Support named pipe connections

[vaintroub]

Named pipe connections on Windows are not supported. (Unlike e.g Unix domain socket connections, which are supported).
When implemented well (not like in C/NET, but e.g like in MariaDB's JDBC ), local named pipe connections can be a lot faster than TCP.

[bgrainger]

When implemented well (not like in C/NET)

@vaintroub I'm not familiar with C/NET's implementation (I try to not look at their code) but am wondering what you consider the hallmarks of a "good" implementation?

I already have a transport layer that works over Stream; is using that with NamedPipeClientStream going to be good enough, or would more low-level operations be needed to get good performance?

[vaintroub]

Good is fast . I do not know why, but in C/NET pipe is substantially slower than TCP, and it should be maybe 1.´5-2x faster than local TCP connection, for simple queries like "do 1", or even slightly more complex ones like "select 1" . I think NamedPipeClientStream is going to do OK, but if you could benchmark this against TCP, you'll know more.

[bgrainger]

I've got some initial performance numbers back, and they're not great.

TCP

Method	Mean
OpenFromPoolAsync	61.57 µs
OpenFromPoolSync	44.11 µs
ExecuteScalarAsync	112.51 µs
ExecuteScalarSync	85.40 µs
ReadBlobsAsync	178.99 µs
ReadBlobsSync	150.11 µs
ManyRowsAsync	803.64 µs
ManyRowsSync	752.27 µs

Named Pipe

Method	Mean
OpenFromPoolAsync	180.8 µs
OpenFromPoolSync	155.5 µs
ExecuteScalarAsync	186.5 µs
ExecuteScalarSync	171.8 µs
ReadBlobsAsync	315.5 µs
ReadBlobsSync	332.5 µs
ManyRowsAsync	847.5 µs
ManyRowsSync	828.5 µs

OTOH, they're much better than MySql.Data 8.0.11:

MySql.Data 8.0.11 Named Pipe

Method	Mean
OpenFromPoolAsync	431.5 µs
OpenFromPoolSync	441.5 µs
ExecuteScalarAsync	764.5 µs
ExecuteScalarSync	774.3 µs
ReadBlobsAsync	1,109.3 µs
ReadBlobsSync	1,093.1 µs
ManyRowsAsync	130,283.0 µs
ManyRowsSync	133,221.1 µs

I'd love to benchmark local TCP/IP connections with SIO_LOOPBACK_FAST_PATH enabled; that might be the best way to get high-performance local communication on Windows. (But I assume that would require building a custom version of MySQL Server.)

This shipped in 0.41.0 with these performance numbers. I can potentially revisit it in the future based on user feedback.

[vaintroub]

I doubt that any TCP (even with FAST path) is better than named pipe. Can you share your code?
MariaDBs JDBC is substantially faster via named pipe, as is native C connector. IIRC, JDBC is using BufferedStream for input (but not output). Also, the pipe name is important , \\.\pipename is much better than \\hostname\pipename

[bgrainger]

Named pipe is opened in this function:

MySqlConnector/src/MySqlConnector/Core/ServerSession.cs

Line 824 in dce98de

private Task<bool> OpenNamedPipeAsync(ConnectionSettings cs, IOBehavior ioBehavior, CancellationToken cancellationToken)

Reading/writing the stream happens here: https://github.com/mysql-net/MySqlConnector/blob/dce98defdffaf8ccffb4b795187157d096e13f17/src/MySqlConnector/Protocol/Serialization/StreamByteHandler.cs

I/O is buffered here: https://github.com/mysql-net/MySqlConnector/blob/dce98defdffaf8ccffb4b795187157d096e13f17/src/MySqlConnector/Protocol/Serialization/BufferedByteReader.cs

. is used as the host name if possible:

MySqlConnector/src/MySqlConnector/Core/ConnectionSettings.cs

Line 26 in dce98de

HostNames = (csb.Server == "." || string.Equals(csb.Server, "localhost", StringComparison.OrdinalIgnoreCase)) ? s_localhostPipeServer : new[] { csb.Server };

Does the JDBC driver use a "stream" abstraction, just talk directly to the Win32 API, something else?

[vaintroub]

JDBC uses java.io.RandomAccessFile for reading and writing ( but it extends Socket , because this is how different transports are implemented in this driver).
https://github.com/MariaDB/mariadb-connector-j/blob/master/src/main/java/org/mariadb/jdbc/internal/io/socket/NamedPipeSocket.java

It uses native code, only for "busy pipe" workaround (Java would throw FileNotFoundException on many concurrent connect requests). If native code is not possible, there is just retry after some sleep.