As a client of grpc I want to be aware of which threads are being
created by grpc, and giving them recognizable names makes it significantly
easier to diagnose what is going on in my programs.
This provides thread names for macOS and Linux. Adding support for other
platforms should be easy for platform specialists.
This patch introduces an additional ALPN protocol, grpc-exp, intended to
take preference to h2 and indicate to the server that the connection
contains only gRPC traffic. This allows servers and intermediate boxes
to distinguish gRPC from other HTTP/2 traffic.
The choice of grpc-exp as a protocol identifier indicates that this
scheme is currently experimental and should not be relied upon. The
protocol is not in the IANA TLS registry.
This patch also introduces client/server handshake tests that validate
the preferential treatment of grpc-exp in an end-to-end manner.