Support Tracing

[ethernoy]

I am experiencing some difficulty when troubleshooting a slow ratelimit installation. I believe adding tracing of any format (preferrably zipkin or openTelemetry) to the ratelimit service can be of great help.

Happy to submit a PR if this is ok.

[mattklein123]

Sure, though I would go straight to Open Telemetry.

[ethernoy]

Sure, though I would go straight to Open Telemetry.

Great, then let me work on it

[ethernoy]

Sure, though I would go straight to Open Telemetry.

@mattklein123 Have a question in mind: if we are going to send out OTEL span when calling memcached and redis, it probably needs the caller to pass the parent traceId in gRPC request body, which isn't around for now according to the proto file in envoyproxy project:

https://github.com/envoyproxy/envoy/blob/main/api/envoy/service/ratelimit/v2/rls.proto
https://github.com/envoyproxy/envoy/blob/main/api/envoy/service/ratelimit/v3/rls.proto

Should we consider to add such data in the ratelimit request protocol? Also we will need to add the implementation in envoyproxy in order to produce a full trace.

[mattklein123]

Yeah we can add this to the API for sure.

[ethernoy]

Yeah we can add this to the API for sure.

Nice, then let me finish the implementation from ratelimit side first

[zirain]

fixed by https://github.com/envoyproxy/ratelimit/pull/332？

[ChezCrawford]

Can we close this if it was taken care of by #332 ?