Running dotTrace Remote Agent or command line in Linux Docker container.

Thank you for the feedback! We'll add additional documentation on profiling in Docker containers in the near future.
About Setup 1: there should be a human-readable error message in this case, it's our fault; we will fix this in the next version.
The error code corresponds to the "The request to attach a profiler was denied because a profiler is already loaded" error in .NET. Are you using other profilers or monitoring tools? Have you previously attached to the profiled process? Note that you need to correctly detach from a profiled process, so using the --timeout or --service-input=stdin parameters is recommended.
About Setup 2: indeed, there is no Remote Agent for Linux. Moreover, we are going to discard it even on Windows.

It would help a lot if usage in docker containers would be better documented - if that would be done in AWS ECS Fargate context - would be even better, because there are some limitations in there, especially if you try to profile startup and then get the collected snapshots before your container got killed.

Anyway, I've downloaded linux cmd tools and was not able to make them run in mcr.microsoft.com/dotnet/core/sdk:3.1-alpine image, I've added tools to it like this:

RUN mkdir -p /opt/profiling
RUN curl -L https://download.jetbrains.com/resharper/dotUltimate.2020.3.3/JetBrains.dotTrace.CommandLineTools.linux-x64.2020.3.3.tar.gz \
| tar xzf - -C /opt/profiling

And then when I connected through terminal and tried to execute ./dotTrace.sh it was complaining like this:

./runtime-dotnet.sh: exec: line 25: /opt/profiling/linux-x64/dotnet/dotnet: not found

I've checked - dotnet existed at given path, it had executable rights - so I have no idea what was going on - on my ubuntu virtual machine downloading command and dotTrace.sh worked fine.

I'm in a similar situation to David and Giedrius - How do I profile apps running in Linux containers in my dev env? It all seems... complicated.

I've spent today trying to get some performance timing for code execution with a couple of dotnet5 apps in Ubuntu Docker containers on my local Windows machine. They are built and debugged in VS2019 with a docker-compose run/debug profile (just the standard orchestration generated by VS) which launches the apps and attaches debuggers if required. In each container I can then copy across the dotTrace tools https://www.jetbrains.com/profiler/download/#section=commandline. Within each container I can then attach a dotTrace session to the running application:

./dotTrace.sh attach <pid> --save-to=./snapshots/snapshot.dtp --timeout=30s

I didn't have much success trying to list the PIDs but helpfully enough if you put in something wrong for the PID dotTrace.sh outputs the running processes for you to pick from. Attached to the one from the list and it produces a snapshot after 30s.

Then I can then copy the snapshot files back to the host, but I can't open them in VS2019 with ReSharper as this only seems to want to load .dtt - timeline snapshots. I've got .dtp files so I open these in the dotTrace desktop app and well I don't know what I'm looking at and trying to figure that out but it doesn't have access to source code and fails to decompile from some place it expected to.

Looking forward to these instructions Konstantin!

@Giedriusbanaitis:
About the issues with mcr.microsoft.com/dotnet/core/sdk:3.1-alpine docker image: unfortunately, all musl-based Linux distributives (including Alpine) are currently not supported. We are working on it and going to support them in the near future.

The corresponding issue in our tracker: https://youtrack.jetbrains.com/issue/PROF-934

Steven,

Actually, you've done it the right way. Only .dtp snapshots can be taken on Linux, and currently, they can be opened only in dotTrace Performance Viewer and Rider (and can't be opened in Visual Studio).

You can read more about how to analyze such snapshots in the corresponding section of our documentation: https://www.jetbrains.com/help/profiler/Studying_Profiling_Results__Index.html

Konstantin, ok, I've tried to switch to buster to profile app startup and it is just hard:

root@0ea8475b3137:/app# ./../opt/dottrace/dottrace start -framework=NetCore --save-to=snapshot.dtp ./Api.
dll
dotTrace command-line profiler 2021.1.3 build 777.0.20210525.202333. Copyright (C) 2021 JetBrains s.r.o.
Profiling in progress...
Unable to start profiling. Permission denied.

Have no clue how to proceed further, what kind of permissions are needed and for what. We need more documentation on how it works and how to troubleshoot it :)