feat(dev): Add flamegraphs to live dashboard in non-prod#3313
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thecristen
approved these changes
Jul 6, 2026
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Scope
No ticket, but this tool has been quite helpful for profiling things like the homepage load times. So far, we've been using it by cherry-picking this commit onto different pieces of work, but I don't see any reason we couldn't just commit it.
Caution
It is very important that
flame_on, or flamegraphs in general, not be enabled in production, because it messes with how function calls work and can slow down critical paths. It's currently scoped to not run whenMix.env()is:prod, and the dep is only installed for:dev. We need to make sure to keep it that way.Screenshots
A nice, interactive flamegraph from loading the homepage. Hovering over the entry for
DotcomWeb.Plugs.RecentlyVisited.call/2shows that it accounted for 8% of homepage load runtime.You can click on an entry to zoom in and see more details about what happens within a particular call. Zooming in on the root layout shows that rendering alerts accounted for 39% of its runtime.
How to test
Navigate to the Flame On pane in the dashboard, click the
Flame On!button and have fun!Note
I've noticed that sometimes Flame On isn't able to do its thing, and times out instead. When that happens, restarting my computer seems to fix it.