[PYTHON][RPC] Make rpc proxy jupyter friendly via PopenWorker.

[tqchen]

Previously the proxy relies multiprocessing to start a new process and does not work under jupyter. In the case of proxy however, we still need the tornado to help handle the web assembly wehpage hosting, so still need python in this particular case.

This PR switches that to use PopenWorker instead of multiprocessing.Process. We will send a worker function that:

• Starts a new thread with the latest state in the global function
• return the port to the main side

[tqchen]

cc @rkimball @junrushao1994 @tkonolige

[tkonolige]

I'm trying to run tests/python/contrib/test_rpc_proxy.py with this PR on my Mac, but its failing. The error is

INFO:root:RPCProxy: client port bind to localhost:9092
INFO:root:RPCProxy: Websock port bind to 8888
Traceback (most recent call last):
  File "tests/python/contrib/test_rpc_proxy.py", line 75, in <module>
    rpc_proxy_check()
  File "tests/python/contrib/test_rpc_proxy.py", line 68, in rpc_proxy_check
    check()
  File "tests/python/contrib/test_rpc_proxy.py", line 62, in check
    client = rpc.connect(prox.host, prox.port, key="x1")
  File "/Users/tristan/octoml/tvm/python/tvm/rpc/client.py", line 501, in connect
    sess = _ffi_api.Connect(url, port, key, *session_constructor_args)
  File "/Users/tristan/octoml/tvm/python/tvm/_ffi/_ctypes/packed_func.py", line 237, in __call__
    raise get_last_ffi_error()
tvm._ffi.base.TVMError: Traceback (most recent call last):
  [bt] (7) 8   ???                                 0x00007ffeee90cf00 0x0 + 140732900888320
  [bt] (6) 7   _ctypes.cpython-38-darwin.so        0x000000010199f177 ffi_call_unix64 + 79
  [bt] (5) 6   libtvm.dylib                        0x0000000127bd9526 TVMFuncCall + 70
  [bt] (4) 5   libtvm.dylib                        0x0000000127c4ebfb std::__1::__function::__func<tvm::runtime::$_0, std::__1::allocator<tvm::runtime::$_0>, void (tvm::runtime::TVMArgs, tvm::runtime::TVMRetValue*)>::operator()(tvm::runtime::TVMArgs&&, tvm::runtime::TVMRetValue*&&) + 315
  [bt] (3) 4   libtvm.dylib                        0x0000000127c4dd73 tvm::runtime::RPCClientConnect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, tvm::runtime::TVMArgs) + 99
  [bt] (2) 3   libtvm.dylib                        0x0000000127c4c00a tvm::runtime::RPCConnect(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, tvm::runtime::TVMArgs) + 570
  [bt] (1) 2   libtvm.dylib                        0x0000000126aba42c tvm::runtime::detail::LogFatal::~LogFatal() + 92
  [bt] (0) 1   libtvm.dylib                        0x0000000127bec748 tvm::runtime::Backtrace() + 24
  File "/Users/tristan/octoml/tvm/src/runtime/rpc/rpc_socket_impl.cc", line 73
TVMError: ---------------------------------------------------------------
An internal invariant was violated during the execution of TVM.
Please read TVM's error reporting guidelines.
More details can be found here: https://discuss.tvm.ai/t/error-reporting/7793.
---------------------------------------------------------------
  Check failed: sock.Connect(addr) == false: Connect to ::1:9092 failed
INFO:root:Terminating Proxy Server...

Is this expected?

[tkonolige]

Are these the same on windows? @rkimball

[tqchen]

Thanks @tkonolige The particular error seems to also be the legacy issue of previous code of IPv6 and IPv4 mix. i have updated the test so it now works

[tkonolige]

Looks good! I tested it on my Mac with python 3.9.

[junrushao]

CC @zxybazh

[junrushao]

LGTM!