What problem does this PR solve?

Issue Number: close #361

Problem Summary:

• The compression protocol may help to ease the network bandwidth bottleneck. The protocol spec: https://dev.mysql.com/doc/dev/mysql-server/latest/page_protocol_basic_compression_packet.html
• Now we have multiple protocols in PacketIO: proxy-protocol, TLS, compression, and uncompressed packets. Too many branches in one class make the code harder to maintain.

What is changed and how it works:

• Support the compression protocol in compress.go.
• The 3 protocols can be treated as layered protocols: packet -> compression(optional) -> TLS(optional) -> proxy-protocol(optional) -> raw connection. Each layer doesn't care about what the underlying protocol really is. So I decouple the protocols into:
  • PacketIO still handles MySQL packet reading and writing
  • (optional)compressReadWriter handles compression protocol
  • (optional)tlsReadWriter handles TLS
  • (optional)proxyReadWriter handles proxy-protocol
  • basicReadWriter wraps the raw connection and handles basic connection features like recording the traffic, checking if the peer is alive

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Tested with:

• MySQL client 8.0.33 -> TiProxy -> MySQL server 8.0.33
• MySQL connector/J 8.01 -> TiProxy -> MySQL server 8.0.33

Notable changes

• Has configuration change
• Has HTTP API interfaces change
• Has tiproxyctl change
• Other user behavior changes

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None