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Bug #14340

Updated by Ivan Necas over 6 years ago

While debugging #13293, I've noticed, that it can take a while to load icons, when the machine
is under load. This can potentially lead to layout change (see the screenshots), that leads
https://github.com/teampoltergeist/poltergeist#mouseeventfailed-errors.

Debugging notes:

The issue is pretty hard to debug. Here are some hints to get some additional
tricks that can help to detect the issue:

I've used this snippet so see and compare how the page
looks right before the click event should happen
<pre>
20.times do
visit edit_host_path(host)
assert page.has_link?('Parameters', :href => '#params')
click_link 'Parameters'
save_screenshot
end
</pre>

Another good thing was looking into output of the `click` method
(it returns the coordinates that were clicked). Tracking that
for a while showed this:

<pre>
2016-03-23T19:14:37 [app] [D] ====== click: {"position"=>{"x"=>851, "y"=>385}}
2016-03-23T19:15:20 [app] [D] ====== click: {"position"=>{"x"=>851, "y"=>385}}
2016-03-23T19:15:48 [app] [D] ====== click: {"position"=>{"x"=>851, "y"=>365}}
</pre>

The coordinates of the event when the failure happened were different to the usual
values, which was a good indication that something is wrong with the layout.

Also, running it inside VM with 2GB of RAM and running 2 more tests suites in parallel
to simulate the load in Jenkins helped to reproduce the issue.

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