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etw.net-traceprocessing

Is TraceProcessor Thread Safe?

When I try to parse several ETL files in parallel via 

 using (ITraceProcessor processor = TraceProcessor.Create(myEtlFile, new TraceProcessorSettings
 {
   AllowLostEvents = true,
 }))

I get this exception

System.Runtime.InteropServices.InvalidComObjectException: COM object that has been separated from its underlying RCW cannot be used. The COM object was released while it was still in use on another thread.
Stack Trace: 
  InterfaceMarshaler.ConvertToManaged(IntPtr pUnk, IntPtr itfMT, IntPtr classMT, Int32 flags)
  AddInManagerAdapter.Create(String toolkitPath)
  ToolkitTraceProcessingEngine.Create(String path, ITraceProcessorSettings settings, ITraceProcessorSettings & effectiveSettings)
  TraceProcessor.Create(String path, ITraceProcessorSettings settings)

Is this a bug or a "known" limitation?

Solution

  • This is a known limitation. Given how the underlying native code interaction works, only one trace processor can be created at a time, unfortunately.

    In general, TraceProcessor only supports single-threaded access, even for static methods. Some consumers have found places where multi-threaded code can work, but it's not tested/guaranteed - we generally haven't added locks or done anything to enable safe concurrent access.