trace running dotnet app (flame graph)

finally after figuring out how to do it with nodejs

it is turn for dotnet

imagine we have an application running inside Kubernetes

it is behaves bad and we literally have no idea why

here is how it may be done

choose victim pod

kubectl get po -l app=my-awesome-app

connect to it

kubectl exec -it my-awesome-app-xxxx-yyyy -- sh

install required software if needed

apk add wget
apk add bash

install corresponding dotnet sdk

wget https://dot.net/v1/dotnet-install.sh
chmod +x dotnet-install.sh
./dotnet-install.sh --channel 7.0
export PATH="$HOME/.dotnet:$PATH"

install dotnet trace tool

dotnet tool install --global dotnet-trace
export PATH="$PATH:/root/.dotnet/tools"

find process id (pid) of your app

dotnet-trace ps

it should output something like this:

1  dotnet  share/dotnet/dotnet  dotnet Api.dll

where 1 is your pid

start collecting data for pid 1

dotnet-trace collect -p 1

it will start collecting data and after pressing enter stop in logs you will see

Press <Enter> or <Ctrl+C> to exit
Output File    : /app/dotnet_20250402_074040.nettrace

now you need to copy this file from pod to your local machine

kubectl cp my-awesome-app-xxxx-yyyy:/app/dotnet_20250402_074040.nettrace demo.nettrace

note: nettrace files can be opened with dotTrace if you have it

the next step will be to convert it to json

dotnet-trace convert --format speedscope --output demo.json demo.nettrace

for this to work you need to install dotnet trace tool locally as well

and finally

open https://www.speedscope.app

and upload your json file, you should see an flame graph with details of whats going on