View Source Flame On
Add Flame Graphs to your Phoenix Application or LiveDashboard
Installation
Add :flame_on
to your dependencies:
def deps do
[
{:flame_on, "~> 0.1.0"}
]
end
And then add Flame On as a LiveDashboard page or a LiveComponent in your LiveView page
Flame On as a LiveDashboard page
Modify the live_dashboard
call in your Router
:
live_dashboard "/dashboard",
metrics: MyAppWeb.Telemetry,
additional_pages: [
flame_on: FlameOn.DashboardPage
]
You will now find a Flame On
tab along the top of the LiveDashboard page
Flame On as a LiveComponent in your own LiveView page
<.live_component module={FlameOn.Component} id="flame_on" width="100%" height="100%" />
Usage
Choose the Module, Function, and Arity of the function you want to profile, click "Flame On", and then trigger the function (e.g. make a web request in a new tab). Note that for Elixir modules, you will need to prefix them with Elixir
, e.g. Elixir.Phoenix.Controller
, while Erlang modules take simply the erlang module name, e.g. cowboy_handler
. The default values of cowboy_handler
/execute
/2
are the best way to capture a standard Phoenix Controller DeadView request or the DeadView request that kicks off a LiveView request.
Zooming
Clicking a block will zoom the flamegraph to that block and recalculate the percents for the blocks such that the clicked block is now 100%. You can return to a higher level block by clicking the link for it above the blocks.
Running in Production
Flame On should not be run in critical production environments. Flame On uses eFlambe, which uses Meck under the hood. This swaps out beam code paths and injects mock code that includes tracing. If you do need to use Flame On in a critical production node to diagnose a specific issue, I recommend rebuilding or restarting that node after running it.
Running in a Release
Meck swaps out code paths and therefore you will need to include the beam files in your release. By default these are stripped, so in your release definition in mix.exs
add the strip_beams: false
flag:
releases: [
my_app_web: [
...
strip_beams: false
],
You may also need to explicitly include :meck
as a dependency if it can't find it when trying to run in a release.