Support for WebSocket client metrics

[anthochristen]

Motivation

Currently, Reactor Netty provides metrics support for HTTP client/server interactions, but WebSocket client connections lack similar observability and metrics support. This makes it difficult to monitor and troubleshoot WebSocket connection lifecycles, message throughput, error rates, and latencies in production environments.

Desired solution

Introduce built-in metrics collection for Reactor Netty WebSocket clients, similar to what is available for HTTP clients (MicrometerHttpMetricsRecorder). Like metrics for,

• WebSocket connection open/close count.
• Connection duration.
• Send/receive message counts and rates
• Bytes sent/received per connection.

Metrics should be consistent with existing Micrometer integration and maybe follow OpenTelemetry semantic conventions. (if and when they come up)

Considered alternatives

• Manually instrumenting each WebSocket client with doOnConnect, doOnError, doOnNext, etc., but this is error-prone and inconsistent.

[violetagg]

@anthochristen Would you like to provide a PR?

[LivingLikeKrillin]

Hi, I'm currently developing a production system using Reactor Netty (including WebSocket), and I've also felt the need for more accurate HTTP protocol logging in client metrics.

If it's alright with the maintainers, I'd like to take a shot at addressing this issue and submitting a PR.

Please let me know if there are any constraints I should consider.
Thanks!

[violetagg]

@LivingLikeKrillin Sure, it will be great if you can provide a PR. Branch 1.2.x is the current version that we actively maintain and main is 1.3.0 that we aim to release in November.