I don't have clear repro steps, but somehow my host got into this bad state, where it fails to start with this error:
2016-03-04T00:25:33 System.UnauthorizedAccessException: Access to the path is denied.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.MemoryMappedFiles.MemoryMappedView.CreateView(SafeMemoryMappedFileHandle memMappedFileHandle, MemoryMappedFileAccess access, Int64 offset, Int64 size)
at System.IO.MemoryMappedFiles.MemoryMappedFile.CreateViewAccessor(Int64 offset, Int64 size, MemoryMappedFileAccess access)
--- End of stack trace from previous location where exception was thrown ---
at System.Reflection.Internal.MemoryMapLightUp.CreateViewAccessor(Object memoryMap, Int64 start, Int32 size)
at System.Reflection.Internal.StreamMemoryBlockProvider.TryCreateMemoryMappedFileBlock(Int64 start, Int32 size, MemoryMappedFileBlock& block)
at System.Reflection.Internal.StreamMemoryBlockProvider.GetMemoryBlockImpl(Int32 start, Int32 size)
at System.Reflection.Internal.MemoryBlockProvider.GetMemoryBlock(Int32 start, Int32 size)
at System.Reflection.PortableExecutable.PEReader.GetMetadataBlock()
at System.Reflection.Metadata.PEReaderExtensions.GetMetadataReader(PEReader peReader, MetadataReaderOptions options, MetadataStringDecoder utf8Decoder)
at Microsoft.CodeAnalysis.PEModule.InitializeMetadataReader()
at Microsoft.CodeAnalysis.PEModule.get_MetadataReader()
at Microsoft.CodeAnalysis.PEAssembly..ctor(AssemblyMetadata owner, ImmutableArray`1 modules)
at Microsoft.CodeAnalysis.AssemblyMetadata.GetOrCreateData()
at Microsoft.CodeAnalysis.AssemblyMetadata.GetModules()
at Microsoft.CodeAnalysis.AssemblyMetadata.IsValidAssembly()
at Microsoft.CodeAnalysis.CommonReferenceManager`2.GetMetadata(PortableExecutableReference peReference, CommonMessageProvider messageProvider, Location location, DiagnosticBag diagnostics)
at Microsoft.CodeAnalysis.CommonReferenceManager`2.ResolveMetadataReferences(TCompilation compilation, Dictionary`2 assemblyReferencesBySimpleName, ImmutableArray`1& references, IDictionary`2& boundReferenceDirectiveMap, ImmutableArray`1& boundReferenceDirectives, ImmutableArray`1& assemblies, ImmutableArray`1& modules, DiagnosticBag diagnostics)
at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.ReferenceManager.CreateAndSetSourceAssemblyFullBind(CSharpCompilation compilation)
at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.ReferenceManager.CreateSourceAssemblyForCompilation(CSharpCompilation compilation)
at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.GetRuntimeMetadataVersion(EmitOptions emitOptions)
at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.GetRuntimeMetadataVersion(EmitOptions emitOptions, DiagnosticBag diagnostics)
at Microsoft.CodeAnalysis.CSharp.CSharpCompilation.CreateModuleBuilder(EmitOptions emitOptions, IMethodSymbol debugEntryPoint, IEnumerable`1 manifestResources, CompilationTestData testData, DiagnosticBag diagnostics, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Compilation.Emit(EmitStreamProvider peStreamProvider, EmitStreamProvider pdbStreamProvider, EmitStreamProvider xmlDocumentationStreamProvider, EmitStreamProvider win32ResourcesStreamProvider, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, CompilationTestData testData, Func`1 getHostDiagnostics, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, CompilationTestData testData, Func`1 getHostDiagnostics, CancellationToken cancellationToken)
at Microsoft.CodeAnalysis.Compilation.Emit(Stream peStream, Stream pdbStream, Stream xmlDocumentationStream, Stream win32Resources, IEnumerable`1 manifestResources, EmitOptions options, IMethodSymbol debugEntryPoint, CancellationToken cancellationToken)
at Microsoft.Azure.WebJobs.Script.Description.CSharpFunctionInvoker.GetFunctionTarget()
at Microsoft.Azure.WebJobs.Script.Description.CSharpFunctionDescriptionProvider.GetFunctionParameters(IFunctionInvoker functionInvoker, FunctionMetadata functionMetadata, BindingMetadata triggerMetadata, Collection`1 methodAttributes, Collection`1 inputBindings, Collection`1 outputBindings)
at Microsoft.Azure.WebJobs.Script.Description.FunctionDescriptorProvider.TryCreate(FunctionMetadata functionMetadata, FunctionDescriptor& functionDescriptor)
at Microsoft.Azure.WebJobs.Script.Description.CSharpFunctionDescriptionProvider.TryCreate(FunctionMetadata functionMetadata, FunctionDescriptor& functionDescriptor)
at Microsoft.Azure.WebJobs.Script.ScriptHost.ReadFunctions(List`1 metadatas, IEnumerable`1 descriptorProviders)
at Microsoft.Azure.WebJobs.Script.ScriptHost.ReadFunctions(ScriptHostConfiguration config, IEnumerable`1 descriptionProviders)
at Microsoft.Azure.WebJobs.Script.ScriptHost.Initialize()
at Microsoft.Azure.WebJobs.Script.ScriptHost.Create(ScriptHostConfiguration scriptConfig)
at Microsoft.Azure.WebJobs.Script.ScriptHostManager.RunAndBlock(CancellationToken cancellationToken)