IndexOutOfRangeException when parsing models in multithreads

[jaslawinMs]

version: 1.0.4-preview

When multiple threads are parsing models sometimes this exception is thrown:

Message:  System.IndexOutOfRangeException : Index was outside the bounds of the array.

Stack Trace: 

HashSet`1.AddIfNotPresent(T value, Int32& location)
HashSet`1.Add(T item)
Model.TrySetObjectProperty(Dtmi elementId, String layer, String propertyName, JsonLdProperty propProp, Dtmi referencedElementId, String keyProp, String keyValue, ParsingErrorCollection parsingErrorCollection) line 71
Model.SetObjectProperties(List`1 objectPropertyInfoList, ParsingErrorCollection parsingErrorCollection, StandardElementCollection standardElementCollection, Boolean preserveElementAliases) line 141
ModelParser.ParseInternal(IEnumerable`1 jsonTexts, DtdlParseLocator dtdlLocator) line 168
ModelParser.Parse(IEnumerable`1 jsonTexts, DtdlParseLocator dtdlLocator) line 71

[rido-min]

can we add a test to verify multi thread scenarios?

[jrdouceur]

Not really. Not a deterministic test. It shows up only probabilistically unless we were to use some concurrency test system that allows us to control the interleaving.

[rido-min]

I understand that multi-threading issues are difficult to reproduce, but we could try to reproduce, maybe using some test benchmark like https://github.com/timcassell/ProtoBenchmarkHelpers ?

[jrdouceur]

According to #87:

this can be reproduced when running unit-tests that use the model parser from the Visual Studio unit-test runner, which will execute the tests on multiple threads by default.

So one option may be to change the ci action to execute tests in parallel.

[rido-min]

@jaslawinMs can you share more details about your tests? Do you share any parser instances across threads, maybe using static variables? or is the parser instantiated on each test method?

[jaslawinMs]

tests are executed in parallel (xunit). The parser object is created for each test (a field in a test class). I also used static field and ThreadStatic attribute but it had no effect