) 

I assumed that since the tooltip functionality worked on labels, the jQuery selector for all '[data-toggle="tooltip"]' was working, but no harm in verifying

Ok great, so can we change the tooltip() method for popover() method?

$('[data-toggle="tooltip"]').popover() That seemed to work nicely and I was quite content to stop there initially. However, as I started to make use of these popovers I quickly noticed that the default popover width wasn’t large enough and made reading label lists quite difficult as they spanned multiple lines a lot of the time. I noticed that when the popover is created, a new div is inserted into the DOM with a class of class="popover fade bs-popover-right show", inspecting this element in the console I also noticed there was a max-width attribute defaulting to 276px. What if I were to change that value? $(".popover").css({"max-width":"700px"})

Perfect, well almost…See the problem is, if that DOM element doesn’t exist, the CSS change can’t take effect. In practice this meant every time I opened up a new popover, I’d have to re-run the CSS change.

This could probably suffice for personal usage, it didn’t have to be perfect, but I’ve come this far and since I saw some use in what I was doing I thought to take it a step further and create something for folk across the organisation to use without having to copy and paste snippets every time they loaded the targets page.

First thing’s first, I had to find all the labels on the page and add an EventListener to them.

 1 2 3 4 5  var elements = document.getElementsByClassName("badge badge-primary"); for (var i = 0; i < elements.length; i++) { elements[i].addEventListener('click', myFunction, false); } 

Next up was to package the commands I was running manually into a function which would be called each time the addEventListener is triggered.

  1 2 3 4 5 6 7 8 9 10  var elements = document.getElementsByClassName("badge badge-primary"); var myFunction = function(){ $('[data-toggle="tooltip"]').popover();$(".popover").css({"max-width":"700px"}; }; for (var i = 0; i < elements.length; i++) { elements[i].addEventListener('click', myFunction, false); } 

For some reason, this didn’t work as I expected, what I noticed was that on the initial click, the popover would stay at the smaller 276px size, and subsequent popovers would be sized correctly at 700px. Thinking through why this might be happening I remembered that the popover element is inserted into the DOM when created, when myFunction was called on the initial click the jQuery library wasn’t able to find any elements with a .popover class.

To combat this I added a slight delay of 100ms before editing CSS attributes of the popover using the setTimeout() method.

  1 2 3 4 5 6 7 8 9 10  var elements = document.getElementsByClassName("badge badge-primary"); var myFunction = function(){ $('[data-toggle="tooltip"]').popover(); setTimeout(function(){$(".popover").css({"max-width":"700px"})}, 100); }; for (var i = 0; i < elements.length; i++) { elements[i].addEventListener('click', myFunction, false); } 

At this point I had a small script that did what was needed, so it was time to package it into a bookmarklet so it could be saved and used on the appropriate page. I can’t remember what tool I used to achieve this, but a quick search provides more than enough tools which achieve the same result.

There probably is a bit of cleanup and best practice I should make sure I am following, maybe even add some defensive code so that the bookmarklet would only run the script on designated pages, but since the current user count is 1… it’s probably a little much at this point in time 😄

And with that, thanks for reading.