Here is a brief overview of the new API's we added in IIS8
IHttpContext3->EnableFullDuplex() -- This API tells the IIS pipeline to go into full duplex mode. This enables an handler to issue one read and one write operation in parallel.
IHttpContext3->GetNamedContextContainer() -- This API retrieves the named context container for a given request context. Modules can use the named context container to store request specific container indexed by a named string. The API GetModuleContextContainer() returns request specific container stored indexed based on the module ID.
IHttpCompletionInfo2->GetCompletedOperation() This API returns the operation which completed, when IIS indicates a module of any completion. In a full duplex mode, if both reads and writes are pending, this API helps identify which operation completed. The call returns 1 for read completion, and 2 for write completion.
Custom completion routines for read/write API's. We now support specifying custom completion routines for the ReadEntityBody/WriteEntityChunks API's.