HeapDump actuator produces invalid gcdump file

[bart-vmware]

Describe the bug

A gcdump downloaded from /actuator/heapdump can't be opened in PerfView or Visual Studio.

To capture a gcdump, use the following configuration:

{
  "Management": {
    "Endpoints": {
      "HeapDump": {
        "HeapDumpType": "gcdump"
      }
    }
  }
}

Error in PerfView:

Error in Visual Studio:

The Steeltoe documentation doesn't list gcdump as a possible dump type. However, Steeltoe v4 ignores the configured dump type on macOS and always takes a gcdump.

I was able to hack together the following code that produces a gcdump file that can be opened in PerfView, but not in Visual Studio. It requires an assembly reference to PerfView.exe, downloaded from https://github.com/microsoft/perfview/releases, and a NuGet reference to Microsoft.Diagnostics.Tracing.TraceEvent v3.1.16. It also requires elevated permissions to run, which I haven't looked into any further.

using PerfView;

const string gcDumpFileName = "C:\\Source\\dotnet-gcdump.gcdump";

App.CommandLineArgs = new CommandLineArgs { NoGui = true };
App.CommandProcessor = new CommandProcessor { LogFile = TextWriter.Null };

int processId = Environment.ProcessId;
PerfView.HeapDumper.DumpGCHeap(processId, gcDumpFileName, TextWriter.Null);

The code in Steeltoe to capture heap dumps (including gcdumps) relies on a very old copy of sources from PerfView. The CLR internals may have changed since then. A different approach could be to rely on dotnet-gcdump, which interestingly states the following:

Alternatively, we could drop support for capturing a gcdump entirely. The 3x Steeltoe source at https://github.com/SteeltoeOSS/Steeltoe/blob/release/3.2/src/Management/src/EndpointBase/HeapDump/HeapDumper.cs#L39 shows that a gcdump was taken only on .NET Core 3.x, or when explicitly configured. The 3x documentation states the following:

So it might be that gcdump support is just a left-over legacy feature from a time when it wasn't possible to capture a full dump.

@TimHess Do you have additional context on what happened and what Steeltoe should support?

[bart-vmware]

Here's some background on the different dump types. Heap dumps aren't OS-portable, while (modern-style) gcdumps are.
https://devblogs.microsoft.com/dotnet/collecting-and-analyzing-memory-dumps/